# 6 volt Hobbs meter

• posted

I recently was high bidder for a NOS, 6 volt, Hobbs meter. I served my apprenticeship at Stewart-Warner so what can I say? Just could not resist after seeing the old familiar face. I want to put the meter in the panel of an aircraft I am building, said aircraft has a 12 volt system. What I dont know about electronics and electricty would fill a library so how do I get from 12 volts to 6 volts? Seems I remember when we used to convert the old VW beetles to 12 volts, we kept the 6 volt starter, changed the lights but kept the windshield washer motor 6 volts. How did we do that? Anyway, all help will be appreciated.

Warren

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Gads. I have no idea what a Hobbs meter is. You got one on this old goat. Is it an hourmeter?

Any time you want to go from 12 to 6 volts in a small instrument (if that's what this is) then the best way is to see what the current draw is, and use an appropriate solid state semiconductor regulator chip, in this case it would take in 12 volts and produce 6 volts regulated.

The sticky spot is to see how much power the regulator will be dissipating, and if it's a lot, then to drop some of the power in a series resistor.

Do you have any idea of the current draw?

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

• posted

I think Hobbs meter winding coil's draw a good bit of current every 30 seconds or so in the wind cycle, maybe a 2 or 3 millisecond pulse.

Seems I remember then having a wide operational voltage range, like 4 to

40V or something like that... I'm talking about the old mechanical ones here, not the newer Quartz or digital's.

Erik

• posted

||I recently was high bidder for a NOS, 6 volt, Hobbs meter. I served my ||apprenticeship at Stewart-Warner so what can I say? Just could not resist after ||seeing the old familiar face. ||I want to put the meter in the panel of an aircraft I am building, said ||aircraft has a 12 volt system. ||What I dont know about electronics and electricty would fill a library so how ||do I get from 12 volts to 6 volts? ||Seems I remember when we used to convert the old VW beetles to 12 volts, we ||kept the 6 volt starter, changed the lights but kept the windshield washer ||motor 6 volts. How did we do that? ||Anyway, all help will be appreciated.

Auto parts stores used to keep voltage reducers for just that purpose. You needed one or more depending on draw. This application would just need one.

Still in the catalog and on the shelf. We sold 134 of them last week. Who'da thought it?

Borg Warner number is VR1.

1.5 ohm resistance for up to 4 amp load. Basically a wound-wire resister in a ceramic shell

VR2 is the same thing with a mounting bracket Any parts store should be able to cross it to their brand. Cost is about \$10 Texas Parts Guy

• posted

so how

For the amount of current you are talking about, put a 6.2 volt Zener diode with the requisite power rating (probably written on the meter, if not you will have to measure the current draw) in series with the meter.

Kevin Gallimore

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Dern it, I should have explained better. Yes, it is an hourmeter. Round and made to fit in an instrument panel hole approx 2 1/8 dia. Nope, have no idea what the current draw is. How do I measure that? Semi conductor chip....is this what is called a zener by someone else?

Thanks, Warren

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Well, this is certainly the old mechanical type. Probably a dumb question but here goes. If it just spikes from 4 to 4o volts every 3 minutes or so, why do I have to do anything? Wouldn`t 12 volts work?

Also, the papers that came with it mention models without the instant stop feature would run on for up to 3 minutes after being turned off. Verifies your statement above.

Warren

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Thanks Texas Parts Guy. Just proves they made some tough 6 volt cars in the Good Old Days!

Warren

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Not on the meter or in the literature is there anything about the power rating. Other than 6 volts. If the meter spikes every 3 minutes or so, how can I measure the spike? Or do I have to?

Thanks, Warren

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You would need to know what type of Hobbs meter it is. You could ask Hobbs:

For your purposes, however, a one watt Zener would work with any Hobbs-type meter I've seen, be it electronic or electromechanical. But I would not tell someone else to use it without measuring the current. Put a one Ohm resistor in series with the Hobbs meter. Apply 12 volts. Measure the voltage across the resistor. You will read current in Amps. Alternatively, you could use an ampmeter. Assuming it is an averaging meter, at DC: Volts(12)*Amps(what you measure)= average Watts. Pick a power rating for the Zener that is greater than the power you measure. Zener diodes are available at Digi-Key. Here is a typical data sheet:

When's my ride?

