Figure A1. Simple

There is only 1 external power supply, and 1 item being controlled.

Figure A2. Multiple Items

There is 1 external power supply, and 2 items being controlled.

Figure A3. Multiple Power Supplies

There are 2 power supplies, and 2 items being controlled.  The high voltage DC motor requires a 4.7Ω inrush current limiter to help protect the PS12DC from the large inductive load inherent to a DC motor. See Appendix D for more information.

Figure A4. Multiple Items, Single Supply

5V is distributed to all 6 power supply blocks. All 12 switches are fed 5V from the LabJack.  This is a common configuration for simple testing, since the LEDs will illuminate when the LabJack is powered on, and it does not require an external power supply.

Summary

The PS12DC can be connected several ways, the most common is through the DB15 connector.  The following sections explain how to connect the board by using the extra connectors, and details about using multiple PS12DC at a time.

Single PS12DC

The PS12DC can be connected according to any of the following figures.  All 12 switches will be operational, and their corresponding digital control lines can be referenced in Appendix C - Pinout Info.

Figure B1. Connected by P1 - DB15 Connector

Figure B2. Connected by P2 - DB37 Connector

Figure B3. Connected by P3 - 14 Pin Header

Figure B4. Connected by J1 - 16 Pin OEM Header Location

Figure B5. Connected by J2 - 40 Pin OEM Header Location

Two PS12DC

This section explains how to connect a second PS12DC to each LabJack device, and the number of additional channels provided.  It is assumed that the first PS12DC is connected to a LabJack through the DB15 connector.

• U3-LV:  (10 addtl. switches)  Connect a second PS12DC to the U3-LV by wiring the P3 header to the screw terminals.  A ribbon cable with a rectangular connector is recommended for the task.  Attach the female connector to the board, and splice the wires for the screw terminals on the U3-LV.  DI0-DI7 would be wired to FIO0-FIO7, and two of the remaining digital input lines (DI8, DI9) can be connected to DAC0 and DAC1. Connect the two GND pins to GND on the U3.
  • Something like NKK Switches part number ISDCB812 (12 inch), or ISDCB824 (24 inch) would work, but anything with at least 14 positions, and 0.1" spacing should do the job.  It also works to combine a 2x7 14-pin dual row IDC socket with some rainbow ribbon cable, if you prefer to assemble the cable yourself.
• U3-HV: (6 addtl. switches)  This is the same as the U3-LV, with the exception of the first 4 FIO channels; Since they are dedicated analog inputs, the U3-HV will limit the second PS12DC to only 6 extra channels, instead of the 10 possible for the U3-LV.
• U6, U6-Pro: (10 addtl. switches)^[1][2]  Connect the second PS12DC to the U6 via the P2 connector.  Reference the silkscreen table for corresponding digital lines.
• UE9, UE9-Pro: (12 addtl. switches)^[1]  Connect the second PS12DC to the UE9 via the P2 connector. Reference the silkscreen table for corresponding digital lines.
• T7, T7-Pro: (12 addtl. switches)^[1]  Connect the second PS12DC to the T7 via the P2 connector. Reference the silkscreen table for corresponding digital lines.

^[1]When connected to the DB37 connector on either the U6 or UE9, some of the analog inputs are covered up.  To address the problem, those analog inputs re-appear on the PS12DC, under the P2-BREAKOUT header.  Reference Appendix C - Pinout Info for details.
^[2]The U6 shares CIO0, CIO1, and CIO2 with MIO0, MIO1, and MIO2. They are merely different names for the same digital channels. This causes some interesting behavior when two PS12DC are connected to a U6, since a state toggle in a CIO line will effect both boards.  Switch S8 on P1 will toggle at the same time as S10 on P2 . Also S9 on P1 will toggle at the same time as S11 on P2.  Because of this overlap, there are really only 10 unique channels provided by the second PS12DC, when connected to a U6.

OEM Capability

 

Summary

P1, P2, and P3 are basically just 3 alternate ways to connect the PS12DC.

P1 - DB15 connector (top left): Mates to small and large LabJacks, like a U3

P2 - DB37 connector (bottom): Mates to only larger LabJack models, like a U6

P3 - 14 pin header (top right): Can be used to wire the board to any other digital output source, like an Arduino.

