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Finding parts/getting in over my head?
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Finding parts/getting in over my head?

by Oblivion on Thu Sep 06, 2007 4:49 pm

I'm jsut getting into electronics after a long time away. I heard about Mitch Altman's Brain Machine via 2600.com and recently bought and built a miniPOV kit (great kit and instructions! It worked on the first go and I'm basically a full newb).

Since I need the resistors and caps to make the brain machine anyway, I was thinking of buying in bulk online since i don't like supporting RadioSuck ($1 for 5 resistors, or $1 for 100?). The problem with that is I'd end up paying more in shipping than the parts are worth - even at RS.

So then I came up with the brilliant idea of ordering all of the components for a MIDIsense unit and just ordering the PCB from LadyAda - not that I want to avoid giving her the full $50 for a kit, but b/c I want to maximize my order from DigiKey or whoever.

Anyway, I've built a shopping list on DigiKey for the parts I need for the Brain Machine as well as the MIDIsense Basic and Resistive kits. But I've run across a few sourcing problem.

1) On the Base parts list, "IC1" is a 5V Power Regulator w/ DigiKey P/N LM78L05CT. However searching that number comes up blank. If I leave off the "CT," on the other hand, I'm presented with 12 different options and I don't know which I'd want. Any guidance?

2) Part "XTL1," an 8.00MHz Ceramic Oscillator w/ P/N Abracon AWCR-8.00MD is only available in lots of 1,000 :shock: What would a substitute DigiKey P/N be?

3) Both LMC6482 and LMC6484 come in many flavors, I'm guessing different form factors for various mounting styles - and perhaps other differences. Specifically which ones am I looking for?

4) The description/instructions for the MIDIsense kit says it comes with one light sensor, but I don't see that on the parts list anywhere. What P/N would that be from DigiKey? And what size resistor would go with that then?

5) While I'm stocking up on odds and ends (buying 200 packs of seemingly common resistors and capacitors 10 at a crack), are there any other common, cheap parts I should throw in my cart?

I know that's a lot of questions, which lead me to ask the one in the subject line. Am I getting in over my head? Anyway, if you can help with any or all of those questions, I would be most grateful.

Thank you. And thanks for the great projects.
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by Oblivion on Thu Sep 06, 2007 5:20 pm

i dont really have time to research the parts for you, but if you order them and they fit the PCB then they're fine. lead-free isnt essential.
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by Oblivion on Thu Sep 06, 2007 5:29 pm

Ok, that's weird, my last post seems to have been edited instead of replied. . .

Just for the record, I HAD said:

Ok, I'm trying to do some more research to answer my own questions.

1) Is this an acceptable substitute for the 5V Regulator? LM78L05ACZFS-ND

2) Is this an acceptable substitute for the resonator? X905-ND

3) I figured out I want the DIP8/14 versions of the LMC chips, yes? And lead or no-lead (NoPB) is up to me, correct?

Thanks for any guidance.


One thing I'm still confused on is that there's a LMC6482IN-ND and a LMC6482AIN-ND. I can't figure out what the "A" means in that second model number. I might be worrying too much.
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by adafruit on Thu Sep 06, 2007 5:41 pm

have you considered reading the datasheet? ;)

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by Oblivion on Thu Sep 06, 2007 5:52 pm

I read it, but I don't understand it ;)

The differences I see are:

Vos 0.750 mV/1.35max for the A model and 3.0 mV/3.7 max for the non-A

There are also slight differences in CMRR, +PSRR, -PSRR, in the Av section of the sheet, etc., etc.

I don't know what these mean, or if they're significant.

So maybe I'm answering my main question. In over my head a bit. But that's how we learn, right?

I'll keep trying.
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by adafruit on Thu Sep 06, 2007 6:19 pm

it probably doesnt matter in your case which one you get

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by Oblivion on Thu Sep 06, 2007 8:20 pm

Thanks Ladyada. And at the price, I COULD just get them both just in case. Like I said, I was probably over thinking things.
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Please be positive and constructive with your questions and comments.