Anyone fimiliar with air core gauges?

My project is to make a Dash display system for a race car. I originaly planned to use an RC servo to control an analog gauge on the dash. The analog gauge is much easier to read quickly. The RC servo is easy to implement, but the constant back and forth switch motion will burn it out, and it only has 180deg movement.

I've scrounged some air core movements from a car gauge cluster, and I want to make up a controller. Digikey has an ON Semiconductor controller chip available. It looks fairly straight forward. I'd just like to get some feedback from anyone who has gotten one of these working. I'm sure I'll run into problems. All I have is the movements and the one datasheet. There's almost nothing on the web for this kind of project. Or maybe it's easy enough to program a uC to do all the functions needed to control the movement?

There's some chips already in the gauges. Anyone have a datasheet for a TB9233N?

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Mark Higgins

 

What kind of gauge are you talking about,oil pressure,rpm,fuel....
Most of them have different operating principles..........

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gerty

 

I'm talking about the movement itself. Which has the same operating principle no matter what it's displaying.

This is the only page I could find that talks about these gauges and what it takes to control them.

http://www.mikesflightdeck.com/diy_a...nstruments.htm

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Mark Higgins

 

I found a datasheet on the discontinued lm1819 air core meter driver. The datasheet has alot of good information in it on the workings of the driver.

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Mark Higgins

 

Did you search on "air-core meter driver"? I found products by Philips and On Semiconductor. There may be others.

 

I've already mentioned that I found the ON Semiconductor one. It's the only one I can see available anywhere (digikey). It would be nice to have the SPI chip available, but the only one Digikey has is the one that converts frequency to needle movement, which is still workable.

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Mark Higgins

 

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taken from:
http://floridafieros.org/osg/speedo.html

The speedo needle is driven by a so called air-core meter.
Regular meters work by a needle which is pulled back to zero
by a spring and a coil forces a magnet away from the zero
position if current flows through the coil. An air core meter
uses two coils which are at an angle of 90 degrees to each other.
These coils are called the sine coil and cosine coil.
Each coil produces a magnetic field proportional to the current
flowing through it. Since the two coils are at a 90 degree angle,
the two fields add up to a "magnetic vector".
If a magnet is placed in the middle of this field, it will
point in the direction of this magnetic vector.
By varying the current through the two coils,
the needle can utilize all 360 degrees of the gauge.
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Must admit, this type of gauge is one i haven't met yet.
This mentions varying the current,
i think that includes reversing the current, if needed.

I suppose if the needle assembly is very light,
and it were positioned on a friction basis,
then it would be highly vibration resistant.

Regards, John

 

The LM1819 actually has a nice, if basic, description of who an air core movement works and a little bit on how it's controlled.

I salvaged a few movements out of a gauge cluster. Each movement is made differently. I'm not certain why. Different physical size, I guess to support the speed of movement that each needs.

The full range gauges have a classic air core movement with 4 wires. The ones with only partial movement, fuel, temp,... have a 3 wire setup. I assume they share a positive wire or something. I'd be interested in figuring out what I need to do to control these differently.

I'm sure I can figure this all out with a little bit of experimatation. Unless I get off my lazy ass and try some home made experiments, this project is on hold until I need enough parts to justify a Digikey order. I'll pick up those ON Semiconductor controller chips.

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Mark Higgins

 

A few years ago i bought some digital guages at a garage sale for a couple of bucks. The speedometer and tachometer both had 7 segment LED's in the middle with a semicircular placed LED's to provide the simulated Needle sweep. I know I still have these and I will check to see how they work

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amature tech in hollywood