Hi,

I've now been testing a custom pcb, basically a very simple led bar monitor for a custom gel battery.

voltage range 11.8 - 16.0 V

Have a look at a portion of the schematics below:



So The Led-bar is working good, but the transition between the leds are not godd enough, sometimes two leds light up because of the transition voltages.
Also, maybe I can add some capatiance so that the startup time for each led is f.example 500ms-1000ms. Any suggetions on how to wire these capacitors?

Also the pcb gets very hot, so I need to calculate the power(W) of the components above inside the red circles.
Is it possible here to use larger values instead of using larges size on components from 0602-0802 ?

As a guideline I have very space limitations, thats why I've been using 0603 passives.

Thanks!

David

 

Hi norova,
It seems a very complex circuit for a battery voltage monitor, have you considering the LM3914 IC.?

On comparators, it usually necessary to add some hysteresis to the comparators, in order to ensure correct operation.
Also, using those low values of resistors, for level setting, will add a current load to your battery pack.

E

 

Multiply the value of all of your Voltage-Divider-Resistors by 10X.

To add Hysteresis to the action of the LEDs,
add a 100K Resistor between each Comparitor-Output
and the Non-Inverting-Input ( + ) of that Comparitor.
( after You have changed all the Voltage-Divider-Resistors to 10X of their original value ).
.
.
.

 

You would reduce the power dissipated by 11/12 by putting them all in one chain instead of having separate dividers for each input.
If you don't decide to use the LM3914, which was a very good suggestion by @ericgibbs , then have a look at the datasheet to see how it works.

 

You would reduce the power dissipated by 11/12 by putting them all in one chain instead of having separate dividers for each input.
If you don't decide to use the LM3914, which was a very good suggestion by @ericgibbs , then have a look at the datasheet to see how it works.

Would that configuration allow for "dot mode" without the additional function of the LM3914?

Seems like putting all of the resistors in a single chain would only allow for "bar mode".

It that correct?

 

Would that configuration allow for "dot mode" without the additional function of the LM3914?

Seems like putting all of the resistors in a single chain would only allow for "bar mode".

It that correct?

It won't make any difference - it's just the reference. You can obtain "dot" mode by using comparators with push-pull outputs and connecting LEDs between adjacent outputs. If you must have the LEDs returned to one or other power supply, you'll need 11 ex-or gates.

 

I don't see how it won't make any difference if the OP has to change comparators and the output configuration.

Ok I see now, I have a hard time seeing the values on the image, I see now that the circuit is already in bar mode.

I don't know why the heck I was thinking they were window configured...must be going senile.

I think this statement confused me..." sometimes two leds light up " but now I'm just making up excuses.

 

Hi,

Thanks for all the good suggestions!, this forum is great

I'm not comfortable using something like the LM3914, it's a better option, but if you look at the availability on f.example digikey: https://www.digikey.no/no/products/...mdrivere/729?s=N4IgTCBcDaIDYFsDMBOAjAFhAXQL5A

I need a design that is manufacturable without using time later to find available components due to shortages In the market.

I will Implement LowQCab suggestion, thanks!

Regards,
David