FM Communication

Hi everyone,
I am a mechanical engineer by trade but I like to dabble in electronics. I am trying to design a circuit that will control a relay using FM transmitters/receivers. The way I plan to do this is to have the transmitter transmit 8 bits of data. The receiver side will have 8 dip switches that each connect to an XNOR gate and the second input of the XNOR gate will be the 8 bit signal after going through a SIPO register. Each output from the 8 XNOR gates will go into the input of and AND gate. With this setup it will allow me to compare the 8 bit signal transmitted via FM with a programmed key in each receiver circuit. So just to recap, I have an 8 bit signal coming in which gets compared to a key in the receiver circuit and if each bit agrees a logical 1 is passed through. Now I want to take this logical 1 and have it turn on and off a relay. If a 1 is detected the relay will turn on and if ANOTHER 1 is detected the relay will turn off. My problem is that I do not have a latching relay so I was thinking about using a T-Flip Flop. Since I won't have a clock pulse I was wondering if I could use the logical 1 coming from the AND gate as the clock pulse, essentially connecting the clock pulse pin of the T-Flip Flop to the T pin.

I want to avoid using a microcontrller to process the 8 bit signal so this is why I am using all the gates. As I stated I'm not very familiar with all the IC's out there so this is just me trying to make the described circuit with what I know.

Please let me know if there is a better way to do this and if I can have the CP pin connected to the T pin and have the flip flop still work. I want to have about 10-20 different receivers so there has to be some way of comparing the transmitted signal to a preset key for each receiver circuit.

The obvious solution would be to use a microcontroller, and it would be folly to do a 1970's version with loads of IC's.

However, if you don't have the facilities or skill to program microconrollers?, then check out the Holtek range of encoder/decoder chips - they make some to do just what you're after.

I was going to use a microcontroller for the transmitter portion, but I want to keep the receivers relatively inexpensive. Do you know of any cheap microcontrollers that are easy to program? I am very familiar with the arduino but I feel like $9 for the ATMega is rather expensive plus I want to keep the power consumption as small as possible.
Do you have any specific Encoder/decoder chip recommendations? I guess something like a garage door opener circuit is what I'm after. Also how would I control the toggle function of the relay?

dirtbiker1824 said:

I was going to use a microcontroller for the transmitter portion, but I want to keep the receivers relatively inexpensive. Do you know of any cheap microcontrollers that are easy to program? I am very familiar with the arduino but I feel like $9 for the ATMega is rather expensive plus I want to keep the power consumption as small as possible.
Do you have any specific Encoder/decoder chip recommendations? I guess something like a garage door opener circuit is what I'm after. Also how would I control the toggle function of the relay?

Click to expand...

You can get PIC's far cheaper than that, for that matter you can get AVR's far cheaper as well.

Like I said, check the Holtek range - they probably do what you want - check here for some examples.

**broken link removed**