Short range radio pulse transmitter design?

I need something simple to transmit pulses 2-3 meters to a receiver
The transmitter will output a pulse every few seconds, transmit a small burst at X frequency. The receiver then outputs a short high pulse/outputs high for the duration of the received pulse.

I want this to be as simple as it can possibly be, cost being the primary restriction and power usage being also of fairly high importance, so please no suggestions of Bluetooth or xbee type systems.

It does not have to be a radio based system, however it needs to work without line of sight and of course without connecting wires.

If it helps the overall aim is a 'safety signal' that will set of an alarm at the receiving end if several pulses are missed


EDIT: To clarify I am looking for simple, like really simple. So the transmitter is just a resonator and antenna. What I need is a simple receiver that will respond to a specific frequency, on or off. Does such a thing exist? 

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rickcr6 months ago

I am looking for someone to design and develop a PRF device. If you would be interested in discussing further please contact me.

rickcr6 months ago
denny2452 years ago

http://www.redcircuits.com/Page55.htm This website will give you some information on how to build a near field magnetic pulse transmitter/reciever remote control. Magnetic field penetrates walls and a distance of about 15 feet if tuned correctly. The transmitter is a heavy current user, but it is used intermittently, so a 9 volt battery should last a while. The receiver draws only 150 micro amps in standby, and runs on 3 volts. Very cheap to build. I have played around with these for a while, and the only interference I have seen so far is intermittent pulses from close proximity lightning discharges. There is a company out there working on using near field as a replacement for Bluetooth.

rickharris4 years ago
Your in the Uk so you can easily and fairly cheaply do this with a microprocessor to monitor the pulses and a simple RF transmitter - As always the advice from those who know is buy a system if you a) waht it to work and b) want it to be reliable.


£9 sounds reasonable if what your protecting is worth anything.

same site for the rest of what you need + instructions on how to do it.
Damp Cuttlefish (author)  rickharris4 years ago
Thanks for the suggestion, although its not really what I'm looking for. (Forgot to mention in the question, sorry). I have a microcontroller based system as it is, I'm looking now to implement the same function in the cheapest simplest way possible. I mean cheap to the point of disposable, microcontrollers are just a little too fancy
Assembling the electronics to generate and detect the pulses will in the long run cost as much or more then a small Picaxe - £1.80 with VAT

The radio system you have to have anyway.

Getting RF systems to work is very difficult - trust me on that.

You really need a set of test equipment - Scope, frequency generator etc to get things going because there is so much to go wrong.
Looks like the same stuff that FEC sells !
Could be the radio set is a standard unit.
framistan4 years ago
Instead of using radio frequencies... which are prone to have interference from other sources of radio signals such as fluorescent lights generating pulses etc... you might consider using just an infrared LED to generate pulses and a small glass lens to concentrate the beam. You are only going a few feet (or meters) so the LED would certainly work across that distance. Now it is just a matter of receiving the LED lightbeam... amplify it and use an "AND" gate to see if any pulses are missing. It all depends on what your application is... you might even want to use a visable light LED because the beam is visable and easier to focus and align with the lens.
He says it's not line of sight! so light isn't an option.
Mine and Rick's link (its the same kit) will do what you want, for a tenner.
Linx Technologies has a wide assortment of small short range RF transmitters and receivers. These are modules that contain all the RF circuitry, and you need to only supply power and an an antenna. They are intended to transmitt low speed data (usually no more than 10kbps) and use OOK modulation. I think they would satisfy the technical needs of your project.

DigiKey has a large assortment of these. Transmitters are available in the ~$10 range and receivers in the $15 to $20 range. I don't know if that is outside of your butget.

Otherwise I would suggest infrared, but you said that it can't be restricted to line of sight.
Damp Cuttlefish (author)  LargeMouthBass4 years ago
Is quite a way out of the budget for this, again a little too complex. I don't need any modulation atall really, just a straight on/off receiever
You can buy tiny RF modules which can be driven just as you need for a few quid from the likes of Farnell

And a receiver


I sincerely hope this isn't for a real safety system, there are complex laws and design rules for such things for good reasons.
Damp Cuttlefish (author)  steveastrouk4 years ago
Oh no no no no, its more of a gimmicky proof of concept than anything else. Thanks for the suggestion, looks like the best one so far