Electronics > Beginners
How to use LM3914 bar graph to indicate 7S Li-ion
(1/4) > >>
anishkgt:
Hello All,

I have the attached schematic please advise the correct way to wire these up to indicate the voltage of each cell. The voltage is 7 cells in series at 4.2v and the lower voltage is 3 and highest is 4.2. I saw Dave's video on how he uses the IC with 8.4v but i did not know how it would be in a 7 cell configuration.

Audioguru:
You might be too late because the LM3914 in the DIP through holes package is obsolete and not available anymore. Tiny surface-mount ones are still made and available if you can use them. The datasheet explains how to calculate and wire resistors to show the voltage range you want but I am sorry that I am too busy to do it for you.

If you use surface-mount ICs then calculate that they do not overheat if you use them in the bar mode, they will be much cooler in the dot mode.
anishkgt:

--- Quote from: Audioguru on April 19, 2019, 07:46:56 pm ---You might be too late because the LM3914 in the DIP through holes package is obsolete and not available anymore. Tiny surface-mount ones are still made and available if you can use them. The datasheet explains how to calculate and wire resistors to show the voltage range you want but I am sorry that I am too busy to do it for you.

If you use surface-mount ICs then calculate that they do not overheat if you use them in the bar mode, they will be much cooler in the dot mode.

--- End quote ---
Thank you for the comments. Still searching for the values of the resistors.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

Sent from my iPhone using Tapatalk
StillTrying:
"lower voltage is 3 and highest is 4.2."

As you're dividing the cell voltage by 2 with the 10ks, SIG will be 3V/2 to 4.2V/2, so you need to arrange RLO = 1.5V and RHI = 2.1V.
anishkgt:

--- Quote from: StillTrying on April 20, 2019, 09:52:53 am ---"lower voltage is 3 and highest is 4.2."

As you're dividing the cell voltage by 2 with the 10ks, SIG will be 3V/2 to 4.2V/2, so you need to arrange RLO = 1.5V and RHI = 2.1V.

--- End quote ---
Thanks

My battery voltage is 7s. So is there is max voltage that the SIG can withstand.
I need keep my RHI = 4.2v and RLO = 3. So in a 7s that would translate as 29.4v and 21v.


Www.Georgehobby.wordpress.com

Equipments: DSO104z, Hakko FX888D, Brymen BM869s

Sent from my iPhone using Tapatalk
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod