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Topic: How to NOT use an Arduino for simple wireless (Read 728 times) previous topic - next topic

rwiens

I have a really basic 433 MHz tx/rx pair that I bought and have not played with yet, but understand from reading that it is pretty simple to use the VirtualWire library for communication.  I am thinking of an application where I only need to send three states (fwd/stop/reverse) to a motor, would like to do it wirelessly and think that involving even a basic MCU is overkill (having said that, I haven't done any work with MCUs other than Arduino...perhaps a PICAXE or something like that would be simple enough to be appropriate).

I though about just using two pairs (one for fwd, one for reverse and if neither had a signal then stop), but don't know about the possibility of interference.

I don't mind throwing some other electronics in there but don't have enough background to know what a good approach is.  I know a little bit about 555 timers and thought you could send some different signals (e.g. different pulse width for fwd and reverse) on the tx side but don't know how you would decipher those on the rx side.

Any suggestions or a point in the right direction would be much appreciated.

PaulS

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would like to do it wirelessly

What range? What volume of data? Line of site, or are there obstructions? What is controlling the motor now? What is deciding that it is doing the wrong thing?

The radio alone is not going to be sufficient. You need something with some smarts. An XBee would be perfect, if a little pricy.

AWOL

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I am thinking of an application where I only need to send three states (fwd/stop/reverse)

How about a 1ms pulse every 20ms (fwd), no pulse (stop) or a 2ms pulse every 20ms?
Of course, the doorbell at number 63 may cause you some difficulties, but that's the joy of licenced-free RF.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

billroy

Maybe a Tiny-85 / Tiny Core using VirtualWire?

-br

Tmp2k

I've just done this exact thing, although I dont know if there's a better way or not.

I bought a 433mHz TX and RX for under £10.  Wired a 555 up to the Tx and used different capacitors connected in parallel via switches to alter the 555 freq.

Then I connected a pro mini up to the Rx and used a freq. counter lib that I found.  The received freq changed when different buttons were pressed on the Tx.

However because the Tx is constantly transmitting on/off, I found I'd inadvertently created an RF jammer, and with the Tx powered up I couldn't unlock any of the cars on my drive with the remote fobs!

I think something like this would of done the job a lot better, but it doesn't need to be as high powered...  http://proto-pic.co.uk/2km-long-range-rf-link-kits-w-encoder-and-decoder/

rwiens

Thanks for all the thoughts (and warning about the RF jammer!).  After some further consideration, I think I can get away with fwd/stop (the rev I can do 'manually' to start with), which I can do pretty much with the rx/tx and a simple transistor setup to drive the motor.

rwiens

I should say that I am still interested in how to build a simple frequency counter (like Tmp2k did, but even simpler than a Pro Mini)at the rx end to drive different outputs (again, driving a motor in two directions, probably through an H-bridge of some kind).

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