# Can anyone recommend an idiotproof design for a big variable current regulator?

#### spasticteapot

Joined Nov 14, 2009
4
I'm looking for a simple schematic for a relatively beefy variable current regulator capable of supplying five or more amps (preferably ten) at twelve volts. This will be for an electroplating setup, so high efficiency, low noise, and high precision are not required - I'm looking for something simple and cheap.

Any recommendations?

#### k7elp60

Joined Nov 4, 2008
555
Use a LM338K with an variable resistor or with switchable resistors. See figure 19 of the attached file. Change the resistor for the selected current.

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#### spasticteapot

Joined Nov 14, 2009
4
Use a LM338K with an variable resistor or with switchable resistors. See figure 19 of the attached file. Change the resistor for the selected current.
The problem with this design is the requirement for a low-current high-power rheostat - all the ones I've found are quite expensive. Is there a more reasonably priced option?

#### SgtWookie

Joined Jul 17, 2007
22,201
Yes, use a 12v auto battery charger rated for 5A.

#### Papabravo

Joined Feb 24, 2006
12,301
I'm looking for a simple schematic for a relatively beefy variable current regulator capable of supplying five or more amps (preferably ten) at twelve volts. This will be for an electroplating setup, so high efficiency, low noise, and high precision are not required - I'm looking for something simple and cheap.

Any recommendations?
As a tecnical requirement "idiotproof", does not exactly reek with precision. I would be interested in any elaboration you can offer for this particular requiremnt, especially as it relates to existing equipment with which you may have any specific experience.

#### SgtWookie

Joined Jul 17, 2007
22,201
Something really simple might be a rotary selector switch or a series of toggle switches which connects various size automotive-type incandescent lamps from the +V supply to the load.

Automotive lamps are available in a wide variety of sizes/wattages. A trip to an auto junkyard (for the UK crowd, the breakers) could provide a wide variety of auto lamps with sockets and pigtails (wires) already attached.

A quick search on the Internet would give the wattage rating for the lamps.

#### spasticteapot

Joined Nov 14, 2009
4
As a tecnical requirement "idiotproof", does not exactly reek with precision. I would be interested in any elaboration you can offer for this particular requiremnt, especially as it relates to existing equipment with which you may have any specific experience.
I don't own an oscilloscope, making diagnostics of switched-mode power supplies very difficult. Idiotproof might be too strong a word, but I'd prefer something that doesn't have several dozen components.

I should specify that I'm looking for something that can maintain a preset voltage, not simply a rheostat. The impedance of a plating setup can vary during the plating process, and too much current can cause big problems.

#### bountyhunter

Joined Sep 7, 2009
2,498
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#### k7elp60

Joined Nov 4, 2008
555
Here is a circuit I built a number of years ago to discharge batteries at a constant current. It is adjustable from a few Ma to about 10 amps. I modified the circuit so that the 12V power supply supplies the current.
The post adjusts the current and the op amp keeps it constant. The transistor was mounted on a big heat sink.

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#### SgtWookie

Joined Jul 17, 2007
22,201

#### k7elp60

Joined Nov 4, 2008
555
K7elp60,
Might interest you to know that the NTE251 is a replacement for a 2N6284; it's complement is a 2N6287.

The original parts are almost always less expensive than the NTE brand, if they're still in stock somewhere.

Mouser stocks the 2N6284 for $2.75: http://www.mouser.com/ProductDetail/STMicroelectronics/2N6284/?qs=ljbEvF4DwONq/a6VkK4YLw== They also stock the NTE251, but it's$8.73: http://www.mouser.com/ProductDetail/NTE/NTE251/?qs=sGAEpiMZZMvwLjDpJZyitCboShd2oKdDR18Qumwxxds=
Thanks SgtWookie for the information.
When I built the circuit I worked for an electronic distributor and the my cost was not very much. I built the circuit over 10 years ago.