Andrea De Napoli-
Latching a led light with transistors
09/02/2017 at 23:23 • 0 commentsAt the start condition both transistors and the led light are off, so at the node 2 we have a positive signal.
---------- more ----------By pressing the button the high signal is sent to the node 1, so both transistors conduct.
The signal at the node 2 becomes low when the capacitor discharges on the collector of the Q2 transistor.
By pressing the button again the low signal is sent to the node 1, so both transistors get off.
This circuit works properly if the button is pressed for one second or less.
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Relay based latch circuit
09/02/2017 at 23:20 • 0 commentsWhen you press the button both transistors are enabled, but the coil keeps off because it is supplied by 2,5 Volts.
---------- more ----------By releasing the button, the capacitor keeps on the Q2 transistor for a bit; the relay turns on because the coil takes about 5 Volts. At this point the Q2 transistor keeps on because the relay contact is closed between 14 and 11.
When the button is pressed again the Q1 collector turns down the base of the other one. The coil is supplied by 2,5 Volts and keeps on due to the hysteresis. By releasing the button the relay backs to the start condition.
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Latch circuits
Latch circuits based on transistors, to switch on and off a load with a momentary input signal
