UMI-7774/7772 Trigger pinouts

[Viper]

There is some confusion in the manual about the Trigger signals on the Trigger/Breakpoint connector. The trigger inputs are isolated so they are in pairs of trigger x and return x. However table 3-8 doesn't identify the returns for each trigger. I've tried pins 6/11 (which is definitly wrong) and 6/5 but yet to find the right combination. I am reading the trigger by using configer/enable/ and [read status] in a loop.

My use is to capture an EMC turntable position from its controller signal. The turntable controller outputs a TTL sync signal at defined positions. I want to use this snyc to trigger and synchronize test measuerments.

[BCho]

Hey Viper-

The user manual for the UMI 7774/7772 states that the trigger inputs are sinking inputs that are isolated. This suggests that the trigger lines are not in pairs, or rather, there is no return for the trigger signal. So, I am curious what you are looking for with the pairs, trigger x and return x. How were you planning on using the return line?

See figure 3-16 of the user manual for the wiring diagram for connecting a trigger signal to the UMI-7774/7772.

Please let us know if you have anymore questions.

Ben

Application Engineering

National Instruments

UMI 7774/7772 User manual

[Viper]

BCho,

The return is used to complete the circuit. For fig 3-16 current must flow into the input line through the current limiter to light the LED of the opto-coupler. Then the current must complet the circuit through the reverse blocking diode into the point labeled Ciso. I know that the pin labeld Out is pin 6 for the trigger 1 circuit. I just dont know what pin is Ciso for the current return of trigger 1. It always takes two lines to make a complete circuit.

I guess I'll just use an ohm meter to try and figure it out.

[Viper]

According to the documentation any signal between 3.5-30 volts between Trigger 1 pin 6 and Ciso should latch the high speed trigger if it has been enabled. I cant get this thing to work. I even used a power supply as the sourcing input with 8 volts of input. I repeatedly poll the high speed capture status but it never changes.

My confusion was that these 4 triggers are optically isolated. They are from the +5 VDC but they are not from each other. Each of the triggers uses Ciso as the voltage reference/current return.

[BCho]

Hey Viper-

Sorry for the confusion. As fig 3-16 suggests you should used the Ciso, or Isolated common. In this case you should be able to use pin 6 as your signal and pin 5 as the common. You had mentioned that you had tried this with no avail, so there might be something else that is incorrect. How are you testing this connection that suggested that pins 6/5 were incorrect?

Again, pin 5 is the Isolated Common that you are looking for in conjunction with your signal on pin 6. Let us know if this helps.

Ben

Applications Engineering

National Instruments

[Viper]

Using pins 6/5 and driving it with a power supply it behaves correctly. For 4v of drive I get 7.8 ma. For 20 v of drive it increases to 10.5 mA. If I reverse the 20 v I read 0 mA. So I think the opto-coupler is working correctly.

According to the manual 5-10 I should be able to leave the input open with 0 V and set the capture mode to active-low (inverting). That way when I enable the trigger it imeadiatly latches. However when I set the capture mode it never reads as being latched.

Is there some sort of fault lockout or other thing that could be keeping this from working? Funny that I can contol my motors but can't get this trigger to enable/latch/read.

[Viper]

This is the vi I'm using

[BCho]

Viper-

I am assuming that you are using a 734X motion controller. In the manual on page 5-10, it states "When enabled, an active transition on a high-speed position capture input causes instantaneous position capture of the corresponding encoder count value." So the high speed capture is looking for a transition as opposed to a triggered state. If you are simply leaving the trigger line open to read 0V, it would explain why you are not receiving a capture. If you send a TTL signal to this trigger, do you see the same functionality that you are seeing now?

Let us know if this helps.

Ben

Applications Engineering

National Instruments

[Viper]

Ben,

Yes I am using a PCI-7344 controller. The capture method is configurable. Starting on page 5-9 .... "The polarity of the trigger input is programmable in software as
active-low (inverting) or active-high (non-inverting), rising or falling edge. You can also use a trigger input as a latching general-purpose
digital input by simply ignoring the captured position." I am trying to use it as a general-purpose digital input.

None of those methods give me a sucsessful capture.You can see the vi I wrote to do this in a prior post.

Norm

[BCho]

Hey Norm,

I took a look at your vi. Have you tried using the capture mode "Non-Inverting Level." When running your vi with this capture mode with my own 7344 and no UMI, the high speed capture registered and the program terminated. However, with every other option, a high speed capture was never registered and the simply kept iterating.

Try this capture setting and let us know if you can experience the same funtionality that I am discribing

Ben

Applications Engineering

National Instruments