All posts by ingmarsretro

When the car mirror doesn’t work anymore

I hear and read more and more often about electrically folding exterior mirrors that no longer work properly on vehicles from the German manufacturer with the four rings. The problem occurs with many models that have been in service for a few years and are operated in our local climate. In Internet forums you will find some users who know this problem. Also in my circle of acquaintances there are a few rings drivers who have a stuck electric exterior mirror. As a solution, the manufacturer always recommends replacing the entire unit. If you don’t want to spend your savings pointlessly on newly produced residual waste, you can take on this problem yourself. There is even a fairly small cause that causes this problem. And best of all – it can be repaired without any material costs. The longevity of the repair has also been proven…

The error manifests itself through the following behavior:

  • the mirror makes squeaking, creaking noises when folding in and out
  • the mirror stays in the wrong position and can only be engaged by moving it manually
  • the folding behavior depends on the weather

 

There are many posts about this with possible causes – from defective motors and defective door control units. The best thing to do would be to replace the mirror unit right away and get a new door control unit – yes, of course…

The solution to the problem is simpler: a small steel bolt that is supposed to be pushed out by a small spring gets stuck in its guide. The mechanical part of the mirror is of course also exposed to the environmental conditions and so the area comes into contact with rain, splash water – in winter salt water. Over time, the lubricants lose their properties or are even washed out and the whole “work” becomes stiff. So what helps? Completely disassemble, clean, re-lubricate and reassemble.

For this almost one and a half hour operation, I started by removing the mirror from the door and examining it in the cozy workshop. The easiest way to do this is to remove the inner lining of the door (depending on the vehicle, a few screws and many clips…) The mirror is then connected to the door control unit with a cable and secured with Torx screws.

The easiest way to click out the mirror glass is to use a plate lifter (suction cup). Then carefully – if present – pull off the two flat plugs from the mirror heating (it is essential to hold the contacts on the heating foil against). Next, both plastic halves of the mirror housing can be removed. A little observation helps here, which screws to remove and how the halves are held together.

Now the core of the mirror is there. The two die-cast parts are connected to each other via a hollow axle. The connection cable to the mirror adjustment drive and to the heater runs through the axle. A large steel spring sits above the axle and is attached with a spacer and a clamping ring (I don’t know if that’s the correct term). The spring exerts a fair amount of pressure between the two parts – and this is now the only slightly trickier part – the spring has to come out. To do this, the clamping ring must be levered out while the spring is held under tension. It comes out easily – but putting it back in becomes a challenge if you don’t have the right tools.

The already relaxed spring can be seen in the picture. Now the two parts can be taken apart.

Here the parts are to be recognized in disassembled form. In order to reach the Corpus Delicti, the small gearbox with the motor must be unscrewed. Underneath you can see the bolt, which in this case was stuck firmly in its hole so that the spring was no longer able to push it out.

Cover of the small gear
Bolt can be seen to the left of the mounting hole
Bolt with spring
the guide of the bolt must also be cleaned

The procedure is quite simple – clean everything, remove the corrosion and re-grease with lubricants. After that reassemble everything rejoice. 🙂 Most of the time of the whole job is cleaning.

By the way: the mirror described here comes from an A5…

UV sensor logger self-made

When summer comes, new ideas come. In the summer months, as is well known, the duration of sunshine is longer and the intensity of the sun’s rays is higher. Many use this property of the sun to boost their body’s vitamin D production, while others lie under the source of radiation to darken their skin color due to the high UV component. This, in turn, supposedly increases their attractiveness and stimulates hormone production and the willingness to mate… Unfortunately, the non-visible UV range in the spectrum of sunlight is known to have negative effects on the human body. Sunlight can also be used technically. On average, the power of the sun per unit area is assumed to be 1000W per m². Large-area P-N junctions in semiconductor materials are now able to generate electrical energy with an efficiency of up to aprox. 22%.

But the energy can also be used in other ways, or the UV component. Many retro collectors are certainly aware of the problem with yellowed old plastic cases. In order to get this under control, or to get it back to its original state from 30 or 40 years ago, you use H2O2, i.e. hydrogen peroxide and UV light, to get a bleaching process going. And so I came up with the idea for the following project.

At an online electronics store I found a UV sensor board from the manufacturer Waveshare in the sale. On it is a LITEON OPTOELECTRONICS LTR390 chip including a level shifter circuit. An I²C bus is available as an interface. A look at the data sheet revealed to me that the sensor records two wavelength ranges and outputs them separately. The ALS (Ambient Light Sensor from 500-600nm) and the UV (Ultra Violet range from 300-350nm). You can quickly make a simple logging board with this – I thought to myself. So I figured the board should be able to do the following:

  • Powered by a 18650 cell or USB
  • USB should also be able to charge the battery
  • a micro SD slot for recording the sensor data
  • an RS-232 port for direct logging on the PC
  • a cool OLED display
  • two buttons to operate the logger (interval, start/stop etc.)

The control should of course once again take over a chip from Atmega – the 328er. There are just enough of these in my assortment of boxes. To give you a quicker overview of the structure, I drew the following block diagram:

In the next step I created a circuit diagram from the block diagram in order to be able to create a layout out of  it. Parallel to the creation of the circuit diagram, I also connected the single components  together as a test using “air cabling” and tested whether everything worked as I imagined. And above all, everything should have space in the flash memory of the microcontroller.

