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What is the relationship between input power and torque for pan tilt units?

FLIR offers a brick-type power supply transformer for its pan tilt units (PTUs). Some customers choose to power the PTU with their own supply. FLIR recommends a 3-amp limit for users specifying their own power supply.

Although the PTU will allow basic operation at input voltages down to 12 V DC, maximum speeds and torques will not be achievable. The motors are the major power draw in the system, so as input voltage drops from 30 V, so does the current applied to the motors. The motors are basically connected directly to the power input (there is current limiting and low voltage shutoff but no voltage regulation). So if you supply 30 Volts to the PTU, the motors see 30 Volts; if you supply 12 Volts, the motors see 12 Volts. While not quite a V=IR relationship, lower voltage means less current that the motor can draw. The power mode setting for the motors sets the max current. If the voltage supplied can’t drive that current, then max current will not be reached.

So while a PTU can draw up to 60 Watts in high power mode with 30 Volts input, it will not draw nearly as much power with a 12 Volt input and torque/speed will suffer.

FLIR`s Tech Note 44 describes the PTU torque-speed measurements and implications on system design.