12v relay buzzing at 3v

Could any one help me with a problem I have please

I have a 12v relay that has a dual voltage going to it
basically when I turn my car lights on i have 3v volts going to my new relay and it buzzes because of not full voltage

I would like to stop this and make it operate at around 10v-12v only

could any one help please

new boy UK here

Insert a diode or a few - eg common IN400x series (4001, 4004 etc).
But probably any diode(s) will do - they merely have to handle the relay current.

Each diode will drop about ~0.6V, hence 2 will drop ~1.2V etc.
That should drop the relay voltage below its drop out voltage.

Meanwhile losing .6 or 1.2V off the on voltage of ~12V should not make much difference.


(Exceptions - a relay switching high current; diodes with 0.2-0.3 voltage drops like ancient Germanium & some Schottky.
Strictly speaking, the voltage should be cleaned up thru a comparator or transistor or (maybe easiest) a FET, but suck it & see if it works...)

Thanks for the reply

so i need to put a few diodes in series with the relay

on the 0v- or the 12v+

also some one else said to try a zenor diode would that work ????

A little more info for you on my project

I have upgrade my rear lights on car to leds
my old side light doubled up as a fog when its was given the full 12v
but only 3v volts when in side mode

so ive fitted a relay in line with the supply to the fog light
so when i turn the fog on the relay operates which works but

when the side lights are on the relay buzzes

hope this helps any one with my prob

Zener diode won't work with out either a cap or a resistor I believe but why are you getting 3volts in the system or do you have those POS LED lights. Howie ll THE only real auto electrics guy.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

As above your post

Sorry JR, your post arrived before I completed mine, just proves how good I am at auto electrics! Install a second (LEGAL) rear fog and the problem will go away.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

yes that would be easy

but i would like my new fog light to work properly

and stop the buzzing in my boot

forgot to say

the new lights are from a newer model and are legal but work slightly different to my wiring

I'm with Howie. (Howie ll THE only real auto electrics guy.)

A forward biased zenor is merely a diode.
Reverse biased it doesn't conduct until above its breakdown voltage - eg, a 3.0V zenor would be equivalent to 5 x 0.6V diodes (but mounted opposite direction). Make sure the zenor voltage times its current does not exceed its power rating (Watts).


+ve or -ve side should not matter.

I've tried the two diodes but it didn't really make it much better

so I think ill try a reversed zenor diode

can you advise which I need it a 12v system which should max at 21w

your help is much appreciated

Just figure out the voltage you want to drop times the current thru it.

Presumably the current is just the relay coil current - maybe 200mA - hence 0.2A x 5V = 1W for a 5V drop. Or 4V if 250mA for 1W etc.

Zeners commonly come in 400mW, 1W & 5W sizes (but avoid running them at 100% - the lower the better, but ROT no more than (say?) 70-80% of power rating).

Zener voltages follow the E24 series from ~3.3V up to ~75V (eg 3.3, 3.6, 3.9, 4.3, 4.7. 5.1...)


Are you able to draw the circuit that you have?
I assume the fog is still an incandescent bulb - not a LED?

If the wire is at 3 volts, and it is chattering at that voltage, diodes in series should rectify your problem.  I think it will require more than 2 diodes to solve it.  I know theoretically you should lose .7 volts per diode, but in real world applications it is more like .4 volts per diode.  Try 5 or 6 and it should drop the voltage low enough to eliminate the chatter.

Thanks for the reply guys update.

I've tried a couple of different types of zenor diodes from my local electronic shop but non of them worked, in forward direction they all passed 3v and 12v and in reverse they all passed no voltage at all,

so I think im going to try the diode idea but not keen on having to put 5 in series to lower the voltage. do they have to be wired in daisy chain or can i put them all in a bunch??

Is there not other way to stop anything under 3.5v passing through the circuit what about resistors.

Did you try reversing the zener?

Multiple diodes are just like a zener.

Resistors won't work (reliably).


But I suspect it is a circuit problem - that's why I want you to draw or better describe what you have.
Where are the LEDs?
Where are incandescent or other bulbs?
How is the signal/power being switched?
Where is the relay (coil)?

There doesn't have to be a relay in the circuit if there is another of doing it Im just using at the moment to keep them work.

The leds are standard lights from the manufacture and have a working voltage of 5v to 1.5 volts

I hope this help as i need to sort this prob out pretty soon

thanks for your help

The relay wiring doesn't look right, give us the terminal connection numbers.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

The wiring to the relay is right because it works
All I've none is pick the feed to the relay from the fog light switch wire which has 3.5v on it when the side lights are on and then jumps to 12v when press the fog switch

Phew - it works!

My apologies, I thought you were still having problems.

Otherwise I'd question the commoning of 12.5V & 3.5V, and especially 30 & 86 (NO-in & coil).
You did put the diode(s) between 30 & 86? Sorry - that is now irrelevant.

Yes i put them in series with the feed

So you put the diode(s) between the relay input (power) and its coil....
NOT between [3.5V & 12.5V] and the [Relay Input & coil]?

Next - how have you interconnected the 3.5V & 12.5V... diodes?
Else what is between raw +12V and that join?