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Simple circuit design - newbie!

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New Member

I am a newbie to electronics, and I want to build a circuit using simple components to do the following:

Using a momentary switch, I want to switch a single LED off and on as follows: push-on, push-off, push-on, push-off, etc etc

I am a bit stumped. any help from the "masters" to a novice gratefully received.



Active Member
Hi mgdaviso,

What you are describing is known as a bi-stable.

In particular that group of bistables known as flip-flops,
which in addition to having two stable conditions,
will flip from one condition to the other,
from identical pulses to the same input.

How simple would you like your components to be ?

Relays ?
Solid state ?
Integrated circuits ?

I vaguely recall an arrangement having two small neon lamps
and a few resistors and caps, but i don't recall the circuit.
That was about the simplest i can think of.

You could make a small assembly using two transistors and
a few resistors and caps to do as you describe using a press
button, there are many such circuits about.

Or you could get a ready made chip with a few flip-flops
on it, and just use one of them.
That would be the easiest.

Best of luck with it, John :)


New Member
Thanks for the input so far!

I need to use simple components - transistors, resistors, leds, you know - basic circuit board stuff - I am not into the realm of chips yet - sorry!



Well-Known Member
Here's a no-chips bistable multivibrator. When one LED is on, the other is off. If you don't want two LEDs, replace one with a piece of wire.
I don't know what your battery or power supply voltage is. Select the values of R1 and R3 to set the LED current.

R(1,3)=(VCC-2)/LED current.

So if you want 10ma of LED current and you have a 9 volt battery,

R(1,3)=(9-2)/10ma R(1,3)=700 ohms. Use 680 ohms, which is the nearest standard value.

Connect the positive terminal of your power source to VCC and the negative terminal to GND (the triangle symbol). All wires which have the GND symbol on them (there are 5) need to be connected together.


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