Testing the lm431 shunt regulator

Batteries, Chargers, and Battery Management Systems.
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torqueon   1 kW

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Testing the lm431 shunt regulator

Post by torqueon » Aug 11 2013 7:53pm

I am trying to create a simple BMS just for balancing the pack, my cellogs will take care the rest, of the functions. So my 1st step, is to breadboard a unit to turn on at 3.6 battery volts, 2.5 reference volts.to light an LED, it works but the dead band is .5 volts from on to off seems to wide. Ive been under the impression that these can toggle off/on within .005 volts.

So the question is there a test circuit for the lm431, so I can eliminate the possibility that am frocking up L O L!

Thanks

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bigmoose   100 MW

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Re: Testing the lm431 shunt regulator

Post by bigmoose » Aug 12 2013 11:31am

Best to post your schematic. Something is a bit off.
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dnmun   100 GW

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Re: Testing the lm431 shunt regulator

Post by dnmun » Aug 12 2013 12:19pm

you can save yourself some effort by buying one of the older ping v1 signalabs BMS and reuse the 431 and voltage divider bridge on your circuit. or just use the ping BMS since it is cheaper than what you will pay for parts.

heathyoung   1 MW

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Re: Testing the lm431 shunt regulator

Post by heathyoung » Aug 12 2013 7:44pm

Yep - post your schematic.

You must bias the TL431 properly or it will exhibit these symptoms.

www.onsemi.com/pub/Collateral/TND381-D.PDF‎
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torqueon   1 kW

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Re: Testing the lm431 shunt regulator

Post by torqueon » Aug 12 2013 7:59pm

Thanks for the help. I am posting the schematic, mind you this is micro soft paint so bear with me. Hopefully all will under stand. Any recommendations on a better program for drawing schematics.

Yes I realize the economics of this project are poor, but I have the parts on hand. If anything it will be learning experience. I have a bad habit of pulling ideas of the web and running in to stone walls.
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torqueon   1 kW

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Re: Testing the lm431 shunt regulator

Post by torqueon » Aug 12 2013 8:41pm

After that PDF heath young posted, I am humbled, clearly way over my head!
Thanks for your time

Pete

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bigmoose   100 MW

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Re: Testing the lm431 shunt regulator

Post by bigmoose » Aug 12 2013 9:16pm

A journey starts with a single step, the one after another is added until one reaches their destination and is considered an expert in travel.

Don't be so hard on yourself, and don't give up! Start with the data sheet and ask your questions... no problem with a guy trying! :wink:
"Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God..." all the best, Dave

torqueon   1 kW

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Re: Testing the lm431 shunt regulator

Post by torqueon » Aug 18 2013 6:56pm

Hey !!

Thanks again for the help. the circuit works a charm!! 0 amps to .75 amps, well within a 10 mv difference.

I never did get the LED to work directly off the LM 431. So I used a transistor to sense the shunt and drive the LED, nice and crisp turn on.

I am currently torturing the circuit, to be sure,

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