P2-BREAKOUT - 16 pin header (bottom): For access to covered-up analog inputs when the PS12DC is connected to a LabJack via P2.

When connected to a LabJack, or other digital output source, the name of the output can be determined by looking at the chart below.

Table C1. Channel output and PSU input based on switch number

Table C2. P2 breakout

Example:  Connect the PS12DC via the 15-pin D-Sub connector on a LabJack U3.  You desire to toggle power to switch S9, so you locate the appropriate connector in-use, which is P1, and then follow the row for S9, which points to CIO1.  This means that changing CIO1 from output-low to output-high will change the S9 terminal from 0V to whatever voltage is connected to VS5 and GND5.  

Detailed pin-out

The detailed pin-out information below is for advanced users.  It may be useful to people making a custom board that mates with the OEM PS12DC, or someone who needs to use the rails VM+ and VM- in addition to a PS12DC that is connected on P2.  Most users need not concern themselves with this section.

Table C3. Detailed pin-out information for all connectors on PS12

Summary

• 5 to 28V supply voltage
• 750mA per channel
• Thermal (self-resetting) fuse protected >1.5A per pair
• Flyback protection >33V
• Operating temp −40 °C to 85 °C
• Maximum switching frequency: ~6kHz (see Switching Frequency section)

When at the upper limit of its operating voltage and current, the PS12DC can become hot to the touch; This is normal, but can be managed by supplying a fan or heat sink to the backside of the board.  Reference the information below for further details on current limitations, and behavior at extreme temperatures.

Digital States

What a switch will do in each of the 3 LabJack I/O states.

• Output-high: Switch ON, the S# screw terminal will be at VS#
• Output-low: Switch OFF, the S# screw terminal will be at ~GND#
• Input: Switch is weak ON, due to LabJack internal pull-up resistors.  LED will light up without anything on the switch, but marginal load on the switch will drop the output voltage significantly, and turn off the LED.  Because behavior is ambiguous, the input I/O state is not recommended.

LEDs

Each LED is powered by the voltage connected on VS#/GND# (the power supply provided by the user).  If a power supply is connected to the switch block, e.g. VS1/GND1, and a positive voltage is applied to the digital inputs for that block, the LEDs will illuminate.  An illuminated LED means that the switch is ON, and the voltage applied to the block is available at that switches' screw terminal.  

Current Limit

The 750mA per channel rating is a base specification, but the board actually has a Per Switch and Per Pair rating.  If only a single channel in a channel pair is in use, the per switch limit applies.  If both channels in a channel pair are used, the per pair limit applies.  Channel pairs are distinguished by the grouping of screw terminals.  For instance, S0, and S1 constitute a pair, so you would connect the high current item(>750mA) to S0, and leave S1 un-connected.

Table D1. Current limits based on supply voltages

There is a voltage drop across the switch associated with load current when using the PS12DC.  It is rated at 750mA per channel, but it is recommended that at 5V, a load current of 500mA not be exceeded, since above this current the drop will be significant.  Reference the graph below for details.

From a usage standpoint, the only items in the Typical Applications section that may draw more than 450mA are those involving motors. Before purchase, it is advised that you reference datasheets for the items to be controlled.  If the current draw exceeds 1.5A on a power switching pair, this board will cut off power to avoid damage to itself.

Note: If you need a product that can handle more than 1.5A, the RB12 is a good option, although you will need to purchase the actual relay modules separately.

Switching Frequency

The switching speed of the transistors on the PS12DC are fast(4-18µS), but there is a substantial amount of capacitance on the S# terminals, so the falling edge will be delayed by large load resistances.  Thus, to achieve fast switching frequency, it is necessary to discharge the capacitance through a small resistor.  Simply add a 100Ω resistor between the switch output and the GND terminal (in parallel with whatever you have connected to the switch output). With a 100Ω resistor installed, the switching frequency is on the order of 2.5kHz.

Table D2. Switching frequencies based on load resistance

Note that it is possible to install smaller resistor values(<47Ω) to further increase switching frequency, but the resistor should have a high enough power rating to handle the heat.