The “airy wired” structure consisting of finished components can be seen in the picture above. An Arduino was sufficient for the first tests with the sensor and the OLED display. This enabled me to test the desired functions. So nothing stood in the way of creating the circuit diagram. An 18650 lithium cell will serve as the primary power source. Alternatively, there will also be a USB port that can charge the cell or operate the sensor. Because I’m lazy and component delivery bottlenecks are also a big problem at the moment, I use a ready-made Wemos D1 mini board to charge the battery. Like the OLED display board and the sensor board, this will find its place as a finished component on the circuit board design. As already mentioned, an Atmega328 in a TQFP housing is used as the controller. This will communicate with the OLED display (SBC-OLED01 with SSD1306 controller) and the LTR390 UV sensor board via the I²C interface. OLED and sensor are 5V compatible. However, the SD card is operated with 3.3V. For this, the circuit requires a voltage converter from 5V to 3.3V for the supply and a level shifter for the SPI data bus, via which the SD card exchanges data with the Atmega. Since the Atmega then also wants to be programmed with its firmware, I have provided a 2×4 pin header for connecting a programmer. The programmer needs six of these pins (GND,5V, MOSI, MISO, SCK and RESET) and the two remaining pins are intended for the serial interface. The two interrupt inputs of the Atmega are each wired with a button, which then makes the software operable. The battery voltage is measured and logged via a divider at one of the ADC inputs. The result of these thoughts is the following schematic:

A layout is then the next step. With a size of 12 x 4.5 cm, the circuit board is reasonably “handy”. The printed conductors are routed on both sides and the modules (charging circuit, display and UV sensor) are designed to be pluggable via pin headers.

The two images above show the preview of the “Top” and “Bottom” side of the layout. A circuit board could be created from the production data created in this way.

After some soldering work the hardware was ready. In order to breathe life into this “soldering” , software was required to do its work on the microcontroller.

When tinkering with the software, I used the free “Arduino IDE” development environment. The LTR390 documentation describes exactly which registers are used to operate which sensor functions. But there is also a ready-made library for those who are very comfortable – just like for almost all sensors and actuators that are to be connected to microcontrollers. In the Arduino IDE you can find the “Adafruit LTR390 Library” via the board manager, which you can use to communicate easily with the sensor. In my case, the OLED display is controlled by the SSD1306Ascii library. The “Wire” and “SPI” library take over the bus communication and the “SD” talks to the SD card. The includes then look like this:

#include <LTR390.h>
#include <SD.h>
#include <SPI.h>
#include <Wire.h>
#include “SSD1306Ascii.h”
#include “SSD1306AsciiWire.h”

I’m happy to post the entire code here if needed. However, it is not rocket science, but simple and certainly not optimized lines of code writing 🙂 In the current code (firmware) version 1.3d there is a small selection menu that makes it possible to set the log interval of the SD card recording and of course the start or stop recording. It is logged in a text file. The data recorded are UV index, ambient brightness and battery voltage.

I’ve included an excerpt from the datalog below:

 

 Ambient[lx], UV-indx, Batt[V], Loggingintervall[s]  
 691.60,0.01,3.77,20  
 691.60,0.03,3.76,20  
 1184.00,0.03,3.77,20  
 1184.00,0.03,3.75,20  
 1191.00,0.03,3.77,20  
 1191.00,0.03,3.75,20  
 1198.60,0.03,3.76,20  
 1198.60,0.03,3.73,20  
 1211.60,0.03,3.76,20  
 1211.60,0.04,3.75,20  
 1223.00,0.04,3.75,20  
 1223.00,0.04,3.76,20  
 1234.20,0.04,3.76,20  
 1234.20,0.04,3.74,20  
 1243.60,0.04,3.76,20  
 1243.60,0.04,3.76,20  
 1252.00,0.04,3.75,20  
 1252.00,0.04,3.73,20  
 1261.20,0.04,3.74,20  
 1261.20,0.04,3.72,20  
 1269.60,0.04,3.76,20  
 1269.60,0.04,3.76,20  
 1278.40,0.04,3.76,20  
 1278.40,0.04,3.75,20  
 1288.40,0.04,3.76,20  
 1288.40,0.04,3.75,20  
 1298.20,0.04,3.76,20  
 1298.20,0.04,3.74,20  
 1305.80,0.04,3.73,20  
 1305.80,0.04,3.73,20  
 1313.20,0.04,3.73,20  
 1313.20,0.04,3.75,20  
 1321.60,0.04,3.74,20  
 1321.60,0.04,3.75,20  
 1331.80,0.04,3.75,20  
 1331.80,0.04,3.75,20  
 1341.60,0.04,3.74,20  
 1341.60,0.04,3.76,20  
 1349.40,0.04,3.76,20  
 1349.40,0.04,3.76,20  
 1358.20,0.04,3.72,20  
 1358.20,0.04,3.76,20  
 1365.60,0.04,3.74,20  
 1365.60,0.04,3.73,20  
 1374.20,0.04,3.72,20  
 1374.20,0.04,3.75,20  
 1380.60,0.04,3.75,20  
 1380.60,0.04,3.76,20  
 1386.60,0.04,3.75,20  
 1386.60,0.04,3.76,20  
 1394.80,0.04,3.75,20  
 1394.80,0.04,3.75,20  
 1401.40,0.04,3.73,20  
 1401.40,0.04,3.74,20  
 1408.60,0.04,3.75,20  
 1408.60,0.04,3.74,20  
 1414.20,0.04,3.73,20  

This data can now be processed very easily and displayed graphically. As an Office user, you can use Excel, for example, and import the data there and display them as graphs. But it is even easier and also very fast with tools like Matlab. With a script like the one below you can visualize the log file.

