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Is there a circuit which can detect how much amps are flowing through it, and if the amperage falls below a certain level to output some signal? (e.g. to direct the voltage to a different output)

Due to getting only vague answers on the question How to attain a topping charge for a lead-acid battery?, I decided to rephrase what I need in a different manner. I am very new at these things, so I apologize in advance if there is some way I am not explaining myself well; or maybe this is completely trivial to look up somewhere, and that's the reason I have not gotten any answers other than those of the type "Yes, this can be done".

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Alex
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  • [Sure you will find what you are looking for here.](https://www.google.dk/search?q=current%20sung&safe=off&biw=1491&bih=858&source=lnms&tbm=isch&sa=X&ei=DO-KVemGHIHQsgHwroDQCw&ved=0CAYQ_AUoAQ#safe=off&tbm=isch&q=current%20detector%20circuit) Because I could not comment yet, and this will not disappear, never. – JustMe Jun 24 '15 at 17:58
  • After doing the search, the following page describes what I need: [A Current Sensing Tutorial--Part 1: Fundamentals, EETimes 2012](http://www.eetimes.com/document.asp?doc_id=1279404) – Alex Jun 24 '15 at 18:02
  • Try [this](http://www.planetanalog.com/document.asp?doc_id=527795) or [this](http://www.deeptronic.com/high-side-current-sensing-using-transistor-for-current-limiting-control/). – JustMe Jun 24 '15 at 18:06
  • @JustMe, I stumbled here and tried to see your links. The second link results in 404 error (discontinued/dead link). The first one doesn’t load images, just text. Searching for “high side and low side current sensing” I found this link, but still very conceptual only. http://www.worldofindie.co.uk/?p=216. In case you have similar references to what you meant, please let me know. Thanks! – EJE Jan 26 '22 at 14:19

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Here is a circuit that should do what you want. It uses the LT6100 is that it has variable gain and 0.5% accuracy. I have used this chip in a commercial product.

enter image description here

If you use it with a 100 mΩ resistor, a 1A load with drop 100 mV across the resistor. Using a gain of 20, this will give a 2v output. By adjusting the voltage divider feeding the + lead of the comparator, you can set the threshold you need.

If you combine the LT6100 with a 100 mΩ 0.5% resistor, you will have 1% accuracy for the combination.

The LT6100 is available from Digi-Key for $2.36.

tcrosley
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