triggering swicthes through Labview

[Vance]

I made a Labview program which would control the triggering of my switches (of my CVD machine) into ON/OFF mode. I used NI 6722 to control the voltage which would then control the state of my switches. I made a program to control these 4 switches however, it does not work properly.

My CVD machine has logic circuit (composed of relays, opto-coupler, etc.) hand made us - this is so in order for us to manually operate the machine and at the same time, we could partially control it by automatically (by triggering the switches). According to our specification, we need to input 5 V in order for the machine to work. However, it did not work. Now we tried to input -5V and it work. However, at this -5V, all the switches turned ON when we programmed it to work in the way that 2 switches will turn ON at the same time while the other two at their OFF state. Since this is a swicth, we would want to do the alternating ON/OFF state for several times. So I tried to lower my voltage input to -2.3V. Alas, it worked (2 switches at ON and 2 switches at OFF). But, sometimes, one of the 2 switches does not turn ON or OFF at whatever state it was at that time. So i figured out maybe there is no enough voltage flowing through. I check the voltage reading during the manual operation and compared it at semi-automatic operation and they have the same reading.

I am using the NI-DAQMX software, and I am just wondering if the problem could be here. Since it is my first time to use the Labview, I am just wondering if I might be missing some important points that is tantamount to the control of triggering for my machine? Anybody out there that has the same experience before, i would appreciate your help.

Ryan

[Albert.Geven]

Voltage is not the real problem. It is current .
To control a relay you need a bit more current than you have.
Add an amplifier (one transistor and power for that one) and it can already make it work.

Ask for help from the electrical engineers at your plant.
For sure it is not a LabVIEW problem.

[Vance]

Thanks. We are now looking at our photocoupler since the circuit board was made 15 years ago
so there could be a problem with this. Hope this is the problem that we have been looking for.

 

[Vance]

We replaced the optocoupler already and unfortunately, we are seeing the same problem as before. I am considering your suggestion however I am not sure as to where I am going to add an amplifier - is it on the LED or the transistor side of the photocoupler? And this should be mage for each set of optocoupler?

[AnalogKid2DigitalMan]

Ryan:

Any chance you can post a sketch or schematic of what you are trying to hook up to the 6722?

[Vance]

Here is the rough schematic of what I am trying to hook up to the 6722....