28 April 2020

Longer delay modification for TDL-2023 PIR sensor

I have a TDL-2023 pass-through motion activated sensor that turns on a device. While I have already set the delay to the maximum value with the internal trimmer, the advertised 360 seconds were not enough.

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On the small board there is a BIS50001 IC, whose datasheet can be found online. The delay is set with an RC combination and can be seen on some schematic diagrams that use the same BIS50001 chip. Starting from the trimmer pins I poked around and found a series of 1 Mohm (trimmer) and 56 kohm (fixed resistor marked R0). Since I need a longer delay I decided to replace the fixed resistor with a larger value, 1 Mohm being probably enough.

Click to zoom.
The smallest resistor I could find is 1/4W but it fits into the case if installed as seen on my picture. The delay is now over 8 minutes. Since I have not been able to locate the capacitor of the delay circuit I cannot confirm the datasheet formula, but the ON time "feels" like twice as much as before.

1 comment:

Jeff in MN said...

Change C8 (next to the blue trimmer) to 0.1uF and you will get delays ut to ~35min