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 max
left to right: 580 min 900 max
these 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.
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?
