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3-Channel UHF Rolling-Code Remote Control, Pt.2

Last month we introduced our new high security remote control and got as far as completing both the receiver/relay driver and transmitter. This month we'll put it all together and get the two parts talking to each other - securely!

by John Clarke

We’re assuming that you’ve completed construction, including setting the transmitter and receiver identities, as detailed last month. You will also have given both PC boards a visual check and made sure that there are no solder bridges (except the deliberate ones in the transmitter identity!) or breaks, bad joins or errors.

Click for larger image
We presented construction details for the two PC boards last month. Here's what our completed project looks like. The panel on the receiver is actually an overhead projector transparency glued to the inside of the lid, so you can see the LEDs inside the case.


With IC1 out of its socket, connect a 12V plugpack or other 12V supply via the power socket. Check that LED5 lights and that there is about 5V between pins 5 and 14 of the IC1 socket. The voltage could range from 4.85 to 5.15V.

If this is correct, switch off power and plug in IC1. Place the LK1 jumper in the “out” position and rotate VR1, VR2 and VR3 fully anticlockwise to set the momentary period at minimum.

Apply power and press S1, S2 and S3. This should activate RELAY1, RELAY2 and RELAY3 for about a quarter of a second each with LED1, LED2 and LED3 lighting up during this period. If this test is OK, you can assume the circuit is working correctly. Now it’s time to set the operation of the relays.

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