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Author Topic: touch sensitive resistor?  (Read 1370 times)
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Hey everybody,
I've been trying to build a small musicbox out of an arduino and some buttons and things. First design used 8 different buttons to trigger different tones and then two pots to control delay between beeps and pitch variation. Only having remembered (misremembered?) that I saw some sort of PWM readable touch sensor. Ideally, I'd have it hooked up to the arduino so that the further along on the touch strip the higher the pitch and another one for looping, but I can't find any online. Maybe the problem is that I don't know what to look for? If anyone can tell me anything about what I'm looking for (if it exists :o) that would be great.
- (the_downsmeister)
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Maybe something like this:

http://www.sparkfun.com/commerce/product_info.php?products_id=8680


I think you would just use this on an analog input though. not one of the PMW inputs
« Last Edit: January 27, 2009, 08:32:52 pm by estranged » Logged

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PWM readable
Quote
PMW inputs

PWM (Pulse-Width Modulation) is a method of generating an analog output from a digital output pin.  There are no "PWM inputs", it just doesn't make sense to say that.
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Estranged seems to have hit it on the nose. That's exactly what I've been looking for, thank you very much.

Quote
PWM (Pulse-Width Modulation) is a method of generating an analog output from a digital output pin.  There are no "PWM inputs", it just doesn't make sense to say that.


You're exactly right, Anachrocomputer, I meant to say analog readable (I'm using the analog read function). Sorry for the error, I just started with arduino and I'm still learning my terms. Thanks again,

- (the_downsmeister)
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Glad to hear that you've found what you're looking for!
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From 'estranged' (above)
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How does that thing actually work? (Anyone played with one?)

Seems like it's meant to have some sort of (hardish) 'wiper' set up to run on the 'track'. (From the datasheet 'Wiper' section.) I'd guess that when you release pressure on it, it goes back to full scale. Is that so?
« Last Edit: February 01, 2009, 04:10:02 pm by wdh » Logged

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How does that thing actually work?

It works just like a pot. When you stop pressing the wiper is disconnected so it floats. Therefore you have to put a high value pull up or pull down resistor on the input to define the value un-pushed. In the UK you can get them here:-

http://www.totalrobots.com/sensors-flexforce-c-71_72_77.html?main_page=index&cPath=71_72_77
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... you have to put a high value pull up or pull down resistor on the input to define the value un-pushed
From me, and probably plenty others, thanks for the application note, Mike.
It was clear to me that it wasn't exactly like a trim pot, but it hadn't occurred to me that it was so like one of the metre-long potentiometers in the old school physics lab! Hands off and obviously, the wiper makes no contact. Of course!
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Just had a thought.  :smiley

If you put a small series resistor in one of the legs. Then the pulled value will be outside the range of a pressed value. So at the cost of sacrificing a bit of resolution you could distinguish between pushed and not pushed even if you were pushing on the end.
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