SpudFiles

Hello everyone its been a long time since I posted here, been 2 year member . Anyways me and another user on here won a spot to present at a Youth Entrepreneurship challenge and we need to make a demonstration of our product. Basically it needs to be radio controlled device that can control a camera flash circuit and detect signal strength and beep when the strength gets to below a certain point.

We are thinking of the pager circuit for our radio controller since phones work off of FM signals and a homemade field meter for signal detector. As for the beep were using a simple piezo buzzer. The question is will the field meter pick up a phone frequency? And if so how could we make it activate a switch on the buzzer circuit?

The challenge here is that modern cordless phones work in the microwave band. Therefore you'll have to deal with all the extra issues that come up with using high frequencies.

You could also just build an FM transmitter yourself pretty easily. I've seen alot of schematics around on Google, and they don't look too hard. That being said, I've never tried it myself.

Yeah I have never made a FM transmitter, although I built an amplifier for one which works great. As for the reciever do you think a simple $1 radio from like a dollar store would suffice on triggering the relay?

Well, directly, probably not..but it can be modified quite easily.

Here is my one somewhat useful contribution to this site, it will let you use the speaker output from any device (provided the output is>0.7V) to trigger a relay: http://www.spudfiles.com/forums/the-pho ... 12578.html

Yeah I was going to wire up something similar to that, but the signal strength thing is whats got me stumped.

This guy on instructables made a device that sounded an alarm when a light source was interrupted, you could do something similar. Here's the link.

Unfortunately, I can't really think of a way to measure signal strength without making it a duplex system of one sort or another. You'd probably need another transmitter on the receiver.

Well im open to ideas turbo, I have an entire schools microelectronics class supply to use lol, our high school teacher as agreed to let me use his supplies. So making several circuits isnt a problem.

Alrighty then, make a transmitter on your "receiver", and just keep it constantly transmitting something or another.

Now, on your "transmitter" side, you'll want to add a chip that detects RF signal strength. I know they exist because my buddy built one, but I don't know exactly what chip it is.

Should be pretty simple from there.