Tip Of The Day / Switch Contact Debounce Circuit

This video will cover how to build a very simple switch debounce circuit. It will use a RS flip-flop so no RC timing is involved, which makes it handy for troubleshooting.

[@davidb1669]

Never stop what you're doing!

[@Cyklonus]

The capacitor and resistor itself also works quite well :)

[@0033mer]

Yes, that can work but you are relying on the first bounce to totally discharge the capacitor, which it may or may not. Adding another resistor will help but now the the output will have a slow rising edge which can double trigger logic inputs. To solve that we buffer it with a schmitt trigger inverter. kzbin.info/www/bejne/m2KQnJZmac-Ge5Y

[@Cyklonus]

@@0033mer And that's the beauty of electronics. There are so many different possibilities and solutions :)

[@SigEpBlue]

Nice video. It's helpful, even necessary, for those learning electronics to understand the switch contact bounce phenomenon, and the hardware debounce techniques to alleviate it. There are more methods, however, such as using buffers with Schmitt trigger inputs, e.g. SN74LS13 and 14, and debouncing in software (assuming an input to a microcontroller). Just remember that it's almost always faster, more reliable, and easier to troubleshoot when you do things in hardware rather than code.

[@0033mer]

Yes, exactly

[@webmasterg3526]

Always worth watching, thank you.

[@0033mer]

You're welcome. Thanks for the feedback.

[@ShellacScrubber]

I had not seen the buffer plus spdt combination before.It's quite ingenious. It provides a good illustration of how versatile and useful the 4000 series logic still is. I recently revisited the video you did about using CMOS logic devices in linear mode.It's all fascinating stuff. I even managed to find a design(Everyday Electronics magazine Oct 1978 ) for an AM radio receiver that uses a 4011 quad nor gate !

[@0033mer]

Going from TTL to CMOS was a big step for the electronic industry which enabled all the high end electronics we have today. Have to give credit to all the guys at RCA. Back in the 70s the electronic magazine was our KZbin.

[@ShellacScrubber]

@@0033mer Yes Ken, I look back on those days in the 70s with great fondness. For myself, the electronics magazines were the main source of knowledge, inspiration and with their advertisements in the back pages, component suppliers !!

[@romancharak3675]

Very nice circuits for Microcontroller inputs.

[@0033mer]

Yes, thanks

[@nguyenthinh6188]

Still follow you after years, from fpga cpld videos

[@0033mer]

Thanks for your support

[@caletorino]

I read a document called “A Guide to Debouncing” by the Ganssle group. Helped me a ton. Some people referred to it as the denouncing “Bible” but I must say this video was short and straight to the point. With a touch of old school class. The 4000 series was a welcome surprise. I’m younger but I’m pretty sure this will save me in a pickle.

[@0033mer]

Glad it was helpful. I have also read the Ganssle document. Lots of good information.

[@marios2620]

Very useful! circuit! Thank you for your precious Tutorials!

[@0033mer]

You are welcome!

[@ccv3237]

Excellent video, really great!!! Thank you so much. I subscribed, now I will like this video also.

[@0033mer]

Welcome to the channel.

[@W1RMD]

Great info! Thanks and take care.

[@0033mer]

Thanks, you too!

[@PhG1961]

Awesome tip! I've found out about this many years ago... the hard way.

[@0033mer]

Yes, if you are new to electronics it can drive you crazy.

[@ronen124]

Muy buena conferencia, gracias por difundir el conocimiento

[@0033mer]

You're welcome.

[@Bianchi77]

Creative video, thank you :)

[@0033mer]

You're welcome

[@lohikarhu734]

There's a nice cmos 6 channel switch debounce, adjustable timing... MC 14490

[@0033mer]

The MC14490 was originally made by Motorola and it worked very well. They discontinued the IC and ON-semi took it on. The DIP version is now obsolete and only SMD verions are available. You can get old stock on Ebay but they are pricey. Maxim also has the MAX6816.

[@vanhetgoor]

Very thorough but what is wrong with only a capacitor or two near the switch?

[@0033mer]

Yes, that can work but you are relying on the first bounce to totally discharge the capacitor, which it may or may not. Adding another resistor will help but now the the output will have a slow rising edge which can double trigger logic inputs. To solve that we buffer it with a schmitt trigger inverter. kzbin.info/www/bejne/m2KQnJZmac-Ge5Y

[@AnalogDude_]

3:17 Neat, but it would be better to use a transistor than a little common switch.

[@fibonacho]

For a switch debounce demo?

[@AnalogDude_]

@@fibonacho Yeah, the role of the transistor is high or low, it's never disconnected, even better with 2 transistors and 3 resistors (Schmidt trigger). you would be able to use the al time classic 10 cent switch and serve the same role precise or one of the cd40106.

[@fibonacho]

@@AnalogDude_ Thank you. I'm getting interested in electronics again after many years away. I appreciate you taking your time to reply.

[@AnalogDude_]

​@@fibonacho research RC time contants, placing the correct resistors, using a PNP with 1K on the base from the button aswel a 220pF to ground from the base, 1M from button to GND to drain the capacitor, 33K from the power rail to the emitter of the PNP. the collector of the PNP is tied to GND and your source from below of the 33K. the capacitor will filter out the glitches and is very power efficient, all this is very little power consum. just few uAmp

[@eitantal726]

Yikes, That's a lot of complexity. I do it in software. If there is no software, then I use a capacitor. I Bet a microcontroller will be cheaper than these 2 ICs

[@0033mer]

Yes, that can work but you are relying on the first bounce to totally discharge the capacitor, which it may or may not. Adding another resistor will help but now the the output will have a slow rising edge which can double trigger logic inputs. To solve that we buffer it with a schmitt trigger inverter. kzbin.info/www/bejne/m2KQnJZmac-Ge5Y