thanks for the help but since i have space problems, is there any way to make it without the use of extra voltage regulators

Hi @flipayush

Repeating an earlier question, where are you mounting this LM3914 in a space, that prohibits the use of a ~ 1 Inch sized voltage regulator?
E

 

This would NOT be a second voltage regulator. The LM3914 can operate on 12 volts,, at least I think it can. Si there is only one regulator, AND it is a small one, The "M" regulator is only rated 100mA, and so yes, the display will need to be in the DOT mode, not the bar-graph mode. Fr a battery check that makes more sense, anyway.

 

The TS originally posted this:
Could someone help me how to make a circuit for 18 volts to 25 v battery indicator

It is NOT a 12V source.

As the Maximum source voltage has been stated as 25V, which is the Maximum rating of the LM3914

 

THAT is why I suggested a 12 volt regulator IC,, the LM78M12, delivering 12 volts in a package the size of a small transistor. ONE voltage regulator for both the IC and the LEDs, with one series resistor to reduce the IC heat load. And the 18 volt minimum should support the regulator "head-room" requirement adequately, although just barely.
AND THANKS to E.G. for quoting the data sheet.

 

The TS says quite clearly states he does NOT have the space for a LM7812 regulator.

Have you read his posts????

 

ONE voltage regulator for both the IC and the LEDs, with one series resistor to reduce the IC heat load.

And a 5V regulator can also supply both, as I show in my schematic, since the LM3914 will operate down to 3V.
You seem to imply it can't.

 

Is the TS willing to employ SMT components? I can’t believe he can’t find the space for a SOT-23 regulator placed on the bottom foil layer.

 

It may be that the power heating a linear regulator dropping 25 volts to 5 volts might be excessive. In addition to less heating, the higher voltage operation would be a bit less noise sensitive.

 

It may be that the power heating a linear regulator dropping 25 volts to 5 volts might be excessive. In addition to less heating

For a given LED current the power dissipation will be the same no mater which voltage regulator you use.
The power is just distributed to different locations.

 

I think for this application, the LM3914 circuit, without a regulator, is only viable if the TS is willing to use it only in "dot" mode. Then, a voltage divider could be used to drop the supply voltage. Since total LED current would be limited to one LED, the divider resistors wouldn't be physically too big (1/2 watt, maybe larger). But to me, the visual effect of a "bar" mode display is more attractive as a battery level indicator.

 

But to me, the visual effect of a "bar" mode display is more attractive as a battery level indicator.

Agreed.
Perhaps high-brightness type LEDs could be operated at a low enough current level, while still having adequate brightness (I think some can do that at a mA or less), to allow operation in the bar mode without excessive dissipation being a problem.
At 1mA each, the maximum total LED current would be 10mA, which would require a 5V regulator to dissipate only about 200mW maximum.

 

I did look a little and lowest current LED I could find was If=2mA, Vf=2v. Maybe someone else will have better luck.

 

I did look a little and lowest current LED I could find was If=2mA, Vf=2v.

That's the rated current, but LEDs will operate with significant light well below that rating, especially high-brightness types.

 

I did not think that this was a "Style Competition", but rather an effort to read a remote voltage with a minimum of complexity.

And as for power dissipation being the same, that was not the target. The intention is to keep each device power dissipation within the specification limits. Dropping 20 volts in one small package is a lot of heat, dropping ten volts cuts that in half.

 

I did not think that this was a "Style Competition"

Me either.
Where did "Style" come into the conversation (besides what you just said)?

 

Posts #30 and #31.

 

Posts #30 and #31.

I have no idea what your referring to...

 

Posts #30 and #31.

So "style" is talking about whether the display is dot or bar?
Why does that bug you?

 

So "style" is talking about whether the display is dot or bar?
Why does that bug you?

Not "bugs me", but suddenly i is about LOOKS, not function.
" But to me, the visual effect of a "bar" mode display is more attractive as a battery level indicator. " (quote)
The application is a manually enabled battery voltage check device, not a panel display in a high-priced auto.

 

The application is a manually enabled battery voltage check device, not a panel display in a high-priced auto.

I see no mention of where or how this is to be used, except that there is not much room for the circuit.
If you don't want to talk about "style" then you are free to ignore our posts.