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Registered Member #3139
Joined: Wed Aug 25 2010, 02:20AM
Location: Hudson Valley, NY
Posts: 6
Hi folks,
I have a dual-section 3.1kw Variac which is gear driven with a slo-syn motor. The frame assembly has limit switches, etc. I used this variac in the past on a single-section to control power to my 80Watt Co2 through a pair of 15kV NSTs and it worked well and reliably. I am looking for more interactive control with the device though. I am planning to incorporate the limit switches with some SSRs and use an Arduino programmed uC to run the system. My biggest concern however is transients back down the power line. While I have no doubts I can build the circuitry and write the code to drive this Variac and measure the mains input/output, I'm worried that transient in HV projects may damage the uC itself. While they are cheap, I would rather do it (R)ight as opposed to (R)eplacable. I have some ideas but I'd like to draw upon the more experienced rather than blow a lot of junk up via trial and error.
If someone has built this type of variac control system as it applies to high voltage integration I would be interested in hearing your experience or suggestions to limit collateral damage to the uC.
Thanks for your time and all the useful posts on the site.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Any kind of power factor correction is difficult with load sensitive NSTs.
Most people add inline HV resisters to prevent burning out the tube's electrodes. Some simply control output with a trigger and or Q-switch. However, the vacuum in the photos looks insufficient, and is likely loading your supply.
You may wish to find pre-mix gas from your local supplier as it is less troublesome to manage.
Registered Member #3139
Joined: Wed Aug 25 2010, 02:20AM
Location: Hudson Valley, NY
Posts: 6
Thanks for the response Carbon Rod.
I don't actually have that particular Co2 Laser anymore, I sold it in around '01. It was just an example of what I had used the Variac on in the past. Those photos are back from around '99/'00, I believe. The vac is just an Edwards Speedivac II which was more than capable for slow flow co2 use and the electrodes were water cooled with the DI water loop. I did use a standard premix on the laser and it worked out 'fine' rather than trying to peak the output with manual mixing ;) The co2 was definetly a fun project at any rate.
My concerns is not so much about how to power benign things like a Co2, but how to protect uControllers and other control logic in a high noise environment like one may see with TCs and CD circuits.
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Variac uC sensing in noisy enviroments
