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Question about using alternate high-current OI
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Author:  Jakenbake [ 23.07.2009 23:36 ]
Post subject:  Question about using alternate high-current OI

First time poster here. I found this mod while researching the use of an OI in place of a reed relay and after looking about for a little bit I quickly realized this site is awesome! So many great ideas and extremely helpful walkthroughs. You guys have a great thing going here!

Anyway, this is exactly what I've been looking to do and originally tried using a reed relay but realized quickly that the noise generated by it is a bit on the annoying side. The problem I face is I'm going to be running 32 leds and need an OI with at least a contact rating of an amp but had a hard time finding one. However I did find one capable of handling 2.5A but I'm unsure about how to wire it, or even if it'll work for this application. Below is a link to the datasheet for said OI. If anyone can tell me A) if this [i]will[i] work and if so B) how to wire it for this project. Thanks!

It is in the AQV25 series (second page, second down)
http://media.digikey.com/pdf/Data%20Sheets/Panasonic%20Electric%20Works%20PDFs/PhotoMOS%20hookup%20diagram.pdf

Author:  japala [ 24.07.2009 00:53 ]
Post subject:  Re: Question about using alternate high-current OI

Hmm... from just looking the drawings it could work. On the other hand you could use a regular OI that I used in the article and control a power transistor that would then drive the leds. There are tons of possible transistors that you could use:

http://us.st.com/stonline/books/pdf/docs/4133.pdf
http://eu.st.com/stonline/books/pdf/docs/4103.pdf
http://mht.mht.bme.hu/~beged/elakszim/bd249.pdf
http://www.onsemi.com/pub/Collateral/2N6284-D.PDF

If that AQV25 is easy to get, just try it first. :)

Author:  Jakenbake [ 24.07.2009 01:36 ]
Post subject:  Re: Question about using alternate high-current OI

Thanks for the quick reply Japala! I was considering using a power transistor but ultimately I would like to keep this circuit as simple as possible. I guess I'm just unsure about the wiring for this OI. I'm new to reading electrical diagrams and am wondering if pins 5 and 6 are just reversed when comparing the OI you used and the OI I found. If that's the case, and I'm understanding this correctly, pin 5 would be connected to the cap and then grounded. Pin 6 would be my load input and pin 4 would still be directly grounded. I'm opting out of using the power LED :)

Let me know if that seems right to you. I've already ordered the AQV25 from digi for about 5 bucks so if you agree that just switching pin 5 for 6 in your diagram would work, once it gets here I'll try it out and let you know how it works. Thanks again!

Author:  japala [ 24.07.2009 01:56 ]
Post subject:  Re: Question about using alternate high-current OI

Center diagram with the pin 6 being input and 5 connected to the ground seems more likely to be the correct one. It is just that the cap trick may not work with this kind of mos chip. There is no "base" on the internal transistor to connect the capacitor to. Not the way as we can find it in a regular OI. Because of this I'm not sure if this could work at all... I believe that you may need to resort to the OI + power transistor trick in the end. Sorry :(

Author:  Jakenbake [ 24.07.2009 06:42 ]
Post subject:  Re: Question about using alternate high-current OI

Well damn.. I was hoping you wouldn't say that but that's kinda what I figured.. So about this whole transistor business: obviously the mobo HDD header runs to the input side of the OI.. And after that I have no clue.. Like I've said, I'm fairly new when it comes to actual electrical components. Now I know how other people feel when I start talking about computer hardware =/

So where would I connect the collector, emitter and base pins to? That's where I run into a wall. And would the OI still be wired the same as far as the cap and everything?

I apologize for being so ignorant when it comes to such things. I guess that's why I was so very happy to find a site like this :)

Author:  japala [ 24.07.2009 16:16 ]
Post subject:  Re: Question about using alternate high-current OI

I would imagine something like this working ok. Only thing is that I'm not sure if you need a darlington power transistor for this to make it more sensitive to the current coming to the base. Don't think it would need that but... something for you to test out. :)

Attachments:
transistor.png
transistor.png [ 15.62 KiB | Viewed 52171 times ]

Author:  Jakenbake [ 25.07.2009 00:27 ]
Post subject:  Re: Question about using alternate high-current OI

Well you have been extremely helpful. When I look at that diagram it actually makes a strange kind of sense now. I think I'm in the end going to use both your mod with the fading on/off and have a switch for another circuit for simply just flashing using the AQV25 OI I already bought.

But I guess now my only question remaining is about the transistor, or rather how to tell if it'll work for this project. I'm confused because in the electrical characteristics of those transistors you linked to all say they have a minimum of 60V+ for the collector-emitter sustaining voltage. I have no idea what that means.. As I'm sure you're aware the voltage I'll be running to the transistor collector pin is going to be either 5V or 12V. If that doesn't matter, thank you in advance for taking the time to read this and answering my naive questions :)

Author:  japala [ 25.07.2009 00:36 ]
Post subject:  Re: Question about using alternate high-current OI

If you look at the Absolute maximun rating tables for the transistors they have the same values. It just indicates that with the certain current flowing through they, can handle the indicated voltage. I'm not an expert when it comes to reading the specs of these high power transistors but it seems they function much like the low voltage signal transistors. They just can dissipate more heat, thus are able to handle larger loads. Only question is that if that ability makes them less sensitive. Meaning that they need more juice to the base to make them fully conductive. That potentiometer etc. addition to the circuit should allow you to tweak the signal strength.

Author:  Jakenbake [ 25.07.2009 00:41 ]
Post subject:  Re: Question about using alternate high-current OI

Thank you so much for all your help! I will let you know how the circuit works once I get all the parts I need. If you lived in Denver, Colorado I'd offer to take you out for a drink or two :P

Author:  japala [ 25.07.2009 01:44 ]
Post subject:  Re: Question about using alternate high-current OI

Np, happy to help if I can. :)

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