I'm having a strange problem that I can't track down. I'm using an Arduino to control LED light arrays. Each array is connected through a TIP29C transistor to my Arduino PWM outputs (base resistor: 10k?) and to ground - Vcc for the light arrays is 12 V and is connected to ground through the transistors.
I'm using one transistor for each light array to control the lights. Basically, the problem is that when the ground of the light array is connected straight to the ground (NOT through the transistor), they are very bright - when connected through the transistor (to ground - no extra resistor or anything) the arrays are about 30-40% dimmer.
Any ideas on this? Really hoping to track these down - the lights aren't nearly as cool dim as they are bright.