RoboteQ AX3500 Wire Length Limits, Electrical Noise Reduction Techniques, Important Warning

Wire Length Limits

Wire Length Limits

The AX3500 regulates the output power by switching the power to the motors On and Off at high frequencies. At such frequencies, the wires’ inductance produces undesirable effects such as parasitic RF emissions, ringing and overvoltage peaks. The controller has built-in capacitors and voltage limiters that will reduce these effects. However, should the wire inductance be increased, for example by extending the wire length, these effects will be amplified beyond the controller’s capability to correct them. This is particularly the case for the main battery power wires.

Important Warning

Avoid using long cable lengths (beyond 2 feet) from the main power battery to the controller as the added inductance may cause damage to the controller when oper- ating at high currents. Try extending the motor wires instead since the added induc- tance is less harmful on this side of the controller.

If the controller must be located at a longer distance, the effects of the wire inductance may be reduced by using one or more of the following techniques:

•Twisting the power and ground wires over the full length of the wires

•Use the vehicle’s metallic chassis for ground and run the positive wire along the sur- face

•Add a capacitor (5,000uF or higher) near the controller

Electrical Noise Reduction Techniques

As discussed in the above section, the AX3500 uses fast switching technology to control the amount of power applied to the motors. While the controller incorporates several cir- cuits to keep electrical noise to a minimum, additional techniques can be used to keep the noise low when installing the AX3500 in an application. Below is a list of techniques you can try to keep noise emission low:

•Keep wires as short as possible

•Loop wires through ferrite cores

•Add snubber R/C circuit at motor terminals

•Keep controller, wires and battery enclosed in metallic body

Power Regeneration Considerations

When a motor is spinning faster than it would normally at the applied voltage, such as when moving downhill or decelerating, the motor acts like a generator. In such cases, the current will flow in the opposite direction, back to the power source.

It is therefore essential that the AX3500 be connected to rechargeable batteries. If a power supply is used instead, the current will attempt to flow back in the power supply during regeneration, potentially damaging it and/or the controller.

Regeneration can also cause potential problems if the battery is disconnected while the motors are still spinning. In such a case, and depending on the command level applied at

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