2 TERMINAL FLASHER FOR AUTOMOBILES
This is a two-terminal flasher used to flash the indicator lamps in a car.
It will directly replace the older types which use a heat activated bi-metal strip to achieve the on-off "flash"
It uses no moving mechanical parts (transistor switching)
Therefore there is no "clicking" sound as with the traditional type.
I found the circuit on the web, and have prototyped it to verify that it works.
T1 and associated components form a RC oscillator
of about 1.2 Hz or 70 flash's per minute
The 10K resistor and 33uF cap at T1's emitter determine the timing.
TC= 0.33sec (TC= C x R)
Initially T1's emitter is held near collector potential and therefore T1 non-conducting.
When capacitor is charged; T1 turns on, biasses T2/T3 on , lamp glows and RC network discharges through lamp circuit.
T1 turns off, cycle then repeats
T2 & T3 are a darlington pair; used to give enough gain to switch the lamp current of approx' 1 Amp
As this is a polarized device (as compared with the bi-metal flasher which isn't)
a series silicon diode will peclude any circuit function if "reverse connected"
My example works fine....
Original circuit and redraft.
Uses MJ1000 darlington transistor(s) to replace T2, T3
which reduces component count and build size