Muff's Modules & More

kjackman · Posted: Thu Jun 21, 2012 3:53 pm Post subject:

Hmm, maybe my wire was bad. It was like, 24 or 26 AWG I think - maybe even smaller - and it didn't seem to have too many strands (like, 7?) So maybe I'll have better luck with 22 AWG wire.

It was just a couple of connections on a non-synth project I finished recently, not like I wired up a mega-synth with the stuff. So I don't have a lot of experience to judge from yet.

Good to know.

kjackman · Posted: Thu Jun 21, 2012 3:57 pm Post subject:

kjackman · Posted: Thu Jun 21, 2012 4:15 pm Post subject:

Oh: One more interesting idea.

Twenty years ago, when I actually worked in the electronics industry as an assembly person and then in testing, we had some computerized test rigs set up. We had these special PCBs with spring-loaded test pins on them. We would set the PCB to be tested on top of these pins, which were arranged in a pattern to touch various pads on the bottom of the PCB. They always seemed to make good contact, and we tested dozens of boards a day this way.

They were something like this:

Pogo Pin Electronic Test Fixture

Why not build a board like that, where each test point touches a connection point? Screw the board down for a "permanent" connection. You could lift the PCB right off of it for maintenance if you ever needed to.

Of course, our test rigs only had maybe ten test points. This would need 120+. The spring tension might be pretty hard to overcome. Also, every single pad would have to be aligned PERFECTLY. And it would probably be pretty expensive.

But man, that would be a cool way to do it. Unscrew the PCB to remove it, and it's like it was never wired up in the first place. Put it back on, and WHAM! it's connected again. All it would take is a custom PCB, laid out using Ray's actual bottom layer as a starting point, which I can etch at home (although I'd need a pretty big bare board). I could route all the connections to a nice, neat set of double-row standard headers on the edge of the board, and plug the panel hardware into that.

Maybe I should find out just how expensive that would be, before dismissing it as "too expensive." It might still be worth the expense, if I can make it work...

Here's 100 pins for US$ 11.74 on eBay. That's ... not bad at all. Hmmm.... HMMMM....

Anyone tried this already? Is there a reason not to try this that I'm missing?

decaying.sine · Posted: Thu Jun 21, 2012 7:11 pm Post subject:

RossIngram · Posted: Fri Jun 22, 2012 9:48 am Post subject:

Has anyone tried using pigtail style connections for power and such, similar to PC power supplies? I'm getting ready to build a few MFOS modules and have been trying to work out the best power connection scheme. I don't want to directly solder power to the board, in case I want to rearrange modules. The daughterboard sounds decent, but that means mounting an additional board, which would be a little more of a pain than a pigtail. Or would a pigtail cause too much potential for the cable pulling out of the board?

kjackman · Posted: Sat Jun 23, 2012 4:29 pm Post subject:

Pigtail connectors can be quite sturdy. Many of the Molex connectors in PCs are of the locking variety.

For this particular Sound Lab Ultimate build, though, I plan to use a 6-position barrier strip:

It's quite easy to crimp spade-type connectors on the ends of the wires leading from the power supply board and from the module:

I use barrier strip jumpers to multiply the number of terminals available:

So with a 6-position barrier strip, I get two outputs each for +15, 0, and -15 volts. Sure, I only need one each for the MFOS board, but I'm pretty sure I'm going to add a chipamp and some speakers to the case in the near future - it'll make the Sound Lab so much more playable.

kjackman · Posted: Sat Jun 23, 2012 4:42 pm Post subject:

I decided today I'm NOT going to try using spring-loaded test pins to connect to all the terminal holes in the PCB. It's just more expense and hassle, for a pretty marginal benefit.

I think I'll just solder 24 AWG stranded wire directly into the underside of the PCB. I'll route the wires out in groups, through cable ties, to the 20-pin IDC housings I described earlier. If I need to rework the PCB for some reason, I'll carefully desolder the wires near the rework position, then put them back when rework is complete.

I'm also thinking about creating some custom pot chicklets for the panel pots to drastically simplify that part of the panel work. They're 16-mm Alpha pots with 2mm-wide "PCB" terminals (i.e., NOT solder terminals) that I bought for US 50 cents each from Futurlec some time ago. It's a real pain in the butt to solder wire to them. I've done it several times and gotten quite good at it, but I'm not happy with the results. It's not consistent, and I constantly worry about strain relief. Etching some custom pot chicklets might be a bit expensive, but it'll be worth it, especially because I'm having my teenage kids do a lot of this, and I don't want it to be so frustrating that they're discouraged from working on future products.

Etamin · Posted: Tue Jul 03, 2012 8:11 pm Post subject:

I have a load of the 16mm Alpha pots, and I make chiclets for them by cutting up stripboard which has strips on 0.1 inch centres, so five strips wide does it. I usually cut them 5 to6 holes in length which gives me comfortable space to solder pot at one end and wires at the other end.

I use the 'in-between' strips to carry ground signal when needed,

The chiclets also make it easier when you need to solder a component across the pot terminals - capacitors etc. Just solder them directly to the chiclet.

They aren't beautiful, but they are cheap, and work well for me.

If you cut across the strips, and jumper as needed, you could solder the 0.1 inch MTA connectors at the end of the chiclet, I suppose.

For my flying wires, I use CAT 5 cable with the sheath removed, and tie wrap as needed.For more than 8 connections, I use a second section of CAT 5.

Peter

kjackman · Posted: Wed Jul 04, 2012 8:22 pm Post subject:

Dude... The stripboard chicklet idea is great! I've got tons of stripboard I don't use now that I etch my boards, so this should work quite well. Thanks!

Still want to use IDC wire-mounted connectors if I can, but it's tough to find what I have in mind, for some reason. What I'm looking for is:

- Wire-mounted (not PCB)
- IDC (fits 24 AWG)
- 20 pins or thereabouts
- Polarized
- Locking
- One male and one female connector
- 0.1 spacing if possible
- not super freaking expensive - US$3.50 or less per connector if possible

I've found tons of connectors on Mouser that fit most of these criteria, but not all. Some of these parameters are available as facets for filtering on the Mouser site, but many aren't (especially "locking"), and that makes it pretty difficult to focus right in on what I'm looking for.

So I'm hoping this is a problem some of you have already solved...

I'm not sure what I think of the CAT5 solution yet. Do the twisted pairings introduce any crosstalk, or would that only happen at higher frequencies? Also, for the Sound Lab Ultimate, I would need 16 connectors. Still, I'll keep it on the table as an idea... The connectors and crimpers are quite common and inexpensive, I'll give you that. And they're polarized and locking... Hmm.

Etamin · Posted: Fri Jul 06, 2012 9:40 pm Post subject:

Well, I am a total amateur at this, and probably not very discerning, but I haven't noticed crosstalk problems yet.

Peter

paperCUT · Posted: Sat Jul 07, 2012 2:09 am Post subject:

Chicklets are a great idea, I have to order some for fixing my old DIY jobs.

Here's a pic of my first big build, the ASM-1. I designed the front panels to work like individual modules rather than one huge panel so they needed easily removable connectors to the board. The method I used worked really well actually, each panel had it's own connecter with power and lines for I/O.

Looking at this now I see lots of wasted $$ grin

At the time I worked in electronic retail and could get all this stuff for cost price cool