LifePo4 LED Meter - LM3914 4S DOT 5 x LED Meter

1

Hi All,

I would like run 5 led’s to gauge approx status derived from voltage from a scale of high 13.5v to low 12.8v. I would much appreciate a diagram that utilises an LM3914 and high and low 10k trimmers.

ie:

Full max 13.5

Full min 13.47

High 13.4

Mid 13.25

Low 13.1

Empty 12.8

Would this work and how would I go about it? Thanks in advance

2

Hi Tria
At 3.2V per cell the nominal voltage for a 4S battery would be 12.8V. This is NOT the empty voltage which is 2.8V / cell or 11.2 for 4S so I would think the low level could safely be 12V

Max charging voltage would be 3.6V /cell or 14.4V for 4S.

Above from Wikipedia.
Cheers Bob

3

Thanks Bob,

Do you know how to wire up an LM3914 chip to achieve this?

4

Hi Tris
I think the LM3914 is designed to drive 10 LEDs. So I don’t know about 5. Maybe you can use every 2nd driver. I think the chip has its own divider and maybe you just set the end points and it becomes a linear scale.

I do note there is quite a bit of application notes in the TI (Texas Instruments) Date sheet. I have not time to study it in depth so perhaps you might get enough information yourself or just google LM3914 and see if anything comes up.
Cheers Bob

5

Thanks Bob, i got close but intermittent led behaviour. I thought some one on this forum would be able to sketch a diagram quite quickly. Let’s see. much appreciated

6

Hi Tris
Sorry about that. I have a couple of car issues and a TV reception problem I am trying to sort at the moment. If you don’t have any joy I will have a look for you when I get a chance
Cheers Bob

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