Light Following Robot

Light Following Robot Using 555 Timers.

I actually made this towards the end of March, i became interested in using integrated circuit and micro chips to make stand alone projects as they are cheaper than using an arduino for each project.

There are two configurations for 555 timers mono stable and astable. For this project monostable is used. A great website explaining how they work.

Monostable Operation

"Unlike the astable, which has two unstable states and so continually switches from one to the other and back again, the monstable has one stable state and one unstable state.

When triggered by a suitable pulse at its input (pin 2) it switches from its stable state, in which the output is low, to its unstable state where its output is high. This state exists for a time controlled by the values of R1 and C1, and at the end of this period the output switches back to its stable (low) state. Its primary use is therefore to produce a set time delay, initiated by an input pulse."

Quote and image taken from http://www.learnabout-electronics.org/

Building The LFR

I followed this instructables it was the most simple one i could find, there are other tutorials out there that use potentiometers to set the sensitivity of the LDR's and hence the speed of the motors.

Conclusion

The idea worked however the LFR didnt really move.. i didnt have proper wheels, i cut some out from cardboard. Also the fact i didn't use motors with gear boxes and gave the motors more voltage than they needed resulted in not much torque.

For my first play with 555 timers i am still happy with the out come. Ultimately i decided that having a mobile platform that i could add sensors to and program would be a better use of my time and didn't continue with it.

433Mhz RF Transmitter and Receiver

433Mhz RF Transmitter and Receiver.

I wanted a cheap wireless solution, these are great at little over a pound each. 
This is a great instructables on them with all the specs. Limitations are that they easily loose connection with each other, and don't really have enough power to go through more than one wall (on 5v) a max range of 100 M can be achieved with LOS (line of sight) also the direction of the antenna greatly affects performance.

Virtual Wire

The VirtualWire library allows you to easily communicate over RF. Official VirtualWire Documentation (PDF).

Test project

I wanted to control a coffee machine using these the idea was to have a button on my desk with an RGB LED, off: the LED would pulse red, brewing: the led would stay yellow and ready: the LED would pulse green.

First prototype: got the led to work correctly with me pushing the button it would cycle through the colors no problem.

Second prototype: Modified the example Tx and Rx code from virtual wire library to send a 1 then 0 with a second gap in between. added relay to control coffee machine. 

Third prototype: combined both codes into one found that the LED wasn't working as expected it wouldn't display certain colors and i reasoned it was because the Tx part of the code being constantly sent with a small delay- this delay affected the PWM of the LED. To make it work a micro controller able to run two sets of code at the same time would be needed. But this expense is a little overkill for a simple remote coffee machine.

Forth prototype: i simplified the user experience to a simple on/off, green/red operation.
however the leds flash briefly, assume this is when data is being Tx.

Im not going to use these to remotely control my coffee machine as the connection is unreliable and unable to reach the distance to it. I'm going to test these and see if i have better luck, also i need a way of getting 5-12 V from the mains to power the Rx. 

Hardware Connections

Rx Signal Wire to D12

Tx Signal Wire to D12

Code

As i was only sending 1 or 0 i changed the following line in the set up. This is an array that holds the data you want to Tx.

char Sensor1CharMsg[2];

This line converts an integer array to a character array.

 itoa(ButtonData,ButtonCharMsg,10);
 
Great information on converting CHAR to INT and vice versa.

Nice tutorial on how to send a string although ive not tested it.







Arduino Code Tx, Arduino Code Rx

Multiple Serial Ports

Exploring Multiple Serial Ports Using Arduino Mega.

I searched around for this because i will need to use it in future projects, at the moment i'm gearing up to build a mobile platform- wouldn't it be nice if it could map a room using sonar data... Anyway i found this excellent blog that explains it nearly perfectly apart from the TX to RX bit in step one, just beware, if you don't know what i'm on about I've made a comment at the bottom of his post.

Using a USB to serial TTL cable allows another serial port to be connected to a PC from the mega. 

USB To TTL Cable 

The mega has 4 possible ports to utilize. The green is TX and should be connected to RX on the board the white is RX and should be connected to TX on the board, red is power and is optional (5V external) and black is ground. the USB is simply connected to a port on the PC.

Ive put together a sketch that reads an LDR and prints the value to one serial port whilst the other port is used to keep track of when an led (the on board one connected to pin 13) is turned on and off using a button.

Resistors 10K (theres one behind the LDR)

To view two serial monitors in the arduino IDE open a fresh arduino program and set that to the serial port of your cable, or use Tera Term.

Com7 Showing LDR Values Com9 showing that switch is off

Arduino Code

Bluetooth RGB LED

RGB LED using serial over bluetooth

Im using a HC-06 bluetooth module, its the same coding as sending data over serial but the com port is changed to the bluetooth port.

