Opto Endstop

I am assembling the Arduino electronics and I just got my opto isolators in the mail. Due to the fact that I am in Australia I couldn't get hold of the H21LOI. parts.reprap.org says that the part ZD1901 is an equivalent part. However, when I received them they only have 4 leads and not the 5 that the H21LOI has.

I found this page [reprap.org] saying how to use the ZD1901, but it doesn't say what the pinout is (+5, Signal and Gnd). I figure that the center pin is signal, but I'm not sure if the top pin is +5 or ground.

Any help would be great.

It's a shame that rrrf don't seem to stock the opto isolators and steppers anymore otherwise I would actually have the right parts.

Google found me the datasheet: [www.jaycar.co.nz]

Okay, here goes...

Here's Vik's page on your chip in Reprap...

[reprap.org]

Here's the datasheet that Triffid Hunter got for you...

[www.jaycar.co.nz]

Look at the chip schematic at the lower, right-hand corner of the spec sheet.

Now look at this pic of the chip seen from the top from Vik's page...

[picasaweb.google.co.uk]

Now look at how they represent the detector (left hand side) of the schematic. It's hard to see that same sigil on the chip in the datasheet, but if you look at the link to Vik's pic of the chip seen from the top you can see that sigil on the left-hand post on the chip.

What that means is that if you hold the chip with the apex of the triangle of the sigil that intersects with that bar so that it is on your left it matches with the schematic. Now compare what you see with the schematic. The pins are facing away from you.

Anode is the upper left pin
Cathode is the lower left pin

Emitter is the upper right pin
Collector is the lower right pin

I hope that helps. Too many writers of data sheets assume far too much prior knowledge and too often outright clairvoyance on the part of readers.

Edited 1 time(s). Last edit at 02/25/2008 11:50AM by Forrest Higgs.

> It's a shame that rrrf don't seem to stock the
> opto isolators and steppers anymore otherwise I
> would actually have the right parts.

sorry. i'm trying my hardest, but having everything in stock at the same time requires money. seeing as how the RRRF doesnt have enough if it, its a balancing game. donations are always welcome.

Speaking of which, do you have a donate button that I could put on my blog?

ok I think I have worked it out now.

This is what I came up with:

[bp3.blogger.com]

I don't really understand how it works though.

Shouldn't the collector of the transistor be pulled up. So that when the diode is blocked the transistor will be off and then the signal line will be high?

Or does the arduino not need this (pulled high internally)?

P.S is there a way to embed images in this forum?

"P.S is there a way to embed images in this forum?"

Not that I know of. You have to attach them as files.

once you attach them as a file, theres a 'place inline' button.

steve, i'll email you a button.