40$ bot..Urgent help..plzz..

[zanynik]

I'm having a prob in makin the 40$ robo
link is http://www.societyofrobots.com/member_tutorials/node/59

Problem 1(Is there no breaking mechanism???)
One of the motos is RUNNING based on sensor input of LIGHT/NO LIGHT, but the motor is not 'BREAKING'(means not stopping) once it stops detecting WHITE/BLACK surface. Meaning - The motor is rotating Freely and then coming to stop. (I have used different rpm motor ..cuz..I tought 100rpm is too Less...)

Problem2
The other motor is not at all responding to light variations at SENSOR..
PLZZ HELP ME!!... what might be wrong??
 1) photoresistors spoilt???
 2) Circuit wrong??...

(SInce 1 of the motrs is workin...i think the half of the circuit is right....right?? )

[Pratheek]

I think you have not adjusted the presets. Adjust the preset and try again.
To adjust the preset, for black line following, place the sensors on the white surface and adjust the preset so that the red LEDs glow only when the sensors are on the black line.

[zanynik]

Hey thanx a lot for the reply pratheek....

... I have less knowledge regarding this....
Can u plzz tell me how to adjust the preset?...

n thanx a lot man for the tutorial....(I couldnt find req molex connectors ....so i used a switch..!!)

[Pratheek]

Adjusting the preset for black line following - Place the robot on the place the sensors on the line. With the help of a screw driver, reduce the resistance of the preset completely. Now increase the resistance of the preset slowly until the red LED glows.

Adjusting the preset for white line following - Place the sensors on the black surface and reduce the resistance completely.Now increase the resistance until the red LED glows.

After adjusting the preset, place the robot on track and watch it follow the line .

[Mcrich113]

have u Tried reprograming it?

[airman00]

have u Tried reprograming it?

there is no programing in the microcontrollerless robot ! lol

[zanynik]

At last.... Everthing is working fine....

I dont know wat happened... but We(our team)...Soldered new LEDS n photoresistors and re-Soldered/ removed the messing up in the circuit.... it now WORKS... gr8!!....

One Doubt though:

I didnt connect the COLLECTOR joint of the Transistor to the TRACK pin joint of the POTs..(for one of the motors)... ANd still its working Fine...

Do u think i shud connect it now... OR...is it just Optional... And What Does it DOOO??...

[Pratheek]

Actually both, the collector of the transistor and the track pin of the preset, have to be connected to Vcc. Its fine if you have connected them separately. 

[zanynik]

Thanx pratheek for the tutorial..n thanx to ever1 who helped...

It worked atlast... took it to a competition...  ..cleared 1st round... 

Second round had a Sharp M turn... The robo couldnt do it. .. the width of Line at the turn was more and it covered both the sensors,thus robo stopped.

U got any idea to make it do that???...

[superchiku]

is this a microcontroller based or non microcontroller based robot

[zanynik]

microcontroller-less

[Pratheek]

Second round had a Sharp M turn... The robo couldnt do it. .. the width of Line at the turn was more and it covered both the sensors,thus robo stopped.

Try building a new sensor board where the distance between the left and the right sensor is greater than the width of the line you want to follow. I think that is the only solution.

[zanynik]

If its a white line follower ...then when it detects light(ie when sensors come on white line) I want the wheels to rotate in REVERSE direction....simply said..I want DIFFERENTIAL DRIVE ...I think this will ENABLE the robo to take SHARP turns....   This can be done but the CIRCUIT may be a bit complicated... CAN u do the circuit PRATHEEK..?

[Pratheek]

When you are doing white following and want your robot's wheel to move in the reverse direction when the corresponding sensor detects the line, you will have to make a few changes to th original circuit.
First you will have to connect the sensor output to one of the input pins of the L293d.
Next you will have to construct a not gate, either use an IC or build it from a transistor(google for the circuit.) Connect the sensor output to the not gate input and the gates output to the other input pin of the L293d.
Do this from both the left and right sensors.

[Ro-Bot-X]

If the robot has only 2 sensors, you can build 2 kinds of line followers: a line hugger (sensors outside the line) and a line streamer (sensors inside the line). I have built such a line follower that I could make it eighter one, but I have used a microcontroller. But here are some thoughts:

- a black line hugger will work as a white line streamer if you swap motors and mount the sensors close together
- if you need to transform a line hugger in the same collor line streamer you need to swap motors and invert the sensors output, that is the sensors will not look for white but for black (like Phrateek said)
- for easier swapping a couple switches may do the trick for you, one for swapping motors and one to add inverters to the sensors output