Wiring a 6V Dash Clock Accessory to a 12V system (1 Viewer)

[bdsmitty88]

Hey, all. I thought this would be a much simpler thing to research, but there is a lot of conflicting info out there. I am wanting to install an antique dash clock in my FJ45. Most antique dash clocks run off 6V systems with the FJ, obviously, being 12V. What is the easiest, and safest way to go about doing this? I'm no electrical expert, but I did install a complex stereo system in my FJ and redid a lot of the wiring, so I'm confident I can get it done...just not sure the best way. Whatever way I choose, I'd either wire it directly to the battery with an in-line fuse or to an "always on" peripheral.

1. Simple voltage drop device, inline, between clock and 12V battery - I reckon I'd have to worry about current being too large. I could replace the wiring on the clock with something thicker, but not sure what the higher amperage would do to the clock. Don't want a poor running clock or a fire hazard.
2. Could I run it off one of the outputs to the voltage regulator? Not sure if any of those outputs are 6V. TBH, I'm not sure if the voltage regulator actually has any "drops" in it's circuit or if it only serves to cut on / off alternator current to prevent overcharging of the battery.
3. Should I just throw in a separate 6V battery and wiring circuit? I searched on some antique car threads and quite a few people just threw in a 6 volt battery (into their 12V converted vehicles) and wired the dash clock directly to that - saying to just remove and charge the 6V battery periodically. I don't wish to do this...sounds like a non-ideal solution to something that shouldn't be so hard.
3a. What about a separate 6V battery that is connected to the alternator through the voltage regulator (to prevent overcharging) but with a voltage drop in-line?

Anyone done something like this and can advise on the most appropriate method?

TIA!

 

[charliemeyer007]

I have an adjustable power supply from Amoron.

Amazon.com

I use them to power my electric gloves when in/on a vehicle, so I can use the glove batteries while afoot.

I think the power draw is low enough to leave on for a while, but you can turn it off for like long term storage.

 

[bdsmitty88]

I have an adjustable power supply from Amoron.

Amazon.com

I use them to power my electric gloves when in/on a vehicle, so I can use the glove batteries while afoot.

That looks interesting. Any idea what the max input current to the device is? Also, how about steady state power draw? Since it will be connected to a clock, it will always be running. I couldn't find the user manual, or even that specific device, anywhere on their website.

EDIT: NVMD, found the user manual. It doesn't mention anything about steady state current draw. It's so cheap, I might just order one and find out.

After doing some reading on how those old dash clocks work, I'm thinking that maybe that voltage dropper device might not work. It seems like they are mechanical clocks with a large solenoid inside them that periodically winds the spring. I suspect that the current needed for this would be greater than the max output current from this device. In the same threads, users mentioned that this strong current spike needed would quickly drain any dry 6v battery used to separately power it...so that might not be an option either.

Also, the old dash clocks would likely be positive ground. Wouldn't this not play right with the voltage dropper?

 

[Engineer8000]

A simple 3 pin regulator like a 7806 should work. Do you know what the clock load is?

 

[bdsmitty88]

A simple 3 pin regulator like a 7806 should work. Do you know what the clock load is?

I don't exactly. I haven't found the exact one i want yet...merely in the research phase. My understanding, with a lot of these old dash clocks, is that the clock mechanism itself doesn't draw power, but there is a solenoid that draws a good bit of power (has to be more than the 1.5A from that 7806 output) to wind the clock spring.

TO ADD: Assuming I address anything on the clock that would ground direct to the metal of the car, would it not matter that most of these clocks are 6V positive, since the solenoid doesn't care about polarity?