Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: [email protected] on December 25, 2011, 11:20:15 PM

Title: this in reference to the line follower made by pratheek
Post by: [email protected] on December 25, 2011, 11:20:15 PM
hi guys....
i just wanted to know .......
1)where the push buttons are connected .
2)what is the meaning of IC1 in the figure
3)there are 7 pins at the bottom of the board(just below the ATmeag16 IC),nothing is mentioned about them....so what must be connected to them!
link is http://www.societyofrobots.com/member_tutorials/book/export/html/350 (http://www.societyofrobots.com/member_tutorials/book/export/html/350)
I'll be really grateful to u... pls help me out of this situation.
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 26, 2011, 12:29:44 AM
1)where the push buttons are connected .
PD2 (INT0)pin 16, PD3(INT1) pin 17 & PB2(INT2) pin 3

2)what is the meaning of IC1 in the figure
LM7805 - 5V Positive Regulator


3)there are 7 pins at the bottom of the board(just below the ATmeag16 IC),nothing is mentioned about them....so what must be connected to them!
Look at the photo, it connected to 2 resistors and preset resistor and link to pin 1 of the LCD connector may be for back lights control.

Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 26, 2011, 02:59:00 AM
to billhowl
sir....
1)got to know where to connect the push buttons... now,regarding the connections....the push buttons have 4 pins(the place of their connection has 4 female headers i.e., PD2,PD3,PB2 n GND).SO in order to connect 3 push buttons,is it that,we need to short one side pins of each of push buttons and connect them to PD2,PD3 n PB2 respectively.... and again short the other side pins of the push buttons and connect all of them to the GND????

2)sir,in the figure he has mentioned about the status LED n there r 3 pins for its connection.As far as my knowledge goes the LED has only 2 pins... so how to connect .

3)sir,at the left bottom corner of the figure, there r 3 pins in triangular fashion.... what we should connect there.

4)And finally SIR,u told to connect 2 resistors and a preset resistor(at the bottom 7 pins),if so...what r their values...n i have connected them in the following manner...
   a)i have the PRESET resistor ....connected to the left 3 holes (which looks as a mirror image of L)
   b)one resistor a have connected to other 2 holes (vertical) appearing just besides mirror imaged L
   c)the other resistor is connected horizontally in the next 2 horizontally appearing holes.....

are the connections right..... if not pls tell me how to connect!
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 26, 2011, 08:14:37 AM
1. Yes, one side of the switch connect each of the pins, the other side of the 3 switches short together and connect to Gnd.
2. The status LED is a bi-colored LED like this one in picture, so have three pins, you need to get common cathode.
(http://file.ledease.com/productsimage/2010/9/21/20109211052375.jpg)

for Q3 and Q4, I have attach a picture to show the connection, for the resistors values I give some guesstimate values, please check the datasheet of the LCD to see if a resistor is required.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 26, 2011, 08:56:13 AM
to billhowl......
thanks u sir for your guidance......it has helped me a lot!!
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 26, 2011, 09:01:07 AM
You are most welcome :)
then click on the helpful button :D
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 26, 2011, 09:13:46 AM
to billhowl,
sir...
please dont mind if I interrupt u in the future asking for help!!

THANKS ONCE AGAIN!
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 26, 2011, 12:23:48 PM
to billhowl..
sir i had a query regarding LCD interfacing...
1)where the pin15(LED+) and pin16(LED-) of the LCD module should be connected.

2)where the pin3(contrast adjust) of the LCD module should be connected.

3)where the 1st pin of LCD connector (which is present on our main circuit) must be connected.

4)is the image below correct
   
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 26, 2011, 06:12:26 PM
1) This is the backlight I refer to, connect pin 15 to pin 1 of LCD connector, pin 16 to GND.
2) pin 3 is to be connected to 10K ohms preset at the LCD power connector mid pin.
3) see ans 1)
4) yes, is correct.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 28, 2011, 09:58:03 PM
sir.... this is regarding sensor connections...

