Arduino driven VOR

[Zlatko]

Well, i must admit - if it is a galvanometer, all that make sense.
Thank you for the good explanation provided. So - no more sound cards driving . Arduino plus some current limiting resistors
should work nicely by themselves.

PS:
I am a little sceptic about implementation of an absolute encoder - most of them don't have 360 deg. /resolution . They are more or less like a codding switch with 8 wires and that would result in 8* 8 = 64 deg. For 360 deg. would need 19 wires on the back ( i suppose ) and some port to read them all. And that makes such a fancy encoder really expensive . Analogue resolvers are expensive too. I don't know - i am not that good with electronics.

PSS: 5 * Original price, wow , that is a lot. Why not coming to live and work in Europe - not much talented people here, mostly ingenious bankers and euro-bureaucrats. And some 20% on top of all - VAT - to gather money and feed all those ( doing nothing ) people. But not much engineers and talented people, willing to do business and produce something useful.

[hyamesto]

Zlatko:
Sound cards driving?
How do you are working?
The sound card was an idea to drive the OBS years ago!!!
I´m study for a similar method, using 4 PWM outputs, or 4 digital outs, in sequence to read the OBS setting.
Waiting your explanation.
Regards.
Horacio.

[Zlatko]

I don't really own such thing, working in my house. And in theory - you probably already know, what i know - all is done on the PC -side . For each radial 0-360 deg. one sound file is pre-recorded . Each sound file differs from others by its sample rate. Then the guy, who created that, wrote an application to read FSUIPC offsets and for each particular radial, he made the application sound a different file on the sound. exit. Then hi tied the sound exit to the VOR signal input. Sorry for not being of much help, i am not that good with electronics ( i am a physician by trade ).

All the best .
Zlatko.

[SimSupervisor]

The sound card is just a digital to analog converter, like we use pwm for... It's not a bad implementation if you do not have a microcontroller, but I would still suggest getting an arduino. It's cheap and effective.

Zlatko:

I think Simsupervisor make this way:

The circuit:



The 5 volts on centering pot and ground, must be taken from the same arduino. (or from external power supply, with common ground with arduino.
How its work? Supposed 2,5 volts in PWM (50% dutty cicle), centering pot to obtain 0º deflection on needle.
Now:
If PWM is 5 v, one side of galvanometer is 5v and the other is 2,5v, you get full right (or left) deflection. (left side potencial is +2,5 volts up relative to the right side)
If PWM is 0 v, one side of galvanometer is 0v and the other is still 2,5 v, you get full left (or right) deflection, (right side is +2,5 volts up relative to the left side at 0 volts).
I know i can´t take a PWM like a lineal variable volt, but it´s for simplify the concept.
And the condenser, can be used if the needle got "nervous"....

Maybe Simsupervisor can help if any mistake has be done here...

Regards.
Horacio.

Horacio is right. Except, the meter reacts on way less than 5v... At full 5V and with 50% duty cycle, being centered, you floor or roof the needle with about 10% pwm variation. That is why I used a resistor, to increase granularity. But then the output is no longer centered at 2.5v so having a potentiometer to adjust the needle does help.

Horacio can you get electronics locally? Without getting a stepper shield, a h-bridge can drive a stepper motor, one chip and a few basic components will interface nicely to arduino. I salvaged an interesting bipolar stepper from a broken hard disk that I might use for the heading indicator...

[hyamesto]

Horacio can you get electronics locally? Without getting a stepper shield, a h-bridge can drive a stepper motor, one chip and a few basic components will interface nicely to arduino. I salvaged an interesting bipolar stepper from a broken hard disk that I might use for the heading indicator...

Yes, i can get electronics, but we are living in goverment´s pre-election climax. Time to sit-down, relax and wait.
Dealers are crazy with the price of components (exchange rates are 1 u$s= 16$ argentina).
For example:
A MAX7219 chip only: u$s 7,80.-
A 64 dot led matrix, with pcb, and MAX7219 chip u$s 6,25.- (ready to connect, but i don´t need the matrix)
7-segment led display "Sorry, i have 2 of 3 cms long, 1 green, other red, one common cathode, the other common anode"
Only one dealer to each component, in different cities.
They are crazy, an so on:
Garmin Aera 500: I´m a PPL, and i want to fly in real life and connect to Simulator with GPSout....
Oficial dealer in every place of world, i can buy for u$s 600.- (dollar bill)
Here in Argentina i must pay u$s 1.600.- (in dollar bill too !!!!!!, forget exchange rates).
And stupids dealers: How you can sell a PIC18F4450 without socket, and sell crystal oscillators of every value, except the value needed for that PIC????????

And yes, i salvaged near 20 steppers, sensors, etc , and others motors from old printers, hard disks, etc... they are waiting better times....
Sorry for the response, nothing to do with the VOR....
Regards.
Horacio.

[hyamesto]

Hello everybody: Great news....




This circuit is working better than expected......
The potenciometers are 10K linear, the centering is perfect. Full range from left, to right, setting with limiter pot.

This is the test sketch:


int n=1;
int out=127;
//------------------
void setup()
{
pinMode(6, OUTPUT);
}
//---------------------
void loop() {
out+=n; if (out==224 || out==30) n=-n;
analogWrite (6, out);
delay (20);
}


Range from 30 to 224, that´s 194 steps.....

A recommendation: use shielded cable and multiturn presets like this:


Tomorrow will upload a video, and try the TO-OFF-FROM flag concept.

Regards.
Horacio.

[Zlatko]

That is really exciting .
Thanks. The last thing - how much power galvanometer would consume . Is it safe to tie
it directly to PWM pin.
I think - we should repeat the experiment with 5v analogue voltmeter. ( just the part with the galvanometer made for integration in face panels). They are dirty cheap and readily available on the market .

[SimSupervisor]

Horacio, I used the same type multiturn 10k potentiometer too. 194 steps for the needle is awesome. Glad it's working on yours too and not pure luck on my end

Zlatko, these meters shouldn't sink too much current. I know I am interfacing directly to my pwm and am not worried.
I interfaced with a similar voltmeter as you posted, before. Main difference is that it's not self centered.... Not needing positive and negative is actually easier.

I am trying to find some of those meters with the same dimensions as the ones on a Cessna 150; no luck so far. I guess I will use bigger ones.

Not fully related, but I am strongly thinking about using the casing and obs ring of a broken unit in another instrument, the 360 reading could be useful for the heading indicator.

[hyamesto]

Zlatko:
The power of the galvanometer is in the range of 50 to 150 microamper, (you can connect near 30 to one output!!!)
Look at the black screw in the base of instrument. It is to regulate the rest position of the needle. Some voltmeters can be rotated up to the central position. For more precise operation, you can remove the built-in serie resistor, and use only the galvanometer like the circuit that i use. (Don´t forget limiter potenciometer if you remove the internal resistor!!)


But with my connection, you don´t need that, because you can regulate position with the centering potenciometer. Only disadvantage, is when you power off the instrument, the needle is go to rest the left side.

Or you can put a charge-discharge ammeter as the photo, removing the shunt resistor, and using external potenciometers.



Simsupervisor:
You can disassembled to remove only the galvanometer and build the rest of the instrument.
Or you cand find indicators used in older cars, with more appropriate needles.
Some old indicators have a range of 270º like this......



Later i will upload the videos.

Regards.
Horacio.

[SimSupervisor]

Horacio, I wasn't referring to circular instruments, but the 4 square indicator on the right panel. Volts, amps, gas, temp. They are bigger than the small ones I saw, but smaller than the big ones. If I can't find properly sized ones I'll get bigger ones.