By steven (Walleye713) on Unrecorded Date: Edit

Does anyone know how a snowmobile 13.7 volt ac accessary output could be converted to 12 volts dc so that i could plug in my gps power cord from my argo and use the gps on both machines?
there is no battery in the snowmobile and it is manual start.
thanks
steve

By Kevin Percy on Unrecorded Date: Edit

Steve,
Usually there are two alternator output wires, and if the motor does not have electric start one of the wires is grounded, the other runs to the lights with a regulator tied in and the lights just get AC. To convert to DC output (correct me if I am wrong here anybody) both alternator output wires are run to a bridge rectifier and the negative output of the rectifier is then grounded. The positive output from the rectifier then goes to the lights, battery etc. I think the battery in these systems becomes the regulator, I know that if you don't have a battery in an electric start machine the lights never get very bright.
So unless someone else has a different way, you may have to install a battery, along with the rectifier once you locate the other alternator wire.
Kevin

By BobGraham on Unrecorded Date: Edit

My humble opinion (ASE Master Tech, Jaguar Master , Land Rover Master) , ok, not so humble, if you check the output of the cigarette lighter socket on your car/truck and the power port on your argo , you will find that with the engine running, you will always have more than 12 volts, more like 13.5 to 14.5 volts. 12 volts is what we refer to as "nominal voltage". If your GPS unit is made to plug into a car's cigarette lighter it will handle the snowmobile's output. It's pretty hard to draw all the picture's here but it is a fairly simple thing to understand, your battery in the car acts as a buffer to "eat" the extra voltage. Also, most DC appliances have built in capacitors to duplicate this effect. Get a voltmeter and see what your Argo is putting out, and then check the snowmobile's output, my bet goes that they are very close(within a half volt). Bob

By BobGraham on Unrecorded Date: Edit

I forgot to mention that , I'm betting that ""13.7 volt AC outlet" is in fact DC. Make a couple calls or have a tech look at it , but my money goes that it's DC.

By davidb3rd@aol.com (David3rdd) on Unrecorded Date: Edit

bob, its dc after you put it threw a brige rectifire, your probly going to have to use a zenner diode to control voltage so it stays 12 volts for your gps,

By ksfastman@kscable.com on Unrecorded Date: Edit

stock it's ac.

By Eugene Kochnieff on Unrecorded Date: Edit

Re Ac to Dc conversion.

Put it through a bridge rectifier if there is two wires put them one each on to the rectifier ac terminals. if there is only one wire connect it to one ac terminal and connect the other to frame.

Now either way you will have varing dc on the rectifiers dc output terminals this needs to be filtered and regulated.

Do not connect the out put of the rectifier to frame in either case, one wire will cause a short two wires will work but promote corrosion.
Best if you run two wires to every device you want to power.

You need to know the max out put current for your alternator 5-8 amps would be my guess as tops from a small engine so use a 10 amp rectifier rated at least for 200 volts.

use an electrolytic capacitor on the output of the bridge about 2000 micro farads per amp of expected load is a good rule of thumb.
Buy a cap rated for at least 50 volts with a temp rating of 85C or preferably 105C.

Thats the rectifier and filter sorted.

Now the regulator, this is where it may get difficult.
The best way ( effiency ) is to go out and buy a switching converter from a truck the kind that converts 24v to 12v this will handle any voltage from 14v to 32v and give you 13.8 with little waste.

second best is to go to your local electronics supplier and buy a three terminal regulator such as a LM7812 which is a 1 amp positive regulator.
this device will need to be mounted on a heat sink and inside a little metal project box.There are calculations for the heat sink and the device must be mounted in a way that they are electricaly isolated from the case nut in good thermal contact. the people at the electronics store can help with this info.

If you want more regulated current or to set the voltage to other than 12v exactly a regulator device such as the lm 350 will give 3 amps and has adjustsble out put.

Worst solution is a zenner. to implement this the following must be known.
1 max voltage on filter cap without load. Vm
2 Max Current drawn by Load. Im

now we need to choose a resistor and zenner for the job.
Suppose Vm = 22v And Im = 1A
then R =22-12/1
=10 ohms with 1 amp flowing this needs to be a 10 watt or greater resistor lots of wasted heat!!!
Now the zenner it will need to be 12 watts or greater so it can shunt 1 amp when there is no load, this is a large and expensive zenner with lots more wasted heat. With this set up any more load will drop the voltage and over heat the resistor. a design that can have some current in reserve will require a larger and more expensive zenner.

This is not at all difficult to do but without knowledge of electronics i understand it may be confusing.

email me enquries@granitespeakers.com

By the way i am an electrcal engineering tech.

Eugene Kochnieff.