Sunday, 26 July 2009

I got a new power supply to replace the one that got broken by jitter (two, actually, but one of them doesn't seem to work). This one is from an IBM PC 330 server that I got for $5 from the local second-hand store. I can tell that it works, as it actually spins up a little even when no power is drawn.  This is the label:
However, it's a big and special power supply with connectors I haven't seen described in the usual literature. 
This connector P3 looks a bit like the two old AT style connectors rolled into one, but the wiring color is all wrong.
Front look of P3.
There are also two huge connectors P1 and P2 (not connection to bananas) that I have never seen before. Serious mofos with thick wires (standard harddisk connector shown for comparison - look at the size of those things!). Probably can't use these easily, but I feel certain that it can give the output I need. It also has not 4, not 6, but 8 standard harddisk connectors plus assorted small bits.

Here is a better view of the wires for the non-standard 10-pin connector. The white would be -5V, the gray a power on indicator, the black ground, the yellow 12V, the blue -12V, but I don't know what the brown would be, and the green is a power on input. Maybe the brown is 3.3V sense (only brown I've seen mentioned), but that makes no sense with no 3.3V output.

Update: Tried with shorting the green to black, and with a 7W 1 Ohm resistor between a 5V and ground. The power supply hums merrily, but there is nary a blink of power output. Strange.

Sunday, 19 July 2009

X and Y mostly done

Got the last bolts today, so the X and Y stages are pretty much done. The Y rod has been lined up, and the motor attached. When rotating the motor, the driver LEDs light up. Still need to get the endstops to work, and to get a working power supply - how hard can it be? The new server has one that works, so either I can get power out of that, or I have three supplies I need to do something special to.

Friday, 10 July 2009

Some pictures of the X and Y stages

The Y stage at its current form. Here we see the two main kludges I have made: Gluing together two layers of acrylics, and making the rail bearings from pieces of acrylics with teflon tape around them.

Two of the stepper motors and their drivers.

The top of the X stage. Markings are for aligning the Y stage rails. 

The full X stage underside, with motor attached.

The roller skate bearings and threaded rod (underside of X stage). The teflon kludge is even clearer here. I will probably get the right stuff if these don't hold up (unless I switch to magrail:)

The roller skate bearings aligning the X stage. My macro lens appears to front focus?

Thursday, 9 July 2009

Improved X stage movement

I had noticed that the X stage threaded rod was a little off from the motor drive shaf, and it didn't move very easily. To correct this, I moved the nut to a new position, carefully measured against the actual rail when mounted between the roller skate bearings. After adjusted the nut (it can rotate slightly due to a stupid bend in the holder), it is now near-perfectly centered and movement is much smoother. This is one of the few things where accurate measurement is actually important.

Wednesday, 8 July 2009

Working on Y stage

As expected, doing the Y stage goes a lot faster, now that I've done the X stage. In less than an hour of work, I cut, sanded, teflonized and mounted the four bearing pieces, countersunk the holes for the roller bearings, and mounted the nut for the thread. Currently missing three 8mm flathead bolts, more rail (one piece has its hole too far towards the side, grumpf), an 8mm drill bit that's not dull as all get-go, and 4 more roller-skate bearings. Improvements in this stage: Rounded the sides of the rail bearing acrylic pieces, hopefully lessening the wear. Snipped the corners of same instead of dremelling them down, much easier. Rollerskate bearing bolt holes are now fully countersunk (not that it's really necessary) due to diligent testing and hand-improvement.

This is going to be the ugliest RepStrap evar:)

Monday, 6 July 2009

Progress, and a setback

Today I soldered plugs onto the wires from two of the motors, and tested them with two of my boards. The result: Success! The motors turned, at a rate of about .5 Hz or so, both back and forth. Woo-hoo! The first step towards an army of robots!

However, when I tried to set both motors up at the same time (to check power usage and Arduino connections, and to get a picture of them both moving, they started acting erratically. At first, I thought it was the Arduino connections, cause they had a tendency to pop out real easy. However, I soon found out that the switch I mounted on the power supply was the problem, causing glitches and jitter. Finally, one of the switch wires turned out to just have broken off, so I stripped some more to reattach it. But now, the power supply doesn't do anything anymore, not even with just the car bulb attached. I guess all the twitter must have blown the supply -- possibly just a fuse, but I'll have to open the supply for the first time to check.I might want to hardwire the green line and use a switch on the main power.

Lessons learned:

Gotta get some proper plugs for the Arduino connections.
The heat sinks get warm quite quickly, I'll have to keep a good eye on them.
Power supplies are fragile to loose connections.

Friday, 3 July 2009

Motors figured out

Followed a link from Wikipedia to a page on stepper motor wiring, from which I found the following about my Sanyo Denki 103F771-0611: There are 6 wires, and they are connected with a black center to the pink/pink stripe wires and a white center to the blue/blue stripe wires. So now I should be able to run a test!

Almost got a stage!

Got the teflon all nice and on. Cut the threaded rod shorter so I don't have to fiddle with the hole in the other end. Put the spring-tightened wheels on (instead of countersinking on the bearing arms, I put an extra nut between them and the plate, allowing the head of the bolt room to be there. Much easier. Don't know what the whole countersinking deal is, except to make it harder). Got some 9mm tubing from Dragefisken for free (thank you!). However, my drive shaft on the motors is 6mm, so I'll have to extend it somehow. Best bet is these little drill stops that happen to go from 6 to 10 mm, with a tightening screw. The alternative is to get a 6mm threaded rod, but that would require finding some 6mm tubing, which Dragefisken does not have. Trying with the drill stops first, even though they're 50kr apiece.