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Cheap optopstop alternative

Posted by Joost 
Cheap optopstop alternative
January 13, 2008 08:08AM
Since I had some troubles finding the optopstop components (specifically the H21LOI), and some problems with the micro switches (apparently superglue can break them) I thought it would be nice to have a (cheap) alternative.

I used the components from an old mouse. This is the model that uses a ball and has some opto couplers and (infrared) LEDs inside. Took them out, soldered them on the opto stop PCB (as described in the Wiki) and plugged it in, and this works very well. If you want to try this but need some more info, let me know, I can post some details.

Re: Cheap optopstop alternative
January 14, 2008 10:18AM
its true!

i accidentally broke open the H21L0I and pulled the black thing off and it basically just contained and LED and some sort of receiver. I imagine it would be easy to make your own (or RepRap a housing for regular LED's)

Re: Cheap optopstop alternative
January 14, 2008 07:21PM
Yep it will be a LED probably IR with a photo transistor, back in the old day if you wanted a photo transistor you just carefully took the top of a regular transistor and hey presto a photo transistor, when we get to RepRap electronics would be a good item to start with as size would not be an issue.

Re: Cheap optopstop alternative
January 16, 2008 04:15PM
Ian, why do you think size is not an issue?
As far as I understand, main function of optostops is 0-position determaining. So, if we have 1mm-diameter LED and photodiode, we obtain 1-mm error in zero-position determining.

By the way, maybe good alternative way to make optostops cheaper is just use 3 instead of 6 of them? See [forums.reprap.org]
Re: Cheap optopstop alternative
January 16, 2008 08:06PM
Opto's usually have a plastic cover with a thin slot to get better resolution than the size of the LEDs.

If you are using steppers then you can get four times better resolution than your end stop because you know which phase you are on.

Yes no point in more than three unless you are paranoid.

Re: Cheap optopstop alternative
January 16, 2008 08:23PM
I think that the arduino code looks for all 6 end-stops though. Don't hold me to that, but that is my impression.

Re: Cheap optopstop alternative
January 17, 2008 04:24PM
the arduino code is capable of using all 6 endstops, but it doesnt require them. you need 3 for a full machine, and 6 for doing the 'calibration' which is not required.
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