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LNMP Finishing touches - wiring the battery pack and enclosing - Page 2

post #16 of 66
Thread Starter 

Update time, guys! This first post is a backgrounder on me so it becomes clear to the reader why I'm so totally clueless sometimes. You may want to skip to the next post.

 

I've built literally hundreds of projects since I learned to solder six years ago and had a wonderful time thanks in no small part to Tangent's shop and tutorial videos (http://www.tangentsoft.net/elec/movies/) and the DIY audio community. I've done this because for me, it's super fun. Some people knit, I find components and solder them to boards. Through-hole, SMD, it doesn't matter, I'm great at it and I can happily fritter away hours doing it. But the fun ends when the components are stuck to the board.  Unfortunately I am now forced to expand my skills outside my comfort zone again, like when I learned to solder the first time. 

 

The ugly truth is, I don't know how to wire panel components. Tangent's article notwithstanding. (http://tangentsoft.net/audio/pancomp.html) Not only that, I'm terrified (or I was until yesterday morning) of drilling holes in anything smaller than a loudspeaker. I've been unreasonably unwilling to just get over it and learn what I need to learn so I can move forward. Now those days are over because I am no longer able to pretend that I don't have boxes of unfinished projects - literally - enough to fill a suitcase... I know this because at various times, I have kept them in one of my suitcases.

 

Kids, That's A Lot of CMOYs and PIMETAs and DACs and power supplies and tube amps and other miscellany, like pink noise generators and buffers. Too many.

 

Although I took up this hobby to learn things, I have been so afraid of failure when it comes to wiring panel components, that I talked myself into doing that part and everything after that part 'later'. Waaaayyyyy later, apparently. 

 

I understand the concept of a DPDT swtich perfectly. I can draw the drawings. But, on some subjects for whatever reason, and this is not an unknown phenomenon for me, I can have difficulty applying even simple abstract concepts to physical objects. Drop a toggle in the palm of my hand, and I just gawk at it. 

 

Then, this year, I had an accidental breakthrough. It was the LNMP. I've got all these damned power supplies that have been built and rebuilt and obsessed over for years lying around. They're beautiful! I could continue my streak of never finishing anything if I built an LNMP TO TEST THEM, RIGHT? Brilliant. That worked okay until I was done with the board. Then I was in a corner. I had to finish it. I'd also cooked up this idea that building the LNMP would teach me to use my oscilloscope... The really nice one I paid a bunch of money for back when my children were still in diapers.  But not until it gets cased. And they are in the public school system already. All I've ever done with the scope was use it to find the signal shapes output by my Velleman signal generator kit (caseless). That was so long ago I haven't the foggiest idea how I did it. And the signal generator is in one of the boxes with all the other lost souls.

post #17 of 66
Thread Starter 

So, here's the real technical post. Yesterday I drilled my LNMP's metal end panels with some step drill bits I bought years ago specifically for this purpose. It went beautifully!

Look:

 

 

And the inside (ignore that blue stuff, it's not really there. Not all learning experiences teach you that what you are doing is a good idea so I'm just going to pretend I didn't try that 'great idea'):

 

 

 

 

 

Sadly, heady with the rush of success, I went and made a largish mistake on the back panel: Notice the empty hole? 

This means that, on Tuesday, when my pack of ten new end panels shows, up, I'll have the opportunity to do it again, and record how I did it so I can share it with anyone who might be as freaked out as I was about this 'drilling holes in metal' business...

 

 


Edited by saraengelstad - 2/9/13 at 12:41pm
post #18 of 66
Thread Starter 

And here's the actual question that caused me to bust out the camera and the laptop: Wiring the BNC connectors. I'm unclear on how to figure out which is the ground using my meter, and the data sheets were, to me, unhelpful.

