The Doorbell project came about through the annoyance of having to constantly replace batteries in our old wireless unit.
The design here is straightforward and is really a door buzzer – but the title got your attention which is the main thing! It’s relatively easy to build and the battery current in standby is only a few uA’s so the batteries should last a long time. The duration the doorbell is active is controlled by trimmer resistor RV1, which can be set between approximately 1 to 5 seconds. By adjustment of the trimmer resistor RV2 the tone can be set from approximately 100Hz to 1KHz.
Fixed value resistors could have been used here, however making these settings adjustable caters for personal preference and could be quite distinctive.
Parts list
Over the next few weeks we hope to be able to show some of the construction pictures.