Kevin Gallimore

• posted

Hmmm... it just draws a brief pulse of current periodically when it winds, and the rest of the time is electrically 'dormant'.

What I meant, is I 'think' they (or some models anyway) were ok for use with a supply voltage in the range of 4 to 40 Volts... or some big range like that. I wouldn't bet my life on it though.

Funny, I had an old (NOS, less than an hour total time showing) square Hobbs meter someone gave me years ago.... sold it on eBay in the last year or so. Got a lot of bids on it too. I had some GREAT, super sharp macro photos in the ad... it really makes a difference.

Good Luck!

Erik

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I would probably go with a three terminal regulator like a 7806 for this application. Though, the zener might work.

He could also just put 7 or 8 silicon diodes in series to drop the six volts.

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

• posted

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"Even if you are on the right track, you'll get run over if you just sit there." - Will Rogers (1879-1935).

• posted

First, I'll answer your other question, about converting 6v VW's to 12 volts. I recall the VW mechanics telling me how they left the 6v starter, etc., in the car, so the engine would REALLY spin during the cranking. They also applied the full 12 volts to the 6v ignition coil, during starting only, to get a REALLY hot spark.

If the Hobbs meter draws current in short bursts, chances are you could use the full 12 volts. If the wind-up is self limiting, the pulses would be shorter than standard, and probably work perfectly.

If you want to be really safe, you could wire some resistance in series with the meter. Use enough so the meter doesn't work, and then keep reducing it until it sounds like it is pulsing normally. That would be a way to do it if you don't have a meter, or if your meter won't deal with short pulses (most of them won't.)

• posted

I have one of those meters on my 56 porsche. if you really want to regulate it to 6V, use a 7805 chip and a capacitor - that will give you very accurately regulated 5V (which will be fine with the meter) for about 50 cents.

• posted

Two capacitors - one on the input and one on the output. And use a 7806 - which will regulate at +6 volts.

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

• posted

I would try the 7806 as others have suggested.

Mount it on sheetmetal to serve as a heatsink. The tab is electrically ground.

It's a low-risk proposition:

They only cost a buck or two at Radio Shack

They're self-protected against burnout. If they overheat they just shut down

They'll deliver an amp or so until they overheat

If the Hobbs just draws short pulses, it's quite unlikely that the

7806 will overheat.
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...

RS will probably not carry the six volt version. He would have to order that from Newark or Digi-Key I think.

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

• posted

To all who replied: This has been a real learning experience for me. Never heard of a Zener before! There are many "off the shelf" gismos that will do the job and can get expensive. I like to tinker and experiment so I am going with

1. resistor of; 1.99 ohms, 32.16 watts.
2. Zener of 6v.24.12 watts.

I got these numbers at the Zener diode selector

My meter would not register the spike for the rewind stage, so I hooked the Hobbs up to the battery charger switched to 6v in and 6amp. When the spike came, the meter jumped about 1.5 amps. I used 2000 mA for the diode selector.

And to Kevin Gallimore...probably be a year. (90% done and 90% to go) But if you want a ride in the Marquart Charger, come on down and we will bore some holes in the sky!

Regards and Thanks to All. Warren

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||To all who replied: ||This has been a real learning experience for me. Never heard of a Zener before! ||There are many "off the shelf" gismos that will do the job and can get ||expensive. ||I like to tinker and experiment so I am going with || ||1. resistor of; 1.99 ohms, 32.16 watts. ||2. Zener of 6v.24.12 watts. || || I got these numbers at the Zener diode selector || ||My meter would not register the spike for the rewind stage, so I hooked the ||Hobbs up to the battery charger switched to 6v in and 6amp. When the spike ||came, the meter jumped about 1.5 amps. I used 2000 mA for the diode selector. || ||And to Kevin Gallimore...probably be a year. (90% done and 90% to go) But if ||you want a ride in the Marquart Charger, come on down and we will bore some ||holes in the sky! || ||Regards and Thanks to All. ||Warren

Nice looking aircraft, Warren. Do you have it apart, or what?

Texas Parts Guy

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