Other precision data
acquisition products
PDr2 Optically Isolated Power Driver

block diagram
PDr4 Proportional Drive 1/3HP 48V Motor Drive

3-Axis Motor Control Expansion Board for Model 302

The PDr2 is an optically isolated power driver for solenoids, valves, DC heaters, DC motors, and other DC loads. It provides a stabilized current output from 0 to 2.5 amps, or more. 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 PDr2 can replace expensive loop controllers in many applications.


Output up to 2.5 amps, or more, at 8 to 24 volts, isolated or not

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

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

Input control voltage impedance 100K

Efficient, so that no extra cooling is needed. Only 5 deg C temperature rise in still air driving a 1 Amp load

Power input current 6 ma typical at 1500 Hz modulation frequency
Modulation frequency is preset, and 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 middle 90% of the range

1.9" x 2.7" x 0.6"
Efficiency over 98%, no heatsink or fan needed


An offset adjustment trimpot can be added
4-20 MA input can be added
The optical isolation can be removed, if it is not needed
Normally ON or Normally OFF versions available

Other variations include
Voltage Output
Higher Voltage or Current ratings

The PDr2 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. Typically, above a 250 mv control input (0 -5 volt range), the output is fully linear. There may be a similar non-linear band as the maximum power is appoached.

Because the control is modulated, dithering in the hardware is not usually necessary.


Contact us for sales or technical assistance   lawsnlab@lawsonlabs.com
This page last reviewed/modified: