DC current sources

Clifford Heath · 2017-05-03T12:15:36+00:00

A friend works in concrete reinforcing corrosion remediation, and has been asked to take over a project that's underway despite not having been properly designed or specified. The contractors are installing 400 anodes into the structure, and each one needs a specific amount of charge to be deposited into it, all over a week or two. The resistance is unknown and could change from day to day, but the voltage must not rise above +9V, or the titanium wires rapidly corrode. So they want to adjust the current for each anode, probably in the range of 100ma to 3000mA. They're intending to feed the whole protection thing from banks of 12V lead acid batteries, I guess because it's a remote site. The initial thought was to walk around and measure the current on each anode every day, and switch off any that have dumped the required charge... but that's quite labour-intensive. So I was thinking about current regulators. What's the easiest way of sourcing 400 adjustable DC current sources in a short time? I was thinking of LM350T regulators, programmed with a power resistor in the range 0.6-10 ohms... but the 2degC/W heat sink for each one could be an issue (thinking 2A, 14.7V, shorted to earth; 30W). Is there any other off-the-shelf quick solution that comes to mind? Clifford Heath.

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Robert Baer 9 years ago

You have just confirmed that current is not charge.

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Robert Baer 9 years ago

YES! but here in the colonies we use V for volts,not U.

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Jan Panteltje 9 years ago

On a sunny day (Fri, 05 May 2017 22:09:14 -0800) it happened Robert Baer wrote in :

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tabbypurr 9 years ago

ISTR making 2 transistor smpsus that just switched off when inductor current reached a set value, and on again when it dropped. And a screw for an inductor core.

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tabbypurr 9 years ago

Parallel 317s do the job with overheat protection - external pass lacks that unless you complicate things.

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tabbypurr 9 years ago

That's close to what I was thinking. Select voltage tapping to keep current lowish. Mark the battery with the number of charges at each anode. NiMH wo uld handle it better than lead acid. Very quick & dirty but it would do the job. And no mucking about building stuff time.

NT

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Lasse Langwadt Christensen 9 years ago

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Set it for 9.5V output and add current sense resistor and a PNP to pull up the FB pin to control current

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Steve Wilson 9 years ago

Constant Current, Constant Voltage IC's:

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Josh_Caldwell.pdf

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The LT3081 doesn't need an output cap. This is great when you are testing LED's. Other power supplies have a huge output cap that can blow the LED.

You can parallel the LT3081 for higher current. Still down't need an output cap:

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Robert Baer 9 years ago

.....and what does that to do with the price of rice in China?

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Jan Panteltje 9 years ago

On a sunny day (Sat, 06 May 2017 20:47:36 -0800) it happened Robert Baer wrote in :

Y knot?

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DC current sources

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