Basic wiring for your robot.

There's been lots of questions concerning how to wire all of the components of a robot together.
For the most part the majority of the robots are relatively simple in the electrical requirements So this page will try to keep it's explanations as simple as possible.
 


Wire Size Chart
No matter what you are trying to power you must always use a wire that can handle the current flow. Always use a bigger wire than you need. Your wires should never get hot even during heavy loads. Do not use aluminum wire! Use multi-stranded copper the more strands the better. Solid core wire has a tendency to break with vibrations and impacts. Multi-stranded always provides better current flow especially when using D/C power. Temperature also effects the wires ability to carry current. Wires flow less current when they get hot. So keep it cool Daddy-O.
 



 
Battery connections series/parallel
Since electric motors used in Robotic combat come in several different voltages you may have to use more than one battery to provide the correct voltages. So you have to wire them in either series or parallel.

The above drawing shows how to wire two 12 VDC battery's in Parallel. You can even add more battery's for even more capacity as long as you keep every connection in parallel. Which means plus to plus and minus to minus.

Producing Higher voltage from 12 volt DC battery's.

A lot of the competitors use 24 VDC for their robot main power. the above drawing shows how its done. You have to provide a series jumper between the positive terminal of one battery to the negative terminal of the other battery.This is colored blue in the drawing it is made from the same size wire as you battery cables.   Then you take your 24 VDC off of the other two terminals.

When you put battery's in series your battery capacity or Amp Hour rating will be the same as the Amp hour rating of the SMALLEST battery's Amp Hour rating that you use. So if you use battery with a 12 Amp hour rating and a Battery with a 7 Amp Hour rating your total capacity will only be 7 Amp Hours. But you will produce 24 VDC.

Of course you can continue on for higher voltages. This is where you should use large wire for maximum current flow. Remember the blue wires are just the same wire size you are using for battery cables.
 
 

You can still tap 12 VDC off of ONE battery to power 12 volt circuits. You could even use the other battery to power other 12 VDC circuits but these 12 VDC Taps CAN NOT BE TIED TOGETHER (EVER)!!! or you will have a fire. So I usually just use one battery for this purpose so I don't screw up bad. Of course one battery will drain a little quicker because of the extra load  put on it by the 12 VDC circuits you are powering. Its a good idea to use different colored power and ground wires for different voltages used in your robot so you dont mix up the power connections.
 
 

Robot main power shutoff.
The combat rules require that the must have a main power switch  so that the arena attendants (Crewbots) can shut your machine off with little or no special training. This switch or switches will disable the drive system and the weapon systems.
One of the first things to consider is what is the maximum current that your entire robot will require to run all of the motors and weapons that it uses. This will tell you how much current that the switch or the main power solenoid will have to provide. A lot of the larger robots can use 200 to as much as 1000 amps of current. These kind of current draws require large switches or more likely a Continuous type solenoid. Automotive starter solenoids are usually not designed for continuous operation. So always check with the parts supplier when purchasing a solenoid. One of the nice things about solenoids is they can be controlled with common toggle or push button on/off type switches. The way I usually use a main power cut off solenoid is to control the main battery(s) ground wire. When the solenoid is turned on ground travels through the solenoid to power the rest of the robot. When the solenoid if off no ground is provided to the robot. You can also control the positive side if you want it's up to you. Either side will work. You can also use a Relay to do the same job as a solenoid but I have found that some large current relays use a spring loaded  mechanical contact between the armature plate and the contact points.  You can have point bounce  because of the springs during heavy impacts which is a bad thing. One solenoid that looks good to me is made the Reactor company it has a 200 amp continuous rating and a 600 amp surge. Check out Summit racing products. They also sell battery cutoff switches. You should order their catalog.

The above drawing shows how to wire in a simple main power cutoff using a solenoid for the high current load and a small switch to control it. The circuit also has a diode connected across the solenoid control coil for radio noise suppression. A 1N4001 diode will work just fine. Make sure its silver banded side is connected to the positive side of the coil. The control coil in the solenoid may require an amp or two so I usually use a switch that will handle 5 amps just to be sure.


 

Radio receiver requirements.

