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Teach in 2014 - Raspberry Pi series -...

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theduffers
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Username: theduffers

Post Number: 1
Registered: 12-2013

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Posted on Sunday, 22 December, 2013 - 03:15 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I am a beginner so apologies if I appear a bit thick...

I am trying to work through some of the examples in the above topic and am struggling to work out the diode that I should use as D1-D8 in the output driver on page 42. (December 2013 issue)

I am slowly learning but when trying to find a diode there are thousands to choose from and not knowing what properties are essential is difficult.

If there is a generic type of diode i should use I can then order those. Any suggestion for components to have in my bits box would also be useful.

Thanks in advance. I seriously have a lot to learn. Not wrong with the deepend:-)
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arw
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Username: arw

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Registered: 04-2005

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Posted on Monday, 23 December, 2013 - 05:35 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Welcome aboard!

I couldn't quite make the diodes out from the photo on page 43 but they look like standard glass silicon diodes, so they're probably a 1N4148. It's the ULN2803 that's doing all the hard work so the inputs (= current passing through the diodes) are logic level signals only.

An alternative to try would be the 1N4001, the standard junkbox silicon rectifier.

Unless anyone else can help, I'll try to get the definitive word from the authors in the meantime, so please watch this space. I'm sorry for the omission.

-- Alan W / EPE
Alan W -- EPE

More online resources at www.epemag.net
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theduffers
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Posted on Tuesday, 24 December, 2013 - 01:11 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thanks for the quick answer...Appreciated

Regards
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mike_tooley
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Username: mike_tooley

Post Number: 23
Registered: 10-2010

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Posted on Wednesday, 01 January, 2014 - 07:34 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi there! Please don't apologize for being a 'newbie' - we were all at that stage sometime! Sorry that we didn't specify the diode types but, as Alan suggested almost any silicon diode would work OK. The best type to use would be a general purpose low-power diode like the 1N4148 or 1N914. It's worth having a few of thee around as they are used in a great number of circuit applications and only cost a few pence each. In fact, the circuit will work OK without the diodes (just replace them with a short circuit) but they are there to offer the Raspberry Pi some protection in the unlikely event that one or more of the driver transistors fail or are mis-connected. Good luck with your Raspberry Pi projects and do get back to us if you need any more help.

Happy New Year!
--
Mike Tooley - EPE Teach-In 2014

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