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I have a basic kit consisting of a TP-132-042 (4WD All Terrain Robot Platform – IG42 SB) and TE-900-004 (Programmable xBee Control Interface Package). So far, I am using the Arduino/Xbee package as received. I’ve made no modifications or additions to the code. The issue I keep having is that sometimes the performance is smooth and other times the robot will start/stop and act very jumpy while I am moving the joystick. My robot will literally take short hops instead of moving smoothly. I’m using 78 RPM motors. On the robot, I have the electronics mounted on the top surface. I hold the controller such that there is no obstruction between the transmitting XBee and the receiving XBee. Sometimes the robot won’t move at all and I have to recycle power to the controller to get it going again.
These are all tell tale signs of a noisy system. We have lots of support topics on noise. Check for ground loops. Try capacitors across the motors. Shielded wires for the motors. Shielded wires for the serial signal. Short runs for the serial and control signals. Ferrite beads. Make sure the xbee is far away from motors and other electrical noise. Don’t run power and signal along the same path, ideal is perpendicular for any crossings, but keeping as much distance as possible. Twist wires (the plus and minus) if they are not shielded. Best to have a separate power source/battery for controls and xbee than the motors, if you do this make sure the same ground is used and no ground loops. There are probably other tricks too. I doubt you will have to do all these fixes, but you are definitely going to have to do some of them based on your description.
Thank you for the quick reply. I attached a photo of my robot. It shows the two 12V batteries feeding the Sabetooth controller. From there, 24V is fed to the regulator and the regulator output is fed to Arduino. I added a voltmeter to show the battery voltage. The lines from the motors are shielded and trimmed as close as possible to the controller. As per recommendations in a previous post, I removed the 12 capacitors on the motors.
I agree that it could easily be a noise issue. It could also be a connection issue. The output from Arduino to the controller is a simple pin stuck in the header and this isn’t the best way to make a connection. I will look into soldering it to the pad beside the header instead.
I will also try powering the Arduino from a separate battery, either a small 12V SLA or possibly a 9V battery. I don’t know what the current draw is yet, but for my requirements, I only need to run the robot for short periods of time in my test lab.Of course, I will connect the ground from that battery to the ground on the Sabertooth. In this case, I can eliminate the regulator circuit.
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