DDL or test load not working properly

[Camin]

I am building a DDL driver and when I went to test the voltage over the 1ohm resistor, I only got 11.7mV and if I changed the pot, nothing would happen. At first it I though it was the pot's fault, so I de-soldered it and flipped it around, then I tried a new one, but still have the same problem. Can anyone help me? I have included some pics.

The power supply is two 18650's I just realized they were only at 4V instead of 4.2, So I am going to charged them the rest of the way and try again. Any advice in the mean time?

 

[Cyparagon]

It looks to me like you forgot to connect the pot's wiper to anything. Tie it to one of the other legs.

 

[foulmist]

It looks to me like you forgot to connect the pot's wiper to anything. Tie it to one of the other legs.

Yep tie it to the highest resistance leg.

That way if your pot burns out or the wiper is disconnected from the rest of the pot you will have maximum resistance instead of zero (which will pass max current and kill the diode if it's over it's rating) :beer:

 

[Cyparagon]

It doesn't matter which leg. In either case, wiper failure leads to max resistance. The leg you chose will only effect which way you turn the pot to increase current. Tying it to one leg will mean you turn the pot clockwise, and tying it to the other leg will mean you turn the pot counter-clockwise.

 

[foulmist]

It doesn't matter which leg. In either case, wiper failure leads to max resistance. The leg you chose will only effect which way you turn the pot to increase current. Tying it to one leg will mean you turn the pot clockwise, and tying it to the other leg will mean you turn the pot counter-clockwise.

oh yeah... I thought he was using the wiper instead of the leg as connection >.<

 

[Camin]

Ah thanks you this worked