I want to send a high low signal over radio waves... Or I guess just a high. Whenever I ask about it I get referred to sparkfuns radio transmitter and receivers. The thing is I don't need to send any fancy info. Just a default to Low and send a High signal when needed. Can I do this more simply than with one of those sparkfun transmitters?
I'm thinking for example those remote outlet switchers that you plug a lamp into and they have a one button remote than simply toggles it on and off. That's how simple im looking for.
Can I do this more simply than with one of those sparkfun transmitters?
No. Is there some part of this you don't understand?
I'm thinking for example those remote outlet switchers that you plug a lamp into and they have a one button remote than simply toggles it on and off. That's how simple im looking for.
The transmitter is NOT sending HIGH or LOW. It is sending some encoded data that the receiver decodes to HIGH or LOW.
You need to do the same thing. The radio is simply a means to get the signal from one place to another. The formulation of the signal to send, and the conversion of that signal, on the receiving end, is where the art is.
If all you want to do is emulate one of those devices, get one and a servo. Make the servo push the button as required.
The point is that you can't send a DC signal over the radio. The best you can do is to transmit two tones one for high and one for low. Then use a tone detector chip on the receiver. You need to distinguish between high, low and the receiver is not getting anything.
Grumpy_Mike:
The point is that you can't send a DC signal over the radio. The best you can do is to transmit two tones one for high and one for low. Then use a tone detector chip on the receiver. You need to distinguish between high, low and the receiver is not getting anything.
Back in the day, one way this was popular to do was with a pair of 567 ICs, which could generate DTMF tones (touch-tone phone). You'd generate the tone with one, and decode with the other; then - just rig up a pair of cheap toy walkie-talkies for the radio link and you were good to go. Many homebrew robots used this kind of system for a cheap (compared to what could be bought at the time) and easy type of "modem" for telemetry.
Doing that nowadays would only be worth it if you had the parts lying around, along with a pair of radios (family radios could potentially be used - but it might not be legal - I'm not sure if you can transmit data over family radio or not; I know it wasn't legal over CB radio, here in the USA).
Ultimately, though - you'd probably spend more time and money going that route than using a pair of those cheap and legal transceivers from sparkfun or elsewhere.
So with those wireless light switches, or a wireless doorbell they have to be sending a tone for low all the time they aren't sending high? Or am I not understanding right. Forgive me, I'm just trying to understand.
oh it's sending a code of high and low... I get it. thanks.
And check the schematic on the last page of those pdfs. That circuit shows 4 pushbuttons on the transmitter side that will appear as logic levels on the receiver side automagically. In addition to those two items, a decoder and encoder chip are needed, HT-12D and HT-12E, available from futurelec: