Tower bell - David Bagley optical sensor design for Multi Bell Interface
This section describes a tower bell sensor design that uses infrared photocells to detect when the bell would normally ring.
There are two components in the optical sensor: the sensor head itself, which is mounted on the bell frame next to the wheel and contains the electronics; and a single reflector mounted on the wheel itself. The sensor head and the reflectors should be positioned so that they are opposite each other when the bell is down and at rest.
Tower bell sensor circuit for Multi Bell Interface
The circuit diagram for the sensor head is shown above. The output of this circuit is "low" when the reflective tape is opposite the sensor, and should be fed into the appropriate input on the Multi Bell Interface. The sensitivity can be adjusted by changing the value of R4 - increase its value for longer ranges but at the expense of sensitivity in high ambient light conditions.
Once installed, you must then configure Abel as described in Configuring External Bells and check that the program can detect the signals from the MBI.