Breathing LED

270

05:34:04

555 timer.  Resistor and capacitor odd values were tweaked to get the best result when breadboarded.  Slightly different behavior in the simulation.  Couldn’t get this circuit to work well with 5V in simulation but works well at 5V on a breadboard.  ???

published 6 years ago

fatcat2

6 years ago

Did you try changing the current of the LED?

Molar

6 years ago

Fatcat, on the breadboard, I used 5V source, a47uF cap, 57k resistance(10k +47k) on the 555 and 220ohms on a red led). Led pulses as smooth as butter. In the simulation, have to lower current top low on the led to get 555 to work.

wyoelk

6 years ago

Try these settings and I moved the base of the transistor to the other end of the 11k resistor. http://everycircuit.com/circuit/6381884626698240

fatcat2

6 years ago

Try this:- http://everycircuit.com/circuit/5229785352241152

Molar

6 years ago

Thanks for the suggestions guys. I built a soldered “dead bug” 5V version with the specs I posted and it worked great too. Any idea why those numbers won’t even come close to working in the simulation? I’m new to this software and just trying to get an idea of how it differs from the built circuits. I know that heat and capacitance can play a part but don’t think those apply to this circuit.

fatcat2

6 years ago

EC can simulate most circuuts but the diference arises because the BE-junction voltage drop in EC doesn't match that in real life. Also, you need to carefully set the D.C. gain of the transistor, preferably by measuring it by hand; I use my multimeter to do so. Finally, the LED you have may not have the same voltage and current as that in EC. That's why the resultant voltages are different but tolerable. Heat and miller capacitances come to play when dealing with amplifiers and oscillators.

Molar

6 years ago

Thanks, fatcat. I will check the DC gain of the transistor and the LED specs in my breadboarded circuit and make adjustments to see what happens.

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