Multimeter analog

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Unigor 6e (ca. 1970)

A good friend of the older generation of technicians is certainly the analog multimeter of the manufacturer Unigor. In this case, it is the model Unigor_6e from the 70s.

An excerpt from the preface of the operating manual:

The electronic instrument Unigor 6e combines the advantages of classical measuring technology with those of modern electronics.

It was specially developed for measurements in the field of electronics and for all those applications where practically no power is required. The high sensitivity is achieved by means of a battery-powered transistor amplifier.

The field effect transistor chopper for DC measurements and the multiple negative feedback guarantee high stability and negligible drift. The large measuring range and the high accuracy of 1% at AC and DC, allows universal use in the radio and television service in test field and laboratories.

The „6e“ offers a total

  • 54 DC and AC / voltage ranges
  • 13 dB ranges
  • 12 resistance and capacity ranges
  • 2 temperature ranges
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measuring ranges

The electronic components of the meter are powered by four 1.5V batteries and take a current of about 2.5mA. The working range of the electronics is between 4V and 7V. The battery is switched on with the rotary switch (which also represents the R, C adjustment knob at the same time). To check the battery voltage, a check position is provided on the measuring range shutter.

The Unigor 6e also offers a variety of protective devices and is therefore protected against damage caused by incorrect handling and overload. (I can remember quite well from my school time that this is not always the case: D)

The Unigor 6e has an electromechanical circuit breaker function. Its relay responds to overloads with DC and AC and requires no auxiliary power. The protection therefore remains fully effective even when the battery switch or battery is switched off. The restarting in case of permanent overload is prevented by a special switching mechanism.

Furthermore, fuses provide protection at the higher current ranges to respond in the event of a short circuit or tripping of the circuit breaker.

Against overvoltages at the inputs are voltage arresters at the input terminals whose breakdown voltage is lower than that of the internal circuit.

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Scale sheet of the Unigor 6e

 

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The flame licker

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A small mechanics project occupied me this time. It is again about a hot air engine. This time not about the Stirling engine, but the so-called „flame eater“.

During the search in the World Wide Web, I found, among other things, the website of Mr. James Maiwald. Mr. Maiwald is an ambitious modeler and specialist in the field of Stirling and vacuum engines. He develops and manufactures his own models in all variants and also offers them as a kit.

More precisely, it is a vacuum motor, which is popularly also called a flame eater. He is one of the hot air engines, but unlike the Stirling engine is an open system.

Technically speaking, it is an atmospheric engine, since here the external air pressure does the work (comparable to the first gasoline engine). As a result, the maximum piston force is limited to the product of piston area and air pressure. (Wikipedia)

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Detail view slide valve

And exactly one such model (lying the flame eater) is here. As I assemble the engine and the first time commissioning is seen in the following short video …

More information and interesting models and kits can be found on the website of Mr. Maiwald: www.kellergeist71.de

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Radioreceiver in retro look – The finishing

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The wooden case is painted

Now that the front panel is milled, it can be cleaned and the engravings are provided with black paint. After the varnish has dried in the indentations of the engraving, the supernatant paint is removed with solvent. Now the entire panel could be painted with clear lacquer.

While the paintwork on the front panel is drying, it’s time again for the wooden cabinet. The mounting holes for the boards, speakers, etc. were drilled and then the wood was embedded with a slightly darker wood stain. After drying, the wooden case also gets a clear coat.

In the next step, the operating elements (switches and rotary encoders) and the LC display are attached to the front panel. The milled webs for the speaker panel are covered with black fabric. (For the fabric had to serve a T-shirt).

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The painting of the housing dried about a day. Now you can start mounting the speakers and the board.

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Installation of the speakers

 

Die Platine wird mit Abstandhaltern am Gehäuseboden verschraubt.