1) outputs from the sensor array, i have taken from, pin 8,7,1 n 14 of both the comparators(LM324)  ,thereby constituting 8 outputs.

2) pin2,6,9,13 of both the comparators (LM324) are shorted.BUT nothing is connected to them.... is it that we need to connect something there?

3) two pins just below the comparator (i have highlighted them).... what must be connected there?

4)the preset (i have highlighted it) ... doesnt have all the 3 of it pins connected.

5) how to supply power to the sensor array?


 

Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 28, 2011, 10:02:41 PM
ALSO SIR, the figure below has more than 8 output wires taken from the sensor array...what r those wires and to where they are connected on the sensor array as well as on the main board?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 29, 2011, 04:02:37 AM
1) outputs from the sensor array, i have taken from, pin 8,7,1 n 14 of both the comparators(LM324)  ,thereby constituting 8 outputs.
Correct
2) pin2,6,9,13 of both the comparators (LM324) are shorted.BUT nothing is connected to them.... is it that we need to connect something there?
Yes, both chips had to connected to the 20K ohms preset resistor mid pin.

3) two pins just below the comparator (i have highlighted them).... what must be connected there?
This two pins for supply +5V and Gnd to main board.

4)the preset (i have highlighted it) ... doesnt have all the 3 of it pins connected.
Connected to all the inverted input of the LM324
5) how to supply power to the sensor array?
two pins just below the comparator (you have highlighted them).



Title: line follower made by pratheek
Post by: [email protected] on December 29, 2011, 09:28:29 AM
sir....
in the below figure there are two set of wires....
1)from sensors,which are 8 in number
2)i think second set has 4 wires ..... where are they from?.... if we give Vcc n GND then there should be only 2 wires,right?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 29, 2011, 10:54:42 AM
The connector look like having only two wires. (brown and black)
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 29, 2011, 12:43:51 PM
oh yes sir..... its quite confusing though!... thanks
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on December 29, 2011, 10:49:32 PM
sir in power supply to sensors....
pin 4 is Vcc and pin 11 is GND,right?(4 n 11 are pins of LM324)
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on December 29, 2011, 11:53:44 PM
Yes, correct.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 04, 2012, 11:17:36 AM
sir,
what must be the height between the sensors and the ground(track).?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 04, 2012, 12:04:13 PM
May be 3 to 5 mm.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 05, 2012, 02:36:38 AM
sir ,
in the figure...
1) u have connected a 33 ohm resistor.Isn't is too less?

2) whats the use of 100ohms preset mentioned in the diagram?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 05, 2012, 05:07:12 PM
1) u have connected a 33 ohm resistor.Isn't is too less?

2) whats the use of 100ohms preset mentioned in the diagram?

1) 33 ohm resistor was part of the voltage divider to control the Backlit of LCD, you may adjust the values.

2) preset use to control the Backlit of LCD
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 07, 2012, 04:39:29 AM
sir....
 
1) 10k ohm preset is for the back light adjustment of LCD,isn't it?

2) whats the purpose of 100 ohm preset?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 07, 2012, 07:00:49 AM
sir....
 
1) 10k ohm preset is for the back light adjustment of LCD,isn't it?

2) whats the purpose of 100 ohm preset?

10k ohm preset is for lcd contrast adjustment and 100 ohm preset for the back light adjustment.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 17, 2012, 09:35:56 AM
sir,
i have built the board,
1) i'm getting 5v as the output of the 7805....but when i checked the voltage across the terminals(3 boxes highlighted) there is no        voltage (0v)...

2) when i checked the continuity between pin 2 n 3 of the preset(in accordance with the diagram)... its shorted.Since pin 3 is GND and 2 is Vcc... i feel Vcc n GND itself r shorted .... n hence i'm not getting any voltage at those 3 boxes...?

how to sort this problem?
 
