# need circuit for potentiometer for 12V backup alarm for RV

Discussion in 'The Projects Forum' started by dtsnyder, Oct 8, 2008.

1. ### dtsnyder Thread Starter New Member

Oct 8, 2008
1
0
Hi folks,

I have a backup alarm on my RV that is too loud when we back into a camping spot late at night in a campground. I would like to insert a potentiometer that would allow me to control the volume of (and even turn off) the backup alarm. This is a 12-volt DC system. I am a novice with regard to designing circuits but am reasonably handy with a soldering gun. I would appreciate knowing specifically what potentiometer I need to purchase (suggestions as to where to purchase would also be appreciated) and how to install it including what gauge wire I should use.

The backup alarm is Wolo model BA-64 http://www.wolo-mfg.com/back-up.htm. I have followed the installation instructions (http://www.wolo-mfg.com/ba-52 ba-64 english span.pdf) and connected one end to the lead of the back-up light and the ground is through the bolt connecting the alarm to the vehicle frame. The backup alarm works great, just too loud at night.

Sorry, I have no information on the electrical specs of the backup alarm and could not find any online or on the package.

Your help would be greatly appreciated by my family and I as well as our fellow campers.
-Dan from Oregon

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
It would seem as if a resistor in series with the beeper should cut the volume. Most potentiometers are rated at 1/2 watt or less, which could be a problem. Do you have any idea of the beeper's current draw? That figure will let you figure its effective resistance (R = E/I, where R is resistance, E is the battery voltage, and I the current).

Using the resistance, get some resistors of about 1/4 that value, and rated to dissipate about the wattage of the beeper - that's the product of current times the voltage. If one doesn't cut enough, add another until the volume seems enough lower. Use a switch to select day/night.

If you want to be adventurous, get 10 4.7 ohm 2 watt resistors and see how they work, as in the above example. If they get hot, you may need more dissipation. But then, how long to you stay in reverse?