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Assembly of the board

 

Now a suitable power supply is missing. For this purpose, a small power supply was built, which consists only of an iron core transformer with subsequent rectification, smoothing and voltage stabilization with a LM7809, ie 9V DC. For this, a small board was made (about 5x8cm) and also built into the housing with spacers.

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Power supply 240V AC to 9V DC at max. 350mA

 

Now that everything is assembled, the amplifier metrics and levels are again set and optimized with signal generator and oscilloscope.

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Adjustments

 

The finished radio receiver now looks like this from the front …

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Radio from the front

 

und die Geräterückseite ist im nächsten Bild dargestellt:

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back

In the short video, the radio can be seen in operation:

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TEDDY automatic

IMAG1321From the years 1970-1972 the radio receiver TEDDY AUTOMATIC 100 comes from the German manufacturer ITT – Schaub Lorenz. It is a multi-band receiver that covers the wave ranges of long wave, short wave, medium wave and ultrashortwave.

It is designed for mains and battery voltage (110-127V / 220-240V and for battery operation for 4×1.5 volt size AA cells).

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The output power is 0.8 watts and is transmitted with a dynamic oval speaker.

The technical structure according to the manufacturer consists of 6AM circles and 9FM circles. The receiver principle is a SUPERHET with ZF 460kHz and 10.7MHz. The housing is made of plastic (thermoplastic) and has the dimensions of 215x127x70 mm with a weight of 1.2kg.

 

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Connection for external sources
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Switch for receiving frequency

 

 

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torsion pendulum clock

A patience-related work is the restoration or repair of a rotary pendulum clock.

A rotary pendulum clock is, as the name implies, a mechanical clock that generates the clock from a pendulum rotating around its own axis. The vibration energy is transmitted here with a torsion spring (Horolovar spring), ie a very fine steel wire special alloy. IMAG1268_1 The rotary pendulum clock is also called annual clock, as due to the very slow oscillation and corresponding mechanical implementation of the escapement, a lift of the spring accumulator only once in 300-400 days is necessary.

Of course, this also requires a certain precision of the mechanical components. If something is not set correctly here, the clock will switch off after a few minutes. Even the fine adjustment of the accuracy requires some patience. And just like a clock has done to me. In an online auction house, I have a cheap ‚defective‘ but purchased from the components ago complete rotary pendulum clock and immediately started to disassemble and clean the parts.

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Knurled screw for the pendulum diameter

 

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suspension spring

After this work we went back to the assembly. The Horolovar feather was replaced by a new one. Now we went to the adjustments. First, I had to find out how many pendulum oscillations, more precisely half vibrations, should make the clock in one minute. At my watch (a Kundo) these are eight beats. The easiest way is to use a stopwatch to measure the time it takes to reach the 8th half-cycle. For example, if the measured time is over one minute, the watch will run too slowly and must be adjusted with the thumbscrew (the one that changes the position of the pendulum weights in diameter). Turning the thumbscrew clockwise will make the clock slower and counterclockwise faster, of course.

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Escapement with anchor plate

It should be a precision of +/- 1 minute per month possible. So a deviation of 12 minutes a year. Of course this requires optimal environmental conditions. (constant temperature and humidity, as well as a firm, vibration-free state)

 

 

 

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Surrounded by radioactivity?

After the self-made Geiger Müller counter and the associated experiments, I noticed that there is one or the other radioactive element in our environment.

With the SOEKS 01M Geiger counter, an industrially manufactured device, I have now again „scanned“ objects in the area.

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SOEKS 01M

Again, I realized that some of the old clocks in my collection are equipped with radium-painted dials. The SOEKS shows here a radiation exposure of about 1.11 microSievert per hour. The environmental load is displayed at approx. 0.14 uSv / h.IMAG1290

But in my mother’s kitchen, I found a beautiful, colorful old vase that displayed about 10uSv / h. (The thing is now in the far corner of the cellar).

