Need help on 6 V semaphore

[Bruce]

[Aussiebug]

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.
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Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com

[Bruce]

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
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[turbolaz]

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

thankjs.
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shipping extra,paypal ok at 4% added to parts.
parts are sold as is.

[1955oval]

[bedjo78]

Ok..thanks Guys for all the input..

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

cheers
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Splitty Bus 66
baywindow 78
bug 67

[Fabian Godinez]

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.

[Bruce]

[Lars B]

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.

[53 0val]

[Bruce]

[manxcraig]

A 12 volt battery is a group of six two volt cells. They are connected inside the case by lead bars between each cell. So a 12 volt battery is really six two volt batterys connected together in series.
Drill a small hole through the top of the case into the connecter bar between the third and forth cell, and connect a wire (with an eyelet) with a sheetmetal screw. Use an inline fuse holder, and run this wire to your six volt item. Ground the item to complete the circut.
I learned this from an engineer at a battery manufacturing plant 35 years ago.
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69 Meyers Manx II on 65 pan, 1 owner !
WANTED, Meyers Manx license plate frames, repo OK, don't like the new smiles per miles ones.

[53 0val]

Put in a six volt battery and run them seperately from the rest of the car.
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"What a fool believes he sees, no wise man has the power to reason away." Dobee, Dobee, Do

[RareAir]

I'm running a 12v system in one of my cars. Haven't burned a semaphore yet either. But at the same time, I don't have the semaphore lit up for more than 15-20 seconds at a time. I know it'll fry if I have it up for too long, so I'll aviod that problem all together.
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1947 Typ 11a
1954 Typ 117
1956 Typ 151
1959 Typ 117
1959 Typ 265
1961 356B
1966 Typ 151
1966 Typ 241

[Alan Willis]

I find flaws in your calculation; if the draw on the semaphore is now 12A then how come the 8A fuse doesn't pop even when I have the brakes applied? True the solenoid will get hot if left on too long, but I havent had a problem yet. As for leaving the bulbs 6v in a 12v car; the FILAMENT can't handle it. Its the same as running 12v through a 6v starter;its been done for years with no problems.
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die schwarzen Schafe #666

[Bruce]

You might think that if you double the voltage in the semaphore, you will create double the heat in the windings. Not so. Follow along with some help from Georg Ohm.

V=IxR
A semaphore's resistance is 1 ohm. Apply 6V to it, you get 6Amps of current flowing through the winding because of this equation:
I = V/R = 6V/1ohm = 6A

The power in a cct is found using the following:
P=IxV, in our case, P = 6V x 6A = 36W.

Now hit it with 12V. The resistance is still 1 ohm. I = 12V/1ohm = 12A.

The new power being dissipated is now P = 12V x 12A = 144W.

By pumping 12V through your semaphores, you are creating 4 times the heat in the windings. It is no wonder they start to smoke in less than 1 min.
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[DrDarby]

Yes my system is 12v and yes Bruce is correct. While most of my original harness has had terminals replaced / cleaned etc I left the turn signal circuit 100% alone. The only time I got smoke was after the first few times I used them and I attributed it to the oil I used to ease their old hinges etc. They haven't smoked in years now.
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Midwest Autosavers, Inc. Crystal Lake, IL

[Bruce]

[Alan Willis]

[ssbn659]

bedjo78

I just want to thank you, you found what I need to reduce the voltage going to my wipers
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57 Oval (with creative engineering)
64 Mercury Parklane Convertible
68 Pontiac Firebird
71 Plymouth Barracuda