Relay energized by a DAQ

[smm]

For the application I am developing I am using 3 relays. I am using PCI 6515 as my DAQ unit. It is configured as follows.

The normally connected (NC) of relay is is connected to the common (COM) of relay 2. The normally open (NO) of relay 1 is connected to the COM of relay 3.

NCs and NOs of relay 2 and relay 3 are connected to resistors for the purpose fo simulating temperature.

Leaving aside the details, what I want to know is using the DAQ, how does the relay function. That is if I write a 1 (or True) tot he port where relay 1 is connected will it switch to the NO position?

Thats is does writing a 1 (or True) make the relay switch to NO and writing a 0 (or False) make it switch back to NC?

I am having trouble getting the relay back to the original NC position of realy 1 at the end of the process. Please advise.

[JB]

1. What are the expected voltage and current to control the coil of relay 1 ?
2. How is the coil of relay 1 wired to the DO ?
3. Is relay 1 a non-latching SPDT relay ?
   
4. Has relay 1 an integrated diode or do you use an external one ?
5. Does relay 1 switch as expected when unwired to relay 2 and relay 3 ?

[smm]

1) 12V dc

2) The COM of relay 1 is connected to a terminal called SEN1  and the bases of all the resistors are connected to SEN2. These sensor connections are then plugged to the thermostat I am trying to test.

3) The relays in use are TSC-112L3H by Tyco electronics. Don't really know what type.

4)external diode

5)all these relays switch correctly sometime, and incorrectly most other times.

[JB]

It is a SPDT relay --> OK.

How is the COIL of relay 1 wired to the DAQ board ? Please compare your wiring with the figures on page 4-5 and following in the user manual of the DAQ interface. In this case, LOAD represents the coil of the relay. I have just noticed that there is already a diode on the DAQ board itself.

Do you use an external 12VDC power supply ?

How are the coils of the two other relays controlled ?

Would it be possible to provide your schematics ?

[smm]

Everything circled shows the relay contacts

[tnek]

Hi smm,

From a quick look at the schematic you posted, it looks like some of the relays require 24V to switch while other ones only require 12V. I would make sure the relay that you are currently testing is getting the correct voltage. Also, are you providing this external voltage to the PCI-6515? JB provided a great link for the NI-651x user manual which should give you more information.

Regards,
Kent
Applications Engineer

[smm]

actually thats an error.... all relays which are in the circled parts require 12 V

[tnek]

Hi smm,

I was wondering if you could clarify your answer to JB's second question. You seemed to have explained the circuit that the relay is a part of but did not specify details on how you are controlling the relay. What pins are you connecting the digital output to? If the digital output is connected to the correct pins on the relay, what happens when you send a digital high on the line? Similarly, what happens when you send a digital low?

Regards,
Kent
Applications Engineer