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 17, 2012, 04:43:31 PM
(http://i305.photobucket.com/albums/nn236/pratheekn/IMG_0903.jpg)
You need to jumps a few wires to complete the circuits, 5V line is one of them.
Refer to the schematic.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 18, 2012, 07:52:06 AM
sir ,
i made all those connections .... n the circuit worked.... thank u sir.

1) but after some 5 minutes, the 100uf capacitor (indicated in the figure) exploded n was burnt.I was using a 12 volts,1.5mAh lead  acid battery for the power supply....so what to do (shall i use any other kind of battery)?

2) since i had built the sensor array also ....i connected it to the main board.All the IR emitters were working fine.

3) i also connected the LCD display to the LCD power pins,but i didnt get any LCD back light.IS it that after programming, the LCD starts working? i haven't started programming the board yet.
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 20, 2012, 06:35:58 AM
1) but after some 5 minutes, the 100uf capacitor (indicated in the figure) exploded n was burnt.I was using a 12 volts,1.5mAh lead  acid battery for the power supply....so what to do (shall i use any other kind of battery)?
Not seen 1.5mAh lead  acid battery. What voltage on the 100uf capacitor you use? it should be 16V or 25V

2) since i had built the sensor array also ....i connected it to the main board.All the IR emitters were working fine.
You can measure the out put of the LM324 using multi-meter to confirm the working of the sensor array.

3) i also connected the LCD display to the LCD power pins,but i didnt get any LCD back light.IS it that after programming, the LCD starts working? i haven't started programming the board yet.

Yes, LCD back light is control by the micro-controller pin, you need to program the micro-controller for it to work.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 20, 2012, 06:42:56 AM
i'll check out the capacitor ratings....
thank u sir.
Title: Re: this in reference to the line follower made by pratheek
Post by: trisuliswanto on February 20, 2012, 06:50:15 AM
please help me...
I just Successed build this robot by tutorial given by Pratheek and with a little modification, I add the push button on board and add a reset button, but now i dont know how can I get the right tuning configuration for my robot.
please give me an explanation how to perfectly configure the robot!
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on February 20, 2012, 08:20:42 AM
to billhowl sir,

now i'm totally done with all the electronics as well as the mechanical stuff....

i need to start with the coding.... as of now, i don't really have a fair idea so as what to do n where to start from....
please tell me .. how should i start programming?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on February 20, 2012, 09:27:55 AM
Download this source code
http://www.societyofrobots.com/member_tutorials/files/Code%20V2.2(SOR)_0.zip (http://www.societyofrobots.com/member_tutorials/files/Code%20V2.2(SOR)_0.zip)

and read this
http://www.societyofrobots.com/member_tutorials/node/361 (http://www.societyofrobots.com/member_tutorials/node/361)
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on March 04, 2012, 11:33:07 AM
sir,
how to disable the JTAG pin of the micro controller?
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on March 04, 2012, 04:27:24 PM
Read this
http://www.engineersgarage.com/embedded/avr-microcontroller-projects/disable-jtag-port (http://www.engineersgarage.com/embedded/avr-microcontroller-projects/disable-jtag-port)
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on March 06, 2012, 07:53:49 AM
sir,
what should be connected to the in number 12 and 13 of the microcontroller ?
in the schematics its is mentioned as XTAL1 and XTAL2 ... is it that we need to connect some crystal oscillator...????

but nothing is given in the ckt diagram. i have highlighted them.
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on March 07, 2012, 06:20:08 AM
XTAL1 and XTAL2 are for connecting external crystal oscillator, but this project using internal oscillator so no need to connect these two pins, just let it open.
Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on March 08, 2012, 09:52:05 PM
sir,

i read the JTAG disabling tutorial in the link mentioned by u.
there i found the method for disabling the JTAG fuse permanently..... it was mentioned to take the values of lfuse as 0xff and hfuse as 0xc9 (it was mentioned that the value of the fuse bits needs to be 0xc9ff in order to disable the JTAG).

