circuit that supplys voltage when 12v removed

Home / the12volt's Install Bay / Relays / circuit that supplys voltage when 12v removed (

Topic Closed)

Welcome Guest :)

Members

< Prev Topic Next Topic >

trekkerjmm

Member - Posts: 3

Joined: March 22, 2010

Location: New Jersey, United States

Posted: March 22, 2010 at 2:32 PM / IP Logged

Hi . I am a new member to the forum and have been around electronics for many years but need a little help with this one. I did a search and looked through all the relays I found on the website but cant find what I'm looking for. I am looking for a relay that will supply 12v to a buzzer when 12v is removed. What I want to do is when my fog lights are on I want a reminder that they are on when 12v is removed (shut off key. I have a buzzer that I want to energize. Something similar to a headlight or door open buzzer. Thanks...Tj

As Always Thx for the help...Tj

Ween

Platinum - Posts: 1,364

Joined: August 01, 2004

Location: Illinois, United States

Posted: March 22, 2010 at 2:55 PM / IP Logged

hi,

you'll need a relay (spdt bosch type will be fine). connect the positive side of your buzzer to your fog lights (+ term). connect the negative side to NC (term 87a) of the relay. connect ground to C (term 30) and coil-(term 85). connect ignition to coil+ (term 86). the relay will give a ground to the buzzer only when the ignition is off, and the foglights will supply power when the are on.

you could just have your switch that triggers the fog lights or fog light relay connect to ignition, then they'll turn off with the key.

trekkerjmm

Member - Posts: 3

Joined: March 22, 2010

Location: New Jersey, United States

Posted: March 22, 2010 at 3:11 PM / IP Logged

Thank you very much. I will build it tonight...Tj

As Always Thx for the help...Tj

dualsport

Silver - Posts: 983

Joined: September 27, 2005

Location: United States

Posted: March 24, 2010 at 8:02 PM / IP Logged

You can do it without any relays- if your buzzer is low current (I'll assume you're not going to use a car horn or anything extreme like that)

you can just connect it with a diode in series between the fog light power and ignition circuit.

When the ignition is off, it'll provide a virtual ground, and if your fog light is on, it'll provide 12V. The 12V through the diode will buzz your buzzer until you switch the fog lights off.

The diode is to prevent your buzzer from going off when you have the ignition on and the fog lights off.

trekkerjmm

Member - Posts: 3

Joined: March 22, 2010

Location: New Jersey, United States

Posted: March 30, 2011 at 12:53 PM / IP Logged

Hi I had asked a question a long time ago on building a circuit to remind me when I leave my fog lights on with a standard relay for switching and you were very helpful but I lost the diagram and need to make another one.

I have a 12+ wire running off the fog lights and it went to the center of the relay (#87a) and I want the buzzer to go on when I shut the ignition off so I know they were left on and I want the buzzer off when 12+ gets put to it. I had it working great but someone took my console out and disconnected everything. There are 3 or 4 wires running to it if that helps...Thx

As Always Thx for the help...Tj

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: March 30, 2011 at 4:53 PM / IP Logged

Why a relay? 12v+ power to fog lights, join and take to pos side of buzzer, neg side to driver's door switch, assuming the pin is a switched negative.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: March 30, 2011 at 5:05 PM / IP Logged

Buzzer to #87a (other end GND)

+12V to #30.

#85 to GND

#86 to the switched +12V (the one that when off, you want buzzer on).

But you shoud also be able to connect the (low current) buzzer with +ve to +12V and its -ve to that same switched source (#86 above) - hence saving the relay. (Assumes low current buzzer -say 250mA or less....)

mtrhd329

Member - Posts: 20

Joined: January 26, 2007

Location: United States

Posted: March 30, 2011 at 6:06 PM / IP Logged

N-66.

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: March 30, 2011 at 6:38 PM / IP Logged

Finally n-66 and I thought the answer was 42.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: March 30, 2011 at 8:30 PM / IP Logged

42 was the original answer. It's a different question this time.

And yes, my answer/reply above is the same as yours. (The old "using load as an earth/ground" or "virtual connection" solution - brilliant, yet so often overlooked!)

Sorry, you can NOT post a reply.
This topic is closed.

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.

circuit that supplys voltage when 12v removed

Sorry, you can NOT post a reply.This topic is closed.

Sorry, you can NOT post a reply.
This topic is closed.