Temperature sensor for IV-11 DCF melody

A functional update for the IV-11 DCF melody watch is available from gr-projects. It is a radio temperature transmitter. The special thing about it is, that the transmitter operating in the ISM band 433 MHz is equipped with a photovoltaic cell (solar cell). Depending on the version, a small rechargeable battery or a CR2032 button cell can be installed in the transmitter. The battery is thus supported by the solar cell in the sunlight or in the battery version it is charged during the day and then keeps the transmitter in operation over the dark time.

The assembly is easy. The kit consists of a transmitter and a receiver. The boards of transmitter and receiver are equipped with few components quickly. Here, however, some attention is required and you should read the documentation carefully, because due to the lower number of kits, the boards are manufactured without component imprint and solderstop.

transmitter module

The radio modules themselves are completely pre-assembled (SMD) and only need to be soldered into the corresponding circuit boards. Optionally, a trim potentiometer can be connected in parallel to the temperature sensor (NTC) for adjustment purposes. The transmitter, like the receiver, is installed in a small PVC housing. Here, except for a 3mm drill hole and possibly some silicone for the sealing of the solar cell (for operation outside the window sill) no further tools are needed.

transmitter complete with PV-cell

To connect the receiver to the clock, make a few minor changes to the clock’s mainboard. First, the microcontroller is replaced – logically – because there is indeed a new program that then displays the temperature in the date line. A resistor is removed, one is added and a jumper can be swapped. The connection between the clock’s motherboard and the radio receiver is made with a piece of cable. Three lines are required (GND, + 5V and the data signal from the receiver controller to the clock controller). That’s it then already. The clock can go into operation. After a few seconds, the received temperature is displayed in the tube.

receiver in it´s case


A video how to solder the circuit is available here:

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USB stick defective?


Again and again it happens to me that a USB memory stick loses its function and is suddenly no longer recognized. Often the stick is still registered as a drive in the system, but it lacks the disk, or even the system reports that the stick is not formatted. And even though he just recently, full of important data, has worked in another computer. 🙂 (Here would now be the story with the backups or backup copies …). All these problems are mostly due to operator errors or mechanical problems. For example, an operator error may be that the stick is being pulled while one more writing is in progress. The stick is then de-energized during a process. And depending on whether the controller or flash memory can handle it, the stick will survive or not. Often, mechanical defects are the cause of breakdowns. So it may be that the solder joints between the connector and the board break, or get the connecting pins of the quartz or oscillators contact problems.

In this case, I got a miniature stick from extrememory, which does not want to give away its stored data. It is displayed in the system administration, but if you want to access it, the message „no data carrier found“ comes. The attempt to format or partition over diskpart from the commandline did not work. Also various tools like „SDFormatter“ or „USBstick_Formattool“ failed. Even with Linux or on MAC systems, no success was achieved. So a stick for the barrel … But I thought, even if the stick in its small design rather not close to a mechanical defect – why not take a look anyway 🙂 And at 16GB I will not give up so fast.

So I tried to gently open the case by first removing the metal case of the USB connector.

That works quite well. After I wanted to take a closer look at the appearing small printed circuit board with its tracks, there suddenly appeared something familiar.

That looks like an SD card. More specifically, like a microSD card.

That’s the way it was. The USB stick is nothing more than a MicroSD card reader, in which such a card is installed. Using tweezers, the SD card could be levered out.

Apparently here again the problem is with the contacts, or contact springs between card and card reader. It is the cause of the problem, because the SD card worked fine in another card reader and all the data was available. It pays to invest in front of the garbage bin for a few minutes and to inspect the innards of the device.

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