How to Wire a Fighting Robot - Novice
-Matt Bores
Last Updated - September 2006

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Build Responsibly.

There are many decisions that need to be made long before you just start wiring a robot. This tutorial will help guide you and teach you the correct way to wire a combat robot for safe operation. Also included will be some tried and tested tips for methods on keeping your robot from failing in combat due to a loose wire, which seems to be a leading cause of robot failure.

The first thing I would like to cover is what type of wire is right for your application. Obviously you don't use the same size wire throughout all of the weight classes, there are different wires sizes (gauges -aka AWG: American Wire Gauge) to handle different applications. The smaller the gauge number the larger in diameter the wire is. In combat robotics a wide variety of different sizes are used from 20 gauge wire in the very small divisions all the way up to even 2 gauge wire in the much bigger classes.

Using too small of a wire gauge could result in your wires melting since they will not be able to handle the current you are passing through them as well as loss of power due to resistance, and using too big of a wire gauge just takes up space and weight and is not necessary. If you are unsure, it's best to go a little bigger than you think.

Below is a table that will help you decide which AWG is right for you. Only the even AWG's 2-24 are included, anything out of this range is most likely not necessary for combat robotics. You will be referring back to the chart below later on in this tutorial.

Now that you have a good understanding of what wire gauge you will need for different applications, it is now time to go over how to wire the bot. Before moving into wire preparation you will need to know what gets wired to what and how, so that you can make the proper adjustments to your wires. Below is a simple diagram that shows how to wire a basic setup using victor motor controllers.

The Basic Wiring Scheme

Below is a very brief summarization of the basic wiring schematic for a robot with a simple two motor drivetrain. All robots do not use the same drivetrain and therefore all examples cannot be covered in this tutorial, however the basic idea is given here. It is also a good idea to go over this before bench testing to be 100% sure you wired your robot right before firing it up.

I like to start with the motor controllers, they are the heart of your robot because everything is pretty much wired to them. In any basic robot setup your batteries must be wired to your motor controllers, and there must be a master switch somewhere in this part of the wiring, the best place for it is along the positive battery wire before it splits into multiple wires. Also wired to your motor controllers are of course your motors. Lastly your motor controllers plug into your receiver so they can convert the signals from your receiver into electrical impulses to drive your robot. That's pretty much it, it's not really that complicated. Now for a in depth look at this that should put you on the right track to wiring up a safe reliable drivetrain for your robot.

Note: The examples and explanations in this tutorial are of a basic two motor drivetrain. If help is needed with more complicated drive setups feel free to contact us for help, if we get enough inquires an addition to this tutorial can be made.

Diagram Description

Don't let this be intimidating, below I will describe the purpose of each wire as they are numbered in the diagram:

1) This is the wire attached to your receiver battery pack. It simply just plugs into the battery slot on your receiver. This will be one of the last things you want to plug in before you run your robot.

2) These wires are called PWM cables. They come in red, white, and black strands of wire attached together with the proper plug (male/female) attached to the ends. When using victor motor controllers it is necessary to buy the PWM cables with the signal booster in them, so you don't have any communication issues between the receiver and the victor motor controllers. These plug into the desired channels on your receiver (consult your transmitter manual to figure out what channels you would like) and then into the victor motor controllers. Be sure to plug them in the right order on the victors, it is labeled which colors go from left to right. Also be sure all three pins on the PWM cables fit into their proper slots when plugged into the victor, it is fairly easy to accidentally plug it in and have a pin miss the slot which will cause the victors to not function.

3) This wire is simply wiring the two 12 volt batteries in series, which outputs 24 volts from the two remaining battery terminals. I could have used a parallel setup as well but I just chose to do it like this since most drive systems in the upper weight classes are 24 volts. See next section for further explanation on this.

4) These are the positive (+) and negative (-) wires going from the batteries to the motor controllers, the dots are where one wires splits into two. Here you will need a master switch for safety reasons that you will manually turn on and off before and after fights with an allen wrench or other tool...see number 6.

5) These are the wires that go from the motor controllers to your motors...nothing fancy here.

