[simpits-tech] N1 & N2 Gauges

[Jeroen Huijben]

I presume that you want to leave the gauges intact.


The simplest method would be a three legged H bridge consisting of a pair of FETs per phase.

Then the microcontroller would cycle each phase through high, low and off in the proper order and phase offset.

Then you would increase and decrease the rate with the engine RPM.


If that turns out to be too crude you could PWM a sine wave.

Then you use an opamp to buffer it, and then add a 120 degree phase shifter, second buffer, second phase shifter and third buffer.

If the gauge requires a lot of current you can add another amplifier to each phase's buffer..


Or use three PWM outputs and let the microcontroller deal with the phase offset.


Any idea on the gauges voltage and current requirements?


Vriendelijke groet,
Jeroen.


________________________________
From: Simpits-tech <simpits-tech-bounces at simpits.org> on behalf of David C. Allen <dca911t at gmail.com>
Sent: Monday, August 7, 2017 8:04 PM
To: Simulator Cockpit Builder's List
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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