read from thermostat to DAQ

[smm]

I am trying to automate thermostat testers. As of now, we have manual testers to test the thermostats. I'm trying to use LV and NI USB 6501, 24 line Digital IO DAQ unit to automate these testers

i am starting off with a simple prototype, where I want to be able to read data froma set of LEDS. Below is the explanation for my circuit.

I have a thermostat, which has several connections viz  W, Y, B, O , G. Each one is activated according to the process conducted by the t-stat. For example, if the fan is turned on, the G connection is on. I have put LEDs by each connection to suggest accurate working of the connections.

As of now, I'm trying to map the LED readings to the DAQ. I am trying to use the rRead Dig Chan,vi to do the same.

But when I change the LED configuration from the t-stat, the output doesn't change while running the VI. I know the circuit is working accurately but I don't know how to map the readings onto the DAQ.

It will be great if someone could help me with this. Thanks!

[Brian_Beal]

Before you assume that it is a DAQ configuration issue, tell us about your LED to DAQ wiring.  Are you running parallel wires off of the LED to the digital inputs?  What voltage do the LED's operate at?  Which pins are you using on the DAQ board?  Which polarity is being switched to turn on the LED?

[smm]

I'm using pins P2.0-P2.4 for the wiring. The LEDs are just to indicate the correct operations at the terminals W, G, O, B etc. So it just indicates which terminal is active. I'm trying to replicate  this LED output in LV.

The LEDs are connected to the terminal block, and each terminal block is connected to each port (channel) by means of a wire. '

The voltage is 5V, which I am acquiring from the DAQ unit itself.

There is an interface board between the thermostat and the DAQ unit, to help me replicate the actual output.

[Brian_Beal]

I'm still a little confused.  Are the LED's part of the circuit?  Is the DAQ card the only signal source?  Maybe you could post a sketch of your circuit.

[hoffiz]

Hi Smm:

If can you take a look in the manual NI USB-6501 User Guide and Specifications, page 7, it has the connections for driving and reading voltages from the digital input and ouput lines. A simple draw of your circuit will help a lot figuring out what is the problem? Make sure that the “anode (positive)” of diode is going to the digital line (input) and the “cathode (negative)” is going to the digital ground. If I were you I will try reading the 5 volts removing the phisical LED.

Message Edited by Jaime F on 10-10-2007 06:48 PM