6) This master switch is required in the rules and it's just plain crazy to not have one. As described above the switch is simply turned on and off via a turn key, allen wrench, or some other tool. This switch must obviously come before any splits in the wire or else it will not be effective.

7) What there is no 7 in the diagram? Correct there is nothing labeled 7 in the diagram but I am putting this here to represent the robots antenna. When you buy an antenna instructions will come with how to attach it to your receiver. Be sure to keep it at least 1 inch away from any metal.

That was a very basic setup you can use to drive any bot using two drive motors. Some proper tuning is probably necessary which we will go over in a bit.

Wiring the Batteries

There are two different ways of wiring two batteries together, these are known as series and parallel. The two diagrams below are to show how to wire two batteries in series and parallel and what it does. When dealing with more than two batteries, combinations of both series and parallel can be achieved but that will be left for a more advanced tutorial.

In the two diagrams above I chose to use 12 Volt 5Ah batteries. The 5Ah is the reserve capacity of the batteries. This means the battery is a 5 Amp/Hour battery - or it can source 1 amp continuously for 5 hours, or 5 amps continuously for 1 hour. If you want to figure out the reserve capacity you need for a 3 minute match, figure out how many amps your drive motors will draw continuously, and add them together. So if you have two 12 Volt drive motors that each suck 20 amps each continuously, you will need to supply a total of 40 amps continuously for a 3 minute match. The 40 is a rough estimate, there will be periods where you will get in pushing matches and draw more current so it is critical to have a little extra battery power.

Anyway if we have a 12 Volt 5Ah battery and need to supply 40 amps continuous the math is quite simple. If the battery can supply 5 amps continuous for 1 hour, then it can do 10 amps continuous for a half hour. As you double the current you divide the time by two. The battery can do 20 amps continuous for 15 minutes or 40 amps continuous for 7.5 minutes. Therefore this battery would be more than enough for the mentioned drive setup. Taking this further to a 3 minute match, the battery can do 80 amps continuous for 3.75 minutes. We can stop here because 3.75 minutes is a good safety margin, although we have more than enough battery power. Read more about this in our battery tutorial.

Time to go over what series and parallel does :

Series: When wiring two 12Volt 5Ah batteries in series you wire the positive red (+) terminal on one battery to the negative black (-) terminal on the other battery. What this does is double the voltage of the two batteries while the reserve capacity of 5Ah remains the same. So now your two remaining battery terminals are going to output 24 volts with a 5Ah reserve capacity, in other words you can look at the system as one 24Volt 5Ah battery now.

Parallel: When wiring two 12Volt 5Ah batteries in parallel you wire the positive red (+) terminal on both batteries together and the negative black (-) terminals on both batteries together. This doubles the reserve capacity of the batteries while the voltage remains the same. So you can now look at it as one 12volt battery with a 10Ah reserve capacity.

If you need any more information on batteries other than these general wiring techniques please check out our other tutorials.

Choosing your wire

When you go out to buy the correct gauge wire(s) be sure to remember it is crucial to buy both red and black wire. Red for positive red (+) terminals and black for negative black (-) terminals.

OK! so now lets say you have your two drive motors mounted in your robot. You should know how much current these drive motors will be sucking, usually the place you buy them from has a table with this information on it. Lets pretend you have two drill motors that will be sucking about 40 amps continuous per motor. According to the AWG table above 12 gauge wire can handle 41 amps. This is cutting it a little close and we don't want our wires to get hot or lose some power due to resistance so instead 10 gauge wire is probably the smartest choice. 10 gauge wire should be able to handle 55 amps continuous, and much more than that for a 3 minute match. As mentioned before, you will get into pushing matches and may even see current draws from your motor as high as a few hundred amps for brief periods of time. Make sure your motor controllers can handle these current surges, and your wire too! Therefore, 10 gauge wire is a good choice to use when wiring your batteries and motors to your controllers because we now know how much current will be passing through these wires.

All you have to do now is figure out roughly how much current will be going through each of your wires and figure out what size wire you need using the chart at the top of this tutorial. After this is complete you are ready to begin wire preparation.

Wire Preparation

As mentioned above, buy both red and black wire! Also, buy lots of extra wire, it is good to have 5-10ft extra of red and black wire, just to take to competition and incase you prepare a few wires wrong.

