how to pwm out on NI-9477

[DIESEL62]

Hi Im a new user and are trying to pwm out on NI-9477 module fitted in cDAQ-9175

I am trying to get 250 hz output with duty cycle to control an actuator .

I have searched for sample code but most seems to use the counter in the CDAQ base (NI 9477) will not accept this

Can anyone help please

Thanks    

[samantham]

Hello,

I am assuming that when you mentioned the NI 9175 that you in fact meant the NI 9172 cDAQ Chassis.  This chassis does offer backplane counters accessible through slots 5 and 6.  Unfortunately, the NI 9477 is a static digital module and cannot link to these counters.  Thus, this module only support on demand generation mode, since it cannot link to any counters.  If you had a correlated digital module it could link to one of the chassis’ backplane counters.  I would look into counter output or correlated digital modules.

I did double check and look into other options.  I have attached a PWM example.  This example outputs a signal controlled by a duty cycle input.  However, the waveform is created in a loop and it would not work to link this waveform output to a digital write function. 

[DIESEL62]

Thanks for the reply Samantha I do appreciate it

You are correct it is a cDAQ-9172

I managed to get a pwm signal out with software timed signal generation.

I have just heard fron the NI engineer that specced the module , it is not right for the application but a good lesson anyway .I still have plenty to learn .not too many training sessions down here in New Zealand

thanks again

[Arnaz]

Is it possible to get this file in LabVIEW 8.2.1? Thanks.

[jschwartz]

Hi Arnaz

Here is the example saved for LabVIEW 8.2. 

[Arnaz]

I'm trying to make comparisons between NI9477 and NI9401. So it seems the 9477 can sink up to 1 Amp and hence it is very easy to control pumps and valves since not much additional circuitry is required (see Fig 2 on page 8 of NI9477 User Guide). But if you want to actively control the voltage to the actuator lets say based on feedback by using PWM the 9477 is not capable because it does not have access to the cDAQ backplane counters. To use the counters you need the 9401 but this module can only sink or source 2 mA. Hence the actuator cannot be connected as easily, you would need additional circuitry to basically use the PWM output as a gate input to to a transistor.

Would you agree with this? Any thoughts? 

[Arnaz]

Thanks Jim.

[DIESEL62]

This is the same problem I had . I was trying to control an actuator with PWM and as I got further into it the solution just got too expensive .I was also trying to control  a timed actuation solenoid .But I believe I had to change to CRIO and then purchace the real time module on top of that .

Hope you can find a solution