Bistable On Off LED Soft Switch Using Transistors

447

11:44:47

Here is a working example of using two transistors to turn on/off a LED using a momentary soft switch. A relay or SCR can be added along side the LED. Is there a way to reduce the "off" power usage in this circuit?

published 10 years ago

sumitdhingra

10 years ago

Bi stable multivibrator will not work in simulation because the program assumes every transistor to be exactly same while in real-life it is not possible. In actual circuit there is different time delay in both transistors unlike simulation that's why the circuit works in real life not in simulation

Sine_eyed

10 years ago

sumitdhingra- it is true that ideal components are used here, but your notion that a bistable won't work here is ridiculous. I've made many- they're quite simple lol. drexful- use the searchbar to find examples that might help you define where you're having problems. I have posted a few as well if you want to check my page feel free..

sumitdhingra

10 years ago

Sine_eyed - I saw your bistable multivibrator and it uses two switches not one, that's why it's working. I would like you to see bistable multivibrator by "jdlogic". He explained it very well and you have agreed with that in comments too.

drexful

10 years ago

@ sumitdhingra would it be possible to change the hFE values to achieve the bistable multivibrator functionality in the sim? Essentially, I would like to determine the values needed for 5 to 6 volts to make this circuit work. I've changed resistor and capacitor values without much luck. Also, is there a way to make this work with a single LED? I've searched for examples on here but nothing jumps out using a single "soft switch" configuration. Thank you.

sumitdhingra

10 years ago

Changing hfe won't do anything here. If you need values then you can calculate them by Kirchoff rule. Just choose the current according to your need and take voltage between collector and emitter to be half of power supply and now just choose resistances accordingly. You can see various designs of single switch on Internet but I don't think they will work here. Bi stable multivibrator using diode is very common.

drexful

10 years ago

Modified circuit to meet my needs

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