I set up a GUI with processing using the control P5 library which sends the values to the bluetooth COM port.

Desktop App

Module to Arduino RX to TX and Vice Versa

Processing Code, Arduino Code.

 

Xbox Pad

Xbox pad

This is something me and Ben worked on using the procontrol library he found to get and use values from the xbox pad.
Eventually he wants to use this to control an RC plane and the camera on it!

Using a pitch, yaw, gimbal to demonstrate.

Processing Code, Arduino Code.

Solar tracker

Solar tracker 

Update..

Its been a while! ive got a few more projects that im working on. Im looking into building a balancing two wheeled robot, the chip im using is a MPU-6050 6-axis accelerometer/gyroscope which im having trouble getting my head around.. i found code to get values from it ive just got to find a suitable project to demonstrate it, i am also in the process of building a P.C.

I was interested in this because the code can be used for a line following robot, also for solar panel applications.

Components

A servo
Bread board
Cardboard and tape to separate the two LDR's
2 LDR's
Two resistors, im using 550 ohms
Arduino
Wires

Code

The voltage received from the LDR's is compared with each other with a tolerance of 10 added, this is to stop the servos from jittering when say a cloud passes over one of them. If one voltage is bigger than the other the servos will move in 1 degree increments untill they are equal.

The Circuit

The left LDR is connected to A1 the right to A2, between these connections is a resistor connected to ground, with the other leg of the LDR's connected to 5V.

Conclusions

The positioning/angle of the LDR's really affect the accuracy of the system, and should be as symmetrical as possible.

Code

  

Sound Sensor with Relay

Creating a "clap on" "clap off" light switch

Warning!

Because we are using mains power i feel i should give a little warning, the picture below shows cut wires with masking tape covering them, masking tape is not enough protective insulation! This was a quick test done in the middle of the night, as you can probably tell from both wires being cut!

Components

A strange sound sensor i found on amazon code HOT UK05, couldn't find a data sheet for this and hardly any information.

A Cheap version of a SainSmart relay module (4 channel).

An LED for debugging.

And a lamp you can cut the wires to.

Sound sensor

I set the sound sensor as a digital input and adjusted the sensitivity using the onboard potentiometer. That way when sound was detected above a certain threshold the pin was set low and this lit the LED up.

Relay module

Heres a really good website with lots of information about relays.

The Circuit

Conclusions

Using the sensor as a digital input it only has two states, on or off, if i wanted more accurate readings and control i would have to use it as an analoge input.

After programming this i feel alot more confident about checking states, last states then toggling a switch.

Code

LCD Display

Displaying two variables on a SainSmart LCD keypad shield

Intro

Displaying information on an LCD display is something i want to use in future projects.

I am trying to create a menu using the buttons on the shield but this is a little above my programming level at the moment. 

I could have made a simple menu where if i held "down", temperature is displayed or "up", the light level is displayed, however i want to create a "Real Menu" using arrays to store the different things to be displayed on the LCD and counters to control where we are in the menu and what is to be printed to the LCD.

The circuit

Code
Awesome code showing a menu
Good advice
Wiki

PIR and Light Sensor to LED

Using two variables to control an event, in this case turning an LED on.

Automatic light

The Plan

Using a photo resistor and a proximity sensor i want to recreate the automatic light!

Photo resistor

When placed in darkness resistance is high and vice versa.
Used in a voltage divider circuit. We analog read the pin giving a reading between 0 and 5 volts which is then assigned a digital value between 0 and 1024. A great video on voltage dividers.

a voltage divider circuit

PIR

Stands for Passive infrared sensor (HC-SR501) 

Left pot. Adjusts sensitivity,  clockwise more sensitivity and vice versa

Right pot. Controls amount of time (delay) between movement and re-trigger i.e. when set to mid point the time between is 5 seconds. This is only useful if not using a micro controller,  however when using a micro controller the delay can be programmed. A more in depth explanation on how they work here. 

PIR sensor

The circuit

Conclusions

A relay could be wired up and this circuit could be used to control a light with more power.

Code

Ultrasonic distance sensor

The aim of this session is to become familiar with the HC-SR04 distance measuring sensor and have it control a servo.

Original code taken from here

Findings...

So wired it up and pasted the code in... 

It worked, its only really accurate up to 50 cm's (possibly because of the material it was reflecting off, it was pointed towards my window and a curtain) and the "wall" a of piece of paper i was using to test the distances must be at right angles to the sensor otherwise you get a wrong value . How it works is explained here.  

Add a servo...

When i added the servo it would jump around a lot because of the random values returned from the sensor. I wanted a smooth motion i.e. as an object is brought closer to the servo, the servo would move in one direction and vice versa.

