So I've ordered quite a few parts over the past few weeks hoping that everything would ship during my spring break. The UPS guys really came through because almost everything I ordered made it here during the week. Here are some pictures of the new goodies
I've been looking all over the web trying to find some really cheap 4-pin connectors that would allow for 2 Amps of current per pin. Finding some suitable connectors wasn't too hard, but I wanted to have up to 6 motors connected to Hydra so the price for 6 panel mount connectors and 6 plugs goes up real quick. I originally wanted to get some 5-pin DIN cables that are usually labeled as MIDI connectors. These are pretty professional and rated for 2 Amps, but the prices I was finding were all pretty high. So finally, after looking through a bunch of different places I found these little gems. They are the really old CB radio connectors that have 4 very beefy pins that will be able to handle more than 2 Amps per pin pretty easily. Best part is that the whole order for the 12 parts was only $25! Guess these legacy parts go pretty cheap nowadays!
The 2 pieces slide together very snugly and even have a locking ring to make sure they don't go anywhere
Remove 1 screw and you can get an the 4 internal connections so you can use your own wire to make cables with a custom length.
I also found this 4-wire, 22 gauge, shielded wire at my local Home Depot for 30 cents a foot! The motors I am using have 22 AWG wire for the connections to the motor so I assume 22 gauge will be find for the maximum current ratings. Something a little larger would have been nice, but all the larger wire was solid copper and not very flexible at all. I want this to be able to move along with the axis carriages so hopefully 22 gauge will be enough! Also the shielded part is very nice as these lines will be carrying high voltage switching signals which tend to cause interference on other lines around them.
I also snagged a 18" x 18" x 6" steel enclosure off of Ebay that I will be using to house all the electronics in (the ECB I mentioned previously). While I don't have any pictures of the box, construction should be beginning on that during the next week.
2 Drewtronics PCB milling bits, both a 45 degree and 60 degree bit. I plan to pickup some 2-sided copper clad from Radio Shack for the first few PCB milling tests. I have heard of some problems with the flatness of these boards, but I don't plan on making anything bigger than 3" x 3" so I'm hoping it won't be a problem.
Amazon also came through and delivered my new router that I will be using for rotary applications on the machine. The Bosch Colt has a 1/4" collet and I also ordered an adapter to allow it to use 1/8" bits (such as the drewtronics ones and a whole lot of other bits made for dremel-like tools). The Colt has a 1 HP motor and can go from 15k to 35k rpms. I turned the thing on to test it out and WOW. This thing has a ton of power! Puts my Dremel 395 to shame. It also appears to have really good runout although I haven't tested that officially yet. It is going to have no problems cutting PCBs and low strength aluminum with smaller cutters that will handle the higher speeds.
Packaging
So it's been a pretty exciting day opening all of these packages. Next week I should have several orders of electronics parts coming in from digikey and mouser as well. My hope is to have the machine moving around by the end of next week. Once we are able to mill PCBs with it I can switch over from these PIC based stepper drivers to the a3982/3983 drivers I have been designing. That will definitely help smooth things out and allow for much higher speeds for prototyping. I'll try to keep updating over the next few weeks so keep an eye out!
On the 22 Gage wire, it's common (in electrical work) to have the fixture have a smaller wire than is permitted to be run to it. This is OK, as the short run of wire (the one hooked to the motor) being smaller isn't as much of a problem as a long run of wire being to small. This is simply because the resistance (and thus voltage drop, power loss, etc) of the wire is related not only to how small it is, but how LONG it is as well.
ReplyDeleteFor instance, it's common for the wires being run out to parking lot lights to be HUGE - 8 gage or even 4, even though the wires to the light fixture are only 12 or even 14. That's an extreme example though.
It's always best to oversize your wires, and even though the wire into the actual motor is 22 gage doesn't mean that you can run that size to it. That said, it should be just fine. It's not like you're running it 200 feet. Or even 10 for that matter.
Shielding helps. Are the pairs twisted? That helps too.
I'm curious to see how things work out for you, I'll be following your blog here. Through the aggregation pipe, of course.
@John - that's good to hear! Most of the current ratings that I had found for different gauge wire had the current rating labeled as "max amps for power transmission", which I figured meant it was intended for long distance travel. See here for an example: http://www.powerstream.com/Wire_Size.htm
ReplyDeleteI don't think I will have any wires longer than 5 feet so I can't imagine the resistance being too big. And the wires are not twisted pairs. I know that helps a lot, but these are only power lines for the motors. I plan to use RJ45 (ethernet) cables for my signal lines (limit switches, encoders, thermocouple, etc). RJ45 cables have 4 sets of twisted pairs to if I wire one of each pair to ground I can use the other for a relatively noise free signal back to the motherboard. I believe CAT5/6 cables are also shielded so I can't imagine any trouble there.