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LNMP Finishing touches - wiring the battery pack and enclosing

post #1 of 66
11/16/12 at 6:01am
Thread Starter 

Hi guys,

 

I'm ready to wire the battery packs together, but I'm unsure of how to do this, so before I solder, I wanted to be sure it is correct.

From Tangent's instructions (http://tangentsoft.net/elec/lnmp/steps.html), he writes:

"you’ll have to tie the center pair to each other directly; the board has no provision for this."

 

I'm unsure of what this means. So, here are the two ideas I came up with this morning:

 

A: 

http://www.spookyaudio.com/spooky/batt3.jpg

 

B:

http://www.spookyaudio.com/spooky/batt4.jpg

 

What do you guys think?

 

Also, now that I have it, I'm unsure about the enclosure I bought. 

Here, (http://tangentsoft.net/elec/lnmp/pguide.html) 

Tangent says:

Don’t use a plastic case, because RFI getting into the circuit will wreck your measurements. With 60 dB gain, this is a very real possibility."

 

I thought bought the recommended case, but with the reading and re-re-re reading of the instructions, realized that I got the version with plastic front and end panels, not metal.

 

http://www.digikey.com/product-detail/en/1455L1202/HM895-ND/1090707

 

Am I now with a spare case? Do I need to get the one that is completely metal?

 

Thanks so much!

-s


Edited by saraengelstad - 11/16/12 at 6:02am
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post #2 of 66
11/16/12 at 3:56pm

You want the second arrangement. This is called a series connection: the positive lead from the lower battery holder connects to the negative of the upper battery holder. That leaves the positive lead of the upper connector free for BATT+ and the negative of the lower for BATT-.

 

As for the case, it's less than ideal. It's not a setup for certain disaster. It's more like choosing not to wear a seatbelt: you're choosing to do without a measure of protection.

 

I'm not sure which way I'd jump in that situation.

 

Replacement end panels and bezels are available, but you generally have to buy them in packs of 10 each.  So, a new case ends up cheaper.

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post #3 of 66
11/27/12 at 6:35am
Thread Starter 

Well, I'll take my chances with the plastic, I'm terrible at casing, so likely I'll make a mess of it the first time through and have to retry anyway..

Next question:

 

What kind of wire should I use to connect the jacks, etc. to the board?

 

I have some small guage cardas wire lying around, but I was thinking, since I need to place an order with these guys anyway, something like this Belden wire from handmade:

http://www.hndme.com/productcart/pc/viewCategories.asp?idCategory=19

 

But what guage, and is this even appropriate stuff?

 

Thanks again,

 

-s

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post #4 of 66
11/28/12 at 5:14am

I believe the holes in the LNMP will accept up to 22 ga wire. I like stranded myself.

 

As for Teflon-coated wire, its main practical advantage comes in when the equipment will be exposed to the elements. Salt air, high humidity, etc. Navies love the stuff. But, it requires the better sort of wire strippers to cut, and it doesn't actually buy much in practicality other than the durability.

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post #5 of 66
11/28/12 at 7:22am
Thread Starter 
So, where is a good place to get good wire.. Is random radio shack stranded decent? Maybe, i should ask: where do you get yours?

Also, when you say, 'up to', do you mean it will accept smaller, like, 30 ga or larger, like, 14 or 18? Also, i understand that for general power supply, 18 is recommended?

Thanks!
S
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post #6 of 66
11/28/12 at 7:25am
Thread Starter 
I think I know: more or bigger wire = more impedance, correct? So do I, in general, want to go with smaller (higher numbers) guage wires?
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post #7 of 66
11/28/12 at 9:20am
Quote:
Maybe, i should ask: where do you get yours?

 

First, I forgot one advantage of Teflon coated wire: Teflon's melting point is way above normal soldering temperatures, so it can give a nicer finished look, if you're prone to making joints slowly.

 

Regular PVC insulation does melt at soldering temps, and when it does, it shrinks back away from the joint.  So, not only may it expose some wire even though you started out with the insulation butted right up against the board, if you keep the iron on the joint it will then start to blacken. AFAIK, PVC-clad wire is all Radio Shack carries. (Ignoring the lacquer-clad magnet wire.)

 

But, there is another wire type that has this same benefit, and it's priced between regular PVC and Teflon: irradiated PVC. I use Alpha Wire from Mouser.

 

Quote:
bigger wire = more impedance, correct?

 

 

Exactly backwards. Both resistance and inductance go down as wire size increases.


Edited by tangent - 11/28/12 at 9:27am
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post #8 of 66
11/28/12 at 12:57pm
Thread Starter 
Awesome, thanks!
Here's another one, what temp should i solder components with? I'm using 600 degrees F now. To hot?

I like the Teflon because i have a programmable iron that can get really hot to tin the Teflon wires.
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post #9 of 66
11/28/12 at 3:10pm

I think you need to watch several of my videos.

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post #10 of 66
11/28/12 at 4:09pm
Thread Starter 
I've watched them- several times each. Thank you for them- they rock! But everyone talks wattage and my iron you set specific degrees.
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post #11 of 66
11/29/12 at 8:27am

You're sure I never cover soldering temperature?

 

The rule is, you look at the datasheet of the parts involved, and set the iron at that temp or lower.

 

If you can't be bothered to do the checking, 300C works for most small electronics parts.

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post #12 of 66
11/29/12 at 8:58am
Quote:

Originally Posted by tangent View Post

SNIP...

 

As for the case, it's less than ideal. It's not a setup for certain disaster. It's more like choosing not to wear a seatbelt: you're choosing to do without a measure of protection.

 

I'm not sure which way I'd jump in that situation.

 

Replacement end panels and bezels are available, but you generally have to buy them in packs of 10 each.  So, a new case ends up cheaper.

would some of the aluminum tape used for duct work on the back of the plastic panels work as a degree of shielding instead of buying new panels?  just wondering...

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post #13 of 66
11/29/12 at 4:45pm
Thread Starter 

Well, 300C is around, what, 570, so 600 is pretty close. I found it by experimentation. Thanks! I was really lost on the whole wire business, and relying on highest price wasn't really going  to get me where I wanted to go.

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post #14 of 66
11/29/12 at 8:30pm
Quote:
Originally Posted by vixr View Post

would some of the aluminum tape used for duct work on the back of the plastic panels work as a degree of shielding instead of buying new panels?  just wondering...

 

You'd have to tie it into the case somehow.  Maybe the panel components would do that, but you'd want to check it with a continuity meter at least. I believe the specified BNC jack is isolated from its metal body, for example, so you couldn't count on it to tie the front panel to ground, or V-, or whatever you choose for the case shield connection.

 

You'd still have gaps along the edges, and where the stuff tears after you wrench the mounting nuts down, and...

 

It'll certainly help. But, don't count on halfhearted trickery to get your project past an FCC emissions test. :)


Edited by tangent - 11/29/12 at 8:32pm
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post #15 of 66
11/30/12 at 5:20am

Understood...thank you sir.

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