light sensor

[4electros]

i need circuit schematic using light sensor detector or something like that. so it will light a lamp when dark and switch off the lamp when light..

 

[dknguyen]

Ldr

https://www.electro-tech-online.com/threads/ldr-circuit.21398/

 

[ZIGGY_DAN]

a potential divider will do,
i have included a picture, variable resistor 1 is to set the threshold at which the circuit turns on, if a heavier load is to be drive replace LED1 with a relay and reverse bias a diode across the relays terminals to prevent electromotive feedback.

hope this helps?

 

[4electros]

it helps but i need tha practical circuit schematic , is that enough to use only one transistor and three resistors for accuracy working? and if the load requires high current draw and voltage about 220v as neon lamp.. i know that relay can lead high power elements but the supply here in only 9v, how would it be?

i need more clarify please , thanks

 

[ZIGGY_DAN]

you could power thecircuit via a transformer, or i suppose it could be powered from the mains if rectified as long as componets with suitable values were chosen, the variable resistor might pose a problem, if the variable resistor had a metal base it would have to be earthed and the circuit placed in a plastic box(or earthed metal one). The light would not either be on or off, it will illuminate proportionally to the darkness.
the circuit below will be definite on or off as it uses a relay, this is one way of doing what you require another is without the transformer(the bottom schematic) personally i would use the one with the transformer.

hope this helps?

 

[Nigel Goodwin]

Please don't post diagrams (or anything else) as BMP files, they are stupidly huge, use either GIF or PNG instead, exactly the same quality and probably only 1/100th the size!. Don't use JPG though, although it's a LOT better than BMP, it's still much bigger than GIF or PNG.

 

[ZIGGY_DAN]

sorry about that, i did it quickly on paint, ill use photoshop next time

 

[audioguru]

You can make a sketch in Paint, then simply save it as a GIF or a PNG and attach it here.

 

[4electros]

you can do it with paint and save it as PNG or GIF

 

[4electros]

you forgot to add voltage regulator in your schematic , the transformer may give us about 24v and we need just 9v supply


you didnt answer my question concerning accuracy , would it be correct to use such diagram practically?

 

[4electros]

i've made the circuit on PCB and tried to check it, my two-connector relay swirched on at first but then no resonse from it with the same experiment conditions...that's when relay is not loaded ( I havent yet load it)
is there any relation between switching and relay loading?

 

[TronicBrain]

Hi 4electros
I suggest this diagram
It’s accurate, simple and practical

Or you need to design one using Op-Amp as comparator which works on the same principle.