i wrote the  command “avrdude –p <microcontroller code> –c <programmer type> -t” in Command window....
but, in the pictures shown in the website m32(microcontroller code) was used.
since i'm using atmega16 i replaced it as m16...
 also the default values of lfuse n hfuse were different to that compared in the website...but i followed the remaining steps as mentioned...everything went right n the process was over.....
BUT ... thereafter i'm unable to even to program or erase the chip....
it shows the message as "powering on failed"....

now i'm unable to use that particular micro controller.....i think that the lfuse n hfuse values are different to that of
mentioned in the link.....if so is it possible to change the fuse bits again.

Title: Re: this in reference to the line follower made by pratheek
Post by: [email protected] on March 09, 2012, 09:05:19 AM
sir,

how to generate hex file in avr studio?
i have read the article in engineersgarage.com...... i'm getting a lot of errors.... i have added all the things... source codes lotl.c and lcd.c     and the header files lotl.h , lcd.h and myutils.h.... still i'm unable to build the hex file...
Title: Re: this in reference to the line follower made by pratheek
Post by: dpmntrs on April 14, 2012, 09:29:31 PM
Dear sir,
thanx for the valuable info i recieved here.
im done with pratheek circut diagram of line follower but im not able to connect 4-5wires red black n yellow at the backside of  the board
please spell out those connections, ill be thanlful to u.

Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 09, 2013, 12:43:26 AM
1) This is the backlight I refer to, connect pin 15 to pin 1 of LCD connector, pin 16 to GND.
2) pin 3 is to be connected to 10K ohms preset at the LCD power connector mid pin.
3) see ans 1)
4) yes, is correct.

Sir, Iconnected the 1st,2nd and 3rd pins of the LCD module to the 'LCD power connector' and 8th to 15th pin of LCd module to 'LCD data connector'. 16th pin of lcd module is connected to GND as u suggested. Now where does the 4th,5th,6th and 7th pin of LCD module go ? Please respond.
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on August 11, 2013, 09:42:07 AM
You connection was in-correct, The connection as follow

Code: [Select]
LCD MCU
Pin Port

01 GND GND
02 VCC +5V
03 Contrast Mid pin of 10K preset
04 RS PC4  Pin 4 of LCD Connector
05 R/~W PC5  Pin 3 of LCD Connector
06 E PC6  Pin 2 of LCD Connector
07 D0 No Connection(NC)
08 D1 NC
09 D2 NC
10 D3 NC
11 D4 PC0  Pin 8 of LCD Connector
12 D5 PC1  Pin 7 of LCD Connector
13 D6 PC2  Pin 6 of LCD Connector
14 D7 PC3  Pin 5 of LCD Connector
15 A B-LED Pin 1 of LCD Data connector
16 K B-LED GND


B-LED  Backlight LED
Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 15, 2013, 09:34:54 AM
You connection was in-correct, The connection as follow

Code: [Select]
LCD MCU
Pin Port

01 GND GND
02 VCC +5V
03 Contrast Mid pin of 10K preset
04 RS PC4  Pin 4 of LCD Connector
05 R/~W PC5  Pin 3 of LCD Connector
06 E PC6  Pin 2 of LCD Connector
07 D0 No Connection(NC)
08 D1 NC
09 D2 NC
10 D3 NC
11 D4 PC0  Pin 8 of LCD Connector
12 D5 PC1  Pin 7 of LCD Connector
13 D6 PC2  Pin 6 of LCD Connector
14 D7 PC3  Pin 5 of LCD Connector
15 A B-LED Pin 1 of LCD Data connector
16 K B-LED GND


B-LED  Backlight LED

Sir imade all the connections and my robo is working. I also burnt the hex file given by pratheek into the mcu. But my robot aint following the line. it jus moves straight when started. :(