 

Because when I'm being blockheaded about something I need a picture, AND a sign, AND a guy in a lab coat pointing. So, if anyone would be so kind as to:

 

A. Verify my suspicion that the outside pin is Ground.

 

and/or 

 

B. Explain to me, in painfully simplistic terms, how to figure out the answer for myself, and for the benefit of anyone else who might be kinda lost in what seems to be home turf for everyone else. I dunno, maybe you guys all had an electronics class offered at your high school. I didn't. I took all the sciences they offered, but nothing in chem or in physics prepared me for this problem.

 

Thanks all! wink_face.gif

-s 

post #19 of 66
Quote:
Originally Posted by saraengelstad View Post

I drilled my LNMP's metal end panels with some step drill bits

 

I hope you used a padded bench vise.

 

You can get away without the vise on aluminum panels this thin, but you risk getting cut if you're holding the panel in one hand and drilling with the other, and the drill bit binds up. The panel then turns into a blunt propeller. Cuts happen because of the sharpened edges on the holes you did prior to the incident. :)

 

(Ask me how I know.)

 

(No not really. You've guessed already.)

 

You can get away without the padding if your vise has smooth faces and you're not too picky about marring the panels.

 

Padding doesn't have to be anything special. I use a 8" square of denim from old cut up jeans, draped into a U shape in the vise jaws just before I close the jaws on the panel. Other people make them from a 1/2" - 3/4" thick hardwood plank, replacing the serrated metal jaws that come with the vise. Don't have any hardwood laying around? Maybe you have one too many cutting boards you'd be willing to trim a couple of 1" strips off of? There you go. You can use a cheap plastic cutting board here, too, instead of hardwood.

 

 

Quote:
I'm unclear on how to figure out which is the ground using my meter

 

The outer shell is ground, and the center pin is the signal.

 

(It doesn't technically have to be that way, but there are at least two good reasons for it to be that way.)

 

So the ground is the yellow wire. (Kidding.)

post #20 of 66
Quote:
Originally Posted by saraengelstad View Post

 

Sadly, heady with the rush of success, I went and made a largish mistake on the back panel: Notice the empty hole? 

This means that, on Tuesday, when my pack of ten new end panels shows, up, I'll have the opportunity to do it again, and record how I did it so I can share it with anyone who might be as freaked out as I was about this 'drilling holes in metal' business...

I hate to tell you this now, but maybe it will help in the future.  Next time, just call Hammond Mfg.  Tell the secretary/receptionist that answers the phone that you messed up drilling holes on the endplates of their Hammond #whatever.  She will send you a couple of new endplates in the mail - free.biggrin.gif

 

As for the rest, Tangent has taught me more than he'll ever know.  However, I simply get a block of wood, use wood screws in the endplate mounting holes to mount the endplates onto the wood, and everything is absolutely locked in place.  Then all you have to worry about is clamping the wood, not the endplate.  Yeah, you drill holes in the wood, but who cares?  Usually a nice piece of 1x4 finish pine is all you need, but I've even used pieces of 2x4 studs when I didn't have anything else. wink.gif

http://www.diyforums.org/MAX/MAXcasework.php

 

EDIT: That link shows drilling endplates with a handheld drill, but the wood can be easily clamped into a drill press, which is how I do it nowadays. 


Edited by tomb - 2/9/13 at 3:32pm
post #21 of 66
Thread Starter 

Thank you! Well, I've got two things up first.

 

A. The wire. 

Hahahahaha, yeah, I get it, and I laughed. There is actually a (possibly well reasoned?) line of thought behind why I used the same color wire - I am pretty sure that each wire color is all I have of a particular gauge: 22, 21.5, 23, etc. So, I was a little cautious, especially on the BNC wiring, about using two different gauges. We are building a very, very sensitive instrument here, are we not? So I fell on the blade of safety and used the same color. Once I knew which was which, then I went with my convention of marking with heatshrink, like so:

 

 

 

 

So, I'm very interested to hear the pros and cons of doing it this way.

 

B. This is the setup I used: Part of my Dremel tabletop vise,  and my table, and my drill:

 

I clamped the thing down as tightly as I could, I marked the center and then the spot where I wanted the hole with my center punch as below.......

