Let's Make Robots!

Question: How to choose the wire?

Yeah, I know this should be the basic question but I flip the page too fast and skip that chapter.

OK, the situation is the wire getting very hot when motor is running. Basically there are 2 sizes of wire I am using, thin and thick. From the image below the battery wire is thick one and the wire on controller is thinner one. Also, wires from motor are thinner, too and that's why I thought thinner wire might work as well? Now, please notice the wire after the connector from battery become thinner, this is the section getting hot when operation is going.

Do I need to replace the thicker wire in that section?(battery to controller) Or if anyone could please tell me how to pick correct wire for bigger current?

Now I just came up 2nd question. Each motor draws 60A max and the controller could handle 50A per each channel. Does that mean motor won't run up to MAX speed? I know it's not good to reach max speed but just curious.

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This is the motor driver you need.

Too expensive :( I just need a motor driver up to 10A. 

Those drivers usually very expensive if you want to handle large AMP.

http://www.robotmarketplace.com/products/0-SABER2X12-RC.html

Wow, thanks for the find. The driver has nice features such as BEC for the reciever. Exactly what I was looking for! Gonna find out how to get in to Germany.

Are there just IC motor drivers like L293 with higher current? L293 provides 1A per channel. If only there were 2A chips you could just stack five of them and get same 10A per channel for much cheaper cost.

Personally, I don't think you can STACK those because they build in one piece. I am not expert to say YES or NO but those controller are really good and easy to use. They have video there to guide you how to set it up. However, I do spend a little time to figure out the DIP switch on board. They got a site for you to do easier config. FYI: http://dimensionengineering.com/datasheets/Sabertoothdipwizard/start.htm

The simple theory with fuses is that they only protect things AFTER them so your main big fuse should be as close to the battery as posible. This way, the part of the wire that is unprotected (between batt + and the fuse) will be as short as possible. Next, you may want to run a fuse on one of the wires going to the motors themselves. If you use a fuse lower than the max current the motor driver can put out, you will protect the motor driver --I.e. the fuse will fail before you max-out the driver. I like the glass fuse holders --the ones where the fuse comes out with the cap and the cap is removed with a slight push and a 1/4 turn. The spade ones are just fine too, but they are always a pain to pull out of their holders.

What motor driver are you using? I need a 10A one.

Got it... The tank with the awesome tracks, huge bearings and tons of chains --How the hell did I forget?

I think everyone else pretty much got everything covered but here are a few that I have learned the hard way...

  • Take care of your chains!! You are not going to stall when stuck in a corner (the wheels or treads will slip). You are going to stall a motor when you throw a chain. It happens very quick with no warning.
  • Clean connections all around. Tighten everything well and keep it tight. Fewer connection total is better.
  • "Ramp" everything. Take the time to add gradual speed changes to your code. The amp spikes come A) from start-ups but mostly B) from fwd/rev changes (this "ramping" keeps chains on the sprockets as well)
  • FUSES!! Oh, for all that is holy in the world, FUSES!! And for cryin' out loud, buy spares. When you are coding and testing, you are not going to stop and drive to the store for another fuse, you are going to stick a paperclip in there so you can keep working. Now your robot is on fire. Add a main fuse. Add a main fuse. Buy spare fuses. Buy spare fuses.
  • Eliminate 0 and 255 from your code on the RC recieve loop. When you turn a transmitter off, the robot's serial recieve will "see" either a bunch of 0's or a bunch of 255's. This usually throws your robot in full speed forward or full speed reverse. I simply "code-in" to do an all stop when it gets these numbers.
  • You would be really surprised to find out what a 30kg mass can do at even as slow as 1/2 meter per second.

Bottom line for me? You have simply put too much work into this project, and it looks so good, there is no reason at all to go cheap on anything, let alone something as important as wiring. Use big wire.

 

Hi Chris,

Thank you for all inputs and tips. I am going to get plenty fuses today. As I post following IG's reply and according to what I got. Where should I add these fuses and what size should I use? I am thinking to get 50A for each on B points.

Or any better suggestions?

just make sure the fuse is in between the battery and your circuitry and it shouldn't matter where you place it. Can the driver handle 50Amps continuous or a spike? If your motors stall at 60 they will blow the fuses every time your system stalls.