How to get a DIO output out of the SCB 68 for a relay

[MSUbiolab]

In setting up a thermocouple that would switch a relay at a designated temperature I cannot get the SCB 68 to swith on the relay. Using the pin P 0.1 for example there is no voltage being put out. So if there is anything else in the DAQ configuration that I might be missing please advise. The systems works when the +5 volts pin is used but I need the switch to be controlled by the temperature.

[Dennis_Knutson]

The SCB-68 is just a dumb terminal block and cannot output any voltage of any sort without it being connected to an actual DAQ device. If you have one of those connected, provide the model number. Also provide the current requirements of the relay. As you would see from the numerous posts on driving relays, you often require a current amplifier since most of the DAQ cards cannot output enough current.

[johnsold]

That's what you get when you let biologists play with electricity larger than action potentials.

1. The SCB 68 is just a connection.  What kind of DAQ device is connected to the other end?

2. Does the device have open collector (or open drain) outputs?

3. How are you connecting the relay?

4. What kind of relay? What are the voltage and current requirements for the control input to the relay?

5. How are you controlling the P0.1 output?

The more specific information you give us, the better chance we can help you.

Lynn

[MSUbiolab]

Ok it looks like I am using the wrong tool for the job with the scb 68. The whole set up is like this; 4 thermocouples as inputs which I would like to control 2 different pumps as outlets. So is there a DAQ device that you would recommend that I can attach 4 thermcouples and have at least two outputs that would supply power? Outside of the DAQ there are the relays that switch the pumps on and off depending if the DAQ output gives them power, these only require about 2 to 5  V. The whole system is connected to a 12 V supply and the motors for the pumps are 115V.

So I am willing to ditch the scb 68 all together inorder to get the system running asap.

Thank you

[Dennis_Knutson]

You will possibly still need the SCB 68 in order to physically connect the signals from/to the DAQ device. With your current setup, you don't have a cable going from the SCB 68 to a card in the pc?

[MSUbiolab]

The only thing connected to the computer is the 68 pin I/O connector. Previously, before I was given the task to expand on this project, there was only one thermocouple plugged into a DAQ signal accessory which has a Relay DIO5 200mA max built in which controlled the one pump. Is there anything like the DAQ signal accessory that can handle 2 relays and 4 thermocouples?

As far as the scb 68 goes I have a transistor hooked up to it and like I said when I use the 5 V pin it does work just not controlled by the vi program. So are you saying there is a way to plug something else into the computer and the scb 68 that would give outputs power to control an output or no?

I appreciate all the quick responses, thank you.  

[Dennis_Knutson]

That makes no sense. If you have a cable connected from the SCB68 to the computer, you are connected to a DAQ device. There should be a label on the device that is in the computer. Read it. You can also open up Measurement & Automation Explorer (MAX) and that should tell you what sort of DAQ device is inside the pc. The SCB-68 has to be getting +5V from somewhere. If you cannot determine what is inside the pc, we might as well stop right now.

[MSUbiolab]

the DAQ device is a PCI-6220. I am looking for pins that correspond to the DIOs. I thought that "dev1/port0/line5" in labview would correspond to PIN 51 (P0.5)  of the scb 68 via the reference label but this did not work for me.

[Dennis_Knutson]

So you obviously knew there was a DAQ board present since you were aware of P0.5. Why did it take so long to provide this vital piece of information?

As answered a long time ago, you need to provide the current requirements of the relay. If it is greater than what the digital line can source, you need to provide a driver between the digital output and the relay coil.