[jonh]

Is there an easy way to use battery voltage (12 to 14v) and hook it to a dc regulator or something to end up with a constant 1.35v dc output?

Thanks,
Jon

 

[Tegguy]

So basically you just want to take 12VDC down to 1.35VDC? Is there a reason you wish to do this?

 

[Coppertop]

I don't know what you need to power (so I don't know what kind of current draw you have), but if it is roughly 1 amp or less, AND you're good at building things out of electronic components, I would recommend the LM317T regulator. It's simple requires only a few external components and accurately regulates the output. It would be more then capable of a 1.35 volt constant output.

It's available [yet] at RadioShack:

http://www.radioshack.com/product/index.jsp?productId=2062601

 

[jonh]

Joe,
I want to remove (2) 1.35v batteries (Mallory RM 12 R) from a Tach Transmitter. When I start the car a 12v wire will excite the Transmitter.
Can you tell me what I need and maybe give a schematic. I am hoping I can put the part inside the transmitter box.

Thanks again,
Jon

 

[Coppertop]

Jon,

Sent you a PM

 

[onovakind67]

Are you referring to these old Sun tach transmitters?

It appears to me that the 2 batteries are in series, which would call for a 2.7v output. Depending on the load, you may be able to use a simple zener diode as in this tutorial:

http://www.electronics-tutorials.ws/diode/diode_7.html

You have to remember that your battery powered tach transmitter is floating on the batteries, while any power supply you make from your car battery will be referenced to chassis ground. If your tachometer has an internal ground for the meter you may experience problems.

Here is a link to some more info:

http://www.jalopyjournal.com/forum/showthread.php?t=467635

If you google a little, you find that the Mallory RM12's are used in a lot of old clocks and telephone equipment. Their remedy has been to use a simple 1.5V AA battery in place of the mercury one.

 

[Ark68SS]

I found out that the old 1.35V mercury batteries were outlawed, and were replaced by the 1.5V alkaline and lithium style. Older 35mm cameras used the 1.35V batteries, and when you change to the 1.5V, the automatic exposure calibrations are thrown off, and the pictures don't turn out like they should. I don't know if this would make any difference with the tach's accuracy or not.
http://www.weincell.com/
BillL