Category: Workshop

Aug 16 2011

Workshop updates, August 15th

Recorded a little bit of video from the workshop last night. Dumped it up to YT. Going to try and do this more often.

Aug 07 2011

Enclosure arrived!

The enclosure found on ebay arrived today. My guestimates (since internal size wasn’t mentioned) look to have panned out, and it’ll contain all the parts quite nicely.

Fortunately I had a piece of aluminium plate left over from my grandfathers materials which will provide the needed backplate for the plastic box. It feels nice using something that was his in any of my projects.

The driver board will just about fit in, though I’ll need to be creative with mounting the power supply. I’ll be cutting some holes in the top access panel for the driver’s D-connectors, the IEC connector will probably go on the top or side where gravity shouldn’t let it fall out. Bottom is probably going to have the illuminated mains switch and the five 4-pin XLR connectors for the steppers and motor drive. The left-hand panel will have the filter-protected exhaust vent.

A fine wire filter grill will be going on the front panel to direct air onto the PSU, which will flow across the box and out the exhaust. The box should be kept at positive pressure. The box is far more environmentally sealed than I really need. All I really want to ensure is no dirt and spiders get in it.

Also found a few little 12v fans that should replace the defective one on the driver board. Got a 24v 80mm fan for the front that came off an old LaserJet printer. Not sure where to put the emergency stop yet. Got to be the soft-off interlock on the driver board I think, since cutting power might still leave steppers moving for a short time. Also might not want it on the enclosure itself, but remote.

Mounting the readout is also a puzzler, but can be done later.

Aug 05 2011

Bothersome circuit

Very tired and about to go to bed, but traced and ID’d most of the parts on the old treadmill motor controller board.

It drives a motor rated for 180v DC, but my measurements say it’s putting out 330v DC which would make sense for rectified UK mains. I suspect on looking at the board that for UK use they dial the speed control trim-pot down to half so the PWM signal never goes above 50%.

Still means the motor’s running at twice the voltage it should though, which’d explain the overheating issues.

I don’t understand the circuit fully though. For one thing there’s a half-bridge rectifier essentially bridging the motor terminals. Surely that’d mean it’s perpetually shorted out? I don’t understand it, but suspect it might be something for dealing with back-EMF from the motor.

I also don’t understand how the MOSFET’s driving it. It all seems to be coming through a 5Watt resistor and some very thin traces, especially since the motor’s 2-2.5HP (1400Watt+). Maybe it’s because it’s late, maybe I’m just not seeing it and it’s just the trigger. Just can’t see it right now. But the circuit does work (even if the fuses and current breaker don’t. If something shorts it ALLWAYS knocks out the 30Amp breaker for the workshop).

It’s a single-sided PCB. Here’s my notes on it. A few figures are missing, but all components are marked.

I’m planning on making a much simpler control circuit, but it does involve a very large 220-110v transformer to get the proper 180v DC.

It’s been a good day. Castings done, experiments done, oscilloscope usable again, found artial pressure cooker for new vacuum degass chamber, some clearing up done.

Jul 30 2011

CNC parts so far, video

Will add more info at a later point.

Good day tho! A gift I’ve been working on on and off is ready to hand over tomorrow (there shall be photos) and I repaired the Hackspace Espresso machine at last, by fabricating a new drive sprocket from brass.

Two projects down. Accomplishments!

Jul 08 2011

New Mill Project

With the money I’ve been gifted, I’ve just put a deposit down on a BIG milling machine in the last few hours it was on special offer pricing. A Chester Eagle 25. I’ve also bought a Chinese 4-axis CNC driver board.

The mill is out of stock currently, so I’ve got a 12 week wait there probably, and 12-24 working days to wait for the driver board. Once the driver board’s here I’ll be grabbing the four steppers and PSU rather than have them sit around untested. :)

While it sounds like an unpleasantly slow process, it will give me the extra time I need to sell the current mill and replace workbenches it’ll all be going on.

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