The LJTick Relay Driver (LJTRD) is a signal conditioning module That Allows two digital outputs to each control up to 50 volts and 200 mA. The 4-pin design plugs into the standardDIO / DIO / GND / VS screw terminal block found on newer LabJacks zoals the U3 and UE9.
Extending from the back of the LJTRD are four pins. The first two pins providence +5 volt power and ground from the Labjack, Although +5 volt power is not used by the LJTRD and osmanthus is not connected to anything. The other two pins connect to digital I / O on the Labjack. The four-pin plug directly into the 5.0 mm spaced screw terminals on the Labjack U3 / UE9 as shown in Figure 2. The LJTRD shouldering be plugged into a digital I / O block, as Opposed to an analog I / O block.
The LJTRD Has A 4-position screw-terminal connections providing the Following:
RA / RB: The high side of each output switch. When IOA / IOB from the Labjack is set to output high, the respective switch is closed. When IOA / IOB is set to low output or input, the respective switch is open. Each switch can hold off up to 50 volts and can sink up to 200 mA.
GNDR: The low side of both output switches. Connected to Labjack GND via a 22 ohm resistor (resistor is on the LJRTD).
VR: Connect the load voltage to this terminal to bias the internal clamping diodes on each switch. If each switch Has A different load voltage, the highest voltage shouldering be connected to VR. The clamping diodes help suppress switching transients, and can be important Particularly When dealing with inductive loads zoals mechanical relays or solenoids. Although this connection is optional, there is no reason Usually not to use it.
When connecting a relay or other type of load, there will be a voltage drop depending on current. Below is a chart-which Represents the voltage drops That can be expected at various currents.
If operating at high frequencies, please note the Following table. Axis current through the Relay Driver Increases, the cutoff frequency ook Increases, Which Means That if you encounter problems at high frequencies, the load resistance shouldering be Decreased to allow more current to flow through the Relay Driver. This behavior is almost never a problem When controlling relays, relays since Typically draw 3 to 20mA, and the Labjack U3 will not output a PWM frequency Exceeding 732Hz.