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External Power Supply for SCB-100

I have 2 PCI DIO-96 boards and SCB-100 interface blocks.
I will be controlling 180 solid state relays.
Can I use an external 5 VDC power supply, and how do I connect it into the system?
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Message 1 of 13
Hey dlhendel,

What would you like to use the power supply for?  You do not need an external power supply to power the system.  You can power the SCB-100s using SH100-100-F cables connected from your PCI DIO-96 cards.

I hope this helps!
- Erik
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Message 2 of 13

Where do I get the power for the logic side of the solid state relays? 

Will the PC provide this? 

Will the PC handle 180 SSRs switching on and off rapidly in a random order (used to control heat zones in an oven)?

The SSRs are rated at 10 ma (current regulated) each, so that would be 1.8 amps when all are on.

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Message 3 of 13
You should refer to the solid state relay data sheet for input specifications. Usually the input current is 20mA max. Most digital outputs can handle 20mA but you should refer to the specifications of the board you use.

In the worst case (all relays activated) the total input current will be 3.6 amps.

If your pc power supply can handle this extra current you can connect a cable to one of the internal power supply plugs. I have seen slot covers with banana plug sockets and cables to power external circuitry with the pc power supply.

But - any short on the external circuitry will cause power failure of the pc. So I think it is a better choice to use an external (well-regulated) 5VDC power supply. The GND terminal of this power supply should be connected to GND of the digital outputs.
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Message 4 of 13
Sorry - I did not read your calculation of total current.

Since today's pc power supplies can supply 25 to 40 amps on the 5VDC line 1.8 amps extra should not matter too much.

In case of an external supply the GND terminal MUST be connected to system GND.
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Message 5 of 13
Thanks, but I'm still not clear how I would connect an external power supply.  You seem to imply that I can in your last statement.
Do I just connect the external supply GND to pins 50,100 and +5 to the solid state relays?
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Message 6 of 13
I am not familiar with the SCB100 interface blocks, and I cannot study all the data sheets in detail.

In general, if you use external power supply/ies together with a control system, the GND terminal of the power supply must be connected to system GND. I think most interface or break-out boxes should have a GND terminal which is connected to the control system GND.

This is NOT necessary (and even NOT recommended) if your interface has opto-isolated outputs. GND connection in this case depends on the configuration of the outputs and cannot be determined from the distance.

On all SSR I have seen you can connect the (low voltage) power supply directly to the (+) terminal of the input. The (-) terminal of the input should be connected to the digital output of the control system. Since your SSRs need just 10 milli-amps excitation current this should not pose any problems to most control boards - most can handle up to 24 milli-amps.
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Message 7 of 13
I'm using a DIO-96 board for relay switching and digital reading, too. The difference to your system is the operating voltage of the relays: 24 VDC. I separated them galvanically with TTL compatibel optocouplers in source connection to the board DO channels and supply the relays with external 24V power through the optocouplers' output...This works, but I think it would be even better to drive the optocouplers in sink connection with an external 5V powersupply the same way you'd like to do with your solid state relays. Take a look at page 3-11 PCI-DIO-96/PXI-6508/PCI-6503 User Manual! Maybe it's better to use the 6509 "high current" model if you use the internal power connection (if you still have the option to change).
Do you have already some experience with your application?
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Message 8 of 13
I have set up a system on my workbench with a single SSR.  I have an external 5 vdc supply (Rhino, 20 watt from AutomationDirect).

I wired the DC common (-) to terminal 100 on a single SCB-100, and the DC hot (+) to the positive terminal on the SSR.  The negative terminal on the SSR is wired to one of the output terminals on the SCB-100.  Of course, the outputs are negative logic (ie, output a "0" to turn the SSR on).

Everything appears to be working fine, but I have 2 channels that do not appear to turn on/off cleanly, other than that, all appears well.  In about 2 weeks the real test will take place when I move everything into the field.

Thanks to all for your help.
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Message 9 of 13
can you give me a PDF file of the SCB 100 (Terminal Block)

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Message 10 of 13