Range on PWM circuit not good

[chesschaser]

Hi guys,



I have built a PWM dimmer for a 12v 20w halogen lamp using 555 timers but the brightness range isn't good, even though according to the formula, the duty cycle range should be decent. As you turn the potentiometer, there is very little change until it suddenly drops down from 11v to 4v. The schematic is shown above. Any ideas why this isn't working very well?

 

[Alec_t]

Wire up U2 the same way as you were advused in your other post, to get ~0-100% duty-cycle variation.

 

[bertus]

Hello,

You already have a thread for your halogen pwm dimmer:

https://maker.pro/forums/threads/is-there-anyway-this-circuit-could-be-improved.301445/

Bertus