Blinker circuit issue

ScottWang

Joined Aug 23, 2012
7,397
Another crazy idea - what happens if you leave out the 100 ohms, that is, put a short in its place? Decades ago, we made flashers out of neon bulbs, using a very similar circuit (except that the supply had to be 100 volts or more). If there was too much resistance in series with the bulb, the lamp would just lock "on" dimly rather than oscillate.
I just tested the circuit used a wire to replace the 100Ω as you said, and the frequency is going down.
 

Thread Starter

CTRL+X

Joined Jul 1, 2009
27
So I removed the 100 ohm, resistor and still constant on. Then I swapped in a yellow led in place of the red one, and what do you know, it blinks.
Changing the 1k or cap value changes the rate of blinking.
 

DickCappels

Joined Aug 21, 2008
10,152
Did you design the circuit and for what reason?
Do you think will it more easy to damaged than the normal method as c connecting to positive and e connecting to negative?
Scott, I put the circuit together for fun only (it was not really "designed" because the operating parameters are unknown). Easy to damage? Maybe since the transistors were not designed for this kind of operation.
 

Thread Starter

CTRL+X

Joined Jul 1, 2009
27
It doesn't look to have an integrated resister. The voltage drop across it measured the same as they yellow one when hooked up to constant power, so I'm not sure what the difference was.
I'll have to try some more led's to see if I can figure it out.

Regardless, I now have a better understanding of the circuits process. Thanks to all for the help and input.
 

ScottWang

Joined Aug 23, 2012
7,397
Scott, I put the circuit together for fun only (it was not really "designed" because the operating parameters are unknown). Easy to damage? Maybe since the transistors were not designed for this kind of operation.
So it just for fun, the bjt was worked with a pulse has small duty cycle, I think it may not so easy to damaged.
 
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