Measuring PWM in lights

A new tool in the lab

Image - An upcoming review scope capture with the light at half brightness. Duty cycle is 41%.

Thanks to BudgetLightForum user Terry Oregon, I am now able to measure the PWM of lights even when I can’t get my oscilloscope probes directly on the emitter wiring. In 2018 he wrote a long article about his testing of 13 light sensors to determine which ones could work to show the PWM of a flashlight. One of the best performers was a PIN photodiode, part number BPW34. I recreated his example circuit and it worked as expected. Total cost was about $6 for 5 sensors from Amazon, some junkbox parts, and a little time. Thanks Terry!