[simpits-tech] N1 & N2 Gauges

[David C. Allen]

Update to getting the N1 & N2 gauges operational?

Found the part number, for the N1/N2 tach generator, and found one on eBay
for $25
Hooked it up to a drill motor to look at the output amplitude and
frequency. This also allowed me to check my N1/N2 gauges for operation.
Found 2 bad ones.

Looks like generating sine wave approach that used the Arduino's PWM
channels is the one I will try.

David


On Mon, Aug 7, 2017 at 1:53 PM, Matt Bailey <dabigboy at cox.net> wrote:

> It's pretty straightforward. You can do this with just an Arduino and one
> of the cheapo L298N H-bridge boards on ebay. I did it very crudely and
> easily, and ended up with poor control below about 30% RPM (on my
> particular indicator), but totally smooth response above that. Another
> fellow I know adapted a sine wave approach that used the Arduino's PWM
> channels, which gave good control all the way down to 0.
>
> Check out the overhaul manual for your indicators. You're basically
> building a brushless speed controller.
>
> Matt
>
>
>
> Sent from my Sprint Samsung Galaxy S® 6.
> -------- Original message --------
> From: "David C. Allen" <dca911t at gmail.com>
> Date: 8/7/2017 1:04 PM (GMT-06:00)
> To: Simulator Cockpit Builder's List <simpits-tech at simpits.org>
> Subject: [simpits-tech] N1 & N2 Gauges
>
> Hello
> I was wondering if anyone has used a Arduino to get the N1 & N2 gauges
> operational?
>
> From the information I have found there is a 3 phase generator for the N1
> & N2 mounted on the engine. The gauges have a 3 phase motor connected to a
> flux coupling (like is used in a mechanical speedometer) to drive the
> pointer. Once the engine is operating the N1 & N2 are self powered.
>
> I found a chart that lists the generator RPM vs Indicator % RPM
>
> 0 gen = 0 %RPM
> 840 gen = 20 %RPM
> 2520 gen = 60 %RPM
> 4200 gen = 100 %RPM
>
> So a question on frequency of the generator, would vary with generator RPM
>
> Looking at one leg of the generator
>
> 0 gen = 0 Hz = 0 %RPM
> 840 gen = 14 Hz = 20 %RPM
> 2520 gen = 42 Hz = 60 %RPM
> 4200 gen = 70 Hz = 100 %RPM
>
> Just looking for ideas
>
> David
> N9070U 737-222
>
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