Other precision data
acquisition products

PDr4 Proportional Drive
1/4HP 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 4 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 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.


Continuous output 4 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 20K

Efficiency up to 99%, no extra cooling is needed. Only 5 deg C temperature rise in still air driving a 1 Amp load

Power input current 12 ma typical at 18 kHz modulation frequency Modulation frequency is preset, but can be adjusted to suit

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"

Efficiency over 98%, no fan needed for almost all applications


Modulation frequency can be factory set

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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