 %% Setup the Import Options and import the data  
 opts = delimitedTextImportOptions("NumVariables", 4);  
 opts.DataLines = [3, inf];  
 opts.Delimiter = ",";  
 opts.VariableNames = ["Ambientlx", "UVindx", "BattV", "Loggingintervalls"];  
 opts.VariableTypes = ["double", "double", "double", "double"];  
 opts.ExtraColumnsRule = "ignore";  
 opts.EmptyLineRule = "read";  
 opts = setvaropts(opts, ["Ambientlx", "UVindx", "BattV"], "TrimNonNumeric", true);  
 opts = setvaropts(opts, ["Ambientlx", "UVindx", "BattV", "Loggingintervalls"], "DecimalSeparator", ",");  
 opts = setvaropts(opts, ["Ambientlx", "UVindx", "BattV"], "ThousandsSeparator", ".");  
 datalog = readtable("F:\ingmarsretro\datalog.txt", opts);  
 clear opts  
 x=size(datalog); % groesse der tabelle  
 measurement=x(1); % anzahl messungen   
 uvi=datalog{1:measurement,2};  
 ambient=datalog{1:measurement,1};  
 messzeit = linspace(0,(measurement*datalog{1,4}),measurement); %zeitvektor von 0 bis zeitintervall aus datalog spalte4 * messungen  
 figure(1);  
 title('UV - Index');  
 subplot(2,1,1);  
 plot(messzeit,uvi);  
 title('UV - Index');  
 xlabel('Zeit [s]');ylabel('UV - Index');  
 subplot(2,1,2);  
 plot(messzeit,ambient);  
 title('Beleuchtungsstärke');  
 xlabel('Zeit [s]');ylabel('Beleuchtungsstärke [lux]');  

If the script is executed, you get a plot that visualizes the measurement data.

The technical information on the sensor can be found in the manufacturer’s data sheet. Here are a few key points:

The LTR390 consists of two photodiodes, one for the visible spectrum of light and one that is sensitive in the UV range. The photodiode current is digitized in internal ADCs. An internal logic controls the ADCs and the connection to the outside world is established via an I²C interface. The resolution of ALS and also UVS can be configured in 13, 16, 17, 18, 19 and 20 bits. The sensor chip is housed in a 2x2mm 6pin package. The detector opening has an edge length of 280×280 µm.

Source: LTR-390UV data sheet https://optoelectronics.liteon.com/en-global/Led/LED-Component/Detail/926
Source: LTR-390UV data sheet https://optoelectronics.liteon.com/en-global/Led/LED-Component/Detail/926

 

 

Selfmade Nixiclock

The fact that the topic of retro has become more and more of a trend in recent years has not escaped me either. The “Industrial” and “Steam” style has also found its way into many households. People put many things on the shelf again, which represent the robust technology and the appearance of the past decades. For example, LED lamps flicker in the rooms, which were visually modelled on the light bulbs of the Wilhelminian era. The brass lamp holders are held in place by a cable sheathed with fabric mesh. Instead of the carbon or tungsten filaments in the bulbs, modern LED filament works. Thematically corresponding to this style, mechanical watches and electric clocks with illuminated displays of all kinds, for example, are in demand again. In keeping with this trend, I have already reported on the VFD watches in older blog posts. (VFD = VaccumFLuoreszenzDisplay) Until the end of the 90s, for example, this display technology was still frequently used in video recorders, hi-fi devices and various radio alarm clocks. After that, LED and LCD technology was standard. Today, the small OLEDs are finding their way everywhere. As part of the Retro Revival, VFDs are assembled into watches in the form of single-digit display tubes. These watches are available as finished devices or as kits (grother.de). Since these display tubes are no longer manufactured and only old stocks (new old stock) are available, prices are also rising. But it is even worse in terms of price – a technical development from the 1920s is a display technology based on the principle of the glow lamp. In this case, in a glass flask filled with noble gas, a digit bent from wire is attached as a cathode, in front of a thin metal grid as an anode. If a voltage is applied, the noble gas begins to glow along the wire formed as a digit. Seen from the outside, this creates the impression of a luminous number. In such a tube, the digits from 0-9 are usually accommodated and for each digit there is of course a separate connection. Many of the readers will surely know this type of tube. It is called NIXIE – display tube (comes from the designation “Numeric Indicator eXperimental No. 1”

A watch with such display tubes is still missing in my collection. So I wanted to own one. But buying is easy – and also very expensive. So I decided to build a Nixie clock myself. It all started with a lengthy search for the tubes, because even for these you have to lay down a lot in the meantime. And I need at least six pieces, because my watch should also have a second display. So I searched the Internet on various platforms – and in the bay I found what I was looking for. There a board equipped with Nixie tubes was offered, which was broken out of some old device. The function of the board was given as “unknown” – but it was very cheap. The seller had two of them. So I risked it and bought the two boards equipped with five Nixies each.

The tubes were then successfully soldered out with some caution. The type of tube is the Z574M, for which you can also find the data sheets in the network and thus also has the socket circuitry.

