Using a dc motor controller for an anodizer?

L6steel

L6steel

Joined
Sep 23, 1999
Messages
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Well, after looking at some of CH Morris' folders tonight, I've decided to get or build an anodizer.
This got me thinking about a power supply.
Why can't you use a dc motor controller for the power supply?
Anyone ever built an anodizer with a dc motor controller?
Thanks!!
Michael
 
Michael;
Aithough I haven't used a motor controler, I don't see why not. You would have to test the DC coming out of it. Connect meter leads to the output, slowly rotate the dial and see if the output is steady. 90vdc I guess. I am using a Varic with bridge rect. The dial on the varic and the meter readings are not exactly the same. Sounds like it is worth a shot. Don't stick your finger in the jar to see if it works :eek:
 
Michael,

A DC motor controller sounds like a great idea, but only if you already have one on hand. Otherwise, building an anodizer for a tinkerer such as yourself should pose no problems at all. Bob Warner has some great plans on his site. I believe however, that if you can't scrounge materials and the variac cheaply, you are better off to just buy one from IMG or someplace. If I had to do it all over again, that's what I would certainly do. BUT! A 180volt DC controller could get into those higher currents with little effort, but you'd have to rig it for 240v to achieve that.
 
See my final post below before using idea.


Michael,

Yes, it works and I've done it. But I need to add some to that.

Those controllers are sensitive animals and use load feedback from the motor. They do weird things like shut off the current and monitor the current coming back from the motor.

So, you do it with the motor connected and running!

When I tried it, I used the DC motor on my disk grinder. It worked just fine.

What scares me is shorting out (touching the anode and cathodes) I'm sure the controller will freak out, or hopefully just blow a fuse.

FWIW: I bought one of those motor controllers from Harbor Freight (9 - 12$) and a bridge rectifier from radio shack. That works too, and isn't so freaky.

Hope that helps,

Steve
 
Thanks for the response guys!!
I checked Ebay out for Variacs and there are tons of em but the majority are older ones and you have no idea if they even work. The new ones seem kinda high for something on Ebay. I'd rather get it from a company if I'm paying bigger bucks for it.
JH, does IMG have a web site? I wouldn't mind buying an anodizer if I could get one at a decent price. Reactive Metals sells them but the cheapest one they have is over $400.
 
p moore said:
The dial on the varic and the meter readings are not exactly the same.
Click to expand...

The reason is that the volt meter kinda averages voltage. You see the voltage coming off a bridge rectifier isn't clean by any means! While the voltage doesn't go negative (like AC) it is fluxuating.

So, a variac is producing a good steady AC cycle of whatever voltage. If you measure the AC output of the variac you'll get one thing. However, what's coming from the bridge rectifier is a mess.

Your volt meter is not reading the peak voltage from the bridge. However, the peak voltage is what is going to set the color on the titanium. You probably noticed (I did and wondered what was going on!) that your results did not match what the titanium charts said.

In other words, the charts say Blue at 20 volts. But if you go by your volt meter I'll just bet if you set to 20 volts you'll get a pale blue or something very light. Or if you do get blue your volt meter probably says 10 or 15.

Now if you use a machine with filtering or better DC conversion, the metered voltage and peak voltage are gonna match.

Not that it matters much, because you get what colors you get.

Steve
 
Steve
Could you explain how you hooked together the Variable controller from HF and the Rectifier from RS...Please!
Maybe scan a little diagram.

Thanks
Robert
 
Robert,

I'm gonna retract everything I said!

Here's why. It works but I couldn't get all the colors very smoothly. I think that controller from HF doesn't have the exact voltage output like you get from a variac.

I think the system (including the DC motor controller idea) has voltage spikes above what you'd want.

(Gee I wish I still had an oscilloscope).

I'm looking at my sample again, and remembered how hard it was to get the colors I wanted and some colors could never happen.

In fact it would jump right past purple and green stuff and create a yucky yellow. My ability to get certain colors had to do with too many factors for me to understand.

So, while I got it to work I don't think it's a good system to use.

Sorry,

Steve


PS 2 car batteries connected plus to minus should give a real nice color blue.
 
Steve is right about the output of the DC motor controller. They approximate a DC level by alternately connecting the output to zero Volts and some high voltage, like 311 Volts. The ratio between the time connected to zero Volts and the time connected to the high Voltage is what determines the average output voltage. You should see this if you connect an oscilloscope to the output of your DC motor controller.

If you use a variac connected to a rectifier and you connect an oscilloscope to it, you should see half-sine waves that look like "humps" or "parabolic arcs" occurring at the rate of 120 (or 100 outside of US and Canada) times per second. The voltage will range from zero to some peak value. The peak value will be dependent on the setting of your variac. This "mess" will cause most meters to give inconsistent or incorrect readings. One must use a "true RMS" meter to get a proper reading. This reading would be 70.7% of the peak voltage. I would guess that this variation in voltage may be what is giving you problems with your colors. It is possible to smooth out the humps by adding one component but I don't want to suggest it unless it is really necessary.

If anyone have one of the commercially made anodizers and is willing to take some measurements with a meter. It would be helpful to us all to understand what is needed.

1) Measure the output voltage with the meter set on DC Volts.
2) Measure the output voltage with the meter set on AC Volts.

Phil
 
Thanks Phil!

That's what I was beginning to believe based on my results.

BTW, from how I understand titanium reacts to voltage, the average voltage doesn't matter, really. It's the peak voltage that counts.

The oxides create a layer that is like a resistor. Say you give it 10 volts. The oxide will become a certain thickness and then no more current flows. Colorizing halts at that point. If you increase to 20 then it becomes thicker to a point. etc. The thickness dictates the color.

What I was seeing is that the peaks were so short that it looked like I got the color I wanted. However, if I leave it in longer I bet it will slowly 'color up' to the peak voltage. You'll never get an even finish.

That was a big help Phil! Hope no one else ran out and bought the HF thing before I re-tracted. Like I said I can use it, but it's not the best.

Steve
 
Hello Tracy!!
I was looking for you at the meeting last night!
Charlie emailed me and invited me to the meeting and I sure am glad I went!
What a grand bunch of folks!
Got to see some amazing knives too!
I''ll soon be the newest member of the Deep South Knife Collector's Club! :)
Take care and see you at Cranford's next month!!
Michael
 
Hey Mike, email me I will build the anodizer from the parts you sent me and a few more and get it back to you... it will work at least as well as my reactive metals one... with a digital voltage readout!!!

Let me know if you wanna take me up on the offer...:) Its only good once!

Alan...

alanfolts@hotmail.com
 
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