What could be the possible issues sir ? Do ineed to calibrate my sensors? If yes, then how ? Pleaseeee help :(
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on August 16, 2013, 07:29:10 AM
http://www.societyofrobots.com/member_tutorials/node/361 (http://www.societyofrobots.com/member_tutorials/node/361)
Quote
Tuning the PID control
   This is the most interesting part in building a PID control. In this step one should tune the Kp, Ki and Kd values to get the best results. I cannot give you the values because what works for me will not work for you. The optimum Kp, Ki and Kd values vary a lot from robot to robot. And the best way to determine the optimum values is by trial and error.
First, set all values to 0 and start with tuning the Kp value. First time I just gave an approximate value. Seeing the robot perform will determine what you should do next. If the robot wobbles a lot reduce the Kp value, if the doesn't follow the line (goes straight in curves) increase the Kp value. Tune the Kp value till the robot smoothly follows the line. By now you will have observed that the robot goes with no acceleration on straight lines. Now, tune the Kd term. After tuning the Kd term move to the Ki term. After which, you will see the robot first center over a straight line and then accelerate also.
Note: The optimum Kp, Ki and Kd values vary a lot even from track to track. You can only know these optimum values by testing.

Have you change the Kp, Ki and Kd values?
Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 16, 2013, 09:41:25 AM
http://www.societyofrobots.com/member_tutorials/node/361 (http://www.societyofrobots.com/member_tutorials/node/361)
Quote
Tuning the PID control
   This is the most interesting part in building a PID control. In this step one should tune the Kp, Ki and Kd values to get the best results. I cannot give you the values because what works for me will not work for you. The optimum Kp, Ki and Kd values vary a lot from robot to robot. And the best way to determine the optimum values is by trial and error.
First, set all values to 0 and start with tuning the Kp value. First time I just gave an approximate value. Seeing the robot perform will determine what you should do next. If the robot wobbles a lot reduce the Kp value, if the doesn't follow the line (goes straight in curves) increase the Kp value. Tune the Kp value till the robot smoothly follows the line. By now you will have observed that the robot goes with no acceleration on straight lines. Now, tune the Kd term. After tuning the Kd term move to the Ki term. After which, you will see the robot first center over a straight line and then accelerate also.
Note: The optimum Kp, Ki and Kd values vary a lot even from track to track. You can only know these optimum values by testing.

Have you change the Kp, Ki and Kd values?


No sir we didnt because What happened was that the three pushbuttons - ( connected to PD3,PD2 and PB2 of atmega)
when used, two pushbuttons were decreasing the values only. No pushbutton cud increase the values on the LCD screen. We cudnt get what the problem was beacuse all the connections are made right. Thats why we cudnt adjust the Kp,Kd,Ki values through trial and error.



Secondly,
When our sensor array was connected to 5V VCC and GND, IR leds werent emitting light. When giving direct 9V from the battery they were emitting light. Iguess they arent getting enough current. Should be we using 1K resistors instead of 10K to solve this problem ? or what ?

We have our competition coming soon. please help sir.
Title: Re: this in reference to the line follower made by pratheek
Post by: jwatte on August 16, 2013, 11:13:44 AM
You should not use any resistors on the VCC or GND lines. You should supply the right voltage, with as low source impedance as possible.
Title: Re: this in reference to the line follower made by pratheek
Post by: billhowl on August 16, 2013, 01:06:12 PM
Secondly,
When our sensor array was connected to 5V VCC and GND, IR leds werent emitting light. When giving direct 9V from the battery they were emitting light. Iguess they arent getting enough current. Should be we using 1K resistors instead of 10K to solve this problem ? or what ?

We have our competition coming soon. please help sir.

The IR LEDs was supply by the 120 ohms resistor R1, the 10K resistor was for the photodiodes,

what do you means by "giving direct 9V from the battery"?

to which part of the circuit?

Giving 9V may kill the MCU Atmega16 which only operate on 5V.

Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 16, 2013, 10:57:49 PM
Secondly,
When our sensor array was connected to 5V VCC and GND, IR leds werent emitting light. When giving direct 9V from the battery they were emitting light. Iguess they arent getting enough current. Should be we using 1K resistors instead of 10K to solve this problem ? or what ?

We have our competition coming soon. please help sir.

The IR LEDs was supply by the 120 ohms resistor R1, the 10K resistor was for the photodiodes,

what do you means by "giving direct 9V from the battery"?

to which part of the circuit?

Giving 9V may kill the MCU Atmega16 which only operate on 5V.

Sir, Atmega mcu is working on 5V only. We gave 9V to the sensor array only with another 180 ohm resistor in series.(By making a 2 pin power supply separtely for the sensor array on main board). So that IR leds could get enough current. And then only the IR leds were emitting light. Idont know if thats the right thing to do. ? Please guide sir.
Title: Re: this in reference to the line follower made by pratheek
Post by: jkerns on August 17, 2013, 10:38:29 AM
OK - we are talking about providing power to light up LEDs?  You need to determine the appropriate current limiting resistor based on the supply voltage and the LED voltage / current specification.

Let us assume that your LED takes 1.2 volts and has a current rating of 20mA (0.02A)  and you want to run it off your 5 volt regulated supply (note: I am just making these numbers up - use the real numbers for your LED)

We will have the resistor and the LED in series. If we want to have 1.2 Volts across the LED, and we have a 5 volt supply, 5 - 1.2 = 3.8 Volts that have to be dropped across the resistor. If I have to drop 3.8 Volts, at a current flow of 20 mA (from the LED spec) then we can apply Ohms law to find the appropriate resistance.

R = V/I  = 3.8 / 0.02 = 190 Ohms

Pick the next larger standard resistor for your circuit - something like 200 or 220 ohms.

If you have tried hooking up the LED directly to your power supply (either 5 or 9 volts) you need to buy a new LED.
Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 17, 2013, 11:35:58 PM
OK - we are talking about providing power to light up LEDs?  You need to determine the appropriate current limiting resistor based on the supply voltage and the LED voltage / current specification.

Let us assume that your LED takes 1.2 volts and has a current rating of 20mA (0.02A)  and you want to run it off your 5 volt regulated supply (note: I am just making these numbers up - use the real numbers for your LED)

We will have the resistor and the LED in series. If we want to have 1.2 Volts across the LED, and we have a 5 volt supply, 5 - 1.2 = 3.8 Volts that have to be dropped across the resistor. If I have to drop 3.8 Volts, at a current flow of 20 mA (from the LED spec) then we can apply Ohms law to find the appropriate resistance.

R = V/I  = 3.8 / 0.02 = 190 Ohms

Pick the next larger standard resistor for your circuit - something like 200 or 220 ohms.

If you have tried hooking up the LED directly to your power supply (either 5 or 9 volts) you need to buy a new LED.

Sir, Iget your point. But in this tuorial given by pratheek sir, (http://www.societyofrobots.com/member_tutorials/node/360 (http://www.societyofrobots.com/member_tutorials/node/360))
he had connected 8 IR led's in parellel with a single 120ohm resistor. The supply voltage is 5V.

 I made the same connections with the same resistor value and 5V but my led's didnt light up. ( Forward led voltage=1.5V for a  forward current of 20mA).
Igoogled this problem and it suggested a 8-10ohm resistor for the same.

But pratheek has used a 120ohm resistor. why is it so ?




PS- My IR led's lit up when supplied with 9V instead of 5V. as imentioned before.
Title: Re: this in reference to the line follower made by pratheek
Post by: jkerns on August 18, 2013, 08:23:58 AM
He has 8 LEDs in parallel - at 20 mA per LED that comes to 160 mA total current at 1.5 volts per your spec.

Subtracting 1.5 from 5 we get 3.5 V  3.5V drop at 0.16 amps gives us 22 Ohms. I would use something larger than 22, but 120 Ohms seems to be high.

