Sunday, March 18, 2012

Blinkn' LEDs with NPNs

I'm trying to learn more about the hardware side of electronics. So, after sorting my collection of parts with ecDB, I created a blinking LED circuit with a NPN. Scheme below. I found, obviously, that when i changed the values of the caps/resistors, the time each LED was on and how long between each on period changed.

I believe that i understand what is happening, but i am not exactly sure:
1. The first cap is charged, which causes the second NPN to allow current to flow.
2. That completes the circuit on the second LED and charges the second cap. 
3. Now the first cap is depleted, but the second cap is charged, so the first NPN and LED turn on.
4. The second cap is discharging and the first cap is now charging.
5. Repeat.
They are blinking, but the camera doesn't have a fast enough shutter time to detect it.

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