Post by thread:PIC16C54-RC/P in remote controller

I was in a car repair workshop yesterday & I saw a poster advertising cloning of your remote control for your car door opener & car burgler alarm. The poster had a photo of their clone & it had a PIC 1654 in it. There didn't appear to be much more to it at all - one transistor, 1 capacitor, an LED & maybe a coil. It had 4 buttons & apparently each button is dual purpose (whatever that means). Anyway, this has me really interested - I would love to be able to get hold of something like this - the units are being sold for US$35 each, but the main problem is that they do not sell any type of receiver - they only clone existing transmitters. Does anyone know of a circuit diagram for the transmitter & receiver for this toy? I actually want to transmit data back from a robot to my PC, so this small multi-channel transmitter would be perfect as these remote controllers normally have a good range & don't need line-of-sight. Failing that, are they available commercially - tx & rx at a reasonable price? I definitely prefer PIC based units, as I already have the development software & hardware & a little bit of experience with them. Dave -- ------------------------------------------------------------------------- | David Baker | Internet ID (home) - spam_OUTdavidTakeThisOuTbaker.pc.my | | Electronics Engineer | Internet ID (work) - .....davidKILLspam@spam@gmetra.po.my | | | Fax - 60-3-2612870 | | Kuala Lumpur, Malaysia | Compuserve ID - 70461,2360 | -------------------------------------------------------------------------

{Quote hidden}>I was in a car repair workshop yesterday & I saw a poster advertising >cloning of your remote control for your car door opener & car burgler >alarm. The poster had a photo of their clone & it had a PIC 1654 in it. >There didn't appear to be much more to it at all - one transistor, 1 >capacitor, an LED & maybe a coil. It had 4 buttons & apparently each button >is dual purpose (whatever that means). > >Anyway, this has me really interested - I would love to be able to get hold >of something like this - the units are being sold for US$35 each, but the >main problem is that they do not sell any type of receiver - they only >clone existing transmitters. > >Does anyone know of a circuit diagram for the transmitter & receiver for >this toy? I actually want to transmit data back from a robot to my PC, so >this small multi-channel transmitter would be perfect as these remote >controllers normally have a good range & don't need line-of-sight. Failing >that, are they available commercially - tx & rx at a reasonable price? I >definitely prefer PIC based units, as I already have the development >software & hardware & a little bit of experience with them. > The canned modules available from Digi-Key are probably a good way to get familiar with the technology and do the robot project. For someone more interested in how the transmitters and receivers work, and eventually hoping to spend less than $11.00 each for them, here is what I know about them: The frequency in the US is usually 310-315 MHz. On/off keying is used with digital modulation of about 1 Kbaud. Usually pulse-duration, pulse-position, etc. coding is applied. The transmitter RF hardware is thus a simple L-C oscillator with provision for switching it on and off by digital control. The receiver is almost always a super-regenerative type. Overall, it's an RF amplifer with intentional feedback so it wants to oscillate. The signal from the antenna is coupled into it. While a signal is present, this will cause the oscillation to become stronger. Using positive feedback theoretically increases the gain of a single amplifier stage to infinity, though at the price of stability. Sometimes, though not usually, a conventional RF amplifier stage is added before the regenerative one. This helps keep the oscillations from back-coupling out on the antenna as well as improves sensitivity. In order to keep the receiver from simply locking in an unstable mode (i.e. becoming a transmitter, one reason the regenerative is not used for general radio devices any more), a second R-C feedback path is present that makes the overall bias oscillate between the unstable and stable regions at about 500 KHz. The average time spent in the stable region is longer if no signal is received at the antenna. The operating voltage or current changes depending on whether it is oscillating or not. This voltage or current, filtered of the 500 KHz self-oscillation but still containg the 1 Kbaud modulation, is then amplified with an op-amp or similar device up to digital levels and then decoded. This kind of receiver doesn't work particularly well, but for short range and low selectivity that is required of alarm remotes and garage door openers, it does fine. For a 'cloning' device, assuming the transmitter can be held very close during the copying process, a simple diode-detector receiver would probably work. This function could probably be shared with the transmitter by using the transmitter at low or no bias and rectifying the signal picked up by the antenna. -Mike

David Baker writes: PI>Does anyone know of a circuit diagram for the transmitter & receiver for PI>this toy? I actually want to transmit data back from a robot to my PC, so PI>this small multi-channel transmitter would be perfect as these remote PI>controllers normally have a good range & don't need line-of-sight. Failing PI>that, are they available commercially - tx & rx at a reasonable price? I PI>definitely prefer PIC based units, as I already have the development PI>software & hardware & a little bit of experience with them. Here are sources I know of for radio remote control stuff: Electronics 123 (Ming) 800-669-4406 (see ad in Circuit Cellar) Visitect 510-651-1425 (they sell kits too) Buy and tear apart an X-10 radio xmitter-recv'r unit Micrilor radio modems ($$) 617-246-0130 Linear Corp (I don't know their phone #) Infrared is an entirely different topic, drop me a line if you want to talk about that. Hope this helps, Gary Skinner