I am trying to reverse engineer this RF remote. I'd like to integrate it's components on a different board.
IC is a VD5012 Encoder
Transistor is KSP 10-D2Z UHF/VHF
Some questions:
I don't recognize the blue component to the left. It seems to have a phillips adjuster screw down the middle. What is this?
This board was designed to run on a 12v battery. It seems to work on my breadboard at 9V, but would I expect less of an RF signal power? That is, would I get a better/more reliable connection to the receiver at 12v?
The blue component might be a variable (tuning) capacitor, judging from its location over what appears to be a PCB antenna. What radio frequency is used by the remote?
While the encoder will work at 2V, is the signal strength reduced as function of voltage?
What is the best way to determine the RF frequency? Device purchase or an easier way?
To improve the RF transmission quality/reliability could I replace the PCB based antenna with something external?
I guess I need to be pointed down a path (so I can research further) for RF remote design. I'd like to be able to understand the frequency, signal strength, encode/decode process, and signal analysis / measurement techniques.
What is the best way to determine the RF frequency?
If the frequency isn't listed on the device packaging, there should be an FCC ID code. Search that to determine the frequency band.
The transmitted RF signal strength depends strongly on the supply voltage.
You can add a 1/4 wavelength straight wire antenna to the transmitter to increase the range, however you must know the transmitting frequency. In your case, adding the antenna will probably detune the transmitter.
OK, so if I added the antenna I would need to adjust the tuning capacitor to properly match the original signal? Seems I need a logic analyzer to pull this off...
How do I measure the signal strength of the RF transmission?
It seems to be a remote control with a free-running oscillator, judging by the hair-pin coil and the blue trimmer.
Educated guess, around 1Ghz.
Bad idea to connect an aerial to this low-tech device.
Leo..
That's a free running oscillator with a loop antenna which is part of the tuning circuit. Frequency ? I'd guess 400MHz ish, but it won't be accurate, and will drift terribly with temperature, battery voltage, environment
( how near your hand is) and general component ageing.
If you tried to couple an external antenna to it it would detune enormously and may not work at all.
Frequency ? - find a spectrum analyser and have a look - you'll be horrified.
Please don't use this as a basis of a new design - they're awful.. Find a modern OOK chip using a SAW or crystal as it's frequency reference..........from any of several manufacturers.
Or, better still , buy a premade approved module from again, many suppliers.
If you're going to make lots of these, you should get your local approvals agency to check it for conformancce to the specifications appropriate in your country - here in the UK the RA govern conformance to MPT standards, now absorbed into european ETSI specs - ENxxxxx. In the states the FCA do this. You use accredited test houses to run the tests and confirm conformance.
The process isn't cheap. I've done it quite a few times with various products.
If you get it wrong and sell lots of these, and they interfere with other devices, you're in for a big fine, confiscation etc etc.
I agree with a possible lower frequency. Hard to judge size from a picture.
Could be 433.92Mhz.
That VD5012 chip only generates a digital signal for the transmitter.
Chip looks like a Holtec HT12E.
Any SAW-filter based transmitter can be used to transmit the data.
Leo..