With the help of the wiring, it can then be easily contacted and thus check digit by digit of each tube. The characteristics of the 574 are:

  • Anode ignition voltage: 150V
  • Anode burning voltage: 140V
  • Anode extinguishing voltage: 120V
  • Max anode voltage: 170V
  • Cathode current min: 1.5mA
  • Cathode current max: 2.5mA

With a suitable power supply unit, I was able to quickly set the necessary supply voltages for the functional test.

You can see here that the tube draws a current of 2.8mA at a burning voltage of just under 140V. This corresponds to an output of 392mW. So if I extrapolate and all six digits of the watch are continuously energized, then the power supply for the tubes must bring about 2.3W.

So the tubes already work. Now I can think about what the clock should look like and even more how I want to design it.

The idea is that a microcontroller should control all six tubes. I want to realize this with 8-bit 4094 shift registers, of which four bits each are used for a tube. These four bits from the shift register should then control the tubes via binary coded decimals (i.e. BCD). However, since the tubes have a connection for each digit, ten separate digit controls must be generated from the four BCD lines. This will be done by a CD4028. The IC CD4028 is a “BCD to Decimal Decoder”. To switch the relatively high voltages of the Nixies, the BCD decimal decoder will drive a suitable transistor. This is where the MPSA42 will do its job. This is an NPN bipolar transistor with a collector-emitter dielectric strength of 300VDC at a maximum collector current of 500mA. In order to be able to use the tubes as flexibly as possible, I have come up with the idea of designing a separate circuit board for each tube. These individual display boards should then be plugged into a main patine. So if a digit is defective, you can simply pull out the board in question and repair it. Then you don’t have to solder around the motherboard.

The microcontroller should find space on the motherboard. The low- and high-voltage supply and the shift registers are also to be accommodated on the mainboard. The display boards only carry the Nixie tube and its driver transistors and the BCD decimal decoder. By means of post connectors, they should be easy to plug into the motherboard. To make these formulations a little easier, I have made this sketch:

Based on this idea, I now began to draw the circuit diagrams. So it started with the display board on which the tube is located. The circuit design is very simple. Two opposite post connectors should give the board a stable hold on the motherboard. One of the connectors supplies the BCD decimal decoder (CD4028N) with the four data inputs and the 5V supply voltage for the logic. On the other side of the board, the “high voltage” is provided for the tube.

From this I could then simply create a layout and then produce it as a prototype as a board.

Nach dem Ätzen und Bestücken der ersten Platine und fünf Weiteren war der erste Schritt der Nixieuhr getan:

In order to test the first part of the work, I had a DEB100 digital experiment board available at my workplace. The following short video shows the test result:

After all six boards were equipped and tested, I had dealt with the planning of the motherboard. At the beginning, of course, there was again the creation of a circuit diagram. From an external 12VDC source, which should ideally be a simple plug-in power supply, the supply voltages had to be generated. On the one hand I needed a 5VDC supply for the microcontroller, the shift registers and the BCD decoders and on the other hand a “high voltage” of 140VDC for the Nixie tubes. The 5V supply was done quickly – here a 7805 linear controller should do its job. Since the power consumption of the digital components is relatively low, no complex measures were required here. The 7V difference on the 7805 at the few milliamperes he packed without great power dissipation heat dissipation. For the generation of the 140V I made a step-up converter with an MC34062 (Inverting Regulator – Buck, Boost, Switching) controller, which switches a 220uH inductor via a FET. Via a voltage divider with trimming potentiometer at the output, a voltage feedback can be sent to the comparator output of the controller and thus the output voltage can be adjusted. As a microcontroller, I always use Atmega328 and the like for most of my projects (due to the stock level :)). This is also the case here. The result is the following circuit diagram:

From this I made a layout again and etched and equipped a board again. However, this prototype test board was only a version with four digits. The reason was also that I did not have a larger raw board available 🙂

From this I made a layout again and etched and equipped a board again. However, this prototype test board was only a version with four digits. The reason was also that I did not have a larger raw board available 🙂

After various successful tests with the prototype board, I ordered professionally manufactured boards from the board manufacturer I trust. After assembling them, I then created a test program that could control all digits. A short test video is linked below:

The following photos show how the clock looks with the “beautifully” manufactured boards. To make the whole work even more nostalgic, I had the idea to mount the boards on a milled wooden panel. (Thanks to Gebhard for the woodwork). In order to keep the watch electronics permanently dust-free, I had a transparent Plexiglas hood made.

Sketch for the arcyl glass hood

As so often, I made the software with the Arduino IDE. To flash the microcontroller I use the AVRISP mkII Programmer. If somebody is interested in the code, I can also post it here on the blog.

 

I’m looking for ONE button from the Commodore Plus4

The title says it all. I am looking for the RUN/STOP button for a Commodore Plus 4 computer. The model that I prepare is already finished except for this missing button. I’ve looked on the bay and at flea markets, but nobody can help me there, or you can get whole keyboards, but unfortunately at an unfair price. So if someone has a Plus4 standing around to slaughter and can help me with the key at a fair price – I would be very happy.

Speech output in the 80s – Speak and Spell

Many of the readers of this post may be familiar with the Hollywood movie E.T. (The Extra-Terrestrial), in our regions in the translated version: “E.T. – Der Außerirdische”.

