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Fri Dec 15, 2006 11:52 am

I have measured 6 of my Semaphores. And the resistance is around 1ohm.

So to get a voltage drop of 50% you can add a 1 ohm resistor.
Connect the resistor in series with the semaphore.

And raise the voltage to 12 Volt , and the voltage will still be 6 Volt over the semaphore.

What about the wattage of the resistor
I*E = E^2 / R make 36 Watt when running 6V and 1 ohm. So a 40 watt 1 ohm resistor works well. If you want a cheap resistor, use a 40 watt head lamp.

Both the resistor and the lamp will get hot (40Watt). so mount it on a heat sink or where it cant make any damage.

Here is a Ohms Law web calculator
http://ourworld.compuserve.com/homepages/Bill_Bowden/ohmslaw.htm

So you can check out the math youreself.

Sat Dec 16, 2006 4:07 am

Lars B wrote:
What about the wattage of the resistor
I*E = E^2 / R make 36 Watt when running 6V and 1 ohm. So a 40 watt 1 ohm resistor works well. If you want a cheap resistor, use a 40 watt head lamp.

When I looked for a high power resistor, I found only 25W and 50W. Here's a 50W resistor:

Mon Dec 18, 2006 6:19 pm

If your still looking for way to drop voltage to semiphores. J C Whitney sells a voltage reducer from 12 volt in to 6volt out 6-8 amp s. I have used this on my Ovals before and it works fine. # CM128181 about $20.00 plus shipping.

Tue Dec 19, 2006 2:33 am

Ok..thanks Guys for all the input..

Now I understand properly and start searching for resistor or volt drop..with confidense... :)

cheers

Wed Apr 25, 2007 5:27 am

bedjo78 wrote: Hai All,
...
I found a converter from cip1.com...
http://www2.cip1.com/ProductDetails.asp?ProductCode=ACC%2DC10%2D5754

..

Did anyone find out what resistance this one had?

EDIT: I did; 4Ω so it wont work with the semaphores.
I bought equivalent in 1Ω / 50W.

Sun Jun 15, 2014 9:59 am

Hello Bruce can you tell me where to order this resistor? .9 ohm 50 watt

thankjs.

Thu Jun 19, 2014 5:24 pm

I don't have a source yet for a 0.9 ohm, but you can get the 1 ohm resistor here:
http://www.thesamba.com/vw/classifieds/detail.php?id=1653917

Thu Jul 03, 2014 4:14 am

One small thing here Bruce. If you change the BULB to a 12v bulb of the same wattage, the resistance of the bulb will be doubled. Since there is only one power wire for the semaphores, the power runs in series through both the bulb and the slider electromagnet. Therefore the electromagnet will be seeing a lower voltage than would be the case if the bulb resistance was the same. It will probably still be higher (I haven't done the actual math) than running on 6v, but it wont be double, so would take some time to overheat, if at all.

That's why some folks find they can get away with just changing the bulb to 12v. Just don't put a double WATTAGE 12v bulb in there or the resistance is the same as the lower wattage 6v bulb so the electromagnet WILL see double the voltage and overheat quickly.

Thu Jul 03, 2014 1:34 pm

Aussiebug wrote: , the power runs in series through both the bulb and the slider electromagnet.
Not correct. The bulb is wired in parallel to the solenoid coil.
The main power wire from the turn signal switch connects to the lower terminal of the semaphore. Connected to this is one side of the coil, plus the wire leading up to the bulb. The other end of the coil and the bulb is connected to chassis ground. (or earth as the Brits say)
If you install a 12V bulb into a 6V semaphore, the coil will then see double the voltage. The bulb will be ok, but you'll cook the coil.
My buddy reported that when he ran a 6V semaphore with 12V, he would start to see smoke after about 45 seconds. YRMV.

Aussiebug wrote: That's why some folks find they can get away with just changing the bulb to 12v.
The only benefit to fitting a 12V bulb is that you don't pop the bulb. You'll still burn out the solenoid coil just as fast.