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 Post subject: Not doing anything
PostPosted: 14.06.2008 12:25 
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Junior Modder
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So, made up the circuit today, one of those parallel experiment boards.

Everything is fine, all joints have been tested, correct resistor and a 47uF 16V electrolic is being used.

When I plug it all in, the led just flashes like it usually does, no fading or delay, just on/off flash like normal.

I tested the cap with a 9V battery, and watched the voltage drop normally with a multimeter.

What else can I test?


Thanks for any help.

edit: can post pictures if needed.


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PostPosted: 14.06.2008 14:03 
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Hmm, odd as you the first person that have this happen... I know there are suttle differences between the optocouplers from different manufacturers so perhaps in your chip there is no proper connection between the pin 6. and the internal phototransistor. Could you try another optocoupler from another manufacturer or model?

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 Post subject:
PostPosted: 14.06.2008 14:33 
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Junior Modder
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The optocoupler is a 4N25, so there wouldn't be a problem there, unless you were inferring that it could be a faulty chip?

And in case of a misunderstanding, I meant that I was using one of those boards with lots of copper strips along the bottom, rather than one of the plastic prototype boards covered in holes.

Will try a new chip if I can find one, contacted the store (only one that I could find that had them in the first place) and they only have one manufacturer, so it would be a while before anything happens, is there anything else that I could try in the meantime?


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PostPosted: 14.06.2008 18:48 
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At this point all I can say is to check the connections again and then once more. :) Especially now that you use the stripped veroboard, make sure that the cuts that you have made to the strips are not conducting.

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 Post subject:
PostPosted: 15.06.2008 03:28 
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Junior Modder
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I checked all the connections, all that are meant to be there are fine, and all the breaks are fine.

Image
Image
Image

Excuse me for asking, not trying to dispute your work. But how does the cap get charged in the first place? Its sitting on the base leg of the transistor, which explains the fading effect, but is it something to do with the phototransistor that puts voltage back through the base line into the cap?


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 Post subject:
PostPosted: 15.06.2008 03:33 
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Yes, that is the idea. I was quite surprised to find out it actually works like this as it didn't make any sense. I'm just glad that I happened to try it. :)

From the looks of it, you have built the board correctly. Because of this I think that it is the opto that is not working the way we are hoping for. Perhaps it doesn't have that pin 6 connected to the base at all...

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 Post subject:
PostPosted: 15.06.2008 03:59 
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Junior Modder
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Could it be that a subtle difference between a 4N25 and a 4N35 is this back-charging? The store has a 10-pack of 4N35 as another option. What are the other uses of these (not in a fading status led context)?


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 Post subject:
PostPosted: 15.06.2008 11:17 
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Well, you can separate things from each others electrically. Meaning that you can have high voltage parts on the other side and it can control for example something connected to an USB port on the other side. If the high voltage side gets a short circuit or something, it won't affect the USB port side as the only connection between them is an optical one.

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 Post subject:
PostPosted: 04.07.2008 04:40 
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Well, eventually got the chance to go back to the store and get some 4N35s.

Its working perfectly, looks awesome thanks for the idea.

Can't say I'm an expert at any of this, but when looking up datasheets, it claims that 4N35s are matched with 4N36 and 4N37. Maybe (just trying to think logically) the difference between the 4N2x and 4N3x is the polarity of the photodiode. Irrelevant anyway, its working.

So, planning to connect the other status light (P182) to the network card, an optoisolator will also be used there. But that still leaves me with 8 (plus the original 4N25) to play around with. Any vague ideas that are a little more of a challenge than the HDD eyez?


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 Post subject:
PostPosted: 06.07.2008 21:03 
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I used the same circuit on the original xbox to indicate hdd and network activity. Works great and doesn't need any alterations.

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 Post subject:
PostPosted: 09.07.2008 11:24 
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So if I wanted to use them as normal optoisolators, say just like a relay, would I just connect pins 4 adn 6?


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 Post subject:
PostPosted: 09.07.2008 11:41 
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Pins 4 and 5 then. 6 is not normally used for anything.

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