Temperature Related Characteristics

The PS12DC becomes warm under continuous usage; This is normal, but if the average board temperature becomes too hot, the fuses will trigger somewhat before their rated 1.5A maximum, and the board could end up cycling on/off intermittently depending on how fast it cools between cycles.  

This temperature dependency is directly related to the thermal derating curve on the resettable fuse.  The fuse trip current drops about 50% at the highest end of its operating temperature.  See the graph below for further details.

Adding heat sinks to the transistors can increase the per switch current limit, but exact figures depend on factors such as heat sink material, passive vs active cooling, and establishing good thermal contact with the transistor case. Bear in mind that the current limit of the resettable fuse is still temperature dependent, so any gains due to heat sinks would still be limited by the fuse holding current, which is 1.5A at 25 °C.

Large DC motors

If using a larger DC motor (above 12V DC, or bigger than 1" diameter as a general rule), we recommend installing supplementary snubber diodes, and inrush current limiters, as large flyback and inrush currents can overwhelm the protection circuitry on the PS12DC, resulting in damage. 

In DC motors
Voltage equation is V = E - IaRa
where
V = terminal voltage
E = Back emf
Ia = Armature current
Ra = Armature Resistance

In the beginning E = 0 and V = IaRa
where Ra is always very low, about = 0.01 ohm

So, if you calculate for Ia = V/Ra, you will get large current. 

Using the equation above, if you have a 24V DC motor, and the armature resistance is 0.01ohm, the current spike would be very large. In order to protect the PS12DC, a 5Ω to 15Ω inrush current limiter installed in series with the motor wiring would be sufficient to protect the PS12DC. This B57153S479M 4.7Ω inrush current limiter  is a good option for 12V to 24V DC motors in the 750mA to 1.5A range. We also tested this B57153S100M 10Ω inrush current limiter up to 28V DC, and it worked well.

Select an inrush current limiter based on the current required during normal operation. For example, if I'm using a 24V DC motor, and normally the motor will draw about 1A of current, I would select a limiter of 4.7Ω at 25C, and around 2A steady state max.  Inrush current limiters basically have some resistance when their temperature is equal to ambient, and then as the part heats up, the resistance drops substantially. So if the motor draws 1A of current during normal operation, the resistance of the current limiter will drop from 4.7Ω to a lower resistance(~0.5Ω) during normal operation.

If you don't mind sinking some extra power, and a voltage drop, you could simply install a very high wattage resistor in series. A 5Ω 20Watt resistor would protect as well as an inrush current limiter, but at 24V, and 750mA, there would be a voltage drop of 3.75V.  The resistor would get warm (super hot) because it'd be sinking 18W of power during normal operation. Here is an example of a 5Ω 20W resistor.

Multiple Power Supplies Example

Lets say you want to control a 9V fan, a 9V motor, and a 5V relay.  The configuration closely resembles Figure 3 of Appendix A - Wiring Diagrams. 

Connect the 9V power supply to an inward facing VS/GND pair.  Next connect the 5V power supply in a similar fashion. The image shows a 9V PSU connected to VS4/GND4, and the 5V supply on VS3/GND3.  Finally, wire the fan and motor to a switching pair, with the positive side on S6, S7, and the negative side on GND4.  The remaining relay is connected to the same area as the 5V PSU, positive side to S4 and negative to GND3.

Note: In the image the 9V supply is also spread to remaining switching pairs, similar to Figure 4 of Appendix A, but they are unused.  

Turning the equipment ON/OFF is done by referencing the chart printed on the center of the PS12DC.  Since the LabJack is connected to P1, that is the column of interest.  Scan down the side locating switches number S4, S6, and S7.  Next to S4 you will see EIO4, S6 -> EIO6, and S7 -> EIO7.  It is not readily visible in the photo, but Appendix C - Pinout Info also contains the chart.  Turning each external device on is as simple as toggling the state of those digital lines(EIO4, 6, 7) to output high. 

Video Example

The video below shows the two PS12DC boards controlling several 18V solenoid valves. A C++ script issues commands to the U3-LV, which in turn controls the solenoid valves to open and close rapidly. The setup is a prototype for an automated bartender; Each valve will be connected to a different alcohol, and will mix together to create a unique drink.