COLOUR SENSORS

All color sensors work on the basic principle that when light of some color falls on an object , if the object is of same color as of the led , then the object absorbs that color which means there is no reflection.

We would be making the ckt in the same way as we did for the IR led detector ckt , but we wuld be using LDR for our detection purpose , (IR cant be used as they catch only IR waves) , and in place of the IR transmitter we wuld be using three leds of red, blue and green.

WORKING:
Light up each of the leds one at a time , ie red , then blue n green , if the obstacles are of red blue and green colour then you wuld be getting different outputs ( REMEMBER VIBGYOR) .

With micrcontrollers , lit up the red led if there is reflection take the ADC reading
do the same for other leds and take thier ADC reading , we will know which colour its detecting.
One sensor wuld be lit up always .





Use a potentiometer with each of the LEDs to get a better reading , as there wuld be slight color difference .The circuit will be the same as for the ir sensor which i have explained in my previous post , with litlle changes .Hope u njyd it

BUMP SENSOR

So, you've fitted some motors to your robot and its happily driving around but it probably keeps colliding with obstacles and getting stuck. You need a way for your robot to detect collisions and move around objects. Enter the humble bump sensor:

A bump sensor is probably one of the easiest ways of letting your robot know it's collided with something. The simplest way to do this is to fix a micro switch to the front of your robot in a way so that when it collides the switch will get pushed in, making an electrical connection. Normally the switch will be held open by an internal spring.

Micro switches are easy to connect to micro controllers because they are either off or on, making them digital. All micro controllers are digital, so this is a match made in heaven. Micro switch 'bump' sensors are easily connected to the Robocore, simply plug them into any free digital socket and away you go.

The following diagram shows a typical circuit for a micro switch bump sensor. The resistor is important because it holds the signal line at ground while the switch is off. Without it the signal line is effectively 'floating' because there is nothing connected to it, and may cause unreliable readings as the processor tries to decide if the line is on or off.

If you dont get these microswitches u can make one easily , using a spring mechanism.

DC MOTOR BRAKING

We will discuss different ways of braking in the robots , there are 3 different ways as usual which goes from mechanical to electrical .This is basically needed when u want to go down the slope r up the slope, though these are not tat great braking as comapred to the real vehicles but of much help to us.

Mechanical Method :
The mechanical method is what is used on cars today. Basically you need something with very high friction and wear resistance, and then push it as strongly as possible to your wheel or axle. A servo brake works well.People think of using door stoppers but they are not of much help , I tried it n they just wasted my money and time .
Controls Method :
This method requires an encoder placed onto a rotating part of your DC motor. You will have to write an algorithm that determines the current velocity of your motor, and sends a reverse command to your H-bridge until the final velocity equals zero. This method can let your robot balance motionless on a steep hill just by applying a reverse current to your motors.

Electronic Method :
This method is probably the least reliable, but the easiest to implement. The basic concept of this is that if you short the power and ground leads of your motor( connect both the +ve leads of the battery to the two terminals of the motor), the inductance created by your motor in one direction will power your motor in the opposite direction. Although your motor will still rotate, it will greatly resist the rotation. No controls or sensors or any circuits overheating. The disadvantage is that the effect of braking is determined by the motor you are using. Some motors brake better than others.


So how do you short the leads when it is on a robot? Simple. Connect a MOSFET (transistor) and a relay as shown. The MOSFET turns on the relay, which creates a short between the motor leads. Turn the MOSFET on (set C high) with your microcontroller when you want to brake. Basically your motor will still have an H-bridge for normal control, but when you brake you turn the H-bridge off and use the braking circuit. And don't forget the heatsink and flyback diode! Important, or your circuit will melt/blow up.

SENSORS WITH TSOP CKT

This is a simple yet effective IR proximity sensor built around the TSOP 1738 module. The TSOP module is commonly found at the receiving end of an IR remote control system; e.g., in TVs, CD players etc. These modules require the incoming data to be modulated at a particular frequency and would ignore any other IR signals. It is also immune to ambient IR light, so one can easily use these sensors outdoors or under heavily lit conditions.
Such modules are available for different carrier frequencies from 32 kHz to 42 kHz.They cost some thing around 20Rs.
In this particular proximity sensor, we will be generating a constant stream of square wave signal using IC555 centered at 38 kHz and would use it to drive an IR led. So whenever this signal bounces off the obstacles, the receiver would detect it and change its output. Since the TSOP 1738 module works in the active-low configuration, its output would normally remain high and would go low when it detects the signal (the obstacle).

In the reciving part instead of using IC555 u can use the time from u r muc.

Simple IR LED CKT

We will be using over here an irled pair and a comparator .When the reciver led recivers the signal the voltage acros it would be going high.This we would be putting across the + ve of comparator, n to the -ve of comparator we wuld be using a potentiometer . When the reciver does not recive any signal the voltage across the pot wuld be set up in such a way tat voltage across it is high so the output wuld be zero volts.
Wehen the reciver recieves the signal the voltage at +ve of comparator would be more than that of -ve end so the out put wuld be high.The pot is used to adjust from how much distance the reciever is able to detect .

THE LED WHICH U C IN THE CKT FROM LEFT ARE 1ST ONES A IRLED TRANSMITTER ,2ND ONE IS A IR TRANSMITTER AND THE 3RD ONE IS A NORMAL LED WHICH WILL GLOW MOSTLY RED IS USED
From my xperince i can tell tat this will give u arnd 5 cm obstacle detection , voltage drop across reciver for me was .47V when it didnt sense the obstacle , when it did sense it was giving arnd.58v so now the voltage at the -ve pin shld be brought to this voltage by rotating the pot .
The leb which u c at the ouput will glow when it detects an obstacle.

