Hey All,
I was wondering if someone could explain to me why this is happening?
Please see drawing for full details.
I have a standard PWM module I got from ebay. It works from 3v to 30v I believe.
I have it running on a single 18650, atm it is at 3.9V and runs the PWM fine.
The problem is that when I setup the scenario you see in the picture. The LED is lit and a meter reading across it shows 2.4v. Even though the cap and PSU feeding it show 2V. I verified this via multiple Meters, even disconnecting the PSU drains the cap and the LED goes out. Putting the LED across the Cap or PSU does not light it. It's absolute minimum to conduct is about 2.33V
I figure the PWM is somehow causing the problem. But how?
One odd thing to note about the PWM module is it requires its power source in this case the 3.8V 18650 to have a common ground with the transistor.
Turing off the PWM stops everything. I have tried multiple different types of LEDs. They all seem to light even though they are only connected to a 2V Cap/PSU
I cannot for the life of me understand how the 18650 is feeding the LED.
Happy to post any photos/videos etc to help if required.
I hope I am just doing something very silly here and just don't understand enough about electronics. Cos I am confused AF.
Edit:
I have a DSO and it shows the PWM running fine with the correct square wave. I measured from the ground directly on the PWM out.
Measuring across the led shows a square signal too. I am running at 10% duty.