MATE Triggerfish Trouble Shooting the Sabertooth 2X5 Motor Controller

Sabertooth Documentation The Sabertooth 2X5 motor controller is used on the MATE Triggerfish ROV kit and has shown to be very reliable, versatile, robust, and forgiving. The Sabertooth is produced by Dimension Engineering and their website (http://www.dimensionengineering.com/products/sabertooth2x5) provides a ton of information. The Sabertooth is cleverly designed to accept a variety of input signals and power sources. This can make their documentation a little challenging for new trigger fish builders but highly valued by an experienced Ranger or Explorer ROV Team. For the triggerfish the Sabretooth is using MODE 1: Analog Input so only pages 1-4 and 6-9 of the Sabertooth user documentation is of interest. The purpose of the following information is not to duplicate the Sabretooth documentation but to provide a supplement on how to trouble shoot your controls that use the Sabertooth 2X5 motor controls. 2

OH No.. If you are reading this section it is because there is an issue with your triggerfish Sabertooth motor controls. Don t panic it is fairly straight forward to troubleshoot the Sabertooth motor controllers and all you need to know is how to use a multimeter to read DC voltage and resistance. But before you start the troubleshooting, turn off the power to the ROV, open up your control box and turn it upside down. It is always amazing how many little bits of solder and wire end up in the control box during construction. Any one of these little devils can result in random shorts causing your controls not to operate correctly. 3

Step 1 Power Yes? This may seem counter intuitive but the first step in troubleshooting your controls is disconnect all the wires from the Sabertooth except for the red and black power connections that go into B+ (red or positive) and B- (black or negative). We use this approach to first isolate the Sabertooth from the ROV wiring. What you should see 1) Turn on the ROV power, the status light should be blue on the Sabertooth. 2) With your multimeter set on VOLTS DC touch the red multimeter probe to the B+ screw top and the black multimeter probe to B- screw top. The meter should measure approximately 12Volts across the B+ and B- terminals, this is the input power to the Sabertooth. 3) If you are not measuring approximately 12 volts then there is a poor connection in some of the black or red wires between the Sabertooth module and the incoming power. 5

Step 2 Control Signal OUTPUT The next step is to check the Sabertooth is producing the 5V DC control signal output that will be sent to the potentiometers that are located on the side of the joy sticks. ROV power is on. What You Should See 1. With your multimeter set on VOLTS DC touch the black multimeter probe to the 0V screw top and the red multimeter probe to 5V screw top. The meter should measure approximately 5 volts. 2. Keep the black multimeter probe on the 0V screw top and move the red multimeter probe to S1 and then S2 screw top. In both cases you should read 2.5 volts DC. 3. If you are not getting these readings, remove the joystick wires from this connector and repeat. If the numbers are good, then the joystick has a short circuit. If they are still bad then the Sabertooth might be bad. 6

Step 3A Control Signal INPUT Turn off the ROV power and then reconnect the two black wires from the joystick into the 0V connection on the Sabertooth, the two red wires from the joystick into the 5V connection on the Sabertooth, one of the white wires from the joystick into S1 and the other white wire into S2. What You Should See 1. Turn on the ROV power. Put the black multimeter probe on the 0V screw top and move the red multimeter probe to S1. Initially the voltage will be approximately 2.5V and as you wiggle the joy stick you will see the voltage dance from approximately 0 to 5 volts. 2. Put the black multimeter probe on the 0V screw top and move the red multimeter probe to S2. Initially the voltage will be approximately 2.5V and as you wiggle the joy stick you will see the voltage dance from approximately 0 to 5 volts. 7

Step 3B Control Signal INPUT If the voltage is constant no matter how much you move the joy stick around on either S1 or S2 then your motor controller will not have a valid input signal and will not operate correctly. Several possible problem areas are described below. There could be a short between the white control wire on the potentiometer and either the black or red wire on the potentiometer. Picture on left shows short between white and black wire. There could be a short between the white control wire on the Sabertooth and either the black or red wire on the Sabertooth. Picture on left shows shot between white S1 and red wires. These types of shorts typically happens when too much bare wire is left showing on connections that are side by side and over time as the ROV is jostled around the wires get bent together resulting in a short. These types of shorts are maddening because typically the ROV was working fine and suddenly after being jostled around for awhile it no longer works. 8

Step 3C Control Signal INPUT Another possibility for not having a control signal input (S1 and S2) is that the potentiometers on the joystick are not functioning correctly. This can occur from over heating the potentiometer during soldering. An easy way to test this is to set your multimeter to measure resistance. The omega, funny looking horseshoe, is the symbol for resistance on most multimeters. Hook one of the multimeter leads to the white S1 wire and one either to the black or red wired that goes to the same side of the joystick as the S1. Use alligator clips to make sure the connection to the meter are solid. Turn on the meter. Initially the reading should be approximately 2.6K ohms with the joy stick not moving. As you wiggle the joy stick around and you should be able to see the readings go from 0 to almost 5K ohms. Repeat the same process for the S2 wire and the other potentiometer. If the readings do not vary from 0 to approximately 5K ohms then the potentiometer is damaged and will need to be replaced. 9

Step 4 Output to the Motors The next step is to check the output that goes from the Sabertooth to the motor tether wires. The motor tether wires should still be disconnected from the Sabertooth. What You Should See 1) Turn on the ROV power, the status light should be blue on the Sabertooth. 1) With your multimeter set on VOLTS DC touch the red multimeter probe to the M1A screw top and the black multimeter probe to M1B screw top. Wiggle the joystick for the S1 input and you should see the voltage change from approximately +11.5VDC to -11.5VDC. 1) Repeat step 3 for the M2A and M2B motor connections. 10

Step 5A: Motor Tether Connections If you have completed through step 4 and obtained all the desired readings then congratulations the Sabertooth is working properly. Though, unfortunately you still could have issues with the tether connections to the motors. Sadly this is the most common issue and the biggest source of poor ROV performance. Testing the Motor Tether connections The easiest way to test the tether wiring is to measure the resistance across each set of tether wires going to a motor. Set up your multimeter to measure resistance on its lowest setting (typically 200 ohms Hook one of the multimeter leads one of the motor tether wires and the other end of the multimeter probe to the other motor tether wire. You should get a reading between 3-6 ohms. 11

Step 5B: Bad Motor Connections - OPEN There are two kinds of faulty tether motor connections; bad connections that result in high resistance and reduce the power to the motor and shorts were the motor will not work at all The Wire Splices power point describes how to make good water proof connections. Bad Connections High Ohms Bad motor tether connections can result from not properly soldering the motor and tether wires together. As the wires wiggle around or get pulled the connection get worse and worse and can ultimately completely separate to create an open circuit. Another source of a bad motor connection is corrosion due to pool water leaking into the wire connections. Over time the corrosion can completely eat through the wires. 12

Step 5C: Bad Motor Connections - SHORT The other type of bad motor tether connections is a short. A short is when the metal from the inside of the two motor or tether wires touches together. Keep in mind water conducts electricity so if both of the motor wire connections are not waterproof and are not touching then a weak short can develop resulting in poor motor performance. A range of consequences can occur if the motor tether wires become shorted. Bad Connections Short The best outcome from a short in the motor tether wires is the Sabertooth will turn itself off, due to the high current, and the Sabertooth status light will go red. Your controls will not work properly until the short is cleared. The worst outcome from a short in the motor tether wires is when the Sabertooth burns up. You will know when you smell it. 13