The output which u get from the comparator will be fed to logic gates r micrcontrollers .

OPAMPS n COMPARATORS

As the name implies it is an operational amplifier. It performsmathematical operations like addition,subtraction,log,antilog etc.. Themain reason for OPAMPS used over transistors is that transistor can onlyamplify AC while OPAMPS can amplify AC and DC. You can get good amplifier gain in OPAMPS. The most commonly used OPAMPS are 741 ,LM 324, LM 358N(both of them can also be used as comparator).

Comparator is also the same but with a diff being tat its digital so u have to two states high(5V) and low(0V).
FIGURE 1.
Above figure shows the general ckt diagram of a comparator .If V1>V2 then Vout=+Vcc and if V1 if V1 is less than V2 then Vout is minus Vcc


Lm 324 has 4 such comparator(shown in figure1) them also known as Quad opamp.
LM 358N has 2 comaprator also known as bi opamp.

EXPERIMENTAL PART:
U can use two potentiometers(of 10 K prefarably) and put them across pin2 and pin 3 , and put an led in series with a resistance at pin 1 , when the voltage drop in pot 1 connected across pin 2 is low , u can c the led glow.

Voltage regulator

As the name suggets it regulates voltage tat is it can provide either constant voltage r variable voltage(DC only)

Fixed Voltage regulators (78xx,79xx) [7805 being the most popularly used ]
Variable Voltage regulator (LM 317)

Fixed Voltage regulators
This include 78xx voltage regulators. The most commonly used ones are 7805 and 7812. 7805 gives fixed 5V DC voltage if input voltage is in (7.5V,20V).If the voltage is below 7.5 V u mite get the output voltage as 4.6-4.8 V.

This is how 7805 luks like:

IN is the 1st pin where u give the + of power supply OUT is where u get 5 V o/p + and COM is where u give the negative terminal of the power supply , n take it again as the - ve of 5 v o/p.

CHECK BELOW FOR THE CKT DIAGRAM



Its not really not necessary to use those capacitors , I never used them .
It will be the same for - ve voltage regulators , I will talk abt variable voltage regulators in my next post

MOTOR DRIVER CKT

All the motors (dc) run at 12 v supply but the output u get from u r logic gate ,microcontrollers opamp is 5v which cannot make motor run.Motor driver is the most essential part of any autonoums bots , generally people use L293D for running dc motors , u can run 2 dc motors with this IC though it can take a maximum current of 600 mA per channel which is more than enough for us to drive the motors.


The ckt diagram of it goes like this


M1 M2 are the motors(dc motors) ,M1A ,M1B are the controls of motor M1 and M2A ,M2B are the controls of motor M2.M1A ,M1B,M2A,M2B are the inputs tat u get from logic gates r the muc , opamps, to the recieving end of reciever in wireless module
here is the tabe describing the function of the pins

if pin1 is high if pin 9 is high
M1A M1B FUNCTION M2A M2B Function
H L cloclwise H L clockwise
L H anitclockwise L H anticlockwise
L L fast stop L L fast stop
-----------------------------------------------------------------------------------
make pin 1 low slowstop make pin 9 low slowstop


Pin 1 n Pin 9 make each of the channels high (there r two channels) n the pin 8 voltage can go upto 24v

U get this Ic for a cost of Rs 75 .

hope i have explained evrything in detail

Making a wireless remote

Get rid of those long wires tat tangle all the time , there are different ways of making a wireless module using ready made rc cars n putting relays near the out put u can drive u r 12v motors ,then theres IR remote control though not tat much reliable n then theres dtmf tats thr cell phone n gprs communication, n the most simplest of them using rf modules , in consideration with all the above ways rf module is the most easiest n most cheapes (RS 550) nothing more .

This shows the transmitter(TX) n reciever (RX) which u get in electronic shops. TX 01 ASK MODULE and RX 02 ASK MODULE are used here n shown above .



our basic idea goes like this

The two ics HT12E n HT12D r the encoder n decoders of 4 adress bit this is used as we need to drive two motors ,where each motor takes in 2 adress bit (1 for forward rotation other for reverse ) so in all we need four adress bits
if u want to control more number of motors u need to change encoder and decoders. At place of those switches u can either use push buttons r dpdt switches (ckt of dpdt switch is show here click here)

now near the recieving end u use a motor driver bcoz u get 5V as output but motors need 12v to drive them(i have explained this here in much detail ) The ckts are shown over for transmitter and recieving end








D1 D2 D3 D4 will go to the input of motor driver (check the motor driver ckt) n from motor driver to the motors .

This ckt has been tested by me n was giving a ver good range also.The best place to buy is aplusindia.com it sells it for very cheap and u dnt get much cheaper than at this place.
Hope i have made it very clear .

DPDT WIRED SWITCH CONTROL

HERE IS THE SIMPLE MANUAL CONTROL OF U R BOT USING DPDT SWITCH JUST CONNECT THESE SWITCHES TO THE MOTOR AS SHOWN BELOW AND TATS IT ZOOOOOOOOM U CAN C U R BOT RUNNING

GIVE THE CONNECTIION FOR BOTH MOTORS AS SHOWN .