How can I make a touch activated counting device with lights?

The device would be a string of beads. Each bead would light up if touched and turn off if touched again. It could be led's or whatever. Any suggestions? Thank you. Chris

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jeff-o8 years ago
You could use beads that change colour when heated (ie by your hand). Usually the colour lasts for at least 20 seconds before fading back to its original colour. This would require no power and could be completed in minutes.
There are a few different ways to do this. They depend on a few constraints, too - are the beads conductive? How large are the beads?

There are capacitance sensors that you can buy out there on the 'net, or you could use a darlington transistor pair to do it (if you have physical access to two electrodes on the bead).

Other options could be using a photosensor to trigger the LED, or maybe even just plain analog inputs to a microcontroller (again, if you are able to touch two electrodes).

Let me know more about what you're planning to do/constraints, and I'll help you out more :)

milkyway312 (author)  T3h_Muffinator8 years ago
I want to make a set of rosaries, prayer beads, etc.. One that I can keep track of where I am at in case of being interrupted. So, I am not married to any idea regarding what kind of light to use. I would like this to be portable. Honestly it doesn't have to be beads at all, just 15 individual pieces for tracking the count. Thank you for your information so far and thank you for any additional info you can provide. Chris
comodore8 years ago
Hmm, I think I understand what you want, but it is extremely hard to make something like that, I mean , i saw a lot of electronical schematics, but never have i seen something like this. The thing that comes to my mind is a bit different, it will not light off when touched again... I thought about NTC resistor, so when you touchem them, for about 3-4 secs they light up because of the heat that your finger transfer to a bead and lower the resistance of the NTC resistor, making the LED in a bead light up for s hort period of time... The time that is needs for the NTC to heat up, for the LED to light up varies of the resistance of the NTC resistor. Also if it is a string of beads you should connect them either in series, than you need a bigger power supply, more volts, or in parallel, but using a resistor for each bead to another...it's not a good idea to connect LEDs in parallel but it would work...Also to fit all of this into a bead is not easy, you would need a bigger bead... Hope I helped you a bit... If you have more questions feel free to ask! :D Thanks!
PKM8 years ago
The second image at this link shows a simple and cheap way of doing what I think you want. If the small switches were toggle switches, you could just wire up a battery-switch-resistor-LED as normal, put it together like this and encase the LED and switch in whatever you wanted to make your bead out of.

If you used a lithium coin cell like LED throwies, the whole thing could be self-contained inside something perhaps the size of a table tennis ball (although then I'm not sure how you would press the LED to toggle the switch).