Now, given that these are infrared LEDs - how do you know that they do or do not light up? 
Title: Re: this in reference to the line follower made by pratheek
Post by: bhavyabhatia on August 18, 2013, 11:50:26 AM
He has 8 LEDs in parallel - at 20 mA per LED that comes to 160 mA total current at 1.5 volts per your spec.

Subtracting 1.5 from 5 we get 3.5 V  3.5V drop at 0.16 amps gives us 22 Ohms. I would use something larger than 22, but 120 Ohms seems to be high.


Now, given that these are infrared LEDs - how do you know that they do or do not light up?


Yes sir,the resistance used is quite high and that is why my leds wont light up at 5V iguess.
And I viewed them through my digital camera. It was clearly visible in the camera whther they lit up or not.
Iguess ishould try using a lesser resistance with the led's and Ihope they work this time.
Title: Re: this in reference to the line follower made by pratheek
Post by: johnwarfin on August 20, 2013, 02:03:49 PM
It was clearly visible in the camera whther they lit up or not.

you saw no difference? 120ohms is more than enough to see 8 parallel leds light up @5v. in fact 1kohm will do it. they are probably wired backwards. what voltage do you measure across the leds?
Title: Re: this in reference to the line follower made by pratheek
Post by: vibhorsehgal on September 03, 2013, 11:19:00 AM
Hello Sir,
I wanted to ask in reference to the LFR made by pratheek. Ibought 8 IR sensor modules ( instead of 8 Ir led pairs.) . The picture of a single module is attached. It has LM358 IC, IR emitter detector pair, 510K resistor , and two 270 ohm resitors,5K and 100ohm preset and a status led.

My doubts are -
!) Pratheek used two LM324(quad op-amp)  to get 8 outputs from the sensors array. So, here can i use 8 LM358 ( dual op-amp) for the same purpose ?
2) How to iconnect 8 of these modules togther in series to obtain the circuit given by pratheek. Or how do i connect them to make them sense the 'black line on a white surface' in general.

I have completed the robot otherwise. Please respond. This is very important for me. Thanks !

(http://i1276.photobucket.com/albums/y480/bhavyabhatia/20130903_221107_zps194e6f4a.jpg)
Title: Re: this in reference to the line follower made by pratheek
Post by: johnwarfin on September 05, 2013, 09:47:41 AM
lm358 are same op amps as lm324 just different package. to sense a line all vcc and grounds connect together with the 8 op amp outputs going to different mcu input pins.

ive built a working line follower myself and am familiar with that thread. its a great project and very educational but imo amplifiers are not required for photodetectors. modern sensor pairs like tcrt5000 are more than sensitive enough with no external components. and they cost less than the complicated circuit in that thread.
Title: Re: this in reference to the line follower made by pratheek
Post by: jwatte on September 05, 2013, 10:13:00 AM
I would like to second the recommendation for TCRT series (I use the TRCT1000.)

Also, another low-cost way of doing line sensing is to measure discharge time through a photosensor. The Pololu -RC sensors work in this way: http://www.pololu.com/catalog/product/961 (http://www.pololu.com/catalog/product/961)
You charge the capacitor with the MCU pin being "output," then you let the capacitor discharge through the photodetector, and measure the time it takes. Most MCUs can do this for 8 pins in parallel, so it can be a pretty efficient way of doing it.

Title: Re: this in reference to the line follower made by pratheek
Post by: johnwarfin on September 07, 2013, 11:41:25 AM
i favor the tcrt5000 at about 1/10th the cost. super easy to find on places like ebay or alibaba. for less than a buck you can put 8 side by side for a great line follow sensor. capable of vinyl tape down to marker or even pencil trace with a variety of backgrounds. and as mentioned they are so sensitive that external amplification is not required. depending on environment it may be possible to get along with a lot fewer than 8 elements too.