Referring to the diagram above, and after you have mounted all of these components in your robot, you are ready to get out the wire. Be sure to have a wire cutting and stripping tool available. Don't worry about wires 1 and 2 in the diagram right now, those can be plugged in later on before testing.

Now we need to cut the wires to the proper lengths. For wire 3, if you are wiring in series, simply do what the diagram shows and wire the positive red (+) terminal on one battery to the negative black (-) terminal on the other. Before actually wiring it though grab the strand of wire and hold it with your hands where it will wire from and to. Using a marker, mark the wire at the correct length of wire you will need, be sure to leave about 2 to 3 inches excess before marking. It is better to have loosely sitting wires than tight wires that can pop loose under large impacts.

The next thing you want to do is figure our the best way to attach this wire to the battery terminals. Most SLA batteries have screw terminals so for this example it is best to use an eyelet connector which are shown in the picture below the crimping tool. The color band tells you what kind of wire gauge it will accept. when buying these eyelets be sure you buy them so it will accept the gauge of wire you are using and that they will fit correctly around the terminal you are wiring too, not too big and not too small.

Now that we have the wire and connectors taken care of we need to prepare the wire. Strip about a half inch of insulation off each end of the wire you cut. Be sure too look at your stripping tool (your tool should look something like the one above) and use the right slot to strip your wire for the gauge of wire you are using. Take one end of the stripped wire and push the stripped part all the way into the eyelet as far as you can. Take the stripping/crimping tool and put the colored end of the eyelet in the right spot on your tool and crimp it down as hard as you can. To be more sure these wont come loose I like to try to pull them off with my hand (and never have been able to) and if I cant they most likely wont come loose in combat if you cut your wires right. I also like to use electrical tape and tape around the colored band on the eyelet and the wire, and sometimes there will be excess stripped wire hanging onto the circular part of the eyelet, I like to solder it to the eyelet if I can making totally sure I did my best to keep this wire from losing me a match.

You will want to repeat this for every wire you have to make for your bot. Wiring a robot for me can take a couple hours as I want to make sure I do it right the first time. It is a pretty simple process.

1. Choose the correct gauge and color wire then measure the wire and cut it. Remember to leave a couple inches excess so the wire sits loosely in your robot.

2. Strip about a half inch or more off each end of the wire.

3. Use the most suitable connecter (I use eyelets shown above in 95% of my wiring, the only time I haven't used them is when I used drill motors which took a different type of connector). Slide the stripped part of your wire into the eyelet connector and using your crimping tool, crimp it as hard as you can. Try to remove it with your hands, if you can you're not doing a very good job. Now do it to the other end of the wire.

4. Using electrical tape, tape around where the end of the eyelets color band meets your wire. Also if you wish, solder any excess stripped wire hanging out onto the eyelet to the eyelet itself.

5. Now fasten this wire in your robot! Make sure no wires can interfere with any moving parts in your robot.

Now that you have finally completed preparing and wiring all the components in your bot you are ready to test it. Almost!

Final stages of wiring:

Remember those wires in the diagram we said we would save for later. Well, now we are coming back to them.

In the diagram these are wires 1 and 2. For the wires labeled 2, once again these are the PWM signal drivers. You will NEED these unless you're using an IFI Robot Controller. If you're using any other transmitter such as Fut aba or any other brand, you must purchase these PWM drivers. These wires will ensure that the signal from your receiver/transmitter is compatible with your IFI speed controllers.

To wire these wire into your robot, first take the male end of the signal driver and hold it up to the slot where it plugs into the IFI motor controller. Above the slot on the victor it says WRB, this is the order your wire must plug into the victor, it stands for White Red Black. So when plugging the PWM driver into your victor, the white wire must be on the left and black must be on the right, do not plug it in backwards. Also be sure to take your time plugging these in and make sure all 3 pins go into their slots. Do this on both controllers then take the female end of the drivers and plug them into the desired channels on your transmitter...most likely channels one and two but refer to you transmitters manual for further assistance.