At least the older readers will know him. The film was shown in our cinemas in 1982 and I had the opportunity to see it at the time. As a child, you (at least I) always immersed yourself in the stories and lived in them. Briefly told, the story follows a small alien who was accidentally left behind on Earth while his fellow aliens flew away in their spaceship, fleeing from government agents. So little E.T. in a shed where he was found by local children. They befriended him and helped him contact the spaceship. To do this, he constructed a kind of radio system from everyday objects. For example, the antenna consisted of an umbrella, a record player with a circular saw blade, a clothes hanger with a dinner fork, and a child’s toy that could produce synthetic voices. This toy is called “Speak & Spell” and was developed by the Texas Instruments company.

The Speak & Spell is a handheld children’s computer from TI (Texas Instruments) that consists of a keyboard, a display and a small speaker. The heart of the device is a speech synthesizer IC, which makes it possible to generate an artificial voice. An audio output similar to the human speaking voice is achieved via LPC (linear predictive coding). With an internal ROM and optionally also external ROM modules, various tasks (spelling, word guessing games, etc.) can be realized. Selection and entry are made via a keyboard.

The Speak & Spell children’s computer originally came from a three-part toy series with “talking” computers. There was also a Speak & Math and a Speak & Read. You can occasionally find collectors presenting their devices on online video platforms. The devices were initially sold in the USA, Great Britain and Japan. Depending on the country of delivery, there were also different ROM modules with mini-games such as Mystery Word, Letter or Secret Code. These computers were intended for children from the age of 7. Later, more language libraries were released in seven language variations. Among other things, there is said to have been a module for the German language.

The first Speak & Spell was introduced at the 1978 Consumer Electronics Show as one of the first portable devices with a visual display and pluggable ROM game cartridges. This model was also used in the film E.T. known. It differs from later generations of devices only in terms of the keyboard, which in the original version still consisted of “real” keys. The TMC0280 synthesizer chip works inside. This was developed by a small team of engineers under Paul Breedlove † (1941-2021), engineer at Texas Instruments in the late 1970’s. This development began in 1976 as a result of TI research on speech synthesis.

At the beginning of the 1980s, a revised version of the device came onto the market. Here the keys have been replaced by a membrane keyboard. A Speak & Spell Compact version has also been released. In this case, the optical VFD display has been dispensed with and the size has been halved. There was another edition in the late 1980s. This time the VFD was replaced by an LC display and the keyboard got a QWERTY layout. As part of the retro wave (my guess) the company “Basic Fun” brought the classic Speak&Spell back onto the market in 2019. It looks similar to the 80s version, but is technically up to date (everything is generated in a small chip that was bonded directly to the “mini board”). The version also no longer has connections to the outside world.

The following chips are installed on the mainboard of the version sold before 1980:

  • TMC0271 (microcontroller and VF display controller for 9 digits with 14 segments each)
  • TMC0530 (or TMC0351, TMC0352) 128kBit ROM
  • TMC0281 (TMC0280 series speech synthesizer IC)

 

The model that is in my collection is one of the versions sold after 1980. The following ICs are installed here:

  • TMC0271 (microcontroller and VF display controller for 9 digits with 14 segments each)
  • TMC0281 (TMC0280 Series Speech Synthesizer IC)
  • CD2304 and CD2303 (ROM)

 

The VF-display has eight digits with 14 segments each. The supply voltage of 6V is obtained from four C-cells connected in series. The 9V and 21V for the supply of the VFD and microcontroller is provided by a discretely constructed DC/DC converter, which is located on its own circuit board. The membrane keyboard is plugged into a 13-pin Flexiprint socket. There is a small speaker for playing the sound, or you can connect headphones via a 3.5mm jack. The sound is obtained directly from the synthesizer chip. In order to adjust the output impedance to the speaker, a small audio transformer has been installed right next to the jack socket. Another socket serves as an external power supply. A trimming potentiometer changes the playback speed/pitch of the audio output.

The TMC0280, later called the TMS5100, is the single chip speech synthesizer that used a 10th order LPC model using pipelined electronic DSP logic. The phoneme data for the spoken words are stored in PMOS ROMs. The enormous capacity of 128 Kbit was the largest ROM that was still affordable at the time. Additional memory module cassettes can be inserted via a recess in the battery compartment. The contents of the memory modules can be selected using a key on the keyboard. The data rate of the audio output is slightly less than 1kbit per second.

DC/DC Converter PCB

 

 

The weather globe – or the Goethe glass

Again and again I look for simple, interesting things. This time I was fascinated by a measuring device or rather “display device”, whose operating principle is extremely simple and yet very effective. In addition, from my point of view, it is also an eye-catcher – it is the so-called Goethe Barometer. The best-known form is probably the bulbous glass hanging on the wall with a beak, similar to a watering can, in which the water level indicates the air pressure. I found a slightly differently constructed version of this glass on the net…

A little about the history of this structure:

To a gentleman named Evangelista Toricelli (1608-1647), an Italian physicist and mathematician, we owe the knowledge and proof that the air pressure is subject to fluctuations. He built the first barometer named after him in 1643. In 1644 he developed the mercury thermometer.

A small compensation area in the indicator tube protects against overflow

Der deutsche Dichter Johann Wolfgang Göthe, beschäftigte sich auch mit den Naturwissenschaften. Er machte selbst viele naturwissenschaftliche Experimente und entwickelte später ein einfaches, aber wirkungsvolles Barometer auf den Grundlagen des Toricelli.

