Tuesday, January 23, 2007

 

Glowy Things and Shiny Things


I've been considering the design of the motor modules. The serial ring idea is really neat, especially when each chip has it's own built-in UART, but I didn't like the connections... they're hard to key, require different kinds of wire(thin for signal, heavy for power), and besides, mixing power and signal feels like tempting fate. I've fried plenty of electronics already. So I split the power and serial signals.

For power, I'm going to use standard PC power supply MOLEX connectors. I've scrounged up an ancient AT power supply -- no hacking at all to get it running standalone since it's not ATX. Signal was a little more tricky, but it came to me while staring at a pile of dead modems -- I could just use their phone jacks and standard 2-conductor phone cable. Easy to get, come in pairs, cheap, keyed, with cables easily made or available premade anywhere. The picture depicts the signal board plugged into itself, echoing serial signals back to the computer.

Here's a tip for removing through-hole components from scrap circuit boards -- if you don't care if the board survives, don't bother with desoldering tools, use a blowtorch. Clamp the board to something metal, melt the solder, and rip the component right out with pliers. It's much more reliable than trying to suck or wick the solder out. But do it someplace with good ventilation, this can be smoky.

As for shiny things, I've picked up ten of these puppies from ebay -- 1.6A 5V 1.8deg/step stepper-driven linear actuators with 300lbs of force. These should have much less problem driving my syringes than my silly tiny steppers driving their homemade off-center linear threads.

Comments:
For those that saw me posting five of these, apologies. Blogger was going wonky.
 
Wow, nice motors from eBay!!

I was ashamed to mention I use the blowtorch method. But now I know I'm not alone! ;) Apply heat evenly, pull evenly, and most of all, do it fast. :)
 
//Blogger was going wonky.//

I'll say. It's been getting worse on the older blogs since they started switching people over to the new beta Blogger. I wonder when the reprappers blog will get switched over. I guess that'll happen when Adrian moves his account.
 
"Signal was a little more tricky, but it came to me while staring at a pile of dead modems -- I could just use their phone jacks and standard 2-conductor phone cable. Easy to get, come in pairs, cheap, keyed, with cables easily made or available premade anywhere."

Now THAT is brilliant! :-D
 
"Here's a tip for removing through-hole components from scrap circuit boards -- if you don't care if the board survives, don't bother with desoldering tools, use a blowtorch. Clamp the board to something metal, melt the solder, and rip the component right out with pliers. It's much more reliable than trying to suck or wick the solder out. But do it someplace with good ventilation, this can be smoky."

I use the same method except that I use a soldering iron instead of a blowtorch. Not much smoke, you don't kill the board. It's no good for multipin chips, but for resistors, connectors, capacitors and the like it works well.
 
I find I manage okay using a soldering iron with components that have three or less pins. After that, out comes the blowtorch. ;)

I can gather so much electronic debris so fast when I need something from family and friends, and the old find at rummage sales that there is a time element involved. Something can be worth it even if I just use a couple of parts from it, and don't have to spend do much time at it.

Mass production in reverse I guess...
 
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