Name of widget to control amps?

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Reply to
Kris
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Robert Roland wrote in news: snipped-for-privacy@4ax.com:

Still trying to post the graphic :p

Reply to
Kris

one of those adjustement screws will do the thing you want.

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  \_(?)_
Reply to
Jasen Betts

It has already been explained that ohms law is V = I x R. If you vary R the I will change and V will stay the same*. If you make I constant (Say 2A) and vary R then V will change, but it will only change enough to keep the current constant. (2A) You will be varying R because of your solution, contact area, and pressure. The voltage is only important in that it must be high enough to cause the current flow you want with the R caused by your solution, contact area, and pressure. If it were me, I'd try a constant current regulator and practice on test pieces until I found the current that allow me to get the best effect. I don't think it is very critical. My daughter used a 9v battery and some electrolytic (I don't now what) to etch her boyfriends initials on a stainless steel water bottle. It looked good to me.

*In a perfect device V would stay the same, wall warts, batteries and power supplies have some internal resistance and the V could drop slightly. Nothing for you to worry about, but I had to mention it so others wouldn't bring it up.
Reply to
amdx

If you take that lm317 cct and use a rheostat in place of the resistor you will have good control of the current. Bear in mind as said before you will need to supply about 3v (to be sure) above the desired operating voltage.

Reply to
Rheilly Phoull

I wouldn't be so sure about that. The rate of material removal will be proportional to the current. The voltage only matters insofar as it affects the current.

In essence, you need to transfer a certain amount of charge in order to transfer a certain amount of material. Current is charge per unit time. So a constant current will tend to remove material at a constant rate, whereas a constant voltage will tend to remove material faster or slower as the resistance varies (primarily due to the variation in the distance between the electrode and the work).

Most power supplies (including batteries) are roughly constant voltage.

An unregulated supply (such as a battery) will exhibit a reduction in voltage as the current increases. For a battery, the reduction will be roughly proportional to the current drawn as a fraction of the short-circuit current, so if you aren't drawing anywhere near the short-circuit current, the drop won't be significant.

Regulated supplies will make an effort to maintain a constant voltage as the current varies.

Reply to
Nobody

That's because constant-voltage supplies are cheaper and easier to obtain than constant-current, and you're (presumably) looking at sites dealing with this as a hobby rather than electrochemical machining (ECM) as an industrial process.

Constant-current will almost certainly work better, but a bench PSU with constant-current mode will cost between $50 for Cheap Chinese Crap and hundreds of dollars for something from a well-known manufacturer. Whereas batteries and some wire will cost a couple of dollars.

Reply to
Nobody

This newsgroup is a text only newsgroup, which means that you will not be able to post binaries here. Try the dropbox and just post a link to your pictures. Eric

Reply to
etpm

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