First time project. I am so stuck.

[Charizard]

Hi, actually it is my first time doing my school project on electronic circuit. So, I am quite lost and stuck. My project needs to have light sensors to detect the sun and compare the value between two sensors so that the system will follow the track where the sensor senses more sun light.

I wanted to draw out a circuit for a photo diode, 4quadrant photodiode and a H bridge for my motor. I google for the circuit. Then pop out so many diffent type of circuit. So, i am so confuse. Can anyone show me a basic design of circuit for a simple photodiode sensor and a 4quadrant photodiode? I got a H bridge schmetic diagram with values for all the components. But are these values apply to any servo? If not, how should I re calculate?

sorry for asking troublesome question. But I am really really stuck and lost. Thanks for any help and advise. 

[CrashOverron]

Pratheek's $40 robot is somewhat similar to what you're looking for instead of the sun it uses LEDs to reflect off the ground but just take the LEDs out and reposition the LDRs you can make what you're talking about and the way he made the bot you can have it go towards light or away

(http://www.societyofrobots.com/member_tutorials/node/59)

[Charizard]

But is the circuit for photodiode similar to LED circuit? Cause my major concern is I still unable to get a circuit out and unsure are those values for resistor, capacitor work on most photodiode..

sorry, am I asking silly question.. I see others in this forum seem to know quite well about the circuit building..

[Charizard]

ok, i read the tutorial. I am still in mist, can a photodiode construct same circuit as LDR?

[CrashOverron]

im pretty new as well for im not sure on the different values for the photodiodes instead of the photoresistors but are the diodes a MUST instead of the resistros(LDRs)?

[Charizard]

If not mistaken, photodiode can check the light in wider angle. Correct me if I am worng because when I check the part list, I found the acceptance angle for photodiode, but not LDR. So, I think that LDR could only detect the light in front.

Anyway, I can change other sensors to LDR, but there is one part that needs a 4 quadrant photodiode. This is the part where I am lost. 

[octagonx]

If not mistaken, photodiode can check the light in wider angle. Correct me if I am worng because when I check the part list, I found the acceptance angle for photodiode, but not LDR. So, I think that LDR could only detect the light in front.

Anyway, I can change other sensors to LDR, but there is one part that needs a 4 quadrant photodiode. This is the part where I am lost. 

Photodiodes are diodes and photoresistors are resistors.  In photodiodes, the voltage drop (as in diodes) varies with the perceived light intensity.  In photoresistors, the resistance changes.

About the quadrant photodiode, can you post the circuit so some kind people explain it to you?