Low Voltage Alarm

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This low voltage circuit can be used to monitor batteries and other volatile sources of current for problems. The circuit sounds an alarm and lights an LED, but can be interfaced to any number of other circuits for many different uses.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1, R3	2	1K 1/4W Resistor
R2	1	5K Pot
U1	1	LM339 Op Amp IC
D1	1	1N5233B Zener Diode
D2	1	LED
BZ1	1	Piezo Buzzer
MISC	1	Board, wire, socket for IC

Notes

The circuit will operate from 9V to 12V.

Adjust R2 until the alarm goes off at the correct voltage.

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Comments

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Kashinath Low Voltage cut off circuit at 3V for 1A load current Friday, November 15, 2013 12:12:19 AM

hi everyone.. I need to provide battery back up facility to my one project. so for that purpose i used Li-ion battery(Max 4.2V/ 1A) to provide the supply to load. so i need to cut off the load at 3V. can i use above circut for that purpose?? please anyone help me. Thanks in advances

saurabh Low Voltage Alarm Tuesday, May 01, 2012 10:42:02 AM

where do we give the i/p and take the o/p and i hve a 9V battery and 12V zener would it work

anonymous Low Voltage Alarm Wednesday, January 04, 2012 1:44:37 PM

What if I have a 12 volt battery and want it to alarm me when it drops to say 9 to 10 volts. How does this work?

bhanu pp Low Voltage Alarm Monday, April 18, 2011 1:19:29 PM

nice ckt

Doug Low Voltage Alarm Tuesday, March 01, 2011 8:51:26 PM

Substituted a HA17339 for the LM339, used a 6.2V zener, a 2.2V (green) LED and a 6K POT. Left out the piezo buzzer. The circuit works like a charm.

ARSALAN AFRIDI electronics Thursday, December 23, 2010 2:40:39 AM

AOA I WANT CONSTRUCT THE WATER FLOW ALARM CIRCUIT SO PLZ KINDLY HELP ME ABOUT THIS PROJECT ME WAITING OF YOUR REP AND PLZ SEND THE DEMO CIRCUIT FOR TH E IDEA ,,, THANK YOU DEAR

Prash Low Voltage Alarm Friday, April 16, 2010 3:25:43 PM

Nice project..it works perfect..Thank u!

Taylor Low Voltage Alarm Friday, March 12, 2010 8:27:35 AM

The schamatic I downloaded had the Zener backwards and the LED stayed on. Turned around and worked great. Made another on for my neighbors stored RV battery. Thanks

Terry Low Voltage Alarm Sunday, January 31, 2010 8:37:43 PM

hi, i cannot get a 6v zener diode in New Zealand, will a 5.6v or a 6.2v work instead?

Ritesh Agarwalla Low Voltage Alarm Thursday, December 10, 2009 9:21:30 AM

I am planning to trigger the 12V Cutout at 11V so please suggest me the alternative for 5k pot.

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Kashinath	Low Voltage cut off circuit at 3V for 1A load current	Friday, November 15, 2013 12:12:19 AM
hi everyone.. I need to provide battery back up facility to my one project. so for that purpose i used Li-ion battery(Max 4.2V/ 1A) to provide the supply to load. so i need to cut off the load at 3V. can i use above circut for that purpose?? please anyone help me. Thanks in advances
saurabh	Low Voltage Alarm	Tuesday, May 01, 2012 10:42:02 AM
where do we give the i/p and take the o/p and i hve a 9V battery and 12V zener would it work
anonymous	Low Voltage Alarm	Wednesday, January 04, 2012 1:44:37 PM
What if I have a 12 volt battery and want it to alarm me when it drops to say 9 to 10 volts. How does this work?
bhanu pp	Low Voltage Alarm	Monday, April 18, 2011 1:19:29 PM
nice ckt
Doug	Low Voltage Alarm	Tuesday, March 01, 2011 8:51:26 PM
Substituted a HA17339 for the LM339, used a 6.2V zener, a 2.2V (green) LED and a 6K POT. Left out the piezo buzzer. The circuit works like a charm.
ARSALAN AFRIDI	electronics	Thursday, December 23, 2010 2:40:39 AM
AOA I WANT CONSTRUCT THE WATER FLOW ALARM CIRCUIT SO PLZ KINDLY HELP ME ABOUT THIS PROJECT ME WAITING OF YOUR REP AND PLZ SEND THE DEMO CIRCUIT FOR TH E IDEA ,,, THANK YOU DEAR
Prash	Low Voltage Alarm	Friday, April 16, 2010 3:25:43 PM
Nice project..it works perfect..Thank u!
Taylor	Low Voltage Alarm	Friday, March 12, 2010 8:27:35 AM
The schamatic I downloaded had the Zener backwards and the LED stayed on. Turned around and worked great. Made another on for my neighbors stored RV battery. Thanks
Terry	Low Voltage Alarm	Sunday, January 31, 2010 8:37:43 PM
hi, i cannot get a 6v zener diode in New Zealand, will a 5.6v or a 6.2v work instead?
Ritesh Agarwalla	Low Voltage Alarm	Thursday, December 10, 2009 9:21:30 AM
I am planning to trigger the 12V Cutout at 11V so please suggest me the alternative for 5k pot.