ultra Posted January 16, 2009 Report Share Posted January 16, 2009 i'm planning on using a resistive touchscreen that only has a small amount of resistance, and i'd like to scale this to work with ain. i'm not too familiar with the ain module, but i guess it reads voltages and i would like to use a device that can output the voltage to the ain based on what is fed into it by the touchscreen.the resistance ranges are:top to bottom: 120 min 300 maxleft to right: 580 min 900 maxthese work on a range of 3 to 12 volts, so using 5 should be ok.i'm not sure if this even comes into play, but the contact bounce is 5 ms minimum and 10 ms maximum.can someone please point me in the right direction? thanks.ultra Quote Link to comment Share on other sites More sharing options...
bugfight Posted January 16, 2009 Report Share Posted January 16, 2009 just use two opamps, with the x biased so that 580r=0v and gain set for 900r=5vsame with y but 120r and 300r ...you'll probably want one that can use single supply and can go nearly rail to rail, so you can use 5v supply.iirc the lm324 would work... Quote Link to comment Share on other sites More sharing options...
cimo Posted January 17, 2009 Report Share Posted January 17, 2009 http://www.midibox.org/forum/index.php/topic,7812.msg54107.html#msg54107Hope it helps Quote Link to comment Share on other sites More sharing options...
ultra Posted January 17, 2009 Author Report Share Posted January 17, 2009 i think i figured out what to do, and it's pretty simple.i'll use a voltage inverter schematic i posted a while back for those bgmicro lcds (http://www.sub-version.net/images/negativeconversion.gif). one side will get -5v, one will get +5v, and i'll make a divider between the two using the touchpad and a trimmer set to get 0v between them when the touchpad isn't pressed. then i'll get a voltage when the resistance is increased and put that to the ain. this would only give me up to about 3.5v for the y axis, and about 3v for the x axis, but i guess AIN has a pretty high resolution and for a 128x64 lcd, that should be enough. at highest resolution, i'll need values of 0-127 for using this as an x/y controller. from here i'll just have to scale it in the software.cimo your idea i'll probably try on my next parts order. i can't say i totally understand it, but i'm sure i can play around with the parts if i have them.bugfight, i picked up a lm324 but i really don't understand op-amps. i read about them, but i can't see how it applies to this. do you know of a schematic anywhere?thanks,ultra Quote Link to comment Share on other sites More sharing options...
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