[simpits-tech] Beech Flap Gauge

[Matt Bailey]

On Thu, 05 Feb 2015 18:40:57 -0600
Cris Harrison <phoenixcomm at gmail.com> wrote:

> On 02/01/2015 10:07 PM, Matt Bailey wrote:
> > Good stuff! So was it like I thought it might be? :)
> >
> > Matt
>  >>>>
> Matt let me know what the story on the gauge..
> I think what you have there is something like what I have
> You only have three pins correct?
> then
> 
>     1. is ground
>     2. is lamp
>     3. is a volt/milli meter
> 
>   please clarify...
> Thanks
> Cris H.

Unfortunately this one isn't quite that simple. It's not lighted, so
all three pins are for input. It's driven sorta like an air core motor,
but don't try using an H-bridge or you'll get befuddled. You need to
hook all three leads to Arduino PWM inputs (or digital inputs will
suffice, if you want to do software PWM for some reason). For any given
needle angle, you will have one pin HIGH or LOW (you need to decide
before you start coding if you want to use HIGH or LOW for your dead
input)...I used LOW on mine. The other two pins will get a PWM signal
that sums up to your max PWM value (255 on the Arduino Uno, as you
know). Needle position is determined by the ratio of one pin vs the
other. This will move the needle within a given range. To move to the
next angle range, change which input lead is grounded (or HIGH, if you
prefer).

Obviously, check impedance on your particular gauge to make sure it's
safe for the Arduino (I can't recall what value they are needing
off-hand, and I couldn't find it online in a quick search).

-- 
Matt Bailey

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