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RC-Bell-Mod

Motivation

A friend of mine was looking for a cheap Remote for general purpose applications. So he went out and bought a Remote Controlled Door Bell. It's price is about 5Euros. It has an effective range of about 20m (through concrete walls) and works with a frequency of 455Mhz.

Schematics

The output of the decoder chip is only able to drive and sink less than 1mA. Also its output-level is only 0.3Volts (I still wonder why...). Therefore I did connect his output directly to the input of a comperator. The comperator switches a PNP transistor, which drives a relay. The original receiver worked with 2 AA batteries. Since i needed 5Volts (for the relay) I also reworked the power supply. +3V is now derived from the +5V supply with only 3 diodes and one cap. This is really simple and works fine since the receiver only drains a few mA when active.

Done!

The original case looked really ugly, so I mounted everything in a new plastics case. Everyhing is quick'n'dirty glued with some hotmelt.