Can someone show me an effective circuit that will turn on at night and off during the day.

I have been playing around with one circuit I found but the problem was that the LEDs always drew some power from the batteries even when in full light (they should've been off). Then when it was dark they were never bright enough. So in order to increase the intensity of the LED I increased the source Voltage but this also increased the voltage drain when it was off (in full light) .

Justin..

 

There are plenty of circuits on google. Search there first, and then come back if you can not find any.

 

hey! This's my sentence!

__________________
i² = j² = k² = ijk = -1

 

If you use solid-state technology there is always leakage currents. You might not be able to do anything about it unless you use a relay, but then what happens is you need an active to control the relay- which means you need a circuit that will amplify the photo-readings you get to drive the relay. What will happen is you get zero current consumption when off, but when it's on you have the to power the LED and the relay, and the relay probably consumes way more power than the LED. So the power you end up saving when off ends up being used up (and then some) to power the relay when the LED is on.

How much off power consumption did you measure?

 

I was getting a power consumption of 1.6 to .1 when the LED was supose to be off,
I hope that answers the question you where asking ?

 

Uhhh, what did you measure? What units?

 

Please post the schematic an explain properly what you want to do, what application does your circuit have?

__________________

I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

He probably has a photodetector shorting the LED to turn it off.

__________________
Uncle $crooge

 

My batteries are putting out 7.24VDC
The Potentiometer is dialed to a point where I get good illumination when on (in Dark) and apears off when light hits the Photoresistor.

Question 1.
When I try to read the resitance of the pot I get 1.14 when the multimeter is set to 20K, how should this be read is it 1.14 Kohms?


Question 2.
I am taking my multimeter readings from A and B (from the pos & neg of the LED). Is this the correct place to take the reading from ?

Question 3.
The LED Load when on is 5.85V This seems a bit much for a LED that is supose to light at only 3V.
Do you agree ? if so how can I reduce my voltage to the LED and still get the illumination I want ?

Question 4.
LED Load when off is 1.3V
This is the problem because I would expect no voltage to be read when the LED is not lit, can you sugget why it is drawing so much voltage when it apears off and how I can solve this ?

Attached Thumbnails

 

 

Are you reading the resistance in circuit, or out?

I assume you mean the voltage reading?
Put a resistor in series with the LED. Use Ohm's law based on the current spec of the LED.
It seems the bjt is slightly on. I'm not sure I understand why the LED is in parallel with the collector resistor. Why not eliminate the collector resistor and put a series resistor in line with the LED based on Q3 above?

__________________
"Everything that is done in the world is done by hope." -Martin Luther
"There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein

 

Compare this circuit, which works.

__________________
Creationists have a world of evidence

 

Changing the transistor to an NPN confuses understanding the circuit.
But it looks like the original circuit would work backwards, the LED would light when there is light.

__________________
Uncle $crooge

 

I am reading the resistance directley from the Pots leads while it is pluged into the bread board, the battery is turned off.


Yes I mean Voltage reading.


What is the bjt ?

 

Reading the pot while in-circuit is not just the pot resistance, it is with the surrounding circuit, and could be way off - even different when power is applied. The bjt is short for bipolar junction transistor. Try eliminating the collector resistor and put a small series resistor with the LED.

__________________
"Everything that is done in the world is done by hope." -Martin Luther
"There are two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle."-Albert Einstein

 

Is that a resistor going into to Transistor ?