404 Power Supply Sizing

Power Supply Sizing

Sizing your power supply to the Tracker IPm correctly is very important.

Note: By selecting the “Independent Motor Run” option in configuration, you need only to consider the current of one motor in a dual axis system.

Example:  A Kinematics SE3B-62M-24H01-RC 3 inch Slew drive with a 24H01 brushed motor.

This motor draws 2 – 3 Amps during intermittent and continuous operation but peak Amps can be up to 4.5 when starting the motor and may last only for a few milliseconds.

Adding up all the current draw:

  • 24H01 motor  4.5 A
  • mechanical relay 0.069 A
  • Tracker IPm 0.1 A

Total Amperage = 4.669 A

One might think a 5 Amp power supply would be sufficient but if you add solid state proximity switches, anemometers or other input devices that add load you could easily exceed the capacity of the power supply.

The result of an undersized power supply manifests itself in several ways. We must understand that when the current load of the circuit exceeds the rating of the power supply the voltage drops.

The first and most obvious is the chatter of the reverse mechanical relay because relays have a minimum voltage needed to power the coil. This is called drop out voltage and is often 80% of the coil voltage. So a 24VDC coil will drop out when the power supply voltage drops below 19.2 Volts. This is potentially damaging to the motor assembly and throws off calibration because the motor is running and changing direction rapidly until the voltage recovers.

The Tracker IPm has much more safety margin since it can operate between 10-30 VDC so a slight voltage drop which may affect the relay might not affect the controller. Typically if the voltage drops below 10 volts for a long enough period you will simply reboot the Tracker IPm.  The dip can also be so fast that it negatively affect the processors and causes a communications error in both the Serial and Ethernet ports. This may require a reset of the system comm ports.

Our recommendation is to have a 30% safety margin. In this example a 10 Amp power supply is highly recommended.