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Welcome to the CyBENCH Project Pages - 4bit RF remote

Part 3 - Adding power leads and Test leds

The alarm used to have an internal voltage regulator circuit - until we ripped it out.
This used to generate an interal power supply rail of about 10V.

We will directly provide a 9v supply from a PP3 battery.

To do this:

1. Connect Pin 8 of IC4 to +9v of the battery, red wire on a PP3 battery snap.

2. Connect Pin 4 of IC4 to 0v of the battery, black wire on a PP3 battery snap.

Power wires

Test leds

If you wish, you can build a simple tester using four 1k resistors and 4 led's

I needed to do this to prove the system as I hacked it together.

An alternative solution would by to use the 5mm red led that is provided on the flying lead.
Simply connect the black wire to a suitable 0v connection (picture below)
Then use the striped wire to probe the data output pins of the decoder.

NOTE: This is a flashing led with an internal resistor in the cable assembly

0v connection for the test led (black wire)

Test Led in use


When you first power the alarm unit up, no leds should illuminate.

When you press the Disarm button on a keyfob, two leds should light:

br>When you press the Arm button, three leds should light:

When you press both buttons together, all leds should light:

At this stage, there is no way to control the two leds connected to pins 12 and 13 of the decoder.