Changing 12 volt to 6 volt??

[Micro469]

Hey Guys, I picked up an old car horn from the 30's or 40's.... it's 6 volts but would like to put it in one of my cars...... love the sound of the sucker, How do I connect a 6 volt horn to a 12 volt system? It's actually has a motor which turns a plate that vibrates against a steel (tin) plate that creates the sound. Any suggestions??

[dahoon]

John,

You can go to any auto parts store or electronics store and pick up a 12 to 6 voltage drop. I know Cole Hersee for one makes it.

Mike
resident counterman

[emiller]

Here you go John try these http://www.rbsobsolete.com/product.asp? ... _id=171989 or http://www.rbsobsolete.com/product.asp? ... _id=172010 of corse the ceramic one will be cheaper than the electronic one and work just as good.

[jgalt]

Check the amperage first, a car horn can pull quite a bit of current. The 15A might be OK, but I doubt if 4A would work for long.

Have you tried the horn at 12 volts? A DC motor can withstand a wide range of voltages. In fact, many antique cars have 12V systems, but still have the 6V starter. Since the starter runs for only a short time, the over-voltage isn't really an issue. Same would be true for a horn

Might transpose the tone an octave however!

[Chuck Craven]

Running it on 12v will make the motor go faster and may give you a different sound.
Measure the current at 6V, use Ohms Law to find the resistance of the motor.
Like this: 6v, 6amps : divide voltage by current gives you resistance = 1 ohm.
Next: You need to find the wattage. 6volts times 6 amps = 36watts.
To run the horn on 12 volts you will need a 1 ohm 50watt resistor in series with the horn.
The resistor will drop the 12 volts to 6 volts for the horn. You can find high wattage resistors at surplus electronic part houses. Try a Goggle search on “50 watt resistor”.


Chuck

[Micro469]

O.K., so how do I check the amperage? (Electrical waay over my head...)

[Chuck Craven]

Do you have a multi meter?

If so measure voltage across the horn when it is making noise!
Measure current take the meter put it in amps and put the meter in series with the horn + lead. Hook up the red lead to the battery and the black lead to the horn. If you have a digital meter if hooked up wrong it will read – current forget about the – sine. If an analog meter the pointer will try to go the wrong way. Then gust reverse the leads.

Take a look at Goggle or Yahoo! Type in “Ohms law” it will give you the electricity 101 introduction on one of the web sites.
Give it a try!
Chuck

[emiller]

Ron Francis wiring also can help with there wiring systems her is a 15 amp one http://www.ronfranciswiring.com/showpag ... partid=152 or call them they will tell you what you need.

[madjack]

Chuck, just curious...could you measure the ohms of the horn and by a similar sized hi-power resistor ??????? ...aslo, aren't most home use multimeters limited to measuring milliamps unless you have an AMPROBE adapter????????
madjack

[Dale M.]

Chuck, just curious...could you measure the ohms of the horn and by a similar sized hi-power resistor ??????? ...aslo, aren't most home use multimeters limited to measuring milliamps unless you have an AMPROBE adapter????????
madjack

Various "home" volt/ohm/amp meters will go up to 10 amps with out having to have special amp probe. I have 4 meters (two cheap- two expensive) both digital and analog and all have up to 10 amp capacity.

Dale

[asianflava]

Yeah, most meters have a 10A capacity. As long as the fuse inside isn't blown.

[Chuck Craven]

Chuck, just curious...could you measure the ohms of the horn and by a similar sized hi-power resistor ??????? ...aslo, aren't most home use multimeters limited to measuring milliamps unless you have an AMPROBE adapter????????
madjack

Most likely not! The ohm measurement on a multi meter reads pure resistance. Motors have coiled wire, which is inductive reactance, which is measured in ohms also. It’s another one of the things about electricity that can drive one crazy. The horn is using a motor so the current should be some wear around 5,6 amps on 6 volt system.
Being a motor, the brush resistance will be higher when not turning.
And the dropping resistor will be too large and drop the voltage to the motor below 6 volts. Also like a 12v battery, which will measure 13.6v, the 6V battery will measure about 7v with the horn totting. Got to take that in account when doing the math.

Chuck

[madjack]

thanks...Y'ALLL.......(ahhhhh the blissful sound of simplicity) ...................................