How can i used a RF reciever to control a relay which would control an AC lighting unit?
I am trying to design an RF transmitter of very low frequency to make contact with a RF reciever, so when the frequency is obtained by the reciever, it would then turn on the relay which would power on the lights in a certain room of the house. Any help is appreciated. Thanks, this is for my Electronics Senior Project undergraduate level
- billrussell42Lv 710 years agoBest Answer
Just tune the receiver to the proper frequency and amplify it via RF amp, or IF amps. Then detect with a RF diode, and use the DC voltage to drive a transistor that activates the relay.
But only certain frequencies are allowed to be used for this purpose, so check with the various government regulations. I don't know of any that are "very low frequency", which by definition is 3 kHz to 30 kHz. This is a very difficult range to work with as the antenna has to be many miles long.
To avoid false triggering, you may want to modulate the RF with a specific audio frequency and detect that frequency in the receiver. Or a specific pulse sequence for a more elaborate setup. But 30 kHz is so low that it is difficult to modulate.
PS, you can buy these units, fairly cheaply.
- 秦君子Lv 710 years ago
In the receiver RF detector circuit (after the last IF stage where has a signal diode). Taking out the DC part and amplify it until its voltage is high enough to drive a small relay like 6 volts or 12 volts. Using one more emitter follower to enlarge the current to drive the relay. Parallel one set of normal open "NO" contact to the emitter follower between collector and emitter. Other sets of contact to control the lamps. That shall make the relay always ON as RF is detected.
- roserLv 43 years ago
you prefer neither a latching relay or contactor, in case you desire to pass away the relay energized interior the "ON" place. in basic terms use a single pole relay with a usually open (interior the energized place) touch,or the usually open terminal of a double pole relay. maximum relays are rated at for a minimum of five amperes, except you employ an digital accountability relay, and your mild attracts below 2 amps. Relays are available in with 12 VDC coils. attempt Radio Shack.