Diode assistance

[HKJ]

Hi, I was confused by the same point. The rebels I tend to use are not rated for reverse bias at all, AFAIK. Which LEDs have such a high (5 volt) reverse voltage bias rating?

All the Cree data sheets I have looked in specify it. I have also seen it in many 5 mm led data sheets.

Even led that are not specified for reverse voltage might be able to take it and a unspecified polarity protection is better than no protection.

 

[Justin Case]

AMC7135 Datasheet, top of page one, features: "No external component required"

That datasheet statement appears to be for the Jan 2006 version. Check a later datasheet version, such as Oct 2007, P. 4, "Output Capacitor Co and PCB Layout".

 

[HKJ]

That datasheet statement appears to be for the Jan 2006 version. Check a later datasheet version, such as Oct 2007, P. 4, "Output Capacitor Co and PCB Layout".

You are correct, they have obvious found some instability issues in the chip and changed the data sheet to include two capacitors.
But when searching for the datasheet, it is often the old one that is found (Like I did) and then the circuit is made without the capacitors.

 

[Illum]

AMC7135 Datasheet, top of page one, features: "No external component required"

hmm, www.micro-bridge.com/data/ADD/AMC7135.pdf appears to be down, http://www.e-neon.ru/user_img/catalog_datasheets/amc7135_d.pdf has markings for caps, but oh well

saabluster, have you found the diodes you were looking for?
I have a few diodes laying around, 1N4148, 1N4001, N4004, 1N4007, 1N5817, 1N5818, 1N5822...off the top of my head, if you need any I'll send some over free of charge

 

[saabluster]

That datasheet statement appears to be for the Jan 2006 version. Check a later datasheet version, such as Oct 2007, P. 4, "Output Capacitor Co and PCB Layout".

Good catch!

hmm, www.micro-bridge.com/data/ADD/AMC7135.pdf appears to be down, http://www.e-neon.ru/user_img/catalog_datasheets/amc7135_d.pdf has markings for caps, but oh well

saabluster, have you found the diodes you were looking for?
I have a few diodes laying around, 1N4148, 1N4001, N4004, 1N4007, 1N5817, 1N5818, 1N5822...off the top of my head, if you need any I'll send some over free of charge

Yes I think I am ok on the diode front. Thanks a bunch for the offer though.:thumbsup: Now I'm more concerned with the need for capacitors. Thanks for digging up that datasheet. My leads are about 3-4cm and are not on the same board as the LEDs so it seems like I will need some caps. :ohgeez: My prototype light engines seem to work fine without them. What effect do the caps have? I know there are different types of caps even at the same given values but what is best? I imagine some are inherently more reliable than others. I want the best I can get. Thanks again!

 

[saabluster]

OK I found some caps but thought I'd run these by you guys first. The only thing is I am unsure of whether or not the voltage rating matters much or not. Here it is. Thanks.

 

[uk_caver]

It might be more convenient using SMD capacitors.
The lowest voltage rating that Farnell seem to have for 1206 case 1u capacitors seems to be 10V, which should be fine for pretty much any normal 7135 application.

I'm in the middle of making some little underground photography lights using 7135s, and with some 1206 case 1u capacitors, it's fairly easy to solder them onto the KD/DX driver boards (shown I and O for input and output)

Thumbs-up to Illum and Justin for the capacitor/datasheet information.
Having an old copy of the datasheet myself, I hadn't realised that the usage recommendations had changed.

 

[kramer5150]

I hope I'm not trying your patience but I'm unsure what I am supposed to be looking at at that link. I was hoping for some guidance on how to pick a specific diode to use in the circuit. I am actually removing all the 7135s off their boards and using my own setup. Each light will use two 7135s but each board of four chips(1400mA version) only comes with one diode. That means if I want to use all my chips I need to buy more diodes. Seems to me like one of those things where probably a thousand different types would do the job but I really don't know. I like to buy from Mouser since they are only about 50 miles from me. Will just any old diode do? Thanks again.

Sorry for not replying earlier.... Prior to this thread I (like the OP) did not know the details, thanks all for this discussion.
FWIW, the Diodes are D1 and D2 in this pic. Looks like others have provided you with the info you need though. +1 on the rev polarity protection if you marketing a product.

 

[saabluster]

It might be more convenient using SMD capacitors.
The lowest voltage rating that Farnell seem to have for 1206 case 1u capacitors seems to be 10V, which should be fine for pretty much any normal 7135 application.

I went with the one with leads as I am not utilizing the boards. I am demounting the chips. So would the ones I linked to with 35V listed not work? Is the voltage too high?