Also I highly recommend using something to keep these wires from popping out of your victors during a large impact, which they probably will do. Some competitors use hot glue or zip ties, but the robot market place has this nifty little PWM cable clip which is all you need to fix this problem. Be aware that the edges on this clip are semi sharp and may slice into your wire, so you may want a thin layer of tape around the edges of the clip where it comes in contact with your wire.

Now for wire 1 in the diagram. I always leave this unplugged until minutes before my match because I always charge it between my matches...hich is unnecessary but I like to be safe anyway, a lot of the time I have no clue how much charge the receiver battery pack has in it. But since we are testing the robots wiring go ahead and plug this into the slot on the receiver labeled for the battery.

Bench Testing / Debugging

Below is a simple step by step process to bench test your robot to see if you have wired it correctly. Please read through them all carefully before doing the actual bench test.

1. Check to make sure no loose wires are laying in your bot and all wires are fastened securely. Check and recheck to be sure you wired everything correctly and lastly be sure there are no wheels attached to your robot, and that anything which will be moving (hubcaps, shafts, etc) is far off the ground and cannot come in contact with any of your wiring or clothing.

2. Now you can turn the master power switch in your robot ON. At this point the fans on your motor controls should come on.

3. Making sure your transmitters antenna is completely extended, go ahead and turn on your transmitter. Do not panic if any of your motors begin to move slowly, you simply need to adjust the trim. Consult your transmitters manual to find the trim knob/lever on your transmitter and adjust it in small increments until that motor stops turning.

4. Go ahead and start playing with your transmitter to see how your motors respond. If you have a joystick on your transmitter push it slightly forward, if one motor starts turning before the other one, you need to adjust the trim some more so they both start turning at the same increment on your joystick.

Below are some common bugs that are found when first wiring your robot. Please read through them and follow the instructions to debug and fine tune your robots drivetrain for safe and desired operation.

When I turn on my robot and try to test it nothing happens. What is wrong?

Well to start with lets make sure it is actually on. Check the master power switch to be sure it is in the on position and also check to be sure your transmitter is on. Next be sure any batteries in your robot are not dead...this includes the transmitter battery, receiver battery, and the drive motors batterie(s). Also check to make sure your crystals in your transmitter are the same channel as the crystals in your receiver, and that both are properly plugged in. If the problem still persists please feel free to contact us and we will help you work through it.

When I turn my transmitter on, one of my motors keeps turning without me even pressing on the joystick. What is going on?

You simply need to adjust the trim. Consult your transmitters manual to find where the trim lever on your transmitter is and in small increments make the adjustment until it stops turning.

When I press on my joystick really slow one motor starts turning before the other one. How do I fix this problem?

Again this is just another trim issue. You just need to bump back the trim on the motor that is turning first, or bump forward the trim on the motor that isn't turning first.

When I press forward on my transmitter, one motor goes forward and one is going backwards, what is up with that?

This is an easy fix. If you press forward on your transmitter and one or both of the motors are going backwards, you simply just need to go back to your motor controller and switch around the red and black MOTOR wires on the motor that is going rotating backwards. Do not switch around the battery wires under any circumstances.

Only one motor is turning when I move my joystick, what happened to the other motor?

First check to make sure the wires are properly connected from the bad motor to the speed controller, and also from the batteries to this motors speed controller. Also check to be sure the PWM wires are plugged into your victor correctly. As mentioned before it is easy misalign the pins and not realize it. Unplug it and plug it back in carefully once again.

My robot is not responding very well to my transmitter. What do I do?

First, check to be sure that your transmitters antenna is fully extended and that the batteries in both your transmitter and receiver are not dead. If the problem still persists, check to make sure your antenna is at least 1 inch away from any metals. Even if it is not it sill could be picking up interference from the electric and magnet fields created in your robot. See if moving the antenna around helps the problem. If the robot is responding well with the antenna out in the open, then you found the problem.

Well that pretty much covers the basics of wiring a robot. If you need help with anything on your combat robot at all please feel free to contact us. Comments or questions on this tutorial are welcome. If you feel anything should be added to this tutorial please send your inquires to us as well, we do our best to make sure the site is the best it can be. Thanks for taking the time to read this tutorial and good luck with all your robotic combat applications!