Chagrin:
kadamr:
If that were true then it would certainly be far too slow, however, I took 500 ms to be an example value for an input signal to the sensor. I thought it's PWM output would be much faster. I might well be wrong, it's not clear to me. It does say under applications (pg. 1) "Sensor for large format touch panels" - that's what I'm doing, right? Why would they design it to be so slow?That "ms" unit must be microseconds. 38KHz, 1/38000 = .000263, half that is .000131. They show it as "120 ms".
I thought the 38 kHz value is about only detecting modulated IR light (at that frequency) incident on the sensor and that the PWM cycle could be at a different speed and they set it to a few 100 ms for whatever reason. Do you think that the 38 kHz is the PWM speed as well (or instead)? I do like the PWM idea over analogue so if it could work that'd be nice.
If that's the case (about the ms = microsecs) I'll email them to verify. In addition to the Vishay TSSP4P38 (which may potentially be designed for this application, see pg. 1) there are a couple of other options besides using IR phototransistors that is. The Adafruit site recommends/sells Vishay TSOP3802 that seem to have a digital 1 or 0 output only. But this one may also be the 'useless for my purpose' variety, see quote:
Grumpy_Mike:
It says:-IR sensor tuned to 38KHz, perfect for receiving commands from a TV remote control.
True, but useless for what you want. This is because the LEDs need modulation and the sensors only pick up pulses if you send less than 30 or so pulses without a gap.
Is the Adafruit one also just for remotes? Thanks for the info by the way and the port expander idea - I'll definitely look into it.
There is one other option I found. Here is a video showing a Sharp IS471F in an interactive single cell setup, pretty much exactly what I'm aiming for (x288). It can be calibrated for the acrylic surface as well which is ideal. It is really expensive and binary output only however. Does anyone see any issue with this one?
Due to the their really high cost, if I were to buy any I might only make the corner of the screen interactive or something. But if I did have lot's of these - how would the best way to collect their outputs? They are binary output only, right? So no ADCs (not analogue) then - just multiplexing or shift registers (or interrupt port expander if I use lots)?