 

 

And then (not holding a camera in one hand when I really drilled it), centered the drill in the indentation made by the punch and slowly drilled all the way through. This, delightfully, covered my my kitchen floor with metal shavings.  YAY!

 

 

 

 

 

I figured that if the case were that I asked my father if this would work, he'd say "Yeah, that's fine, be careful", so I went with it. I know my dad. And he can be.... confident. But it worked!

 

So, please, tell me, how unsafe, compared to the advice you guys gave me for the retread on Tuesday, was I?

 

And TomB; free end panels. You're killin' me! Oh well. It's okay. This will not be the only time I get ahead of myself and have to take a mulligan. Of course, I guess I'd have to have a few more 1455s shipped..... AH!!!!

 

More to come, shortly, I was busy while I was away. I have a somewhat completed LNMP to show off.


Edited by saraengelstad - 2/9/13 at 4:37pm
post #22 of 66
Thread Starter 

Notice the demo piece? Veneered.... did it years ago but was too afraid to drill it.....

 

I have a dremel drill press, but the dremel won't take my big step bits. 

post #23 of 66

No problem.  It's a good solution the first time out.  I especially like the idea of the "glued-on" template. wink.gif  And unless I'm mistaken with the photo, it appears that you have a wood backing to protect the backside of the drilled hole.  Those are the essentials in drilling endplates properly.  My only thought is that there's no reason you can't have 1-2 inches of wood as a backing.  What that gives you is enough wood to actually "mount" the endplate with screws, meaning it never moves from the wood, no way, no how.  Moreover, it means that a vise or drill press vise works quite well because you can clamp it horizontally - which means there is never any need to touch the surface of the endplate.  That way, you know the only thing affecting the surface finish is your drilling, nothing more.

 

As for Hammond, they are truly good folks in my experience and take a beating around here unecessarily sometimes because people think their product is below boutique-grade (I don't agree).wink.gif  And I don't mean to imply that you can call them up and simply ask for new endplates.  However, if you are completely honest - tell them that you purchased a complete Hammond case with endplates, etc., and then describe that you screwed the pooch, so to speak, with your drilling.  Then describe that your alternative is the huge expense of ordering 10 endplates - what I'm saying is that they will listen and respond.  Under different circumstances, I can't guarantee anything - people wanting to take advantage: BEWARE. mad.gif

 

EDIT: OK, I didn't see the last post - so maybe those were wood blanks that you used for testing.  Still, the wood could've provided decent backing.


Edited by tomb - 2/9/13 at 4:44pm
post #24 of 66

Your drilling method looks okay, except that I'd clamp the work piece a bit closer to the expected hole location, so as to minimize panel flex. Not too close, because we're not exactly dealing with machinists' X-Y tables here. I'd give about 1/8" clearance, to account for hand-drill sloppiness and bit wandering.

 

Pro tip for metal shavings: put a kitchen trash can (~13 gallon, lidless) right underneath the corner of that table. Try to find one just tall enough to fit, so you don't have to be too careful about ensuring the shavings drop straight down. I use an 8-ish gallon one in my workshop, and occasionally miss.

post #25 of 66

Sounds like we're recommending competing methods, so I'll bow out for now.smily_headphones1.gif

post #26 of 66
Thread Starter 

Nothing about my crazy wires? OK guys, here's how I put the thing together. For the short term, instead of messing with the gain switch, I jumpered it (seen below). I put as much as could be grouped together on the bottom - the LED and Battery connections:

 

 

 

 

 

Thoughts?

post #27 of 66
Thread Starter 

Then I slid it into the case, hooked up the stuff that had bottom-board connections... And with the botttom-board stuff out of the way, started hooking up the panel wires, which all connect on the top of the board.,,,

 

 

Yes. I used a dremel to cut sections of the board out around where the BNC connectors are to try and fit it into a smaller case, but ultimately failed and had to use a larger case anyway/ Dang. 

