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guidance needed for radio control

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Newbie level 3
Feb 4, 2007
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I plan to make a radio control for my toy plane. I m planning to use a pic microcontroller but the radio part is a bit dodgy. the off the shelf radio transceiver cost alot, considering addition of video transmission in future

can any one guide me to build a diy digital rf circuit that can be linked to a microncontroller ?

The circuitry for that would be complex even using subsystem ic's, what sort of range do you need?
I think it'd be more cost effective to use radio transceiver modules, you'd then be able to look at video talkback, allthough a radio device that has a wide enough band for video is going to cost more.

approximately 1km range

I actually wanted to build myself wud b fun experimenting with

Fun, yes.

However be aware there's a federal communications bureau whose purpose is to regulate people sending radio signals out into the airwaves with homemade radio transmitters.

If you're not careful you might interfere with public service and air traffic communications. And if the authorities use their directional location instruments to zero in on you then you're in for a hefty fine.

That said...

Find out which band is best for your purposes. Certain frequency bands are reserved for certain purposes. There are bands for radio control devices. Example, 72 mhz for model airplanes. There was a previous band (now obsolete) for which you may find cheap equipment at flea markets.

In your own home you can experiment with weak transmitters over short distances. Avoid transmitting on a frequency which is already carrying broadcasts.

It's up to you to ensure your transmitter is not generating rogue radio harmonics which can disrupt your neighbors tv reception, cordless phone, etc.

The simplest r/c is to make a sinewave oscillator that will transmit a short burst when you press a button. Identical to a morse code transmitter. Do not make your transmission begin and end too suddenly -- it generates bothersome harmonics.

Your receiver is a simple detection circuit tuned for that frequency. The output will go high for as long as you hold the button down.

You may want to start out with a commercially manufactured radio control unit. As long as it's working. Then fabricate your own receiver. Get it to respond to frequency bursts from the commercial transmitter.

The title really grabbed me. I started my first RC airplane in 1952 (age 9, a Berkeley J-3 cub), finished it in 1953, and crashed it on its third flight -- radio range problem. It was great -- most fun I ever had destroying something that took a year to build. I have been hooked since. We built our own transmitters then.

My advice is to buy a cheap RC radio and receiver and/or join a club. How much do you have to spend? You will probably spend more in just parts for something that won't work nearly as well. If you were in the US and near me, I would give you a Tx and RX. Try finding a club in your area. Used equipment is pretty much a give-away to people starting in the hobby, particularly from older folks who want to pass it on.


RFpics a long cry from tuned reeds and triode heptodes from the 50's.
Building your own isnt necessary these days, presumeably the op wants the experinence rather then save money, it'd probably cost more to make than to buy a new system.
RFpics are good and very simple, you wont get a km though, a hundred meters or so, unless you had an exotic aerial like a co-linear stack, but that would be tricky fitting to the plane if you want video talkback, and then the pic wont be briliant at the sort of speed it can handle.

dr pepper said:
RFpics a long cry from tuned reeds and triode heptodes from the 50's.

We were not even that "advanced." Super regen, thyratron to drive a relay, retuned every third flight or so. One pulse = right; 2=left; 3=up, 4= down, blip was throttle by exhaust restriction.

The OP mentioned the high cost of an off-the-shelf receiver (transceiver?). That's why I suggested he consider used/free Tx/RX. He could then use the microcontroller to modify the basic functions, without having to worry about the control link.

At least in the US, people and our government are getting very sensitive over the prospect of using models for terrorism. The safer we make it (i.e., commercial Rx and Tx), the more support we (modelers) will have in our Congress. It is a fantastic hobby, and I encourage the OP to continue. Just be aware that it is no longer a couple of guys in a farm field that couldn't fly far enough to hit a barn. FPV (first-person view = video down link) is an extremely hot topic, as one might imagine. We are doing it in our local club, and it is best to be involved with a credible club when flying that way. No Lone Rangers.


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