Groups > sci.electronics.design > #458550

Re: DC current sources

From	Martin Brown <'''newspam'''@nezumi.demon.co.uk>
Newsgroups	sci.electronics.design
Subject	Re: DC current sources
Date	2017-05-03 14:06 +0100
Organization	Aioe.org NNTP Server
Message-ID	<oeckl4$1eu9$1@gioia.aioe.org> (permalink)
References	<5909c9eb$0$34631$b1db1813$15bdbe48@news.astraweb.com>

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On 03/05/2017 13:15, Clifford Heath wrote:
> 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.

Why not use a high power switched mode DC to DC converter to supply 8.5v 
to the anodes through a crude rheostat and power resistor?

That way the titanium wires can never be damaged by over voltage no 
matter what the engineers do to the anode wiring.

> 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.

You would need to assume in addition that the current was fairly 
constant to work out how much charge had been delivered to each node. A 
quick and dirty LED jig to measure voltage across the load would be one 
way to speed up testing which loads are slow (ie high impedance).

I assume that fast, nominal and slow will be good enough here.

> 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.

LED driver modules but it seems like overkill and unlikely to survive on 
a building site! (also offers no over voltage protection)

-- 
Regards,
Martin Brown

Thread

DC current sources Clifford Heath <no.spam@please.net> - 2017-05-03 22:15 +1000
  Re: DC current sources George Herold <gherold@teachspin.com> - 2017-05-03 05:55 -0700
    Re: DC current sources "Ian Field" <gangprobing.alien1@virginmedia.com> - 2017-05-03 19:40 +0100
      Re: DC current sources tabbypurr@gmail.com - 2017-05-06 00:39 -0700
  Re: DC current sources Martin Brown <'''newspam'''@nezumi.demon.co.uk> - 2017-05-03 14:06 +0100
    Re: DC current sources Winfield Hill <hill@rowland.harvard.edu> - 2017-05-03 11:06 -0700
      Re: DC current sources "Ian Field" <gangprobing.alien1@virginmedia.com> - 2017-05-03 19:43 +0100
        Re: DC current sources Winfield Hill <hill@rowland.harvard.edu> - 2017-05-03 13:02 -0700
          Re: DC current sources Winfield Hill <hill@rowland.harvard.edu> - 2017-05-03 17:22 -0700
        Re: DC current sources tabbypurr@gmail.com - 2017-05-06 00:41 -0700
  Re: DC current sources "dcaster@krl.org" <dcaster@krl.org> - 2017-05-03 06:15 -0700
  Re: DC current sources Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-05-03 11:10 -0400
  Re: DC current sources Tim Wescott <tim@seemywebsite.com> - 2017-05-03 11:27 -0500
    Re: DC current sources "Ian Field" <gangprobing.alien1@virginmedia.com> - 2017-05-03 19:47 +0100
      Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-04 12:41 +1000
        Re: DC current sources "Ian Field" <gangprobing.alien1@virginmedia.com> - 2017-05-04 20:55 +0100
          Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-05 08:39 +1000
  Re: DC current sources "dcaster@krl.org" <dcaster@krl.org> - 2017-05-03 09:37 -0700
  Re: DC current sources Tim Wescott <seemywebsite@myfooter.really> - 2017-05-03 13:53 -0500
    Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-04 12:24 +1000
      Re: DC current sources mike <ham789@netzero.net> - 2017-05-04 00:48 -0700
      Re: DC current sources whit3rd <whit3rd@gmail.com> - 2017-05-04 14:09 -0700
        Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-05 08:42 +1000
  Re: DC current sources mike <ham789@netzero.net> - 2017-05-03 13:22 -0700
  Re: DC current sources whit3rd <whit3rd@gmail.com> - 2017-05-03 13:25 -0700
    Re: DC current sources Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-03 13:45 -0700
      Re: DC current sources whit3rd <whit3rd@gmail.com> - 2017-05-03 15:40 -0700
        Re: DC current sources Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-03 16:04 -0700
      Re: DC current sources krw@notreal.com - 2017-05-03 21:26 -0400
    Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-04 12:27 +1000
  Re: DC current sources John Robertson <spam@flippers.com> - 2017-05-03 22:48 -0700
    Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-04 16:36 +1000
  Re: DC current sources Jasen Betts <jasen@xnet.co.nz> - 2017-05-04 04:59 +0000
    Re: DC current sources Chris Jones <lugnut808@spam.yahoo.com> - 2017-05-04 22:50 +1000
    Re: DC current sources tabbypurr@gmail.com - 2017-05-06 00:53 -0700
  Re: DC current sources John Robertson <spam@flippers.com> - 2017-05-03 23:38 -0700
    Re: DC current sources Clifford Heath <no.spam@please.net> - 2017-05-04 16:45 +1000
      Re: DC current sources John Robertson <spam@flippers.com> - 2017-05-04 11:16 -0700
    Re: DC current sources Winfield Hill <hill@rowland.harvard.edu> - 2017-05-04 14:32 -0700
      Re: DC current sources "Ian Field" <gangprobing.alien1@virginmedia.com> - 2017-05-05 20:21 +0100
      Re: DC current sources Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-05-06 05:59 -0700
        Re: DC current sources Steve Wilson <no@spam.com> - 2017-05-06 14:04 +0000
  Re: DC current sources Robert Baer <robertbaer@localnet.com> - 2017-05-04 19:32 -0800
    Re: DC current sources mike <ham789@netzero.net> - 2017-05-05 00:18 -0700
      Re: DC current sources Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-05 08:28 +0000
        Re: DC current sources Robert Baer <robertbaer@localnet.com> - 2017-05-05 22:09 -0800
          Re: DC current sources Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-06 06:17 +0000
            Re: DC current sources Robert Baer <robertbaer@localnet.com> - 2017-05-06 20:47 -0800
              Re: DC current sources Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-07 08:27 +0000
      Re: DC current sources Robert Baer <robertbaer@localnet.com> - 2017-05-05 22:07 -0800

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