Photo Sensor Project Question

[calpolyarc]

Hello, new to the forums here and somewhat of a newbie to electronics. I have a project I'm working on and was hoping to get some help with the electronic components. So here goes....

I bought 5' of this LED Strip: LED Strip, a 12v 12w 1A Power Supply, and this RGB Controller: **broken link removed**. Everything works great, I've even been able to cut the LED Strip into sections and solder wires between the sections. The part I'm having trouble with is that I want to add a photo sensor, photoresistor, or phototransistor to have the LED's turn on automatically when the room gets dark. Through investigation I've found that there are many ways to do this, but it appears one of the simplest methods seems to utilize an NPN transistor as seen here: **broken link removed** I've tried this circuit with success using this kit: Electronic Snap Kits
Juvenile I know but like I said I'm a beginner and it was on sale at Radio Shack
So how do I integrate this NPN transistor schematic into my project with:
A) The electricity being supplied by the 12v 12w 1A Power Supply and/or RGB controller instead of 2 AA batteries.
B) The LED being a 5' strip or RGB LED's instead of a single LED.
C) The resistor, NPN transistor and photo sensor being bought from Fry's or Radio Shack.


Thanks in advance!

 

[Transistorman]

Hello, new to the forums here and somewhat of a newbie to electronics. I have a project I'm working on and was hoping to get some help with the electronic components. So here goes....

I bought 5' of this LED Strip: LED Strip, a 12v 12w 1A Power Supply, and this RGB Controller: **broken link removed**. Everything works great, I've even been able to cut the LED Strip into sections and solder wires between the sections. The part I'm having trouble with is that I want to add a photo sensor, photoresistor, or phototransistor to have the LED's turn on automatically when the room gets dark. Through investigation I've found that there are many ways to do this, but it appears one of the simplest methods seems to utilize an NPN transistor as seen here: **broken link removed** Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery. The terminal voltage of the battery is indicated through a four level LED indicators. The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when fully charged. The LED voltmeter uses four Zener diodes to light the LEDs at the precise breakdown voltage of the Zener diodes. Usually the Zener diode requires 1.6 volts in excess than its prescribed value to reach the breakdown threshold level. When the battery holds 13.6 volts or more, all the Zener breakdown and all LEDs light up. When the battery is discharged below 10.6 volts, all the LEDs remain dark. So depending on the terminal voltage of the battery, LEDs light up one by one or turns off. LED Volt Meter Circuit Circuit diagram:LED Volt Meter Circuit Diagram LED Volt Meter Circuit Diagram Author: D. Mohan Kumar Copyright: electroschematics.com Electronic Snap Kits
Juvenile I know but like I said I'm a beginner and it was on sale at Radio Shack
So how do I integrate this NPN transistor schematic into my project with:
A) The electricity being supplied by the 12v 12w 1A Power Supply and/or RGB controller instead of 2 AA batteries.
B) The LED being a 5' strip or RGB LED's instead of a single LED.
C) The resistor, NPN transistor and photo sensor being bought from Fry's or Radio Shack.


Thanks in advance!

really accidental

i have the kit when i was nine

btw , what are you trying to do ?

 

[calpolyarc]

It's just some LED accent lighting that turns on automatically when it gets dark.

 

[Reloadron]

The circuit posted would work (pretty basic) for a single LED as drawn. However the transistor would be something like a 2N3904 or more like a 2N2222 driving a small relay in place of the LED. You want to switch 12 volts and 1 amp. That is a chunk of current for a small transistor. So replace the LED in the drawing with a small relay coil. Place a shunt diode across the relay coil and use the relay contacts to drive your load (LEDs). How well the circuit works will also be a function of the LDR (Light Dependent Resistors) Light and dark resistance.

Ron