Hi guys,
I'm new here so I apologize for my confusion. For my first arduino project I'd like to power on led strip when it's dark.
I'll have arduino connected to 5v,
then a photoresistor, and a led strip.
Do I still need a relay for that or I can control powering led strip via arduino? 
Thank you in advance.
Which, exact, LED strip? It depends on the strip how it is controlled and powered.
What sort of LED strip, it matters.
then a photoresistor
You will probably need a resistor to go with that, about the same value as a mid reading from the photo resistor.
I'll have arduino connected to 5v,
Where is the 5V coming from? What is the current capacity of this supply?
Led strip will be powered by 12V 5A adapter on its own plug. It will be smd 3014, 204leds/m.
Length of led strip in use will be around 3.2meters (125cm+20cm+2*39cm+6cm+83cm) separated.
I thought connecting Arduino UNO to USB cable. I can connect it to 12V 1.5A adapter (I have them lying around). Can I use it here?
Do I need a relay for that project?
Do I need a relay for that project?
No. But you will still need a logic level FET to do the switching.
But you do need to supply more information about the strip. Are they addressable? What is the current each does each LED take?
From the information supplied so far it looks like you will need a power supply of 12V at least 2.2A if not a bit more.
Like I said I'll be powering led strip with 12V 5A. They are not addressable, it's led strip 3014 smd, ie.: https://www.v-tac.eu/led-lights-menu/led-strip-accessories/led-strip-3014-204-led/led-strip-smd3014-204-leds-natural-white-non-waterproof-detail.html
Can Arduino take care of logic level FET you mentioned? If not, can you give me an example of that?
See
For a 5V supply it will need to be able to supply 6.6A at least.
But that link you just posted says the strip is 12V, so you can’t power it with 5V.
Let's say I power led strip with over 12V 5A adapter, and Arduino with 5V adapter, will I be able to control logic of photoresistor (for my project mentioned above - light/dark switch off/on) via Arduino or do I need something else?
Thank you.
Yes that will work.
You will need a resistor on the photo detector about the same value as the mid photo resistor’s value going from the analogue input an 5V. Then the photo resistor from the analogue input to ground.
Also you will need two resistors on the FET. One of about 200 to 500R in seriese between the gate and the Arduino output and another one of 10K value from the Arduino output to ground.
Hi,
this is how circuito draw me connections, etc..
You meantioned 200 & 500R, where can I get one? and how to connect them?
I'm sorry if I sound confused, because I really am. I'm a software guy not so much familiar around electricity.
this is how circuito draw me connections, etc..
No idea because I can't look at that site without it asking me to accept all sorts of conditions. This is how we post pictures here:-
image guide
further information
How to use this forum
You meantioned 200 & 500R, where can I get one?
Well it was any value from 200R ( R means ohms ) to 500R. You get them from any electronic retailer, it depends what country you are in.
and how to connect them?
Solder.
No you can not power the LED strip through the Vin on the Arduino. That pin is connected to the power jack through a 1A rated diode, and as we have established that you need more than this then you will burn out your diode if you try this.
You also have not put the resistors in the FET's gate like we discussed earlier.
lednew:
Hi,this is how circuito draw me connections, etc..
https://www.circuito.io/app?components=9088,9442,11021,12022
You meantioned 200 & 500R, where can I get one? and how to connect them?I'm sorry if I sound confused, because I really am. I'm a software guy not so much familiar around electricity.
Hi lednew,
keep in mind that your led strip is different from the one chosen in circuito.io. therefore, you should make some modifications.
your strip has 204 led per meter - it will draw much more power. The fix is easy - don't use the onboard barrel jack.
make to following changes:
Wall adapter 12v (positive) to the 12v pin pf the strip and to Arduino Vin (to power the board)
wall adapter GND to Arduino GND
all regarding the FET stays the same.
regarding the FET resistor - as mentioned in the comments above it would be correct to add a gate resistor, but in practice, it will work fine without it.
Good luck with your project 
Anat from circuito.io
Hi circuitoio,
thank you for your reply.
I hope I'll figure it out once I get the components. Thank you all for your help.
I'll keep you updated.
