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1

I have a project that I am looking to hire someone to assist me on. At the face it is real simple but Im new and this would be a great learning exercise for me.

I want to increase/decrease the current ( digital POT) to rotate a shaft faster or slower based on the GPS speed the device is moving. The shaft has a high/low magnetic prox. I need to get the shaft RPM set to a "recipe" based on the GPS speed of the Uno.

1 Like
2

What are you trying to make?

3

if you can use a library and with a compatible GPS, it's pretty trivial to get the speed as it's calculated for you.

so the structure of the code could just be something like this:

// assumes that you have a 9600-baud serial GPS device hooked up on pins 4(rx) and 3(tx).
#include <SoftwareSerial.h>
const byte RXPin = 4, TXPin = 3;
const uint32_t GPSBaud = 9600;
SoftwareSerial gpsSerial(RXPin, TXPin);

#include <TinyGPS++.h>
TinyGPSPlus gps;

void manageShaft(double currentSpeed)
{
  // Your code goes here
  
}

void  handleFix() {
  if (gps.location.isValid()) {
    double vehicleSpeed = gps.speed.kmph(); // use mph() if you want miles per hour
    Serial.print(F("Speed : "));
    Serial.print(vehicleSpeed);
    Serial.println(F(" Km/h"));
    manageShaft(vehicleSpeed);
  }
}

void setup() {
  Serial.begin(115200);
  gpsSerial.begin(GPSBaud);
}

void loop() {
  while (gpsSerial.available() > 0)
    if (gps.encode(gpsSerial.read()))  handleFix();
}
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4

Are you familiar with a corn planter?

5

I wasn't. So I assume you want a fairly constant number of seeds per inch (or whatever dimension) depending on how fast the planter is moving.

6

Yes. There is a master shaft that drives the planter units. The shaft is turned by a hydraulic solenoid. As the tractor and planter increase or decrease speed I need to adjust the current to the solenoid to get an accurate population per acre.

7

The coding part probably isn't too difficult. Automotive or faming equipment tends to be pretty hostile to micro controllers like Arduinos from an electrical perspective. You will need to defend all the electronic parts from voltage spikes, especially from inductive loads like a solenoid.

8

Why GPS versus getting wheel speed from the planter?

9

My planter doesn’t have any wheels. It is a three point hitch planter designed to get into tight corners.

10

OK. I just remember getting a lot of speed error in GPS when trying to do dead reckoning. It's likely to be worse at lower speeds due to position error. I guess if it's averaged over a minute or so it would be good enough.

11

I think am a good will be good. If it doesn’t work I may be able to get a speed off the tractor tire. Those slip on hills and can give slightly false reads also.

13

Controllino runs 12V/24V, has 12/24IO's and is much more suited for tractor environments compared to the mega or uno.

14

This is a great start. I am waiting on 1 part and then I am going to start implementing.

15

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