'Sweat' laminating brass etches

[flexible_coupling]

After indulging a bit of curiousity thanks to Google - I "nutted out" and successfully built a resistance soldering unit today! And for peanuts... the peanuts would be far fewer if I hadn't had to buy a PC power supply new! It's easy to make it safer than most 'DIY' builds online, using an automotive fused relay module and some 12v trigger switching. I've only briefly tested it, but the results are astonishing and I'm very keenly looking forward to putting it into full service after a bit more "learning" with scrap etch... I got excited and put a blob of solder on the top rail of my 16t wagon kit build... better just clean that off!

 

[adrian]

Always interested to see people making tools - what's the power rating on the PSU? Only reason I ask is that most RSUs will pump out 20A to 30A at 12v, if you're matching that then that earthing cable looks distinctly under specced to me. It might get a little hot in use and I'd consider swapping it for some heavier duty cable.

 

[Heather Kay]

Only reason I ask is that most RSUs will pump out 20A to 30A at 12v, if you're matching that then that earthing cable looks distinctly under specced to me. It might get a little hot in use and I'd consider swapping it for some heavier duty cable.

I thought that, but didn't have the technical words to explain. The home-brew unit I have here, which Best Beloved made some years ago, gets pretty warm after a session, almost too hot to hold comfortably.

 

[flexible_coupling]

The cable is good quality 20AWG with teflon insulation. The power source is running 3.3V at a nominal 29A. I admit that I didn't check the spec table (which theoretically puts 11A as the max handling) - that, and the ~16-18AWG cores running up the umbillical cable, are still a bit lean and they do get very slightly warm. I'm going to 'watch it' tomorrow when I have a bit of a test, and put it in for re-tooling if required. It's a good point though, and I'm glad to have had that brought to my consideration... if I re-do it, I'll have "lost" about $5 of bits/wire here, so getting some 14AWG wire in and building a new handle is about an hours' work and a few more bob spent.

 

[adrian]

I've not checked the calcs myself as I'm not an electrical engineer but this site

http://www.powerstream.com/Wire_Size.htm

reckons you'll have nearly 2.5v voltage drop over 4ft at those amps, which doesn't sound good to me and by my reckoning is about 75W transmission loss, which will make the cables nice and warm. 14AWG sounds better but 12AWG or 10AWG would be even better still if you can.

 

[flexible_coupling]

The power is actually only travelling about two feet total - but you're right, it's still not anywhere near ideal. I'm already looking at some significant revisions, and I've run this first edition for about six seconds!! Haha...

 

[Dog Star]

... I've run this first edition for about six seconds!!

And just how long was the first internal combustion engine run before the builder got on with building a bigger and better engine? The history books tell us "about tens seconds".

 

[Arty]

I've built quite a few RSUs over the years, mine consist of specially wound transformers, either using transformer kits (which used to be available from RS etc) more recently rewinding 200-500w toroids.
Multitapped secondaries 2-3-4v to adjust the power and a footswitch in the mains supply, the fewer connections the better.

You can buy 8 AWG wire from Maplins for your ground and supply leads, some of the other heavy duty copper speaker cables available should be ok for lower power.

http://www.maplin.co.uk/p/shark-red...-entertainment-systems-priced-per-metre-bz92a

I make my carbon electrode holders from X-Acto N0 1 aluminium handles with a PTFE sleeve for a heat insulated
handle. The collet end bored out to suite the carbon electrode.

I can typically sink 50-60 amps from one of these which is probably a bit over the top for all the small stuff, but for G1/G3 comes in very handy