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Topic: Drive an LM3914 from PWM (Read 2826 times) previous topic - next topic

srhart

Hi,

I am trying to drive the input signal of an LM3914 from PWM, however the PWM is causing this to flash the LED set from min to max (imperceptibly so it looks like they are always at max). I would like to use the full rage of v (0-5v). Any suggestions on a capacitor type and value to use to smooth a PWM v5 (0.45v step value) or v1.5 (0.15v step) output so that the LM3914 would see a smooth or steady ish v? I also assume the capacitor would be connected from +sig to ground.

Thanks

Grumpy_Mike

Quote
the PWM is causing this to flash the LED set from min to max


Yes that is what PWM does.

Read:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

srhart

I understand the digital to analogue question, what drivers could you recommend for 20 LEDs? I can't get an LM2698 in a DIL package and I am not sure what other options there are.

srhart

Ok I see Charlieplexing is the way I should go. :) Thanks for the input.

pwillard

This desire to light many leds is most often solved by using Shift registers.

http://www.arduino.cc/en/Tutorial/ShiftOut

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