It should be uranium paint. (To see orange / red painting in the video below)

 

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Taster day in technology

In the last two days we received a visit from two young gentlemen from the fourth year of the Villach High School Sankt Martin. Mr. Martin Ungermanns and Mr. Fabian Treu came to us as part of a „taster program“ of the middle schools. The two students can participate in the „world of work“ and get some insights into the technology.

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deepened in the soldering work

The program included work such as assembling and soldering of electronic kits (the well-known shaker cube), a small series work (flashing of PIC microcontrollers), exposure and etching of circuit boards, milling of aluminum plates.

As conclusion of the two taster days both high school students were allowed to build up a complete „device“.

 

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Martin Ungermanns and Fabian Treu

It was a „clap switch kit“ that detects a loud sound event via an acoustic sensor and then turns on a relay contact. So that this circuit can also be used meaningfully, the circuit has been extended by a self-made power supply, all installed in a plastic housing and equipped with power cable and Schuko coupling. So any consumer (eg a floor lamp, TV) can be switched on and off with this switchgear by simply „clapping“ …

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Radioreceiver in a retro look – Update: The case

IMG-20150130-WA0000-2 It’s time! The first picture of the absolutely real wooden housing for radio electronics is here. A beautifully crafted housing made of glued elements. This work comes from Gebhard’s hands, a master carpenter from the Upper Carinthian region;)

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Housing with holes for the speakers

Jetzt kann das Nostalgie-Radioprojekt wieder einen Riesenschritt nach vorne machen.

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This will be the aluminum front panel

The case is on our table. First, the holes for the speakers were drilled. Later these should be covered by a milled aluminum panel. So the next step is to construct the milling data for the front panel. Here again the layout tool „Eagle“ is used. The data can simply be exported as a „.dxf“ file and imported into the circuit board plotter software.

 

UPDATE:

Barely a few minutes, I went to the circuit board plotter, imported the production data, clamped the „two-cutter cutter“, of course, the aluminum blank and off we went.

The speed for the 1mm cutter I have chosen with 60000 rpm and set the feed rate to 1.5mm / s in both axes. Cooled and lubricated was the way with alcohol.

A not negligible amount of work is, by the way, the cleaning of the plant after the work done … 🙂

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Radio in retro-look – KnowHow for the apprentice – Part 2

… to realize the volume control via the microcontroller, a „digital potentiometer“ X9C102 was simply used. It is controlled directly by the controller with a „direction input Up / Down“ and a „count input“. Internally, this IC consists of 100 resistors connected in series whose „tap“ is determined by counting input. So a simple matter to control the signal level of the preamplifier in 100 steps ….

 

Continued from Radio Part 1
The controller should now be operated via a push / turn wheel (rotary encoder with push button). In order to be able to evaluate the direction of rotation of rotary encoders, a second pulse output is required. The two pulse outputs must be shifted in their sequence depending on the direction of rotation (phase shift). In order to convert the pulse sequence into a direction signal and a clock signal, we have set up a small decoder logic using a JK flip-flop and a Schmitt trigger / inverter …

Turnwheeldecoder

The outputs of the decoder logic are now passed directly to three microcontroller inputs. Thus, now a suitable program can be created, which provides a simple menu-driven user interface. The parameters are displayed on a two-line LC display. The outputs of the controller, in turn, control the „digital potentiometers“ for the volume setting and, of course, the I²C bus, which sends the commands to the FM module. An additional output allows the switching of a relay, with which, for example, the audio input from the amplifier can be switched between the FM module and an external signal source. The LC display is connected to the controller in 4-bit mode and the backlight of the display is also switched by the controller.

