DIY Electro etcher under $20

Transformer output is always in AC. The rectifiers transform it to DC. The switch switches out the rectifier for the AC output. A cheap battery charger will work for the supply also.
 
Sorry guys, I wasn't very clear. I can't find any 12v wall transformers. I did however find two wall transformers, one is 9v AC and the other is 9v DC (output from the wall wort)
zaph1 said:
5. 12VAC wall transformer $3
6. 12VDC wall transformer $3
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Mine are 9VAC and 9VDC wall transformers

EDIT: I guess using the term power supply is what may have thrown you off. I meant wall transformer
 
These are the two that I have. I got them from a thrift store. Not my pictures, but exactly the same. I was planning to hook them up like you hooked up your 12 volt wall transformers.

I don't remember where I read it, but I'm almost certain that I read that they could be less than 12V. Instead of hitting the blade for 3 seconds using the 12V wall transformers, hit it for 5 seconds using the 9V wall transformers or something like that anyway.

So anyone think these would work?

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Charles, I will add a bit from an electrical engineering perspective;

I would be better to replace the DC transformer with a bridge rectifier at the DC terminals on the switch. The AC from the transformer will go to the rectifier and the AC terminals. The rectifier is as cheap, or cheaper, as the DC transformer, and many times smaller. Use a 1000ma 12VAC transformer or larger, as current does matter.

When the switch is in the AC position, it delivers the AC current directly, in the DC position, the AC is rectified into DC and delivered. Using a center off switch is also a better idea, as it will allow you to "pulse" the etch. Several short "pulses" of power are much better than one longer burn. You will get a crisper etch that way.

Heck, for about another $10 you could add a 741 op-amp and make it variable voltage. I bet a $5 dimmer switch would work,too.
 
Yes, it would be very easy to replace the DC transformer with a rectifier. Even cheaper would be 4 diodes you could easily get from scrap. However, the main idea behind this etcher is cheap and easy, using parts a lot of people have laying around. In particular, the ability to just add alligator clips to common wall transformers and do your etching.

For those who wish to use a rectifier instead of a transformer, here are some details. Using an AC transformer, split the lines out. One to the switch and the others to the rectifier or diode circuit. Either use a bridge rectifier with a higher amp rating than your transformer, or built your own from diodes.

On mine, the selector switch is center off. The power switch is "momentary on" to do the etching and a small light to show when the power is on.

brect.gif
 
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Suggested improvement to this elegantly simple design...get an old train transformer off ebay instead (I paid 99 cents for mine, $3 for another). These transformers supply both VAC (usually about 18V) and VDC (18-20V), and the speed control allows you to vary the VDC down from the max. Put my unit together in a cigar box, since I had several lying around.
 
mogedy said:
Suggested improvement to this elegantly simple design...get an old train transformer off ebay instead (I paid 99 cents for mine, $3 for another). These transformers supply both VAC (usually about 18V) and VDC (18-20V), and the speed control allows you to vary the VDC down from the max. Put my unit together in a cigar box, since I had several lying around.
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Could you show yours working? that sounds like a ready made etcher box most of us have in our attic's and didnt know it!

Jason
 
Please forgive me if it's been mentioned.

What are all the bells and whistles for between the AC supply to the ON/OFF toggle?

etcher6.jpg


So I understand the rest please confirm my thought process.
1. AC power in to ON/OFF toggle
2. ON toggle to LED light and to BOTH AC and DC transformers
3. DPDT switch controls AC or DC to output leads

EDIT: I see in another post you added a momentary switch to the power for pulsing. Do you have a link to what type of momentary switch?
 
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Not really sure what the resistors are for. Then came out of the power supply that I took the parts from. I don't use them in my latest units and haven't noticed any difference in line quality. The ferrite coils are to reduce line noise, which isn't really an issue with an etcher.

YES: you have the thought process on the simplicity of an etcher down exactly right.
 
Does this build have any advantages over a computer power supply?
They're usually free, and any ATX supply produces both 5v and 12v with modular plugs.
I've got one sitting on my bench from an old tower, but don't have any proper stencils (major to-do).

-Daizee
 
If you can figure out how to activate an ATX power supply, it might work for the DC current. Of course, you really don't need 30A of 12VDC to etch, so it's a bit overkill. You would still need 12VAC to darken the etch, and the ATX PS doesn't provide that.
 
I know from my playing with computer days that on a atx power supply the main header that plugs into the mother board, its the big one with 20 or 24 pins usually will have two wires that are the power supply switch. You can do one of two things. Find the correct two wires and basically use a jumber between them and then the switch on the back of the atx psu will turn it on and off. You can also instead of using a jumper install a switch and then its just like your computer. The switch on the back of the psu can be turned on then the psu will start up when you use your little jumper switch that you installed.

Would have to look for the wires online. I can remember off the top of my head but they are pretty much the exact same for everyone made since the power distribution on motherboards are usually the same.
 
zaph1 said:
Most ATX power supplies are switching, which means it won't turn on until you have added a load across the purple/orange wires of the 20pin ATX connector. Nearly everybody has 12vdc wall transformers laying around. And, if starting from scratch, a $3 transformer is much cheaper than a $25 ATX power supply. The other DIY involved buying the bare transformers from Radio Shack. I find this to be much simpler and cheaper.
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True except it's not always purple/orange; I use a few of them around my computer shop to run LCDs and things, and I find most are the grey/green combo. Color irregardless (standard atx) it's usually 4th wire from the right looking down on the clip of the connector, flip over and its 3rd from the right. These are not necessarily all the same, but in general that combo works to run the PSU without a computer attached.

Most people don't have computer power supplies laying around for free, but for those that do, that usually works.

Also thank you for the tutorial, I just may make one :) I bought a premade kit from knifekits at one time, and it's nice and all, but it doesn't do either DC or AC, just one, and I forget which at this particular moment.
 
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Yes, that would work, but this is a bit cheaper and probably a bit more reliable.
http://www.ebay.com/itm/12V-1000mA-...397?pt=LH_DefaultDomain_0&hash=item3a6e467115
I've since started using these to stepdown to 13VAC and then use a rectifier to output both AC/DC
http://www.ebay.com/itm/270796366532?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I've considered selling a kit for this. Usually the shipping for the various parts kills the price. I buy them in lots of 10 and could easily assemble DIY kits for the latest version.
 
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Most people don't have computer power supplies laying around for free, but for those that do, that usually works.
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really? dear lord, the number of computers I've salvaged for free and then later recycled in pieces boggles the mind. I owned (free) 5 Sun workstations and a MicroVAX at one point, and that's just the vaguely exotic (to the average user) stuff. Most people, and more to the point, universities, consider the stuff disposable and are happy to have it carted away.

You would still need 12VAC to darken the etch, and the ATX PS doesn't provide that.
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Aha!
I did not know this. Cool, thank you.

I don't recall what I did to get my supply pushing power w/o the motherboard, but it produces juice just fine. It IS a model with a physical switch on it, in addition to the front panel switch that was part of the case.

-Daizee
 
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