Monday, December 20, 2010

Powder Coating Build Follow Up

Update: Build Progress of the next version here; including schematics and board layouts
http://thegreatgeekery.blogspot.com/2011/10/powder-coating-system-mk-ii-progress.html

In case you came in from somewhereelse; Check out the mainpage of the blog: http://thegreatgeekery.blogspot.com/

I havn't done much modifications to my powder coating machine in a while since its been working pretty well.
See the original post here: http://thegreatgeekery.blogspot.com/2010/07/powder-coating.html

I have had a lot of request for schematics and more plans;  I'll use this post to try to get some of the details together.  Nothing too revolutionary about it;

Overall Topology:
The design is a fairly simple topology;  It consists of several voltage rails which come together to generate between 10-25KV.

Air and voltage is controlled via a trigger on the gun.


If there is interest I can have some boards made for the adjustable HV supply.  I have been thinking about making up PCBs for the main part of the supply; including everything after the step down transformer.  Let me know if you're interested and I'll do up a board; or maybe some kits.

Output: 32VDC
Current: 5A
Source: 120VAC
Notes:
Build around a 24V toroid transformer I had kicking around.  Stepped down to ~32VDC using a pair of bridge rectiviers and some filter caps.  Filter Caps are ~1000uF 60V if I remember right. I added a bleeder resistor to discharge the caps when powered off.

Pretty much this circuit; with a indicator lamp and bleeder resistor; 24V transformer instead of 12
http://ecelab.com/circuit-power-supply1.htm




Output: 12-30VDC
Current: 4A
Source: 32VDC
Notes:
This is the main supply used for driving the the flyback transformer; its based around an array of LM317 adjustable voltage regulators in parallel.  The output is controlled via a relay driven by the trigger on the gun.  The relay also drives the air supply solenoid.
This circuit (and much of the rest of the power supply are similar in concept to this design http://www.pocketmagic.net/?p=1162)

Note that I used only one 2N3055 transistors since I don't need nearly as much current.  



Output: 12VDC
Current: 1A
Source: 32VDC
Notes:
Standard 12V supply based around a LM7812 linear regulator; nothing too exciting.  Its used for the 555 pwm generator used for the HV supply as well as for the coils of the relays and solenoids.

Output: 10-25KVDC
Current: ~0
Source 12-30VDC
Notes:
I used a standard flyback driver architecture as seen in the circuit below.  I used a larger driver mosfet and added a diode across the flyback primary and a zener to protect the gate of the drive mosfet.  Used the same totem mosfet driver topology.  The potentiometer off the 555 was adjusted until I smelled ozone and heard the air ionizing around the HV output of the transformer.

I used the 12V supply referenced above instead of using another regulator as in the diagram.






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