[SOLVED] Solar Tracker problem: LDR not equal

[kbtan]

Excuse me, can any one help me with my project. I am going to build a solar tracker but i found out that the LDR of my circuit always have not equal resistance during night causing the motor run non stop at night. I try buy 4 to 5 set of LDR but all the resistance not equal. I am using the comparator to control the solar tracker.

 

[FvM]

You can try with two parallel resistors to the LDRs. They will keep the bridge mostly balanced at low light intensity. Ultimately there should be an additional LDR with a comparator that shuts the tracker down below a certain brightness.

 

[kbtan]

thank you for your opinion. I will try it out

 

[kam1787]

Excuse me, can any one help me with my project. I am going to build a solar tracker but i found out that the LDR of my circuit always have not equal resistance during night

Why not have an 'over-ride' status; if too dark for too long, assume it is night and shut-down for NN hours.

Or put on a timer.

 

[shegzzyy]

The ldr cannot have the same resistance because ldr resistance vary with light intensity

 

[kam1787]

The ldr cannot have the same resistance because ldr resistance vary with light intensity

well that is the property of LDRs!!!!! but the reason is more how they are made and the materials

 

[kbtan]

Why not have an 'over-ride' status; if too dark for too long, assume it is night and shut-down for NN hours.

Or put on a timer.

So I need to use a microcontroller to control the solar tracker ??? In my circuit it doesn't consist of microcontroller to control the operation. I use a comparator to compare the voltage from LDR then drive the motor

 

[prashanttyagi85]

by using microcontroller you can control your tracker more efficiently even in day time also

 

[kam1787]

So I need to use a microcontroller to control the solar tracker ??? In my circuit it doesn't consist of microcontroller to control the operation. I use a comparator to compare the voltage from LDR then drive the motor

hahahhaha No! I am not of those that thinks a micro-controller is needed for everything!

but you would need some logic circuits. I'll let you do a flow diagram.

 

[kbtan]

hahahhaha No! I am not of those that thinks a micro-controller is needed for everything!

but you would need some logic circuits. I'll let you do a flow diagram.

Sorry but i don't quite understand how it operate without microcontroller. Can you briefly explain to me. Thank you.

 

[kam1787]

LDR-----> comparator['1' if voltage indicates 'night']--->long delay pulse generator*--->motor 'switch'------> motor turn-off




* with fast reset

 

[kbtan]

You can try with two parallel resistors to the LDRs. They will keep the bridge mostly balanced at low light intensity. Ultimately there should be an additional LDR with a comparator that shuts the tracker down below a certain brightness.

the resistor parallel to LDR should be higher or lower than the LDR resistance in day time

 

[kam1787]

You can try with two parallel resistors to the LDRs. They will keep the bridge mostly balanced at low light intensity. Ultimately there should be an additional LDR with a comparator that shuts the tracker down below a certain brightness.

Using a resistor across each LDR is the cheapest option. What value is the question - depends on how sensitive the comparator is. It has to be small enough to negate the difference in the dark, yet large enough to not to unduly influence the tracking of the sun.

I agree there ought to be a circuit to shut down the tracker at night.

 

[FvM]

the resistor parallel to LDR should be higher or lower than the LDR resistance in day time

I presume higher.

 

[chuckey]

you don't say whether its polar or azimuth tracking that is faulty. I would use a "master" LDR that when the light has fallen sufficiently returns the polar tracking to due west and the azimuth to 0 degrees then shuts it down until the sun rises the next morning.
Frank