Hello,

I'm here to want help for my project. So I want to make a transmitter to switch on one of seven LED. Here is my idea: I will use a normal FM transmitter and receiver. Instead of audio jack of microphone on the input of the transmitter I will put a 555 timer oscillator that will can generate 7 different frequencies (I choose the one). The idea is when the receiver unmodulate the signal the LED have to activate from the frequency. I want to ask you how to make a circuit that activate DC on the output when we have a specific frequency on the input. For an example - I choose 350 Hz but I put 300 Hz, 400 Hz or else on the input - the LED is off. I put 350 Hz on the input and the LED is on.

Thanks you!


P.S.: I know about the LC circuit but for me it is for high frequencies.

 

Sounds like a CTCSS d/encoder kit, ready made or you're going to have to use a microcontroller for the encoder and decoder.

https://cstech.co.uk/product/ctcss-decoder-kit/

 

Sounds like a CTCSS d/encoder kit, ready made or you're going to have to use a microcontroller for the encoder and decoder.

https://cstech.co.uk/product/ctcss-decoder-kit/

I thought about something more simple. Like RC filter but the problem is to convert AC to DC. I'm not sure that four diodes bridge will work.

 

I would just run with a DTMF Encoder / Decoder. A Google of DTMF encoder decoder will give a few dozen hits. Most will give you 12 channels like a standard telephone keypad.

If you want to build your own decoder chips like the LM567, LM567C have been around for decades.

Ron

 

One approach, use FSK and a simple protocol -

http://www.cypress.com/documentatio...and-psoc-5lp-low-frequency-fsk-modulation-and

Regards, Dana.