Testing photo sensor

Howdy,

I just soldered a bunch of Gen7 opto endstops as per the instructions here: [reprap.org]

I'd like to check if the photo sensor took any damage from the heat, but I don't have a motherboard to wire it up to yet. What's a simple way to check if it's working?

Cheers!
Mateusz

... apply 5V and measure the output when blocking the sensor if the LED won't light up ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hi, thanks for the advice, much appreciated.

I hooked up 5V to VCC+ and GND- [reprap.org] and the LED lit up regardless if I blocket the optical sensor — would this indicate that the sensor is busted, or am I not doing this right?

Did you block it with metal? I think the IR light can go through plastic or paper.

I tested all nine endstops I've made, and on two of them the LED shone regardless if the sensor was blocket or not. I'll take a look at the two which don't work properly tomorrow, but for now it seems I have at least seven working endstops, yay! FWIW, I tried blocking the sensor with metal and paper, and both seem to block IR just fine.

After I desolder the optical sensors and want to test just them, should I measure the resistance across it while blocking/ublocking the IR, or how do I go about testing just that part?

... the opto sensor is simply an IR-led as emitter an a photo-transistor as detector.

You can test them independently but it seems you have overheated the two optos while soldering, so better replace them ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Ok, changed the optos and made sure to be careful not to overheat them. Both board still behave the same, which is the darnedest thing since it's unlikely that I messed both of them up. I can't see any shorts on the board, but if it's not the optos then a short is the only explanation, right? I got the LED polarity right, and there are too few components to mess much else up.

Just to be certain I'd like to test the discarded optos; I have the datasheet but am not certain where to measure what…

... check if your resistors have the right values.

You can test the IR-LED by inserting a piece of paper in the slit and look through the sensor of a digital camera, if it's lighting up when you apply 5Volts through a resistor of maybe 1kOhm (or look in the schematics of the opto for the correct value) to the Anode (+) and GND to the cathode (-).

The transistor should change the resistance from collector to emitter to nearly zero when applying IR- or daylight ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Ok, back after more checking.

All the resistors are the correct ones, and although my soldering isn't pretty, it doesn't seem to short anywhere. (unless flux can cause a short, there's plenty of that)

I applied 5V at 60mA through the IR-diode and measured the resistance on the detector. I got slightly varied but consistent results, with decreases resistance when the power is connected and the diode not blocket. (I can't see anything on my cameras, but I don't know how narrow the wavelength of the IR diode is and perhaps 950nm is invisible to my cameras. Regardless, the optos I thought busted seem to work.)

A thought struck me: What should the amperage be for the assembled optostop? I might have had too high current when testing the first time…

... shouldn't be more than 10 or 20mA ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Re: how i can test a photo sensor without applying any voltage to it