Converting 24v to 12v

elevfan7072

I recently found a 24v scooter on Craigslist. I would look forward to wiring a horn to it. I don't know what kind of resistor I should use.

sophiecentaur

Wire two identical 12V horns in series. That is the easiest solution. Alternatively, you are going to need to waste power in a dropper resistor and you would need to work out its value. Two horns in series will produce twice as much noise and waste no power. Plus, you won't need to do any sums!

davenn

And the other obvious alternative is ....

there are plenty of 24V horns available for trucks etc
take a trip to your local vehicle wreckers and look through the recovered parts.
many wreckers let you look through vehicles yourself and recover the part you need ... take it to the counter and pay for it

Dave

elevfan7072

Oh Or if I only use one I could just use a 7812!

berkeman

You certainly could, but you will need to figure out the horn current and then how much power that means when you drop 12V across the 7812. Luckily the horn will only be used intermittantly, so it may not take much heat sinking of the 7812 to make it work.

A better solution is to use a DC-DC converter (buck topology) to drop the voltage with little power dissipation. The Simple Switcher series of DC-DC converters from National Instruments is a good place to start if you want to try that route...

davenn

you will probably find that the current requird by one 12V vehicle type horn well exceeds the 1A capability of a 7812 regulator chip.

Dave