555 capacitive touch sensors

This is a circuit I built entirely out of 555 timers for the contest at www.555contest.com.

Details on my circuit are at http://www.siliconfarmers.com/post/2011/02/27/555-contest-entry%E2%80%93touch...

Category:

Science & Technology

Tags:

• 555contest
• capacitive touch sensor
• 555 timer

[trufact]

ok I think I understand, but dont you mean leave out the bistable? thats looks to be whats latching? Just a little lost, So i use only the monostable circuit?(1 555 timer), Also am I allowed to use electrolytic capacitors, would this affect the circuit too much. Just so you know you are the best- this little circuit is a life saver- and many people across the world are thanking you just as I am we appreciate you sharing. I don't have much but if its something i can do let me know..

[nikkon27]

@trufact You are right, I meant leave out the bistable. But now that I am more awake, I realize this would give you a 5 volt signal when off, and a series of 0 volt pulses at about 25KHz when touched. That may not be what you want.

The capacitor across the "button" needs to be a small value, I think under 500pF. Electrolytic capacitors are too high value.

[nikkon27]

olavus - There is some unetched copper at the ends of the board, but it's not needed, not grounded.

trufact - There is a link to my blog in the comments (click "show more") with theory of operation and schematics. For momentary push buttons, leave out the astable 555 that is used as a flip-flop to latch the output state. The outputs of the monostable 555's are the momentary outputs you want.

[djblackarrow]

Your link doesn't work!

I am interested in such circuits. I am planning a touch panel consisting of Plexiglas and self-engraved buttons that light up when activation or change color.

I think it will not be easy.

[klint6448]

Hi, can you make a picture from another side. Please an send it to peska97@gmail.com

So thanks for picture

[edwardfastcutter]

question using 555 time for touch circuit, when energized it works 50% of the time, the components are sodered into place and between 7 and 8 there is no resistor so i can use it as a latch. so when I touch it it remains energized across pin 3 until it is powerd off

[trufact]

Hi just wonder if you could give me a little help if it's not too much trouble, I would like to make a switch just like this for my project but I would like to use the buttons as momentary push buttons. can you guide me or steer me down the right path? I played around with your circuit but still dont exactly get why you dont need a analog to digital converter. Anyway anything will help links/schematics/circuits etc my email is macitgood@me.com

[trufact]

Hi just wonder if you could give me a little help if it's not too much trouble, I would like to make a switch just like this for my project but I would like to use the buttons as momentary push buttons. can you guide me or steer me down the right path? I played around with your circuit but still dont exactly get why you dont need a analog to digital converter. Anyway anything will help links/schematics/circuits etc

[olavus]

have used a ground surrounding the sensor plate ?

[olavus]

pretty ALWESOME!