Your radio receiver is for the most part is the brains of your robot. Well at least it gives your brain something to talk to. It's actually sort of easy to control a multitude of motors, weapons, linear actuators, and pneumatic and hydraulic control valves. The rules require that you will provide a receiver power switch. This is usually just a simple toggle switch to turn off either the ground or positive voltage from the battery to the receiver.

This drawing shows how simple the wiring for the radio control system can be. Basically the receiver circuit consists of the battery, the power switch, the receiver,  the antenna and the servos or other devices that can decode the servo signal. The output from the receiver uses three wires 4.8 volts DC,  receiver ground and the servo control signal.
In the drawing I'm controlling the throttle shaft for an engines carburetor with servo 1. The other servo (servo 2) is controlling a micro switch to control anything electrical. As I've mentioned before you can also purchase solid state switches from (Team Delta).
 

The above picture shows an entire robotic system complete with the radio transmitter, the reciever, the motor speed controller, and dual drive motors and even a Team delta R/C switch. This drawing was provided by ? As you can see it's all really easy to wire a robot for combat.

Receiver antenna mounting.
I know you will have to ask yourself. Where do I mount the antenna so it will not get torn off in combat?  Well some robots have been successful in mounting their antennas inside of the body armor. Others have put clear Lexan windows in the body armor to let the radio signal in. Some others like S.L.A.M found this not to work well. I personally use a loaded antenna in which I separated the load from the antenna rod and mounted the fragile load deep inside the robot. Then I built a spring mounted whip type antenna using coaxial wire and some plastic tubing. Our antenna has had a very ruff life but it has survived through many fights I'm sorta proud of that. You will have to experiment with placement with your design because every robot has different effects on radio reception. If you are using a Gasoline engine always use resistor spark plugs. Always try to mount your receiver antenna and servo wires as far from the spark plug wire as possible.
Oh ya when testing your robot at home after you get it working walk away from it about 50 to 100 feet and see if you can still control your robot. If you can do that your antenna works fine. It's also a good idea to test your radio range in different locations other than just your garage because radio signals can bounce around and give you false results.
You can also purchase a loaded antenna from (Team Delta.)



Electric motor control.
Controlling electric motors with a radio receiver can be done in several ways. A very common method is to use a mechanical H-bridge which can be built with two DPST relays or four solenoids. (See My page). H-bridges work well but they do not provide any speed control. For precise control of electric motors you really have to use an electronic speed controller. There are several on the market including Vantec, 4QD, Innovation first. Speed controllers are not real hard to connect to your robot as long as you follow the manufactures instructions. Some speed controllers like 4QD and Innovation first will require an interface board to decode the signal from the radio receiver. Again (Team Delta) sells an interface board for at least the 4QD speed controller. Innovation first makes their own. Before ordering a speed controller for your robot you will need to know a few things first.
1. What voltage does your motors require?
2. What is the motors stall current?
3. What is the motors continuous current?
To determine the current draw of your motor you can use the chart provided on the Vantec web site. You should also try to get the manufactures spec sheet.
 

Connecting wires to your components.
One of the major jobs in building a combat robot is wiring all of the components together. This can take quite a bit of time to complete. A complete rewire job on S.L.A.M takes me about 4 hrs. If its the first time you wire your robot you should take your time so you get it right. This is usually not a good thing to attempt at 2:00 am after you have been working on the robot for 16 hrs already. Trust me I know about this. There's hundred of different types of connectors that crimp, many require special tools. Ive found through experience that crimp type connectors work well . The only thing I do different with them is I always add some solder to the connection after crimping so I get a good electrical connection. Another thing that I always try to do with any wire terminal is to leave a little slack in the wire. Tight wire or short lengths can break when your robot gets hit hard or bent. A 1/4" of slack isn't a bad thing. It also makes it easier to repair after a fight. I also provide strain relief on all of the terminals. Normally I use heat shrink tubing that covers and insulates the terminal and continues down the wire for about 1/2" to 3/4" Also I like to use is the split plastic wire conduit to conceal all of the wires once they are run and strain relieved. After that I use nylon tie wraps or zip ties to secure every thing to the robot frame or other components. You should try to keep all of the wires from moving or vibrating so they don't break at the terminals. And believe it or not. Right before a battle Team S.L.A.M has learned to put Duct tape on all of our battery wires and connections. I hate it when the battery wires get knocked loose. Also it makes nice insulation on things like solenoid terminals that have weird shapes.

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