Touch Sensitive Switch

[BobP]

Hi All,

Just seen a cheap and cheerful toy that uses a ‘sticky label’ with images of buttons. When you place your finger on one of the ‘buttons’ it operates the toy. From what I can see there is no electrical connection through the plastic case. Can’t take the case apart to see what’s inside the case.

I would like to try using this method on my next project (don’t know what it will be yet! But is going to have some buttons) any suggestions on the best way to try this with a PIC?

Bob

[Jerson]

Maybe using one of 'em Cypress PSoC capsense chips (if at all it uses a micro)??? I do remember long ago when I fixed a TV having a similar on/off touch switch.

[paul borgmeier]

Check Out (Mister E) Steve's Version as an option
http://www.picbasic.co.uk/forum/showthread.php?t=2671

[BobP]

Thanks for the replies. When the kids get fed up and forget about it I might find it and take it to bits.

I was impressed the way it senses the finger through the plastic.
Thought it might have been cheap and simple to use! Back to the clunky switches......

Thanks,
Bob

[mackrackit]

Look at the "LED Touch Sensor" and video at the bottom of the page.
http://web.ndak.net/jdgrotte/

[BobP]

Hi mackrackit,

Thanks for the post. It was not what I was looking at but its so unusual that I will have to try it!

Thanks for the post.
Bob

[mackrackit]

LEDs can be strange. The green ones can even produces a small voltage. Saw someone using them as a light sensor for a solar tracker.

The whole point is capacitance, not sure how the gizmo you are talking about works but I will bet the plastic is the di-electric and your finger is the positive side of the capacitor.??

Have you ever done the Leyden Jar experiment? Build a capacitor, charge it, take it apart with out discharging, completely separate the components, put it back together and it will still have a charge.

[rhino]

THIS (http://www.sparkfun.com/commerce/product_info.php?products_id=7902) might be similar to what Jerson is suggesting.

[BobP]

Thanks everyone,

I am sure it is a capacitive sensor but just wondered as it is used in a £3.00 cheap and cheerful toy it was using some simple method that could easily be used with PIC projects.

I think Jerson was referring to this page and the first application PDF in the list
http://www.cypress.com/portal/server.pt?space=CommunityPage&cached=true&parentname=CommunityPage&parentid=32&in_hi_userid=18780&control=SetCommunity&CommunityID=274&PageID=490

Thanks,
Bob