ZiPZap Car to 1 of 8 Remote Control

KMoffett

Senior Member
Though not a Picaxe project directly, I thought this could easily be used with them for a short range RF remote control. I've been playing around with cheap, tiny ZipZap R/C cars, and wondered if I could expand their control possibilities. These are the low end, 47MHz ZipZaps, not the SE's. The transmitter was easily modified with four resistors and NPN transistors to allow logic-level input control. With the correct binary inputs from a Picaxe this can send 1-of-8 commands. It could also be controlled with 8 individual switches and some diode AND'ing logic.

On the receiver end, the Left and Right outputs are open collector NPN's, so PNP drive transistors gave me positive logic level shifting to 5 volts. The Forward and Backward outputs were a little trickier. They form some sort of an H-bridge. The voltages, with respect the battery common, are:

.....Fwd...Neu...Bak
F...1.5v...0.8v...0.0v
B...0.0v...0.8v...1.5v

It turned out to be easier to drive these outputs as 0.0v being the TRUE output, and using NPN transistors for the level shifting. F-out then becomes Backward and B-out becomes Forward. Adding the quad AND gates gave the eight decoded 5V logic outputs.

Ken
 

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KMoffett

Senior Member
OOPS!

Obviously, my decoding on the output section was not bench tested. :(
There are 8 outputs...but not mutually exclusive. This is the kind of thing that usually wakes me up at 3AM with..."what the heck was I thinking!". ;)

Though it gets more complicated, this will do 1-of-8. Ok, it's not bench-tested either, but I think the logic is correct. :)

Ken

I have had a chance to test the 1-of-8 converter section on a simulator and discovered some unwanted output states. The new schematic works.
 

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KMoffett

Senior Member
Since I've been playing around with the circuit I thought I might as well throw a PICAXE into the equation.

Ken

Comment: Note that there is about a 0.1 second delay between the transmit button/logic sent and the outputs of the receiver.
 

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