Lead-Acid Trickle Charger with added features

Thread Starter

iONic

Joined Nov 16, 2007
1,650
Hello all,
I am trying to build a 12V Lead-Acid Trickle Charger, but with some added features.
I'd like a green power on LED and an LED way to monitor the Current drawn.

For example: 1 LED for 20mA, 2 LED's for 40mA, 3 LED's for 80mA, 4 LED's for 160mA, and 5 LED's for 320mA or higher. Actually it might be better to only have 1 of 5 LED's on at any given time.
 

Attachments

Gadget

Joined Jan 10, 2006
613
Have you checked the data sheet of the LM3915.
It has 3dB steps between each of 10 LED drivers, although you would want to use every 2nd led output to get the posted 6 dB steps.... 5 LED's .... Voila
 

Thread Starter

iONic

Joined Nov 16, 2007
1,650
Have you checked the data sheet of the LM3915.
It has 3dB steps between each of 10 LED drivers, although you would want to use every 2nd led output to get the posted 6 dB steps.... 5 LED's .... Voila
I was thinking of the LM3914. Wouldn't I want it linear?

When you say " use every 2nd led output" you mean the ever other output should be unconnected? Or should the 1st and 2nd output be tied to a single led, 3rd & 4th to another, and so forth.
 

Ron H

Joined Apr 14, 2005
7,012
Here is a nice app note about current monitors. You would still have to add the display.
 

Thread Starter

iONic

Joined Nov 16, 2007
1,650
The numbers you posted were only linear on a log scale, i.e., each was twice the previous value of current.

True, didn't think of that.
Thanks for the AppNote...I will read and learn!
 

Gadget

Joined Jan 10, 2006
613
I was thinking of the LM3914. Wouldn't I want it linear?

When you say " use every 2nd led output" you mean the ever other output should be unconnected? Or should the 1st and 2nd output be tied to a single led, 3rd & 4th to another, and so forth.

If your scale was 10,20,30,40,50 mA then yep, the 3914, but its a log progression with 6dB steps

If you use DOT mode, then you will have to pull each LED down via 2 pins of the chip using diodes, if you use BAR mode, then no problem.
 
Top