Category Archives: Arduino Code examples

Antweight motor control – Baby-O

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From: http://garya.org.uk/software/embedded-c/antweight-speed-controller

/*
 * SpeedController.c
 *
 *  Created on: 19 Aug 2013
 *      Author: Gary Aylward
 *   Copyright: Gary Aylward, 2013
 *     Website: http://garya.org.uk
 *     License: Creative Commons BY-SA 3.0
 *
 *     http://creativecommons.org/licenses/by-sa/3.0/
 *
 *     Pololu Orangutan library (c) Pololu Corporation, licensed under CC-BY-SA 3.0
 *
 *     1.0 19/08/2013 Original release
 *     1.1 25/08/2013 Fixed battery monitor filter bug
 */

/*
 * Antweight R/C speed controller using Pololu Baby Orangutan board
 *
 * Set linker to use pololu_atmega328p library.
 *
 * Module pinouts are defined below, the settings used allow other pins to be used for
 * further R/C channels, extra PWM outputs, UART etc.
 * The battery voltage is fed to the ADC via a potential divider so that the ADC sees
 * the voltage of a single cell. If the under-voltage lockout is not required, connect
 * the ADC input to Vcc or redefine dCELL_MV below.
 *
 * Mixing is set up for an R/C transmitter with the following characteristics:
 * Channel 1 = Left/Right, Right = longer pulses
 * Channel 2 = Forwards/Reverse, Reverse = longer pulses
 *
 * Motors are connected with +ve terminal connected to M1B / M2B, -ve to M1A / M2A
 * Motors turn clockwise (when viewed from shaft end) with positive voltage
 */

#include <pololu/orangutan.h>

#ifndef F_CPU
#define F_CPU	20000000	// Baby Orangutan runs at 20MHz
#endif

#define dCHANNEL1	IO_C0	// R/C Ch1 input pin
#define dCHANNEL2	IO_C1	// R/C Ch2 input pin
#define	dLED		IO_D1	// LED output pin
#define dADC_CHANNEL	6	// ADC battery monitor channel

#define dZERO		1500	// Nominal pulse width
#define dMAX		2000	// Max pulse width
#define dMIN		1000	// Min pulse width
#define dMAX_PULSE	2200	// Pulse width for error detection
#define dMIN_PULSE	800		// Pulse width for error detection
#define dTIMEOUT	30000	// 30ms timeout on R/C pulses
#define dMAX_SPEED	250		// Max speed setting
#define dMIN_SPEED	-250	// Min speed setting

#define dFILTER_SIZE	600	// Length of under-voltage detection filter, 6 steps per ms
#define dCELL_MV	2750	// Minimum cell voltage in mV


int main()
{
	unsigned int vVoltage = 0;			// Battery cell voltage measurement
	unsigned char vUnderVolt = 0;		// Under-voltage error flag
	unsigned long vFilter = 0;			// Under-voltage filter counter
	struct PulseInputStruct vPulseInfo;	// Orangutan library pulse structure
	unsigned long vPulseLength = 0;		// Pulse length in ticks
	unsigned char vState = 0;			// Current pulse state
	unsigned long vPulseCh1 = dZERO;	// Channel 1 pulse in ms
	unsigned long vPulseCh2 = dZERO;	// Channel 2 pulse in ms
	int vLeftSpeed;						// Left motor speed
	int vRightSpeed;					// Right motor speed
	unsigned char vError = 1;			// Error flag

	// Configure pins as pulse input channels
	pulse_in_start((unsigned char[]) {dCHANNEL1, dCHANNEL2}, 2);
	// Enable internal pull-ups on R/C input channels
	set_digital_input(dCHANNEL1, PULL_UP_ENABLED);
	set_digital_input(dCHANNEL2, PULL_UP_ENABLED);
	// Initialise LED to off
	set_digital_output(dLED, 0);
	//Set ADC to 10-bit mode
	set_analog_mode(MODE_10_BIT);