Die Funktionsweise:

The barometer shows air changes quickly and precisely. When the air pressure rises, the water column in the indicator pipe falls and when the air pressure falls, it rises. This is made possible by the air trapped in the glass. The volume of the air always remains the same at a constant temperature. If the external air pressure rises or falls, the trapped air is compressed or expanded via the water column. Since the water cannot be compressed, it is the ideal medium to make the pressure differences visible. The height of the water column thus indicates the air pressure. If the air pressure is high in good weather, the external pressure is higher than the pressure of the trapped air and the water column decreases as the trapped air is compressed. At low air pressure, it can expand and the level of the water column increases.

the height of the water level in the pipe indicates the air pressure

This short time-lapse video shows the change in the water level when the air pressure changes:

Neumann KH-120 mystery noise fix

This time, a defective pair of active speakers found me, which comes from the professional corner of sound generating devices. These devices also occasionally have problems or fail. If you do a little research in the forums on the Internet, the KH-120 boxes are very robust and durable. The only issues I’ve read about are power supply failures. Occasionally there are also reports of a clear noise or whistling even if no signal is applied.

Exactly this problem was shown by these devices. After switching on, there was a hissing noise up to slight whistling tones. These could be influenced with the filter and gain switches, but not remedied. If the loudspeakers were in use for a long time – after about half an hour, then the noise decreased.
Unfortunately I didn’t manage to find useful information about these errors on the net, let alone a circuit diagram of the board. So there is nothing left but to search for it yourself, analyze the board and search systematically for the error.
Starting with the removal of the four long Allen screws, the two halves of the housing can be carefully pulled apart. This then reveals two white blocks of insulation. These can easily be removed. The wire connection to the loudspeakers can be detached from the circuit board using a four-pole plug. Likewise the connection to the small LED logo board.

KH-120 is open and the insulation material removed
The picture shows the connector with the wires to the speakers

Next, the circuit board can be unscrewed from the housing. (a Torx bit is to be used here) All screws except for the two black cross-head screws must be loosened. Then carefully remove the board from the housing.

Circuit board of th Neumann KH-120

The board looks very good. All components that can be set into mechanical vibrations and possibly resonance by the sound are secured with elastic adhesive. The board layout is nice and clear. You can see the mains input and the mains filter at the bottom left of the picture. Above it is the large electrolytic capacitor for smoothing the direct voltage generated from the mains voltage.

The power supply is a switching power supply. The Mosfet controlled by a controller chip clocks the transformer. On the secondary side it is rectified again and the symmetrical voltages +Ub and -Ub for the power section of the output stages, as well as +15V and -15V for the supply of the pre-amplification and signal processing are generated. Ub is at -42 or + 42V. The power output stages are two TDA7293 ICs. One controls the tweeter and the other controls the woofer.

backside of the circuit board

In order to look for the cause of the problem, one proceeds systematically. I first checked the supply voltages with a multimeter. Of course they are there. But you only see the truth when you look at it a little more closely. The multimeter is no longer sufficient here. An oscilloscope also reveals the AC component or residual ripple.

The picture shows the AC part of the -15V power supply. At around 800mV, however, it is suspiciously high. The period duration of these peaks with 30µs indicates that the transformer is regulated when the power supply unit hardly has to deliver any power. The switching frequency of the transformer can be seen within the pulses. But what could still be seen and cannot be seen in the still image are lower-frequency, asymmetrical components with an equally high amplitude. Accordingly, there appears to be a problem with smoothing the stress. So I examined the structure of the -15V supply. And look, the +/- 15V are implemented with a series regulator. A 7815 controller is used for the + 15V and a 7915 controller in the TO220 housing for the -15V. In the Note application, capacitors to ground are specified for the IC at the input and output. And that’s exactly what I took a closer look at first. An electrolytic capacitor with 100µF / 35V and 105 ° is used at the input of the 7915. This capacitor had to go out to measure. Immediately after the removal, it seemed to me that the weight of the component was too light – it didn’t feel like anything. So get to the LCR bridge and lo and behold, the capacity was somewhere around 1.4µF.

the polluter

A new electrolytic capacitor was installed quickly and the renewed measurement of the voltages revealed a nice signal again. The AC share was now much lower and the irregular disturbances had disappeared. Only the switching of the transformer could still be seen. What was still noticeable, or no longer noticeable, were the noises from the loudspeakers – the noise was gone.

the cause was built in here

 

 

Video streaming in the car – Android Auto – the cheap solution

Since my leisure activities are increasingly taking place outdoors in the currently somewhat warmer season, writing the weblogs suffers a little. But I’m still working on some projects, repairs and restorations. In this way, a lot of material comes together again in order to write articles from it – in the colder season of the year. This time I was just annoyed about the rip-offs and pricing in the automotive sector and looked for an alternative solution.

It’s about my five-year-old car, which is equipped with an on-board navigation system. The navigation data is saved on an SD card inserted in the vehicle. So far so good. However, the map data of the vehicle are now getting on in years and much is no longer up-to-date. Something like that is particularly annoying if you are on a vacation trip and the GPS does not know the destination or has not mapped the way there. No problem, I thought to myself, map data is on the SD card – there are sure to be updates. And yes there is – but the map updates cost upwards of 200 euros and more. In return, I get a complete navigation device including the latest maps with free online updates.

