What are a couple good sources for flexible and higher quality wiring for FRC bots at an affordable price? Last season we just used spools of wire another mentor had laying around, but it was not very flexible and hard to route (some Home Depot wire).
I’ve been to Powerwerx only so far. I’m told that speaker wire works well also. (and it looks great!)
In addition to this, what are characteristics of good quality crimped connectors (ring terminals mostly). Are nylon connectors better for stronger connections?
We get the same from a local sponsor (Orvac Electronics in Fullerton CA). Not the cheapest stuff in the world but it’s great. It’s amazing how much you end up using in a season.
We’ve gotten plenty of wire from McMaster in the past, it really is good stuff.
For terminals, normal crimp connectors work just fine (we pick them up really cheap at a local surplus store). HOWEVER, you should solder the wire to the connector after crimping it. I’ve seen too many wires pull out of crimped connectors to rely on crimping alone on our robots!
For Heat Shrink, brand really isn’t going to matter. Find something cheap that shrinks down to the diameter you need. Again, I’ve picked most of our stock of heat shrink up from the same local surplus store.
For anything other than heat shrink, we’ve just used electrical tape. It’s not really worth trying to cover the contacts on the motor controllers, but you should make sure the studs on the 120A circuit breaker and the power distribution board are covered! Electrical tape wraps around these easily enough.
We use some compression lugs from McMaster (PN 6926K75 i think… we got them in bulk a few years ago, and my memory is a little hazy). They provide a double-crimp, which we then reinforce with some solder. It takes a big soldering gun to heat up #6 wire, though!
You want machine tool wire (MTW). You can get this online or at a local electrical distrubuter. What most places will try to sell you is THHN. THHN has the an oil resistant coating that makes it hard to bend and work with. Also, make sure you don’t get double rated MTW and THHN as this is not what you want either.
I’ll second the MTW wire. We were able to get a electrical supply house to donate some to us. The flexibility is much better than THHN and you also don’t have to deal with the annoying nylon outer insulation jacket.
As far as the #6 wire connections to the PD: I am very much not a fan of the screw lug terminals that come in the KOP. As a robot inspector, I’m often asked to help diagnose problems with robots that stop working on the field, or even worse are intermittent. The first thing I do is look for those terminals anywhere in the wiring (battery, 120A breaker, PD). Then gently pull on the wires, which usually come out in my hand. We use crimp lugs on all our #6 wires, I don’t have the part number handy but it’s similar to this: http://www.thomasbetts.com/ps/fulltilt/index.cgi?part=CTL614 which we crimp with a hydraulic tool.
We buy our heat shrink at Harbor Freight. Usually with a 20% off coupon
+1 for machine tool wire. It’s really nice and flexible. On McMaster, it’s $109.50 for a 500 ft spool of red or black 12 gauge (part numbers: 71245K41, 71245K44). 500 feet of the red+black stuff listed above would be $600.
For wire we use standard automotive wire that we get at a local auto-electric shop (not a chain store) and they give us the contractors rate. It’s got good flexibility and we’re never had problems with it. We usually twist the black and red wires together by clamping the pair together in a drill while someone holds the spools at the other end of the room.
For wire-to-terminal connections, the quality of the connection follows this hierarchy:
Best: good crimp (note that a good crimp requires a good crimping tool)
Acceptable: crimp + solder (the primary reason that this makes a lesser connection is that the solder makes the connection brittle. For all soldered connections, it is important to make sure that solder does not wick up the wire)
Bad: bad crimp
For ring terminals and connections that shouldn’t need to be unplugged, we use Ideal (the brand) crimp terminals and quick connects from Home Depot and crimp them with a crimping tool similar to these, that we got from Fry’s. You have to calibrate the crimping tool when you get it (adjust how tightly they crimp), otherwise they’ll make trash crimps. In all our years of using this tool, I can’t think of a single crimp failure that can’t be blamed on either using the wrong size terminal for the wire size or not inserting enough copper into the connector.
We use PowerPoles for most wire-to-wire connections. We use the crimp + solder method because the PowerPole crimping tool is pretty expensive, although I’m pressuring the team to get one.
For the battery lugs we use the crimp lugs that come (or at least came) in the KOP (not the screw type). Because we certainly can’t afford the proper crimping tool for these, we solder the connection following these steps: First, if the barrel doesn’t have an opening on the ring side, drill a small hole to feed solder. Next, push the wire into the connector and try to fill all the free space around the wire with solder (do this before applying heat to the connector). I do this by pushing the solder straight into the connector, cutting it flush with the connector, and repeating until I can’t get any more solder into the connector. Then, take a propane torch and heat up the connector until the solder flows. You can use a soldering gun, but the torch is much faster. Finally, feed solder into the small hole you drilled in the connector (this time, keep the connector hot while adding solder). Only add solder from this end to help keep solder from wicking up the wire. Stop adding solder before any is able to wick up out of the connector.
For most of our heat shrink, we use the variety pack from Fry’s. It’s nice and flexible to reduce the strain on the wire. There are befits to higher quality heat shrink, but it’s rarely worth it for what we do.
We finally caved and purchased the crimping tool for the Powerpoles last year and I doubt we will use anything else in the immediate future for wire to wire connections. While a number of students are capable when it comes to soldering connections most of students have never seen a soldering iron before joining the team.
but was wondering if there are any other sources for this. I’m assuming plenty of hobby shops carry the materials to make custom length PWM cables. If you’ve bought from these guys before, what is their shipping time like?
I’ve been using Hansen Hobbies for years for both FRC and personal. You really can’t do much better for hoods, pins, pwm wire than that. His shipping time is pretty quick, but, its shipped US Postal, but I think the longest it ever took me to get an order in hand was like a week.
We’ve been using Zip-Cord from McMasterCarr for the last few seasons. It easy to use, keeps things neater. I recommend it.
+1 for Hansen hobbies PWM. Great prices, fast service, quality product.
Powerpole connectors are also great. They can be connected together to form large plugs, allowing you to easily connect/disconnect a large series of wires at once, without having to worry about plugging them back in correctly.
For wire, the ultimate in flexibility is Dean’s Wet Noodle wire. Pricey, but makes a world of difference, particularly in wire runs you expect to flex during operation. http://www.robotmarketplace.com/products/0C-WSD01B.html
We’ve had the materials to make our own for a while now. We use the following parts from Molex: 16-02-0102 (female pins), 50-57-9003 (1x3 housings). Add to that your favorite 22-24 gauge wire and your set! There’s a crimp tool to go with the pins that we really should get one of these days… we’ve been soldering them into the crimps and it’s worked fine so far.
We’ve found that the PWM cables in the KoP are generally enough to handle the cases where we need the full cable (both male and female ends). We always have encoders, limit switches, potentiometers, or other sensors on the robot that only need the female end in order to plug in. We got really tired of cutting so many PWM cables in half!
Hansen Hobbies is great and they’re significantly cheaper than anywhere else I’ve found (at least when I checked a few years ago). We use the economy wire and economy crimping tool. I will admit it takes some practice to master the economy crimping tool, but it works pretty well.
