LED battery indicator - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th October 2012, 02:24 AM   #1
diyAudio Member
 
Join Date: Jul 2012
Location: Draper Utah
Default LED battery indicator

I would like to include a circuit in my preamp to monitor battery voltage. with some pushing from WSJ I think I am going to try to design it myself.

I found this online and wondered if I could modify it for my purpose. my battery operating range is 38v-50v. How could I modify this to work with my voltage.

Click the image to open in full size.
  Reply With Quote
Old 19th October 2012, 03:14 AM   #2
diyAudio Member
 
Join Date: Jul 2004
Location: Edmonton, AB Canada
In that circuit, the LM358 max. pwr is 32V and LM7805 max. is 35V, so the 50V requirement is too high for many IC's. The 7805 wastes 5mA quiescent current, plus 20mA LED on all the time, which might be too much. Is this a tiny battery pack? Usually a low battery LED is sufficient or do you want the window comparator?

Dropping the supply voltage with a series zener diode, say 24V 1W could work, but you will be wasting ~1/2W as heat. The resistor values (R1,R3,R2,R4) need to be changed too for the higher trip points.

I would also look at the TL431 which contains an op-amp and voltage reference (fewer parts) - but a 36V limit you can use a zener diode to drop that down. See the datasheet battery monitor circuit Fig. 26 which would need some mods to work at 50V. This chip is a bit harder to understand.
  Reply With Quote
Old 19th October 2012, 04:58 AM   #3
diyAudio Member
 
Join Date: Jul 2012
Location: Draper Utah
Quote:
Originally Posted by prairiemystic View Post
In that circuit, the LM358 max. pwr is 32V and LM7805 max. is 35V, so the 50V requirement is too high for many IC's. The 7805 wastes 5mA quiescent current, plus 20mA LED on all the time, which might be too much. Is this a tiny battery pack? Usually a low battery LED is sufficient or do you want the window comparator?

Dropping the supply voltage with a series zener diode, say 24V 1W could work, but you will be wasting ~1/2W as heat. The resistor values (R1,R3,R2,R4) need to be changed too for the higher trip points.

I would also look at the TL431 which contains an op-amp and voltage reference (fewer parts) - but a 36V limit you can use a zener diode to drop that down. See the datasheet battery monitor circuit Fig. 26 which would need some mods to work at 50V. This chip is a bit harder to understand.

Great points!! thanks

I was thinking I would have a button to active the circuit when you want to check voltage. maybe a numerical display would be easier?

There must be some IC for this voltage since golf carts use 48v.

Its a pretty large battery pack - 6ah
  Reply With Quote
Old 19th October 2012, 06:00 AM   #4
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
can you monitor just the cell that has the highest power draw? ie. is this pack made up of several batteries in series? if it is, its as simple as sending the voltage on that.
  Reply With Quote
Old 23rd October 2012, 01:40 AM   #5
erin is offline erin  Australia
diyAudio Member
 
Join Date: Nov 2006
Location: http://www.makeitpossible.com/
Green DC10-90V/24V/36V/48V/72V digital display LED Panel Voltage Meter Voltmeter | eBay

push a button to operate. seems cheaper and simpler to me.....
  Reply With Quote
Old 23rd October 2012, 04:41 AM   #6
diyAudio Member
 
Join Date: Jul 2004
Location: Edmonton, AB Canada
I've got a 30VDC digital panel meter from China, but one that runs up to 100VDC (power) is news to me. I think it uses a buck converter- which makes electrical noise and defeats the purpose of running a pre-amp on batteries.
Maybe an LCD panel meter with its own 9V battery would work.
  Reply With Quote
Old 23rd October 2012, 05:03 AM   #7
erin is offline erin  Australia
diyAudio Member
 
Join Date: Nov 2006
Location: http://www.makeitpossible.com/
It does not defeat the purpose if you just are pushing a button to check the voltage.
The meter is off until you press the button.

The way I used to tell when my battery powered phono stage was flat was by listeing to the sound. It would gradually start to sound not as good. I didnt need any meters to tell me it was getting flat.

The other way was that I knew it lasted about 8 hours before needing charge.
  Reply With Quote
Old 23rd October 2012, 10:58 AM   #8
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by ExtraCredit1 View Post
I would like to include a circuit in my preamp to monitor battery voltage. with some pushing from WSJ I think I am going to try to design it myself.

I found this online and wondered if I could modify it for my purpose. my battery operating range is 38v-50v. How could I modify this to work with my voltage.

Click the image to open in full size.
A discrete circuit can easily be tailored to the application, is simpler, cheaper and takes less quiescent power.
This example uses less than 200µA quiescent current (can be further reduced with a suitable zener) and gives a progressive indication: when the voltage passes below the ~40V limit, the LED begins to flash briefly at a rate of one every few seconds, and if the voltage goes lower, the rate increases up to 3/second.
All these parameters can be adjusted by adapting the components values.

Even when it flashes at full rate, the consumption remains low thanks to the low duty cycle.
Attached Images
File Type: png BattMon.png (95.2 KB, 55 views)
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LED peak level indicator forsakenrider Analog Line Level 5 16th March 2011 02:12 PM
LED source indicator snails07 Chip Amps 5 19th August 2008 11:24 AM
Signal Indicator LED Noise? turantual Solid State 4 15th August 2008 12:13 PM
LED bias indicator scottw Tubes / Valves 6 6th December 2007 12:19 PM


New To Site? Need Help?

All times are GMT. The time now is 10:14 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2