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transistor timers

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hantto

Member
To make a flasher you allways need atleast two transistors, what you have made there is just a led that is controlled via a transistor.
 

daviddoria

New Member
but what if i only want 1 flashing light? do i just connect a jumper from Vs to the collector of the 2nd transistor?

i thought the whole point was the transistor stopped the light from being on until the capacitor charged... so why doesn't it work with only 1??
 

kinjalgp

Active Member
Hi,
The circuit won't work with one transistor because for a circuit to work as an oscillator there should be a positive feedback present which is only possible using two transistors which cause alternate charging and discharging of the two capacitors and thereby turning the transistors alternately.

If you want only one LED to blink, you can use the same circuit but just replace the other LED by a small resistor of 470 Ohm or so. Thus the circuit will have only one LED.
 

Gene

New Member
The secret is the charging and discharging of C1. In the second circuit, C1 never changes state. The problem is at C1.
 
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