 
PCB fresh from production

After all these functionalities had been defined, we were going to transfer this information to the Layout Tool or the schematic.
Finally, a layout was drawn and made. Subsequently, we could start with the assembly of the board and then carry out the first commissioning. After the adjustment of the amplifier quiescent currents, the development of the Arduino code began. Here, the work is extremely facilitated, since there are many finished libraries here, which can be used directly for its purposes. For example, the only challenge with getting an LC display up and running is to connect the few wires to the uC (microcontroller) and pinpoint the pins in the code. Everything else is done by the library. With this simplification, the functions are then implemented quickly and the first test run can begin.

ready assembled PCB

As a result, the software will be even better – perhaps saving multiple stations, and so on. But the next step will be to build the board into an enclosure modeled on the old radio tube radio receivers. It should be made of solid wood. The operating and display elements are to be installed in an aluminum plate placed on the front of the housing … (Another post on this blog will follow.)

The first functional test can be seen in the video below …


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Radio in retro-look – KnowHow for the apprentice – Part 1

THE IDEA FOR THE PROJECT
A project idea that came to my mind as an ideal apprentice project is to plan and build a radio receiver. With this project, our apprentice should apply the acquired skills in a practical way and set up an FM radio receiver according to the components to be used.
This was done gradually. I came up with the concept in the following parts:

THE AMPLIFIER
First, a simple class A audio amplifier should be built. The apprentice should build the amplifier according to the circuit on the breadboard, metrologically examine and understand above all. In the next step, the Class A amplifier became a Class-AB amplifier. Again, the task of the apprentice was to understand the operation and optimize the breadboard function pattern so that a (not metrologically) at least reasonably „good“ acoustic result was achieved.

First functional pattern of the „power output stage“

When this succeeded after some time, he got the task to transfer the determined circuit into a layout tool and expand it to a second channel, while also creating a power supply concept. The power supply should not only supply the amplifier output stage, but also for other components (such as microcontrollers, USB interfaces and what ever came to mind) a + 5V and + 3.3V DC supply available.
After many layout designs, he then presented me with a layout in which the components were symmetrical and technically reasonable (Trimmpotis should be accessible …) were arranged. So he was allowed to make the layout as a functional sample. (etch the board, populate it and try to get it all working).

The learning effect was gigantic: D, because in the implementation of theoretical circuits to a simple breadboard construction and then to the „printed“ circuit on the print, there is a lot of sources of error. And they also want to be found and corrected. Our trainee was able to practice patience and precise work.
But in the end, the 440Hz sinewave of the frequency synthesizer sounded from both connected speakers …

Now it was time to think about the signal source, the actual receiver.

THE FM RECEIVER

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In a Chinese online shipping I discovered an FM receiver module with a very compact design (a print with about 12x12mm) on which a complete receiver is integrated. The module is called TEA5767 and uses the eponymous Philips FM receiver chip.
The connections to the module consist of power supply, audio L and R outputs, as well as an I²C bus to control or set the reception frequencies and an antenna and Muteeingang. So ideal to realize a signal source for our amplifier. But that raised further questions.
How should one generate the control signals for the I²C bus, how should the tuning of the transmitters be done, how should the device be operated by the user at all? For all these questions, there is a simple answer: Take a microcontroller. And as the apprentice likes experimenting with the Arduino UNO board, I decided to use an Atmega328, the Arduino UNO controller.

THE HEART OF THE RADIO – THE CONTROLLER

The microcontroller should therefore take over the complete management of the radio, thus fulfilling the following functions:

  • set the stations (generate I²C commands and send them to the radio module)
  • save the tuned stations (in the internal EEPROM of the controller)
  • show all information on a LC display
    take over the volume control
  • generate operation by means of a push / turn wheel (incremental encoder with touch function should take over the entire operation of the radio)
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blockschematic

So we had to extend the circuit by a few components. The audio output of the FM module had to be pre-amplified. This was done by a small AudioOPAmp. To realize the volume control via the microcontroller, simply a „digital potentiometer“ X9C102 was used. It is controlled directly by the controller with a „direction input Up / Down“ and a „count input“. Internally, this IC consists of 100 resistors connected in series, whose „tap“ is determined by counting input. So a simple matter to control the signal level of the preamplifier in 100 steps.

continue in the next part

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