Voltage reducer for a 6 volt clock on 12 volts - yes or no?

[greyben]

I tend to agree with one of the earlier comments that it will function fine on 12 volts. You should certainly get full extension of the small spring that runs the clock meaning the clock solenoid will need to operate less frequently.

If you are concerned with the higher voltage simply measure the clock resistance to ground at the power input. (Power off and clock run down to assure points are closed.) You could then put in a line resistor approximately equal to the resistance of the clock, preferably a little smaller value. This circuit dissipates very little power as the points are closed less than 1/10 of a second once every few minutes so a huge wattage resistor is an overkill. A half watt resistor would be more than sufficient.

I would avoid exotic designs. Chances are too high that doing the fix will break something else.

[northern]

It certainly sounds as if there are various ways to approach this, and I am grateful for the advice offered. I'm trying to move beyond the belief that electrical components contain "magic powder" to understanding a few of the basics. So please bear with me as I think out loud.

As others have pointed out above, one of the problems with using a resistor, without knowing the exact load requirement, is that the voltage reduction in the 12 volt system will be either more than 6 volts or less than 6 volts. Also, the clock draws varying amounts of current at different times, which raises and lowers the amount of voltage reduction.

So, how about using a voltage divider, comprised of two resistors of equal value connected in series, with the lead for the clock power connecting at the point between the resistors? Would that offer a more predictable reduction from the source 12 volts to the 6 volts required by the clock? If that sounds correct, does it matter what resistance value is used for the resistors? I assume that the wattage of the resistors would have to remain fairly high to dissipate the heat.

Edit: After doing a little more reading on this, it seems that it's not that simple. Adding the load of the clock would reduce the voltage further it seems???

[Jerry Forrester]

I'm not going to advise anyone on how to power their clock. But I have always run my six volt clocks on 12 volts with no problems. I must be the luckiest Stude owner in the world. I think I'll go buy a lottery ticket. (my first,ever)

[gordr]

You don't want a voltage divider. That would draw current, and quite a bit of it, all the time, not just when the clock wound. Your battery would soon go flat.The problem with clocks is not the power they consume when working right. It will wind fine on 12 volts, even faster than it would on six. The problem arises when, for some other reason, the car's battery goes dead. Lights left on, maybe? At some point, the battery voltage is not enough for the clock solenoid to overcome the spring, and the contacts fail to open, so you have a sustained current of several amps going through a tiny pair of contacts. They will burn out, or become so oxidized they no longer conduct. The same thing can happen to ignition points if you leave the ignition switch on for a long period without the engine running. That's why there is an "accessory" position.

[northern]

In case anyone is interested, here's what I ended up doing with the NOS clock for the '54 Commander. I bought a voltage regulator on eBay that reduces the 12 volt voltage to 7.5 volts. http://www.ebay.com/itm/301043673485...84.m1423.l2649 How can the Chinese build these things for less than the cost of the components?

The actual measurement of the reduced voltage with a digital multimeter is about 7.6 volts. I could have bought a voltage regulator that would have reduced the voltage to closer to 6 volts, but decided to go with the 7.5 volt unit instead. The reason for that was the comments on various threads about too low a voltage damaging the points in the clocks. And electrical systems typically put out a little more than 6 (or 12) volts anyway.

So far so good; the clock works well installed in the car. One just does not get that ticking sound with a digital clock!

[RadioRoy]

Cool. I ordered one to play with. Customers always ask for something to run a six volt radio from a twelve volt car. Up until now, all there has been is a hot nichrome wire resistor in a ceramic case, and they are terrible. Additionally, converting the radio to twelve volts requires more work than it is worth, IMO.

This one looks like a chopper with an actual voltage regulator in it. Big difference in functionality.

Thanks for the link/tip.

[northern]

Cool. I ordered one to play with. Customers always ask for something to run a six volt radio from a twelve volt car. Up until now, all there has been is a hot nichrome wire resistor in a ceramic case, and they are terrible. Additionally, converting the radio to twelve volts requires more work than it is worth, IMO.

This one looks like a chopper with an actual voltage regulator in it. Big difference in functionality.

Thanks for the link/tip.

Roy, The unit is well sealed, so I did not look inside. If you do open it up, please let me know what you find. After researching the different ways to reduce the voltage, I'm curious what's in there. Given the stable "out" voltage that does not vary with the load, it must be a somewhat sophisticated design.