Opto Endstop

Ive been trying to build a reprap mendel for a while now and am really only have 1 problem that i cant seem to get round,
its with he opto endstops, i have 6 of them 3x 2.1version and 3x3version. and i can not seem to get any of them to work, and i would have though they would be the easy one. anyways, as i see it and please do correct me if im wrong. if they are plugged in i.e 5v across them, there should be no LED light up unless you put something in the middle, however i do not seem to get any reaction from them no led light up and the stepper boards continue to move in both directions when i command them to do so, however for 2 of the 3 versions i get a led light up and thats it.

i am wondering if anyone has any hints on what could be wrong with all 6 of them and if there is any thign ovbsie i have overlooked.

many thanks

tom

Here are some questions:

1. Are you a beginner at soldering? Is it possible you have a bad solder joint?

2. What are you blocking the opto with? Is it shiny or made of plastic? Try a piece of cardboard or even better, a sheet of metal that has been spray painted black.

3. Do you have 5 leads on the opto part? If so then they can only go in one way, (because of three pins on one side, two on the other.) The resistors can go in either way, and the LED will not function if they are installed the wrong way.

4. Depending on the opto part, the led can light when blocked or light when not blocked. I don't quite understand your post, but if any of them either stay lit or don't light at all, that's a problem with the board somehow. If the LED does change states then it's possible they are working fine and you either don't have it wired to the main board or you don't have a configuration file, (that gets downloaded into the microcontroller), set correctly.

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My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

thanks for the quick response,
out of the 6 i have 3 are ones i bought online (v2.1) and 3 i made (v3.0), i am not a beginner at soldering, the rest of the boards i have made up all do work (now).

except these ones, i did try several deferent types of materials in them however i have nto tried and black metal i have tried some thick shiny metal cardboard, some plastics, and a few other things,

all the boards are made up on pcb, so the opto sensor can only go on 1 way, and i have gone back to the schematic, and checked the led is the right way round, .

i do think i have set it right in the firmware, so that should be ok, but when i put something in the gap with it all wired up, it does not stop the motors, at all,

i hope this is a little clearer, and i appreciate the help

i am also a university student, and am going to try taking the boards, in to one of your labs, and see if i can work out how they are supposed to work,
tom

Are you sure the cables are correct?

The V2.1 uses Ethernet connectors I think. You need straight through patch cables rather than ones that are designed for back to back Ethernet which swap transmit and receive.

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[www.hydraraptor.blogspot.com]

Many types of plastic are opaque to visible light, but transmit IR. A thick piece of cardboard or something ought to be usable.

I wouldn't go on to wiring up the motors until you have the bugs worked out on the endstops. If that LED is not functioning I'd fix that first. It's entirely possible that the LED is burnt out.

You can check to see if your opto part is emitting if you happen to have a cheap camera, (maybe attached to your cellphone). You can test the camera to see if it responds to IR with a TV remote. If you can see the pulses from the remote on your viewfinder, you can verify that your opto part is emmiting IR too.

Got a logic probe? Use it to probe the SIG line while you test.

Once you know the optos are working, move on to the cable.

From what nophead said, you can detect a crossover cable by looking at this diagram [www.telecom.otago.ac.nz] (taken from this page: [www.telecom.otago.ac.nz] )

if one side of the cable is wired to T568-A and the other to T568-B, then you have a crossover cable. If both match, (both either T568-A or T568-, then the cable should be OK.

(Incidentally, and to no one in particular, if the opto boards were configured to use 5-6 as one line, 7-8 as another line, and then shorted together the remaining 4 wires for the third signal line, it would be immune from the crossover cable issue.)

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My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

for the cable im using jsut some 3 pn cable, however i have hooked up 5v acroos it, and then blocked it with no led light up and no change to voltages or resistances on the boad,

It sounds like you have a bad part, a solder bridge, a damaged board, or a wiring error.

Suggestions:

Triple check everything.
Consider jumping the LED/resister with the 5v line and make sure the LED lights
Check for voltage on the correct pin, and for IR output on the opto-switch
Post photos maybe? Perhaps we can see an error?
Where in the world are you located? Maybe someone local can help?

tomganleylee Wrote:
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> for the cable im using jsut some 3 pn cable,
> however i have hooked up 5v acroos it, and then
> blocked it with no led light up and no change to
> voltages or resistances on the boad,

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My blog's Reprap feed: [blog.markbova.com]
I'm currently working on a stock Mendel build with a Seeeduino Mega and four Pololu A4983 stepper controllers.

I would firstly like ot thank everyone for your help, however i have found the problem the actual opto sensor on all of the boards seem to be broken, as after replacing 1 of them it works fine and i have now replaced all of them, and they all work
thanks again for the surgestions,

tom