 

That's not going to screw up the whole deal, right?????

 

 

-

 

Then I slid the lid on and plugged it in: the left LED indicates it is working on battery.

 

 

 

 

And the right-hand LED is flashing, indicating my brand-new batteries are charging.

 

 

Here's the bad casing work on the back, I'll show off how I rectify that next week.

 

 

post #28 of 66
Quote:
Originally Posted by tomb View Post

Sounds like we're recommending competing methods, so I'll bow out for now.smily_headphones1.gif

 

Competing? No, just different.

 

Quote:
Originally Posted by saraengelstad View Post

Nothing about my crazy wires?

 

I can't really praise or criticize it. It's a decent system. Not my preferred method, obviously, but it works, and more importantly than that on a DIY project, it works for you.

 

Quote:
Originally Posted by saraengelstad View Post

Yes. I used a dremel to cut sections of the board out around where the BNC connectors are to try and fit it into a smaller case, but ultimately failed and had to use a larger case anyway/ Dang. 

 

That's not going to screw up the whole deal, right?????

 

They look too shallow to have hit anything, and it's just a 2-layer board, so if you don't see a nicked trace, you didn't nick one. :)

 

 

Quote:
Here's the bad casing work on the back

 

You know, I wonder if you couldn't do something creative with it. Turn a mistake into a feature, kind of thing. Maybe JB Weld a nickel in there?


Edited by tangent - 2/9/13 at 8:33pm
post #29 of 66
Thread Starter 
Quote:
Originally Posted by tangent View Post

They look too shallow to have hit anything, and it's just a 2-layer board, so if you don't see a nicked trace, you didn't nick one. :)

 I was pretty careful, and examined the board under a bright light to make sure, so I think I'm okay.

 

 

Quote:

You know, I wonder if you couldn't do something creative with it. Turn a mistake into a feature, kind of thing. Maybe JB Weld a nickel in there?

 

Now, that's a wonderful idea! I'll have to let that roll around in my brain pain for a while and see what comes out. I dunno what JB Weld is, but I'm sure the internets can tell me :)

 

On to another step: testing. I'm on step 8, and I have to give up and admit that I don't know where to place my probe to find "V-".

Different places that look likely according the the schematic and board layouts give me different readings, which I seriously hope is due to me not understanding  V-.

 

Step 7 testing seemed to go as expected, with the exception of measuring DC volts from V- to S3B while toggling the power switch. I get the battery voltage when PLED is on, but in the other position, which I read to mean, with the power switch toggled the other way, I don't immediately get nothing in the other position, rather, it slowly ratchets down to nothing. I take this to indicate that the cap is discharging, but now that I can't get through step 8, I'm not so confident. 

 

Tangent, can you drop me some tips here?

post #30 of 66
Thread Starter 

My R13 is wrong.

 

Ah, I think I made a breakthrough here while reviewing the LNMP documentation for the nth time.

 

I think I have R13 incorrect. I installed a 1K resistor, which I think assumes that the user has either:

12V adaptor, with 700 mAh cells. The calculation as I work it gives the result .15 OR

16V adaptor with 700 mAh cells, the calculation as I work it gives .2

 

So the value from the schematic gives 1K for, what I assume is a likely blend of possibilities?

 

However, I have is an 18V supply and the AAA batteries they had at batteries plus are 850Ah.

 

My calculations with these values gives me the result 9.6, which diverges from the above values significantly.

 

This leads me to believe I should be using a much different value. I've got a handful of 9K1 and a load of 10K resistors. I'm leaning towards the 9.1 value, especially since the Parts Selection Guide for R13 states, "Lower is okay, especially if you mainly want the trickle charger to maintain the battery's charge" (See below)

 

http://tangentsoft.net/elec/lnmp/pguide.html

 

 

Before I pull the old resistor and put the new one on, anyone have any comments?

Thanks!

-s

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