Knocker Board – Usage

The knocker board has been designed to be flexible in the way it is used.

Power Supply

The knocker board runs from 6-24v using a single supply using the connector labelled 6-24v. If the unit is powered from a mains supply this will be fine.

Unfortunately the regulator on the board takes roughly 200uA even when the board is not knocking. For a battery driven application this means that the batteries will run down relatively quickly. The solution is to remove the regulator completely and use the 5-6V supply pins which supply the microprocessor as well as the 6-24v pins for the to supply the solenoid. In this configuration the standby current draw goes down to 4uA and is ideal for a battery supply.

Solenoid

The board supports solenoids from 6V to 24V at up to 2A. For the best knocking action a solenoid with a large heavy armature is best (or you can weight an existing armature) The armature must have a return spring. To get the loudest knock attach the solenoid solidly to a large piece of wood (or door).

Buttons

The board has two buttons Test and Prog

Test is connected across the BUTT header and is used to test the operation of the board.

Prog selects one of 15 different knock cadences. When selected the board will remember the last setting, even if the power is disconnected.

Extending the knock button

A long cable can be attached to the butt connector to a standard door bell push button. The push button must not have a bulb or LED across the contacts as found in some door bells.