hi, im planning to make a miniature of a daylight harvesting/ closed loop automatic light intensity controller. im making for our project to be passed this week. i just wanna ask is it necessary to use a microcontroller as my light controller or is there any other way? or can i just use 555 ic?

 

I assume this is some type of automated "blinds" or shutters to control daylight? Please provide more info when you want people's help!

A microcontroller would help but you could do it instead with analog closed loop brightness control using a light sensor and opamps and some type of motor driver.

 

im sorry for not stating my confusions clearly. yes, exactly its like an automated blinds and i want to do a miniature of it. im planning to do the circuit without using microcontroller. well thank you, i will try to utilize op amps rather

 

You are just now starting to consider how to do this project and it has to be "passed" this week?

Good luck!

 

Using op amp or darlington driver that it will give you the high sensitivety, and it's easy to use pot(VR) to control the sensitivety.

 

i'll be using ldr as my light sensor then a circuit to convert it into electrical signals then fed to a control unit and lastly fed to dimming control..
unfortunately, well be passing it this friday and i know its too late to design the circuit. id rather do it even its too late than to ask other people to do it. please i really need your guide sir T.T

 

thank you mr scott!

 

You need to describe your system more clearly. On the one hand you talk about using the circuit to control the blinds but then you talk about using the circuit to control a light dimmer. What is being controlled here? If you have more than one thing, then you have potential interactions between them and you probably need a control strategy that says what order they will be controlled in. That's a complexity that quickly screams for a programmable logic approach.

 

i was just comparing my idea to the automatic blinds in the market. actually i was really pertaining to daylight controller(without blinds).

 

Yes, need more infos.
Like as : Power voltage and current and the load, and the order of active.
You can describe the conditions as:
1.
2.
3.
4.
...
The description is more clear that it will more easier to get to the target.

 

in other words, a closed loop daylight intensity controller..
ldr-->comparator circuit-->controller-->output(5v lamp) and ldr also senses the light from the lamp light aside from the external light.
is the system correct sir?

 

mr scott, im planning it to be in a proportional control mode, powered by 12 volts supply to drive a 5v lamp..
its mechanism goes like this, http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/diagram.asp

 

The following site has the feedback and system control from a photosensor, it also has the block diagram, you can take a look and talk about what you think.

Photosensor tutorial.

System diagram for closed-loop photosensor control,

 

mr scott, thank you for entertaining my questions.
with regards to the picture, the gain inside the dotted lines means amplifying the electrical signals from the sensor? is darlington can be used for this stage?

 

ive read already this site and the control algorithm part made me confused. what is with the control algorithm?

 

Whatever you are using op amp or darlington pair, they also can do the job of amplifying, but if you using op amp will more easy to control.

If you using the op amp that you should set a reference voltage it's called Vref, when the V_LDR higher or lower than Vref then the output of op amp will output a hi or low signal, it depends on what you want to setup.

You can using the output signal of op amp to active the bjt or mosfet, and bjt or mosfet to drive the 5V lamp.

The question is that how precisely that you want to control the lamp, you just want to turn the light on or off or you want to adjust the brightness of lamp according to the sunlight from photosensor?

Control algorithm - I'm not sure what the article said, but the control method is similar as above.

 

thank you again Mr. Scott!
i'm starting doing the circuit right now using op amp. but here i think its applicable only to on/off control. id like it to be in a proportional control mode automatically adjusting the brightness of the lamp according to the sunlight and lamplight as well which are being sensed by the ldr.