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PWM LED strip dimmer trouble

Johny05

New Member
Hello, i am new to making electronic circuits... I made a 12v pwm led strip dimmer using 555 timer and when i turn it on the led strip only lights up like 40% of its brightness so i am asking for some help.
 

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rjenkinsgb

Well-Known Member
Most Helpful Member
Most likely, the LED lamp has some internal capacitors that are holding it on for some time after external power is removed.

Try lowering the PWM frequency? eg. make C2 rather larger; 0.22 or 0.47uF?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Or the FET isn't been switched properly?, there seems little in the way of a driving circuit and it may be working more as a linear device than a switching one?. A scope would be useful, for checking what's coming out the chip, and what's on the drain of the FET.
 

Johny05

New Member
so i tried the 1k ohm and its little brighter but still very much the same. And i am using a LED strip.
 

eTech

Well-Known Member
I'd suggest not going below about 33 Ohms, as a power MOSFET may have very large gate capacitance & cause current spikes without some level of limiting.
I didn't think that was a concern since the 555 output stage is totem pole and capable of 200mA.
 

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