Two-coil Gauge Movement

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

I don't think I've necessarily seen one of those in real life. Got a link to a picture?

I don't suppose a crossed-needle meter would do it for you? MFJ Enterprices has those available -- page 78 of the catalog here:

It occurs to me that I could also use a model airplane servo + pot, IF it was flat enough (

They were the ancient car gauges, didn't need a regulator for accuracy, since they were basically a bridge.

Nope :-( ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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I love to cook with wine.     Sometimes I even put it in the food.

GM used them. Try a junkyard or antique car club.

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I need 270° span.

That might work. But it's a low power application, but also very slow movement. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Vector sum the two inputs in a PIC (or analog, if that's your preference) and drive a single coil D'Arsonval movement.

Or have the PIC drive a little stepper motor.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Moving iron meter?

I've read that some modern automobile instrument-cluster gauges use a cross-coil movement... both fuel and tach gauges may be of this type. This design allows the engine control unit to drive the meter with a pair of PWM signals, giving good precision about the resulting vector angle without having to worry much about (e.g.) resistance in the wiring, and can also allow the meter setting to be retained when power is removed and both coil currents drop to zero.

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AKA the electrodynamometer? You're nearly the old fart I am; I not only remember them, I remembered the name. ;>)

Unfortunately, they seem to be pretty much extinct.

There's this:

They were common as dirt on benchtops and in automotive applications at one time but that time seems to be past...

Mark L. Fergerson

I remember seeing meters that will do that. Old war surplus stuff. Look at what Surplus Sales of Nebraska has to offer: (MTR)550RP Stewart Warner Speedometer (!) (MTR)30-01274 Phastron sealed ruggedized meter, 0-15V (MTR)409C610A25 Westinghouse KX241 0=50uA nuclear meter, scale reads 0-1 (MTR)M1957 Nuclear heavy duty, 0-15A (just rat out the shunt if inside) (MTR)643-314 Phastron 0-100A, links with any 50mV shunt (MTR)AT-300 AEA/Vectronic, is a dual needle beastie, limited angle, 200uA (MTR)MMI-10628 GE giant nuclear electronic frequency meter 55-65Hz; needle travels about 270 degrees - EXACTLY what you do not need except the travel is there.

** That is from the paper catalog #8 (old); on-line may not have some and others maybe available now.

AFAIK all of those have limited angle.

Yep. The 270° span got me to thinking old S-W gauges. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Have it wake up, read the inputs and calculate, set the stepper position and then go back to sleep.

--
Paul Hovnanian  paul@hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.

We use Switec stepper motors for this type of application. Designed as automobile 'meters', but actually a very small stepper motor, full 360 deg rotation. You need to provide an end stop to give you a zero point reference. Nice pointers are available.

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Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

*Snip*

Used on early jeeps, MB/GPWs, CJ5's, 3A's & early 3B's. these show up as NOS on Ebay all the time.

H.