Other precision data
acquisition products

PDr4 Proportional Drive
1/3HP 48V Motor Drive
block diagram
PDr2 - Lower Voltage and Power Alternative

3-Axis Motor Control Expansion Board for Model 302

The PDr4 is an optically isolated power driver for DC motors, solenoids, valves, heaters, and other DC loads. It provides a stabilized current output from 0 to 6 amps, or more for brief periods. The current output is in proportion to an analog control voltage. That voltage can be provided by an analog output from a Lawson Labs, data system, or from any other source.

A proportional valve, a fan, a motor, and a heating element are examples of loads that can be controlled with resolution matching the analog control voltage. A Lawson Labs data acquisition system and a PDr4 can replace expensive loop controllers in many applications.


Optically isolated

Continuous output 6 amps, at 8 to 48 volts

Withstands brief 50 amp overcurrent spikes

Input power supply, 8 to 20 volts, reverse-protected

Input control voltage 0-5 volts (or 0-10 volts)

Input control voltage impedance 50K

Efficiency up to 99%, no extra cooling is needed.

Power input current 12 ma typical at 22 kHz modulation frequency

Modulation frequency is preset, but can be adjusted to suit

Hysteretic thermal overload protection

Load can be inductive or resistive

Built-in freewheeling diode for inductive loads

Gain is adjustable via on-board trim potentiometer, 0 - 100% range

Output is monotonic

Linearity is excellent over the upper 90% of the range

1.9" x 3.4" x 0.6"

No fan needed for most applications


Modulation frequency can be factory set

Heat sinks for increased output

4-20 mA input can be added

The optical isolation can be removed, if it is not needed

Normally OFF is standard, a Normally ON option is available

Ask about a reversing version of the PDr4 for bidirectional DC motors.

The PDr4 is ideal for use inside a control loop. The temperature, pressure, position, etc. that is being controlled is sensed and read by the analog data system. Then, the analog output can be adjusted according to a programmed set of rules.

The trimpot can be adjusted for the desired maximum current output with the maximum voltage input.

The current output will be zero with 0 volts in. There is a non-linear zone coming out of zero volts. Full linearity begins between 250 and 500 mv at the control input (0 -5 volt range).


Contact us for sales or technical assistance   lawsnlab@lawsonlabs.com
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