LM3914 for a 12v battery

[madhippiescientist]

In the spec's for the LM3914 (bar/dot driver), I believe I read somewhere
that I can only have the driver top out about 1.5v below the battery supply
(which is powering the "meter"). Is this true?
I want to integrate the meter, up to 13.5v, in steps of around a 1/3v.
However high up (to 13.8v) I can get, even if it's only 12.3v, I'm going to use
the driver. But I was wondering, what components should I use with the chip
(I don't have the circuit with me, but it's the basic driver circuit and it will be
driving another chip <via dot mode> so I don't really need to worry about a
resistor for the LEDs). So if one was to specify the pins/identification and the
resistor values (i believe it's two resistors) I would need to make the meter
go into this range, I would be GRATEFULL !!
If the chip will only go up to 12.3v (w/ a 13.8v supply and the cutout),
then a step of .25v would be better. Any suggestions gentlemen & ladies???

 

[Acetronics]

Hi,

THIS is an idea ...

**broken link removed**

Alain

 

[madhippiescientist]

I appreciate the input, but I'm not much into...French???

Anybody else? Is the limit up to supplyV minus 1.5volts??
The resisitors/potentiometers/other for my desired scale???

 

[Acetronics]

Hi, MHS

from the time I began electronics ...

I had to deal with Spanish, German, Italian, ... and English.

your Advice ... How did I do ???

Alain

PS: at those prehistoric times there where NO online translators ... c'mon it's just a little effort !!!

 

[madhippiescientist]

You did well, but some of that text is beyond me, even though I have two
years of spanish above my belt (maybe that's just the food!). I still need a
little more clarity though...

 

[MrDEB]

found this circuit

havn't looked it over but should be just what you are looking for.


https://www.electro-tech-online.com/attachments/expanded-scale-battery-monitor-png.7921/

 

[HiTech]

MADHIPPIESCIENTIST,
a bit off-topic here but I got to wondering a bit:

1. You aren't truly mad
2. You aren't a true hippie
3. You aren't a true scientist

It's an oxymoron to be all three characters simultaneously.

 

[madhippiescientist]

I used to be mad. But I still have seizures and anxiety/panic attacks...

I did cut the hair off about 8 years ago, it was down to my behind...

As for the scientist, well, o.k., it was a crazy biker dude that coined me
the "Mad Hippie Scientist" about 20 years ago, and it's kinda just stuck ever since...

MrDeb...that circuit looks great, but I was wondering what the "TL071"
is (the name) and what it's doing for the vlow adjustment...If I want to up
the vhigh, do I decrease or increase R7/R8, and/or R3 ??

 

[k7elp60]

In the spec's for the LM3914 (bar/dot driver), I believe I read somewhere
that I can only have the driver top out about 1.5v below the battery supply
(which is powering the "meter"). Is this true?
I want to integrate the meter, up to 13.5v, in steps of around a 1/3v.
However high up (to 13.8v) I can get, even if it's only 12.3v, I'm going to use
the driver. But I was wondering, what components should I use with the chip
(I don't have the circuit with me, but it's the basic driver circuit and it will be
driving another chip <via dot mode> so I don't really need to worry about a
resistor for the LEDs). So if one was to specify the pins/identification and the
resistor values (i believe it's two resistors) I would need to make the meter
go into this range, I would be GRATEFULL !!
If the chip will only go up to 12.3v (w/ a 13.8v supply and the cutout),
then a step of .25v would be better. Any suggestions gentlemen & ladies???

Here is a circuit that I have built. You can adjust the pot so the 13.8V turns on a LED in the bar graph where you want it.

 

[MikeMl]

Generally speaking, you can build a voltage divider that scales a 15V into to, say, 5V, and then set the LM391x to display 0 to 5V. That way, you could actually display 0 to 15V, but you could power the LM391x on only ~8V.

 

[madhippiescientist]

Hey, k7elp60, what is the size of the steps between the LEDs, if I adjust it to 13.8v
for the highest reading LED?

 

[k7elp60]

Hey, k7elp60, what is the size of the steps between the LEDs, if I adjust it to 13.8v
for the highest reading LED?

The voltage steps are approximately 0.22V. Here is what is happening with the circuit. The 10K and 2k in series from pin3 to ground give divide by 6 voltage divider for the input voltage. The 2K resistor from pin 6 to pin 7 gives the LED's in the bargraph 6mA of maximum current from the formula: 10(1.25/2kΩ). The reference voltage on pins 4 and 8 is adjusted by 1K pot.
For 13.8V as the higest voltage to be measured divided by 6=2.3V. This would be the voltage on pin 8 of the LM3914.
Because of some circuit inaccuracy's the steps may not be exactly the same.
But the circuit seems to work fine for me.

 

[madhippiescientist]

I tried your circuit, and it works great !

Thanks a whole-heck-of-a-lot for your assistance sir !! :-> !!!!