Universal-ish power supply unit

Hobbyists and home experimenters will know the feeling. You're working on a little project and you know you're going to need power. Often this results in a mad search for a battery box and some cells that still have a bit of life in them, or perhaps you raid your collection of "Wall Warts" (which usually means you can't charge your phone or use your router until playtime's over). Wouldn't it be nice to have a dedicated power supply for these occasions? What a luxury.

Contemplating this problem earlier today, my gaze fell upon a heap (literally a heap) of old computer PSUs gathering dust in the corner of the Secret Laboratory. I always salvage stuff from old PCs - better gathering dust than going to landfill.. Some of the PSUs were of no further use anyway, being of the old "20-pin" format rather than the "24-pin" that modern motherboards require. Some were rated as low as 200W, which doesn't really cut the mustard with modern PCs. For years I had been tripping over the very solution to my problems. It was a classic "DUH" moment...

So, the next Secret Laboratory project is going to be the conversion of one of these old computer PSUs to a useful universal-ish general purpose power supply. If it's good enough for motherboards, it's good enough for the shit I build.

The plan is to source a compact yet safe housing for the PSU, to prevent busy little fingers from poking stuff (accidentally or deliberately) through any dangerous holes. Terminals will be presented for +3.3V, +5V and +12V outputs (either separately else via a voltage selector switch - I haven't decided yet). I may include -12V for those of you who like to muck about with devices that require it. I never did fully understand why op amps need the dual polarity thing...

If you're following this project, the bit you're going to be working with is the 20-pin connector (usually marked P1), seen here to right of centre. You can ignore the other connectors (far left) - they just route the same power to other computer peripherals (hard drives, etc). You can get everything you need from the 20-pin connector alone.

Of great importance! Mark well the following cable colours:

• Orange: +3.3V
• Black: Ground
• Red: +5V
• Grey: Power Good (optional signal)
• Purple: +5V Standby (optional power)
• Yellow: +12V
• Blue: -12V (optional power)
• Green: Power On

There's some redundancy in there, so you'll find several cables of the same colour. Trust the colours but use a meter to check the voltage lines. I haven't given pin numbers because they differ between the 20 and 24-pin standards.

To turn the PSU on, you must ground the Power On pin. I plan to use a simple on-off switch for that.

+5V Standby is always on, even without Power On grounded. I plan to have a little LED across this just to show that the unit is plugged in and ready to go.

Power Good goes high when the PSU is delivering the right voltages to all outputs. Again, I plan to have a little LED across this one. You can't have enough lights on your unit, you just can't. The more lights, the better it looks (and it's a real babe magnet - well, it's always worked for me).

Regrettably, I must inform everyone that electricity can be hazardous and you really mustn't go mucking about with stuff you know not what of. In particular, do not disassemble the PSU itself and, if you do and you see something that looks like a little can of baked beans for a pixie's din-dins, don't touch it else you might end up all dead (even if you're not plugged in). That's my legal disclaimer. Can we see if we can get through this project like grown-ups?

More news soon, as soon as I've found a suitable housing for the PSU...

The Lindsay Technique for tangle-resistant cable storage

I call this the Lindsay Technique because it was musician and rock climber Andy Lindsay who taught me. The technique is derived from rock climbing practice but it works equally well in the world of live music performance.

Happy tangle-free gigging!

Reclaiming your toothpaste

OK, not an invention as such but a super little tip for all of you with TDA (toothpaste depletion anxiety).

Coming next on The Secret Laboratory - a full video disclosure of the Lindsay Technique for non-tangling cables. A must for musicians...

CRAPULITE® - building material of the future

It is with no small measure of pride (and indeed a huge dollop of smugness) that The Secret Laboratory is able to release details of its latest invention, CRAPULITE^®

This open-textured, lightweight yet strong medium is ideal for repairing large gaps in crumbling masonry or rotting timberwork.

CRAPULITE^® is produced from a readily available and sustainable source of recycled material, combined with an all-purpose filler in a secret process known as “shredding and mixing”. The high content of tabloid material renders CRAPULITE^® impervious to bookworm. With a skim of rendering and a lick of paint, even your surveyor won’t know it’s CRAPULITE^®.

The Secret Laboratory is in the process of negotiating exclusive rights with the construction company Bodgitt & Leggit of Purley.

Drop -Tank sidecar

Current shed project is the conversion of a 1945 Hawker Tempest Drop Tank (used for carrying extra fuel) Into a useable sidecar body for my old Panther motorcycle. I have so far welded in a new nose section (as it was dropped on its nose) and made some cutouts for the passenger.

The cutout weakened the body considerably so I welded some 8mm round bar all round the aperture. This required considerable heating, which is when I discovered all the rivets and seams were sealed with lead! Interesting! Next stage is making brackets to fit the body to an old chassis I have 'in stock'

Bijoux Stomp Box

Saw this on tinternet and thought can't be that hard. Baccy tin with a fax machine speaker hot-glued to the bottom (the fax machine's unfortunate demise was one Monday morning when it refused to take the paper for the tenth time!!), soldered to a mono jack socket which was drilled and mounted in the side of the tin. Critical part is to stick a heavyish metal disc to the shiny dome thing in the middle of the speaker. this one is about 35mm. I reckon a smaller one would give a higher sound like a tom tom.

Well it works ok, lid down and tap it with foot, sounds a bit like a kick drum. Probably would sound great through a PA . I am going to attach it to a plank so I can boot it properly.

Quilted Coffee Pot Cosy

It's sad really but every now and then I get an inexplicable urge to make a quilted coffee pot cosy. Perhaps it's just that I like watching my ancient Singer doing its stuff (how does it grab that loop from the bobbin below?) or perhaps it's just that the simplicity of the cosy allows even talentless idiots such as myself to create something of profound beauty. Many there are that have knitted a scarf but few go on to "turn the heel" of a sock. The coffee pot cosy is the scarf of the quilting world.

I made this one for Angi Webb's coffee pot. Her pot is 8" x 4.5" rather than the industry standard 8" x 4" and so this cosy is truly a custom item.

There you go Angi - a present for your new house, from the Secret Laboratory...