I need a simple circuit to drive a 12v DC (4amp) light. But, it needs to dim to 25% over a specified amount of time. Basically it needs to hold at 25% (4v) for a few seconds then fade and increase to 100%(12v) , hold for a second then fade back to 25%.
Here are the electrical specs: – Input 12vDC @ 5amps – Output from 4vDC to 12vDC (amp draw may be as little as 1 amp or as much as 4.5) – Only 1 potentiometer is used to vary the rate at which the voltage changes from 4-12 – It must increase and decrease voltage in a very smooth way, so that it fades the light to 100% and then back down to 25%
mail from JR
I have a circuit in my website that may serve your purpose, visit Power Supplies Section.
There may be some documentation errors in my circuits. If you are used to building and troubleshooting circuits then it is ok.
Switching Battery Charger with L296
L296 is a switch mode power controller here. In this NTE327 or 2N5038 is used to boost the current output. This transistor is both high current and fast switching. U1A, LM358 measures the load current by reading the voltage across shunt R6 and compared to a current limit setting at R14 using U1B to give a load current control. R7-R8 give a voltage feedback for voltage limit.