So I tried to make myself smart and find a current map on the network and save it on the SD card. But of course that doesn’t work. Some security mechanisms are used here. For example, the hardware ID of the memory card is stored (coded) in the navigation system. So my first attempt to copy the original navigation map as an image on a new SD card failed. It is recognized as an invalid card. And tinkering around with the VCP and VCDS diagnostic device in the navigation computer without instructions is too much effort for me. So another option had to be found. An online navigation system is installed on every smartphone – it’s called Google Maps. And there are also some offline navigation systems that can be downloaded free of charge from the web stores. So my idea was to add a phone mirror function to the car. (These things are called Android Car Play in the fruit department, etc.) Since my old box does not provide any of it in the entertainment system, there were the following alternatives for me:

Either I buy a China Navi to retrofit – and by that I mean the screens that are based on the original on-board monitors of the car, in which an Android computer is then installed. The corresponding apps for navigation and other gadgets can then be installed there. The data of the original image of the car infotainment system are of course still displayed. Such systems are available in the order of 400-600 euros. Then there are a few hours of installation (handicraft) work.

Another option is a retro fit conversion. This means that I install the higher-quality infotainment system with the corresponding range of functions in the vehicle. That in turn means: expanding the old system, buying a new system from the vehicle manufacturer including all necessary control units, cable harnesses, cover panels, etc., then installing it and then coding everything with a lot of effort, importing parameters, etc. The costs are immense and add up no case (> 2500, – if that’s enough) and then the work for the removal and installation. -> everything can be forgotten.

MiraScreen receiver

And here is the last option for all together just 50 euros and with an effort of 30 minutes installation consisting of the following points:

 

 

  • Activate the Video In Motion (VIM) function of the display or the radio unit
  • purchase an AMI cable with composite video in and audio in
  • purchase a MiraScreen WLAN receiver for just 40 euros, which is able to output the video signal via CVBS
  • install the entire part (in this case) in the center console shelf
  • Lay the cable for the power supply of the Mirabox through the shelf to the 12V socket and connect it.

This work is done quickly and the smartphone can be connected via “Stream” (in the Android smartphone under “Wireless transmission in Bluetooth & device connection”). Now the screen and the sound of the smartphone are also reproduced via the infotainment system of the vehicle.

AMI videocable

The AMI video cable is plugged into the AMI socket of the vehicle and the analog video and audio lines are connected to the chinch plugs of the MiraScreen connection cable.

Connector for supply, video and audio to the MiraScreen

I took the power supply for the Mira Screen directly from the 12V socket behind the center armrest. To do this, I pinned the plug of the 12V socket, soldered a wire to 12V and GND and pinned it back in. At the other end of the two wires I crimped a 13.5mm Tamiya coupling. In addition, the 12V line has also received air traffic control. The Mira Screen connection cable, which is threaded through the shelf, is now threaded onto this Tamiya coupling and the corresponding Tamiya plug is crimped on. To get the cable through the shelf, I simply drilled a 7mm hole and put a rubber edge protector into the hole.

Cable entry

Once the cable is connected, the box can be plugged in and stowed in the shelf.

In the picture above, the box is fully connected and can be seen in the center armrest shelf.

If the backrest is folded down, nothing can be seen of the box. They can also be removed quickly and easily after unplugging the connector.

Now that the ignition is switched on, you can select “Media” in the multimedia system and then click on CVBS video input. The start screen of the Mira Screen Box should now be visible. The Mira Screen Box can also be configured by connecting the mobile phone via WLAN with the SSID “MIRAxxxx” and entering the IP address that is specified on the start screen in the smartphone’s browser. The SSID password is also on the start screen.

The photos above show the inside of the box. With this device, the pin header of the stack board had partially loosened from the socket strip and this had led to contact problems between the two boards. The brass spacer (can be seen in the last picture at the bottom left) is 2mm too long, so that the two boards do not stick together properly. As a remedy, I shortened the two spacers by these 2mm and screwed them back on. So I can use the Google Maps in the car without any problems.

 

 

 

Sony Walkman WM-DD11

The portable cassette player from the manufacturer SONY with the type designation WM-DD11 is the content of this article. Colloquially known as “Walkman”, I received this part for my collection. Of course with the comment “defective” – ​​so again a little challenge and at the same time the hope that no mechanical, no longer available parts are affected. My request before the purchase whether there was any damage to the circuit board was also answered in the negative. The device is so far in order, the tape of an inserted cassette is moving – there is just no sound from the headphones. So ideal conditions for a restoration.

But unfortunately you cannot trust every statement and you cannot look “under the hood” beforehand and convince yourself whether the actual condition of a device corresponds to the description. When I held the part in my hands, the first impression was also very convincing. There were no noticeable scratches and dents. The area of ​​the battery compartment that was visible from the outside was also clean. So batteries inserted, also an audio cassette and then pressed on play. Lo and behold, the tape transport runs as described. Even as described, the part does not make any sound. So perfect starting conditions for my mini repair / restoration project.

