Other precision data
acquisition products
Model 302 EXPv3  3-Axis
Expansion Board for Model 302

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


similar expansion board with 2 proportional drive outputs


The Model 302EXPv3 is optimized for three axis DC motor control. The three channels of proportional drive are suited for 12 or 24 VDC motors of up to 45 watts each in continuous operation. Each proportional drive output channel can be individually isolated, or all three can share a single power source. Linear actuators with potentiometer feedback will provide excellent performance at a fraction of the cost of stepper motors. The precision analog inputs (24-bit resolution) and other digital I/O provided by the combination of the Model 302 and the EXPv3 stacking expansion board provide the needed interfacing for robotics, materials handling, materials testing, and a wide variety of industrial equipment and instrumentation.

3  PDr2 Proportional Valve Drivers, both normally OFF (DAC channels 1, 2 & 3)

1  7.5 volt, 100ma buffered reference output.

1  set of three terminals for string pot connection (A/D channel 2)

1  set of three terminals for RTD or thermistor connection (A/D channels 3 & 4)

1  isolated input precision F-to-V converter (A/D channel 1)

8  250 ma current sink digital outputs for driving solid state relays, etc.

1  PWM output from DAC 3

Connector for jumpers to share power with the M302 board

4  tie point terminals for V+ connection for poppet valves, relays, etc.

Analog input features can be bypassed on an individual basis.

2  spare terminals, plus a prototyping area

The EXPv3 expansion board stacks on the expandable version of the Model 302 Data Acquisition System. The expansion board contains a mixture of interfacing circuitry suitable for a wide variety of acquisition and control applications. Inputs can be voltage, current, frequency, or resistance, with accomodation for RTD or thermistor temperature sensors or bridge sensors. Analog Outputs can be voltage, current, or PWM. The optically isolated current outputs can sink 2 amps or more. Digital outputs can sink up to 250 ma.

The individual interfacing blocks are based on proven, high performance products and are designed for use with our 24-bit data acquisition systems. High impedance analog inputs can interface directly to ion selective and pH electrodes. High resolution allows direct interfacing to bridge sensors or even thermocouples.

Proportional Load Drivers, 3 available
Three proportional drive circuits are provided. They are optically isolated power drivers for solenoids, valves, DC heaters, DC motors, and other DC loads. Loads can be inductive or resistive. These drivers provide a proportional current sink from 0 to 2 amps continuous. The current output follows an analog voltage from a corresponding analog output on the Model 302 data system. For continuous operation above 2 amps, optional heatsinks are recommended.

A proportional valve, a motor, and a heating element are examples of loads that can be controlled with resolution matching the analog control voltage. Expensive loop controllerscan be replaced for improved performance and much lower cost in many applications. DC motors with potentometers for position feedback can replace more complex and expensive stepper motors.

Control up to 2 amps continuous current at between 10 to 24 volts, optically isolated
Input side power supply, 12 to 20 volts, shared with Model 302
Input control voltage 0-5 volts
Efficient, so that no active cooling is needed.
Typical modulation frequency 20 KHz
Modulation frequency is preset, but can be factory set over a wide range
Load can be inductive or resistive
Built-in 5 amp 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

Counts-to-Volts input, one available
A frequency or pulse stream can be converted to a precise analog voltage. Resolution is good enough to see a single edge while still being able to handle 380 kHz. The input can be from any sort of pulse or frequency generator, including position sensors and radiation detectectors. A proprietary Sigma-Delta demodulation approach is used for superior accuracy and stability.

18 bit resolution, high stability counts-to-volts converter
Optical isolation on input
Dual sensitivity ranges, 0 to 7.5 kHz or 0 to 380 kHz
Edge triggered, duty-cycle independant
0.25 second time constant, or custom factory setting

See the Model 106 for more details

Digital Outputs
Eight current sink outputs are provided. These accomodate up to 30 volts at 250ma continuous current. 100% overcurrent can be sustained for a fraction of a second.

Digital Inputs
4 digital inputs, logic level or contact closure, feed directly to the Model 302 digital input terminals.

PWM Output
Analog output number 3 is available as a duty cycle on a screw terminal on the the expansion card.

Other Input
Circuitry and connection points are provided for RTD or thermistor inputs. Connections provided for string potentiometer or other ratiometric inputs. Power connections are provided for powering a bridge circuit or other powered sensor. The bridge excitation is 7.5 volts at 100 ma on the standard board. Ask about factory options.

Power Requirement
The expansion card is powered from the Model 302's power supply. The expansion card adds approximately 25 ma plus 4 ma per active digital output to the power requirement. Add the current required by the power reference, if any. Proportional Drive and Digital loads can be be powered by the same supply, if sufficient, or by external isolated or unisolated power sources. All three proportional drive channels can share the same power supply, or each can have its own, isolated, power supply.

As a rule of thumb, if the Model 302/Expansion board supply can provide 100 ma, plus any power reference current, it should be fine.

The system is designed to be easy to customize. Contact the factory for a different mix of features, or entirely new capabilities.

Starting Price


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

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