Tuesday, October 18, 2011

Powder Coating System MK-II Progress

I have had a few questions and requests for additional documentation regarding my next powder coating machine build.

I have drawn up some proper schematics of the powder coating controller including the subsections for variable HV supply.

The full controller schematic is here:

You'll notice I just specified 28VDC input; its really up to you how to obtain this; you can get cheap switching modules off ebay; laptop power supplies, or you can build your own power supply with a transformer and rectifier (My preference as its most robust option).  I didn't go into it here as its pretty standard stuff

I have also done a schematic and board for just the HV supply; again its just a simple switching power supply which drives the flyback transformer.  There are other popular flyback drivers which use the resonance of the flyback itself to set the frequency, but I have found the timer based designs easiest to build and having the easiest to obtain parts.

Here is the schematic:

And the board layout:

I'm going to have boards made for this driver; If you're interested I'll be selling them for $10 each + $2 shipping (I will just send them as "letter mail").  Let me know via e-mail or comments if you're interested as that will get me motivated to put them up on the store http://www.thegreatgeekery.com/store/

I'm also playing with the idea of moving the flyback (and a HV cascade) onto the gun,  I havn't made too much progress in this area, just a box of parts really...


Bartosz said...

Great schematic, thanks for public.
I see in first schematic, capacitor C8 has no value :)

Scott Gibson said...

C8 is just for power supply bypass capacitor to lower the noise on the power supply. A value of 0.1uF should be good.

11andrey54 said...

What resistor VR1 or VR2 can be mounted on the gun to adjust the frequency, and what on the board?

Scott Gibson said...

VR1 and 2 just set the switching time, not needed on the gun. On the gun you would want control of the overall DC voltage going to the flyback. That is what JP2 is for in the first diagram, it allows for external connection of a pot which controls the output voltage.

Anonymous said...

Very impressive. Would you be interested in building a control unit that just has a power supply and adjusts the output voltage from 0-100kv? Similar units cost at least $300 and are hard to find. The unit wouldn't need to control air flow, just the voltage range and the high voltage cascade would be contained in the gun. I don't know enough about electronics to build one myself, but you seem capable enough.

Scott Gibson said...

I'm sure one could be built; but have you considered sourcing something from alibaba (or aliexpress.com)? You can probably get a vendor to send a replacement circuit board for a commercial unit. What cascade are you using? Wondering what the input requirements would be to get the 100kv output of the cascade.

Anonymous said...

What I'm proposing is buying this kit and then I would need a control unit to supply and control voltage. Would you consider building such a device for me?


Anonymous said...

As a matter of fact, I did look at Alibaba and Aliexpress. Besides making me very nervous about ordering anything, I didn't see any separate control units for sale or control unit circuit boards. If you browse ebay, you'll see many Gema clone guns for sale in various forms, but no control units. The cheapest is about $350 for gun and control unit. I see a market for control units.