Robot builder 101

I forgot the correct name of the circuit, but I would like to integrate it into one of my upcoming robots. This is how it works:

You press a momentary button (not a tactile, where it depresses) and it turns on the circuit and keeps it on until you press the switch again. What is this called using a momentary switch? does this require a microcontroller?

ljcox

There have been circuits posted for this in the past - including some by me. Do a search for "flip flop" or "toggle switch".

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Len

Robot builder 101

Thanks, I found one, and I happen to have all the stuff I need there... I think thats a first time ever!

Robot builder 101

Lol, I forgot to write down the site so that I could build it...

I am using a 74HC74. A link would be nice!

ljcox

Try this one

http://www.electro-tech-online.com/e...ghlight=74hc74

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Len

Robot builder 101

I got the circuit working, but I am having trouble with button debounce. any suggestions?

audioguru

This circuit is simpler and works well. You can have 3 circuits from one IC or use the leftover inverters tin parallel to boost the current. The capacitor debounces the pushbutton.

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Uncle $crooge

Robot builder 101

Thanks. Ill test it out right now!

is 47nf a 0.047uf cap? Could I use a 0.1 uf cap?

Robot builder 101

It works amazingly well! The 0.1 cap is a perfect substitute. Thanks!

audioguru

If you jab at the button very quickly and the supply voltage to the Cmos IC is at 3v which is its lowest allowed, then it might not switch when its capacitor is 0.1uF.

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Uncle $crooge

Robot builder 101

I built it with a 5v regulator, then hooked up a 2907A to switch a circuits connection from its negative connection to GND. Pictures up later

audioguru

Ordinary Cmos doesn't need a voltage regulator. It works with a supply voltage from 3V to 18V.

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Uncle $crooge

Robot builder 101

I know, but its fun just to throw one in there.

ThermalRunaway

Well, I was going to help you but audioguru seems to have sorted you out and I don't think I have anything useful to add other than an amusing story (if you have my sense of humour) about a recent application for this circuit.

I modified the side lights on my Land Rover some time ago with green LEDs to match the colour of the vehicle. Took her in for an MOT (that's a compulsory annual test of roadworthyness here in the UK) and she failed for the lights. They're not allowed to be green, they have to be white.

So I took her home, and pondered the situation. I quite like the green glow when the side lights are on and I didn't really want to have to put her back to the original spec. I could Take the green LEDs out, fit white for the MOT and then fit green back in there afterwards but that would be a bit of a drag so in the end I re-modified the light cluster with green AND white LEDs. I hooked them up to a circuit similar to the one AudioGuru has shown here, with a button installed into my dash marked "MOT button". The circuit is powered by constant 12V so it always remembers it's current state.

I took the Land Rover back in for the retest and the mechanic called me over. "These lights are still green!!!" he said. "Push the MOT button on the dash!" I replied, and left him to it. Needless to say she passed, and I drove out with green lights

Childish I know. But hey gotta be done every now and then!

Might think of some more things I can hook up to the MOT button actually. Hmmmm...

Brian

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Electronics Test Development Engineer
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audioguru

I wonder if you could have a MOT button to select the worn out old brake pads or select new pads to pass the test. Then you drive on the old brake pads until they are completely gone.

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Uncle $crooge