How to make it smooth...

I found a smoothing code in the arduino IDE examples i used this to average the values from the sensor so as an object is brought closer to the sensor the values sent from it dont jump from one to another causing the servo to move to quickly from one position to another. I also multiplied the averaged value (the distance in cm) by 1000 then increased the scale to map it with the servo, this made the servo move even smoother. 

The circuit

The three wires leading off go to the servo 

Conclusions

This could be used for obstacle avoidance, proximity applications etc.

The readings could be made even more accurate by adding a temperature pin and changing the value for the speed of sound through the air and using more code.

User manual for HC-SR04

My Code for Arduino ive left the comments as they a relevant if not related.

To infinity and beyond!

So building on the thermometer, i want it to be displayed on a 4 digit 7 segment display... i want to use a shift register to control the LEDs.. but first im going to have to learn what they are and how to use them.

This is from the arduino website but is condensed into my own report

74HC595 Shift Register

"8-bit serial-in, serial or parallel-out shift register with output latches; 3-state."

So this shift register is 8 bit, it can access 8 bits of information in a single machine instruction. Because each bit has two possible states "on" and "off" and there are 8 bits, this gives 256 possible combinations... e.g. 2*2*2*2*2*2*2*2 = 2^8

Serial output

Uses "synchronous serial communication" which means we can pulse one pin on and off communicating a data byte, bit by bit, the bits are separated by pulsing the clock pin.

Parallel output

"asynchronous communication" uses the Serial.begin() function of arduino, the data rate must be set on the sender and receiver. When the whole byte (8bits) are received the register deals them out to each output pin, then they are executed at the same time.

Connecting another

There is an option to use the serial out pin the transmit the serial information out to another register unchanged. Meaning you can transmit 16 bits of information where the first 8 will be passed though the first chip and expressed in the second.

3 states

Means HIGH, LOW and high impedance. This means the entire chip is set to low current, high voltage. Its uses include an LED array that might need to be controlled by different micro controllers depending upon its setting.

The Pin-Outputs are.....

	PINS 1-7, 15	Q0 " Q7	Output Pins
	PIN 8	GND	Ground, Vss
	PIN 9	Q7"	Serial Out
	PIN 10	MR	Master Reclear, active low
	PIN 11	SH_CP	Shift register clock pin
	PIN 12	ST_CP	Storage register clock pin (latch pin)
	PIN 13	OE	Output enable, active low
	PIN 14	DS	Serial data input
	PIN 16	Vcc	Positive supply voltage

What happens inside the chip?

When the clockPin (SH_CP) switches from LOW to HIGH the shift register reads the state of the dataPin (DS). When the shift register is full the latch is switched to HIGH this sends the information to the storage register then to the outputPins.. The rabbit hole gets deeper... 

Creating a circuit

Turning it on

GND (pin 8) to ground

Vcc (pin 16) to 5V

OE (pin 13) to ground

MR (pin 10) to 5V

Connect to Arduino

DS (dataPin) (pin14) to Arduino DigitalPin 11

SH_CP (clockPin) (pin 11) to Ardunio DigitalPin 12

ST_CP (latchPin) (pin 12) to Arduino DigitalPin 8

So whats next..?

Well the code in example two looks interesting i can type a number into the serial and the corresponding LED will illuminate( Pin 15 is 1). I can see how the hardware side works, now ive got to work on the programming..

Phillip`s data sheet for 74HC595

First post, One and a half sugars please

So this is my first blog its more of a log for myself, of my experiments and projects so i know what ive done and how ive done it.

Thermometer:

The temp sensor used is TMP36 the middle signal pin connects to analog input 0 on the arduino.

It outputs 10millivolts per degree c... to allow minus temps it has a 500mV offsett meaning 25c = 750mV, 0c = 500mV..

Convert this from a digital signal analog signal to degrees using maths functions, then displayed using the IDE debug window though a serial connection.

The code used was..

int temperaturePin = 0;    // pins and corresponding inputs are assigned

void setup()    // runs once 

{

    Serial.begin(9600); // initiates serial connection with comp 

}

void loop() // loops over and over

{

    float temperature = getVoltage(temperaturePin);    // float stores the voltage from

                                                                                             // temperaturePin

    temperature = (temperature - .5) * 100;                    // because the offset.. 0c = 500mV

                                                                                            // and each degree is 10mV..

                                                                                            // converts voltage into temp

                                                                                            

    Serial.println(temperature);                                        // prints the result in degrees

    delay(1000);                                                                 // delay

}

    float getVoltage(int pin){                                           // converts from 0 to 1023 digital range

    return (analogRead(pin)  * .0048828814);              // to 0/5 volts each 1 dig range = 5mV

}