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U6, RB12 and Pulse Generator for Valve Control

U6 RB12 PWM

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#1 VHD

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Posted 06 January 2014 - 09:19 AM

Greetings LabJack Community:

 

I have a set-up where I am using a U6 with a RB12 to control 8 pneumatic valves.  These valves are high precision 24V thin film deposition valves that will be pulsed hundreds of times over the course of an experiment.  The pulse times for each individual valve will vary from 200 microseconds to 1 second or more.

 

My interest is to reproduce the pulse width, time, over the course of the experiment.  In order to make sure that I have a reproducible pulse I want to use a Digital Delay Pulse Generator similar to this, http://www.quantumco...tor/9600-series.  Ideally I have one channel of the generator representing a valve with the step curve defined.  I would then trigger that channel to fire that valve via the LabJack.  Unfortunately that above mentioned generator is about 3K so I was thinking of going an Arduino rout in conjunction with the LabJack setup.  The idea I had was to send a signal via the labjack to the arduino that would pulse the RB12 channel for the pre-defined time.  I hope I am making sense.

 

Do you think this rout is feasible or would you recommend another method.

 

Thanks.

 

VHD



#2 LabJack Support

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Posted 06 January 2014 - 04:28 PM

So you need to make a single pulse on 1 of 8 digital outputs.  The pulse width needs to go down to 200us.

 

It is only 1 pulse at a time on 1 channel, correct?

 

From what I understand, the time between pulses is not very important?



#3 VHD

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Posted 06 January 2014 - 04:56 PM

Thank you for your reply, some clarifications:

 

1) There may be more than one channel (2, max 3) that will need a pulse at any one time.

2) The minimum pulse width is about 200us

 

Yes the time between pulses is not very important but in the future I would like for some experiments where the time between pulses is at its lowest about 500 us.



#4 LabJack Support

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Posted 07 January 2014 - 09:00 PM

 

 

There may be more than one channel (2, max 3) that will need a pulse at any one time.

 

If you are making a pulse on 3 channels, what does it look like?  Same pulse on all channels?  Does the pulse start at the same time on all 3 channels?  Same pulse width on all 3 channels?

 

 

 

 

Yes the time between pulses is not very important but in the future I would like for some experiments where the time between pulses is at its lowest about 500 us.

 

In this situation, how many pulses do you need?  Do you need lots of pulses with varying time between pulses, or just a few pulses with 500us between them?



#5 VHD

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Posted 08 January 2014 - 09:25 PM

To answer the questions:

 

Quote:

If you are making a pulse on 3 channels, what does it look like?  Same pulse on all channels?  Does the pulse start at the same time on all 3 channels?  Same pulse width on all 3 channels?

 

Answer:

You would have the same exact pulse on all three channels, a square wave 200 us in width.

 

Quote:

In this situation, how many pulses do you need?  Do you need lots of pulses with varying time between pulses, or just a few pulses with 500us between them?

 

Answer:

We may need 1000 pulses, however not all of the valves will have the same delay between them some may be 500 us while others will be 1 second.

 

Ideally what I would like to do is to program a single channel per valve having exactly one pulse of predefined width.  And then trigger that channel(s) when ever I want that valve(s) on.  That is why I was looking at using an arduino to preprogram a specific channel per valve, trigger that channel to the U6->RB12->valve.

 

I hope that helps.



#6 LabJack Support

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Posted 09 January 2014 - 02:51 PM

I updated our Waveform Generation app note with more information about creating pulses:

 

http://labjack.com/s...form-generation

 

Using WAIT or Timers might do what you need without the Arduino.

 

Looking at the RB12 DC output modules, the Opto22 G4ODC5 has a turn-on/turn-off time of 100/750us.  Not very good for making a 200us pulse.  The Grayhill 70G-ODC5 is 20/50us, so will probably still work fine but you might need to consider those times.

 

http://www.opto22.co...n.aspx?aid=1524

 

http://lgrws01.grayh...d_DC_Output.pdf



#7 VHD

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Posted 28 March 2014 - 11:45 AM

I noticed between the two modules that the Opto22 G4ODC5 Contact Form was DC while for the 70G-ODC5 the contact form was SPST-Normally Open.  The purpose of the modules is to pulse on and off 24 V pneumatic valves.  Is there a big difference between the two types of contact forms?

 

Thanks.



#8 LabJack Support

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Posted 31 March 2014 - 04:38 AM

The G4ODC5 specifies turn on time to be 100 µs and turn off time to be 750 µs. I'm concerned that it will not create a good 200 µs pulse for you. I would go with the 70G-ODC5.





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