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| Battery powered LED PWM dimmer circuit |
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| doublec4:
Audioguru, they look like the same circuit to me... the pot and diodes are flipped upside down but they should have the same effect, no? As for no inline resistor with the load, I put one in line with some 5mm LEDs and built this circuit. Worked fine although it seemed I had a very narrow range of operation on the pot Revisiting this circuit... I can seem to find lots of info online with the "standard" 555 timer PWM circuit with some variability on the duty cycle and a fixed frequency. However, in the circuit posted here, how would I go about calculating the frequency? Thanks! |
| doublec4:
To wrap up this thread, end result was as follows: I ended up with an acceptable dimmed state by using this calculator/circuit: https://houseofjeff.com/555-timer-oscillator-frequency-calculator/ Put in my required 200Hz frequency... ended up with the following values because I had them on hand to breadboard C1:0.01 µF R1:56 KΩ R2:330 KΩ Period:0.005 sec. f:201.5363 Hz. Duty Cycle: 53.9 % Was still kind of bright... found this info here: https://electronicsclub.info/555astable.htm Put a diode in parallel with R2 and the dim state looks great. Looks like the frequency is somewhere around 300Hz + (have to scope it again) but it works... Edit: Thanks to all who helped! |
| Jwillis:
--- Quote from: Audioguru on June 05, 2019, 07:25:09 pm ---Which circuit is correct? Do these circuits both work? --- End quote --- Both those circuits will burn out the LED . A limiter resistor is still required for the LED to keep it below its maximum current tolerance. |
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