But before I start dismantling, I did a little research on the history of SONY’s DD Walkman series. The first model in the DD series was sold in 1982. The designation “DD” stands for “Disc Drive”, which means that the “Disk”, i.e. the flywheel disk, is also part of the capstan drive system (motor). The belt for the other drives (tape reels) is placed directly around the disk. There are / were two price brackets of the DD models – the DD series with one-digit numbering (DD-1, DD-2, etc.) and those with two-digit numbering (DD-11, …). The devices with the single-digit number belong to the “high-end rail”. The device restored here comes from the “cheap line”. The DD-11 is not so high-quality and is also more simply constructed, but defective devices are available for very little money and are also fairly easy to repair. (The DD-11, for example, does not have a center wheel, an often defective part of the high-end series that is broken due to weak material. What then usually remains are defects in the electronics or on the mechanical side – an aged belt The belt is the same as that already installed in the legendary TPS-L2 Walkman and has the component serial number: SN 3-499-042-99 (this source or number has not been verified) You can also find the belt if you go to “TPS -L2 belt “searches on various online portals.But now enough information on the general part. I experienced a sobering and grounding of my restoration euphoria immediately after unscrewing and opening the case. Unfortunately, the circuit board is not at all undamaged. Once again someone did not remove the 1.5Volt cells and left them in the device for a very, very long time.

The batteries that leaked, as it is, have left clear marks on the circuit board. This means that extensive cleaning of the circuit board is necessary before the search for corroded conductor tracks can begin.

After cleaning and removing the battery electrolyte residues, I was able to make out a few defective conductor tracks. Fortunately, these are pretty easy to fix. In most cases it is sufficient to remove the solder resist in the defective area and to tin the exposed copper tracks. Depending on the width of the track, the defective part of the track is then reconnected with individual strands or wires.

Now the time has come to carry out a first functional test after a provisional assembly. And as described, the capstan drive works, the tape is transported – but there is no noise whatsoever from the connected speakers. Now is the time to look at the number one source of failure – the old electrolytic capacitors. Eleven of these are installed on the board.

When I removed the first electrolytic capacitor for a capacity test, the well-known fishy smell rose again. As expected, the capacitance of the capacitor was also well below the nominal value. So I made a spontaneous decision to remove all eleven electrolytic capacitors in order to swap space. (In modern language it is called “recap”: D)

The following values ​​must be renewed:
– 5 Stück 220 µF / 4V
– 1 Stück 100µF / 4V
– 3 Stück  47µF / 4V
– 1 Stück 10µF / 16V
– 1 Stück 4.7µF / 25V

 

I like to replace the SMD electrolytic capacitors with SMD multilayer capacitors, as these are now also available in very small designs in high capacities with suitable dielectric strength.

After the renewal, the board looks nice again. A repeated provisional commissioning shows that the effort was worth it. The music on the inserted tape sounds in the expected quality. The next step is to calibrate or adjust the belt speed. A reference tape is required for this. Years ago I recorded one with a very good tape recorder. The recording consists of a 1kHz and a 5kHz sine tone. This band is now used as a reference in the DD11. To do this, the output of the DD11 is connected to a frequency counter or oscilloscope and adjusted with the trimmer potentiometer during playback until the 1000 Hz or 5000 Hz can be seen exactly on the oscilloscope.

The Walkman can now be reassembled. All screws are properly tightened again and finally the function tested again and the beautiful piece can be put in the showcase …

HomeMatic smoke detector HM-SEC-SD quick repair

This time again a quick article on the subject of “Aging and Homematic Smart Home”. It’s about the following device: The Homematic smoke detector HM-SEC-SD, i.e. the older version of the smoke detector from eq3.

First of all: This article only shows how I put this device back into operation. Since it is a safety-relevant device, an acceptance test by a certified testing company would have to take place after the repair in order to be allowed to continue using it. So the contribution only provides what has become broken in the device.

So what is it about? The radio smoke detector HM-SEC-SD showed the following symptom during the monthly test (yes, you should press the test button once a month):

A short press on the button and there was no acoustic signal – instead the red signal LED flashes several times at approx. 0.5s intervals. Replacing the batteries does not change anything, the behavior remains the same. The radio module of the detector behaves normally. It can be reset and taught again. In this case, a look at the operating instructions (under point 9.2 on page 24)

– If only the LED starts to flash after pressing the button, the smoke detector is defective and must be replaced
So time to open the detector and take a look. My first suspicion fell on the detector chamber and that there is contamination here or that an animal has settled in the chamber …
Smoke detector opened

But after removing the lid of the detector chamber, no animal intruders were to be found. However, a strange pattern could be seen on the inside of the lid:

Streaks on the inside of the detector cover

These streaks, I thought at first, were created during the injection molding of the plastic component and must be like that. But on closer inspection and a “wipe” with your finger, they could be removed. In short, these streaks are dust particles. And when they are on the lid, then also in the entire measuring chamber. So blow it out with compressed air, put the cover back on and test it. -> same mistake as before. So again, put the lid down and take a closer look with a magnifying glass. The coarser dust, if you can speak of “rough”, was gone, but the surface of the photodiodes still had very fine and difficult to see streaks. So I cleaned the chamber and the diodes with a little alcohol on a cotton swab.

thorough cleaning required

Another function test showed success – better partial success. After pressing the test button, the piezo squeaked – but only very, very quietly – and by that I mean barely audible and the LED flashed nine times at an interval of one second. So actually the way it should be. Just way too quiet. So something had to be broken. So I examined the circuit starting with the piezo and quickly found what I was looking for. The piezo is controlled by a 40106, a 6-fold Schmitt trigger. In order to get enough electricity, three “Schmitts” are connected in parallel. The output was low-resistance, which is actually not allowed to be. So unsoldered the 40106 and measured it again. Between pin 1, 2 and 7 (input and output of the first Schmitt trigger and the VSS pin) there was a full short circuit. That means the IC is defective.

6times Schmitt trigger IC 40106

After the IC was exchanged, the smoke detector could finally “scream” again as usual.