NI-900 I/O as a Relay?

"'SET INPUT <channel> <state>"

Set the input channel's active state. An active state can be high (logic high) or

low (logic low or contact closure). Channel changes, Pushes, and Releases generate

reports based on their active state. Setting an input to ACTIVE HIGH will disable

the ability to use that channel as an output.

That just sets the active state on the I/O channels.

SEND_COMMAND IO,"'SET INPUT 1 HIGH" on a logic high channel is on and logic low channel is off.

SEND_COMMAND IO,"'SET INPUT 1 LOW" on a logic low channel is on and on a logic high channel is off.

What pins are you using on the NI-900, Ground and Pin 1?

With the IO port low it's 0-1.5vdc and a high is 5vdc on my tester checking on a NI-3100 I get .65vdc for a low and 4.95vdc for a high. This tester isn't cablibrated, the batteries are week and it's been abused quite alot.

The 12vdc pin is for powering things like PCS2 or PCS. We usually tap off the power + 12vdc supply feeding the master to one side of a relay coil and then the other side of the relay coil to IO pin 1 (in this case).

When used for outputs, the I/O port acts as a switch to GND and is rated for 200mA
@ 12 VDC. You supply the 12vdc and usually some sort of third party relay that uses 12vdc for its control coil.

For this to work you must ,"'SET INPUT 1 LOW" .

OK, I'm having and issue trying to use the IO port on a NI-700 as a contact closure to drive a PC1 power controller. Bellow is the code I wrote for this:

DEFINE_EVENT

data_event[dvIO]
{
  online:
  {
    send_command dvIO,'SET INPUT 1 LOW'
  }
}
    
button_event[dvTP,102]
{
  push:
  {
    Off[dvIO,1]
   } 
}

button_event[dvTP,101]
{
  push:
  {
    ON[dvIO,1]
   } 
}

By default I have 5 Volts between IO1 and ground when I do ON{dvIO,1] I get 6.01 volts between IO1 and ground. What am I missing?

Vining, thanks for your response but, All I need between contacts 1 and 2 of the PC1 is a short to have power in the outlet. Now if I could use an IO port out of NI-700 to do a contact closure I won't need a relay, right? According to what have been said before in this thread and another ones related to the IO port here in the forum, the IO port can be used as a contact closure with low logic. I'm having 5 volts in the IO1 by default when that port is Off and 6.01 when is on. According to some readings you posted before I'm supposed to have 5 volts only when the port is on and in the off state it should be a short to ground isn't that right?

Io ports are a little confusing, but the manual for any of the masters will explain how they operate.

You can set the IO port to detect an input signal (using the port as an input) with either HIGH logic or LOW logic. With HIGH logic, you cannot use the port as an output (i.e. to control anything else). When set to HIGH, a logic HIGH voltage between the IO pin (pin1,2,3,etc) and gnd on the master will trigger the input. Any voltage less than the logic HIGH trigger voltage (check the manual to verify exactly what this voltage is), including a short between the IO pin and ground, will not be detected. So, if you are HIGH and apply 12vdc to the IO pin and ground, the IO light will come on and you should detect a button press -- that is, you can use button events to detect the change in status. If you are using logic LOW, the exact opposite occurs. A very low voltage (or short circuit) will trigger the IO port. An open circuit will NOT be detected as either a HIGH voltage trigger or a LOW voltage trigger.

When you are using a current sensor, you use the IO port as LOW and connect the PCS as shown in the PCS manual, which is available at the AMX website (also included with the PCS). It is my understanding that the +12v pin next to the IO ports is electrically identical to the +12v pin on the Axlink connector and is probably electrically connected to the +12v terminal connected to your power supply. If your power supply is sufficient, there should be nothing wrong with connecting to the +12v pin next to the IO port pins. I believe that the current limit is supposed to be 200ma.

Given all this, if what you are attempting to do is simulate a contact closure, you should be able to do it with the IO port without using a relay. It is not a physical contact closure, but is a transistor being switched on, so some circuits may not be able to detect this. We had a discussion about two output Kramer switches not too long ago and some people could not get their Kramer switchers to detect the ON state of the IO port as a contact closure. Putting an inexpensive relay between the port and the switcher does work, though, so you can easily and cheaply turn an IO port into a reed contact relay.

If you want to power a small, low current device (like a relay or small fan or aPCS) with your NI900 (or any AMX master) you can do it with the IO port. Just use the NI (or its power supply) for the plus voltage and connect the negative voltage to the IO port pin. Use LOW logic and control the device by turning the port on and off with your code. Look at the diagram in the PCS manual to clarify how all this fits together.

vining wrote:

Did that worked w/o a sperate isolation relay? An I/O port basically acts as a switch to its own gound terminal when used to control a relay and the PC1 basically needs an isolated contact closure (switch) to pull in its internal relay so w/o an isolation relay how did you get it to work? What wires did you connect to what?

A PC1 or PC2 is actuated by switching its input connections to its own ground. Connect the PC1 or PC2 ground to the NI ground and the control connections on the PC1 or PC2 (connectors 2 and 3, as appropriate) to the appropriate IO pin and the NI will switch control it by turning on and off the IO ports.

If I caused it, it sure was not my intention. If I caused it, I apologize.

Hedberg wrote:

If I caused it, it sure was not my intention. If I caused it, I apologize.

If this refers to my deleted bad thought post, no. I wrote a response and submitted it but then looked at what I wrote and realized my comment was stupid, so I edited it and put in that line instead.

Use some caution...

I have burned out I/O ports before, so be careful when you are connecting things.

If the relay draws too much amperage (over 200ma) you may burn out the I/O port and it seems to take out the port next to it also. Maybe there is one IC controller for every 2 ports or something, but if this happens, you will have to skip a port and try again. I believe they are linked in pairs like 1/2 3/4 5/6 7/8, so depending on what burns out you just need to locate a good port.

This stumped me for a while when I made my first attempts of using an I/O port to control a tv lift. I ended up burning out ports 1/2 and didn't realize it since they still *appeared* to respond as far as the LED on the master goes, but they weren't actually working. I moved my connections to port 3 (skipping port 2) and it worked great. Of course I first found a relay that only pulled 35ma so as to not burn out port 3 and 4 also!

Hope my experiences help someone...

--Erci