Hobbs hourmeter voltage

[Larry Glover]

I have a 6 volt Hobbs hourmeter that I want to run on 12 volts. Trying to put resistors in line with it has been unsuccessful as it appears to need a higher initial current than after it starts. Any suggestions? If I run on 12 volts will it burn it up?

[Paul Scheuer]

No direct experience with the device. The power will go up with the square of the voltage, so it may be too much. (It will be four times as hot).

If you can get a current measurement during start up and running, we can come up with the right values for a simple, reguluated 6 v power supply to run from 12 v.

[GROOVY]

Larry I had .... have the same problem, Took my hourmeter to an electrical friend . He suggested a 7.5 OHM resistor, now I have not been able to locate a 7.5 resistor. What resistor arrangement have you tried?
I think if you do a search on "hobbs" you can find my older post

[Domesticated_Mr. Know It All]

Hey Groovy Mike!
I did a search on hobbs and this was all I could find. :D

http://members.fortunecity.com/sierra_tango/hobbs.gif
Peace---> Kevin in Ohio

P.S. Don't let the magic smoke get out. ;)

[Del Lansing]

I have not been able to locate a 7.5 resistor Get a 4.7 ohm and file it gently in the center till it becomes 7.5 ohms. This works with carbon resisters. They are build like a pencil with the carbon down the center, by filing a small notch in the carbon resistive material you raise the resistance. File a bit, check with ohmmeter, file, check... till you hit the desired resistance.

[Larry Glover]

Groovy. I started at 3.9 ohms and this was too much to allow the meter to start. I worked down to 1 ohm before it would start. "After starting" the current draw was so small the resistor actually took no voltage draw. The meter took all the voltage drop. I think the meter has a solenoid that starts it and therefore operates at 2 different current flows.

[Del Lansing]

A friend just told me Radio Shack has a 3 pin regulator package that will drop 12v to 6v, around $3. You may need to put a heat sink on it but it should be just what you need.

[Norm Bernstein]

Nine or ten simple silicon diodes in series will do the trick. I'm presuming the hourmeter doesn't draw more than 100 mA or so....

[paladin]

If the device draws less than 100 ma. then a 78L06 regulator from radio shack or Digi-Key will work. Digi-Key, 701 Brooks Ave. South, Thief River Falls, MN 56701-0677....phone 1800-344-4539,
There are input and output pins and a "ground " pin. Tie a .1 mft capacitor from the input to gtound and the output to ground. Now the ground is common for the input and output. Apply +12 volts to the Input pin and the negative to ground and take +6 volts from the output pin and ground.
If it draws more than 100 milliamps the part you need will be a 7806, a larger device in a TO-220 case, same hookup but is capable of handling 1.5 AMPS of current......

[NormMessinger]

The one on my Long EZ works over a range of volts, can't remember what it is but 6 and 12 are within its specs. How about yours?

[GROOVY]

Looks like a trip to radio shack
found this:
http://www.ford-trucks.com/articles/delanty/6to12to6.php

[Paul Scheuer]

After a quick glance at that link, I think it assumes that you have a steady current to the instrument. Your problem is that you have a "start up" current that is much higher than the "running" current. Fixed resistors won't do it. Radio Shack may have a 6 V regulator that will provide the necessary current on demand.

Let us know what you come up with.

[GROOVY]

The next page on that site has the Radio Shack 7806 regulator.. then there is more on output transistors,capacitors and tantalums... and probably something about magic smoke.