	while(1)
	{
		if (analog_is_converting() == 0)
		{
			// Start a new conversion if one isn't already running
			start_analog_conversion(dADC_CHANNEL);
		}
		// Get time since last edge on R/C channel 1
		get_current_pulse_state(0, &vPulseLength, &vState);
		if (pulse_to_microseconds(vPulseLength) >= dTIMEOUT)
		{
			vError = 1; // R/C timeout - signal lost
		}
		else
		{
			get_pulse_info(0, &vPulseInfo); // get pulse info for R/C channel 1
			if (vPulseInfo.newPulse & HIGH_PULSE)
			{
				vPulseCh1 = pulse_to_microseconds(vPulseInfo.lastHighPulse);
				if ((vPulseCh1 > dMAX_PULSE) || (vPulseCh1 < dMIN_PULSE))
				{
					vError = 1;	// Pulse is too long or too short
				}
				else
				{
					vError = 0;
					if (vPulseCh1 > dMAX)
					{
						vPulseCh1 = dMAX;
					}
					if (vPulseCh1 < dMIN)
					{
						vPulseCh1 = dMIN;
					}
				}
			}
		}
		// Get time since last edge on R/C channel 2
		get_current_pulse_state(1, &vPulseLength, &vState);
		if (pulse_to_microseconds(vPulseLength) >= dTIMEOUT)
		{
			vError = 1;	// R/C timeout - signal lost
		}
		else
		{
			get_pulse_info(1, &vPulseInfo); // get pulse info for R/C channel 2
			if (vPulseInfo.newPulse & HIGH_PULSE)
			{
				vPulseCh2 = pulse_to_microseconds(vPulseInfo.lastHighPulse);
				if ((vPulseCh2 > dMAX_PULSE) || (vPulseCh2 < dMIN_PULSE))
				{
					vError = 1;	// Pulse is too long or too short
				}
				else
				{
					vError = 0;
					if (vPulseCh2 > dMAX)
					{
						vPulseCh2 = dMAX;
					}
					if (vPulseCh2 < dMIN)
					{
						vPulseCh2 = dMIN;
					}
				}
			}
		}
		if (analog_is_converting() == 0)
		{
			// If ADC conversion is finished, check the battery voltage
			vVoltage = analog_conversion_result_millivolts();
			if (vVoltage < dCELL_MV)
			{
				if (vFilter >= dFILTER_SIZE)
				{
					// Filter has timed out, leave the fault flag set
					vFilter = dFILTER_SIZE;	// Prevent filter count from overflowing
					vUnderVolt = 1;	// Set fault flag
				}
				else
				{
					vFilter++;	// Increment filter count
					vUnderVolt = 0;	// Clear fault flag
				}
			}
			else
			{
				vFilter = 0;	// Reset filter if voltage is above limit
			}
		}
		// Calculate motor speeds
		vLeftSpeed = ((vPulseCh2 - dZERO) - (vPulseCh1 - dZERO)) / 2;
		vRightSpeed = (-(vPulseCh2 - dZERO) - (vPulseCh1 - dZERO)) / 2;
		// Limit maximum speeds
		if (vLeftSpeed > dMAX_SPEED)
		{
			vLeftSpeed = dMAX_SPEED;
		}
		else if (vLeftSpeed < dMIN_SPEED)
		{
			vLeftSpeed = dMIN_SPEED;
		}
		if (vRightSpeed > dMAX_SPEED)
		{
			vRightSpeed = dMAX_SPEED;
		}
		else if (vRightSpeed < dMIN_SPEED)
		{
			vRightSpeed = dMIN_SPEED;
		}
		if ((vUnderVolt == 1) || (vError == 1))
		{
			// Stop motors and light LED if a fault exists
			set_m1_speed(0);
			set_m2_speed(0);
			set_digital_output(dLED, 1);
		}
		else
		{
			// Set motor speeds and turn off LED
			set_m1_speed(vLeftSpeed);
			set_m2_speed(vRightSpeed);
			set_digital_output(dLED, 0);
		}
	}
}

Arduino window comparitor

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Scenario:

Heater needs to turn on until boiler reaches maximum temperature, then turns off until a lower temperature is reached, then turns on until maximum, then off until minimum… and so on.

Imagine hysteresis at set upper and lower limits, for the heater to run at.

Arduino connected to thermistor to measure temperature, with SSR connected to heater mains circuit to turn on/off heater.

 

A simple comparitor code for arduino allows us to set the max and min limits of temperature (mapped to values 0-100) (temperature in celcius is not required for this task, tho could be usefull – may add later)

LED provides visual feedback of SSR on (the SSR on could have LED on expensive units)

CIRCUIT DIAGRAM TO COME – as is code formatting in wordpress \o/

CODE:
/*
thermistor Input
Measures temperature of thermistor and turns on heater SSR when temperature is in window
turning on and off a light emitting diode(LED) and SSR to maintain temperature.
The SSR heater will be turned on if below heaterHighVal and off when passes window to heaterLowVal.
These values are analogue values obtained by analogRead().

The circuit:
* Thermistor attached to analog input 0
* heaterPin connected to input of SSR – SSR through Live to heater
* LED anode (long leg) attached to digital output 13
* LED cathode (short leg) attached to ground

* Note: because most Arduinos have a built-in LED attached
to pin 13 on the board, the LED is optional.

Created by Nathaniel Poate
30 May 2013
*/

int sensorPin = A0;        // select the input pin for the thermistor
int ledPin = 13;           // select the pin for the LED
int heaterPin = 10;        // select the pin for the heater SSR
int heaterLowVal = 20;    // select the value for low temperature cutoff window
int heaterHighVal = 50;   // select the value for high temperature cutoff window
int sensorValue = 0;       // variable to store the value coming from the thermistor

void setup() {
// declare the ledPin and heaterPin as an OUTPUT:
pinMode(ledPin, OUTPUT);
pinMode(heaterPin, OUTPUT);
}

void loop() {
// read the value from the sensor:
sensorValue = analogRead(sensorPin);
int temp0to100 = map(sensorValue, 0, 1056, 0, 100);

if (temp0to100 >= heaterLowVal && temp0to100 <= heaterHighVal)
{
heaterOn;// turn Turn on heater
}
else if (temp0to100 <= heaterLowVal && temp0to100 <=heaterHighVal)
{
heaterOn;
// turn Turn on heater
}
else if (temp0to100 > heaterHighVal)
{
while (temp0to100 >= heaterLowVal)
{
heaterOff;
// turn Turn off heater
}
}
}

void heaterOn() {
digitalWrite(heaterPin, HIGH);
digitalWrite(ledPin, HIGH);
// turn on heater and LED
}

void heaterOff() {
digitalWrite(heaterPin, LOW);
digitalWrite(ledPin, LOW);
// turn on heater and LED
}