ALD valves not pulsing fast enough

[cahanson]

I am using fast-pulsing ALD valves with LabView to control an ALD reactor. They are suppose to be able to pulse (on/off) for times as low as 0.008 seconds. When I attempt to pulse them at times 0.05 seconds and lower, they become partially unresponsive to labview (the lower the time, the more unresponsive). My labview program works fine, but I need help in pin-pointing the weak link in order to achieve maximum pulse speed. Any suggestions?

[AnalogKid2DigitalMan]

How in LabVIEW are you generating the pulses? What hardware do you have? Does your power source have enough current to drive the valves to their rated speed?

[cahanson]

Im running on ALD valves from Swagelok. I can get the product number if that would help. They are pneumatic and I am certain they are receiving the correct pressure. I have them connected to 2-way actuators (also receiving correct air pressure) bought from Humphrey that have an on/off time of:       012/.010 (DC)     .012/.020  (AC)   Sec.

These actuators are housed in a homemade control box feeding them DC and are connected to an ADR2200 relay I/O interface (which connects to labview). I am not sure if the actuators are receiving enough juice, is this likely the source of the problem?

[AnalogKid2DigitalMan]

I would suspect the ADR2200 mechanical relays may be the bottleneck (just a hunch). You may want to contact the manufacturer to get the ON/OFF switching times for the units.

A faster alternative would be to use solid state relays of transistors/MOSFETS to drive the actuators. You may want to also look at the current needs and switching times for the actuators. I do work with pneumatics that much, I do not know how fast those components can react.

Hope this helps

-AK2DM

[cahanson]

The ADR2200 that we are using only has a max Baud Rate of 9600. Do we need one that is faster?

Sorry I'm clueless but I work in a university research lab and we build all this equipment from scratch and nobody's really an expert.

Thanks for the help!

[AnalogKid2DigitalMan]

I was wondering about that too, I don't think 50msec would be an issue since the command words are so short. 8msec may be an issue. It depends on how much overhead and priority is in the ADR unit to decode and process commands. Again, I would suggest contacting the manufacturer of the ADR2200 to see how fast it can go.

Sorry I can't provide more detailed info.

-AK2DM