Garden lights circuit will this work

[jakethepup]

I am going to use a 6 volt battery to power about 8 leds the white or color changing leds not sure which but both are rated at 3.3 to 3.8 volts. I want the photocell to turn the LED's on around dust and off at dawn.

I am wondering if this would work and would I have to change things around to make this circuit work.

Sorry I don't know much about electronics, so be kind if I am way off base. I found the drawing here on this site and mod, it some to see if you guys think this might work for what I want to do.


Thanks,

**broken link removed**

 

[ericgibbs]

hi Jake,
The 100R will draw 60mA from the 6Vbty and the LED only 6mA.

The battery life could be quite short, what data to you have on the photocell light detector.?

 

[jakethepup]

The Photocells are Cadmium Sulfide that came from radioShack they have no values on the package, kind of a grab bag of 5 different values. I do have a digital voltmeter I guess I need to check them and see what values they are.

Other information I have the battery is a 4.5 AH, 6 volt and the Leds are 3.3- 3.8 volts at 25 ma's.

If the can get the circuit to function I want to add a solar cell to keep the battery charged but will be another project.

 

[ericgibbs]

The Photocells are Cadmium Sulfide that came from radioShack they have no values on the package, kind of a grab bag of 5 different values. I do have a digital voltmeter I guess I need to check them and see what values they are.

Other information I have the battery is a 4.5 AH, 6 volt and the Leds are 3.3- 3.8 volts at 25 ma's.

If the can get the circuit to function I want to add a solar cell to keep the battery charged but will be another project.

hi,
If you post the DVM [light and dark] voltages perhaps we can suggest changes to the circuit.
I dont think the circuit you posted will work..

 

[jakethepup]

In the sunlight the photocell tests at 152.6 and with my finger over it while inside it measures 45.8

Hope that helps some.

Thanks a bunch

 

[ericgibbs]

In the sunlight the photocell tests at 152.6 and with my finger over it while inside it measures 45.8

Hope that helps some.

Thanks a bunch

hi,
I assume those values are ohms.?

What npn and pnp transistors do you have.?

 

[jakethepup]

Yes the value is in OHM's I have not purchased the transistor yet, I thought I would wait and get that if the drawing would work, so the only thing I have on hand are the photocells, the battery, and a couple of the Leds, and some Misc, resistors.

Thanks

 

[ericgibbs]

Yes the value is in OHM's I have not purchased the transistor yet, I thought I would wait and get that if the drawing would work, so the only thing I have on hand are the photocells, the battery, and a couple of the Leds, and some Misc, resistors.

Thanks

hi,
The circuit I would choose is a npn/pnp amplifier.
How do you plan to connect the LED's, how many and what voltage are they.?

EDIT: where are you located.?

 

[jakethepup]

I plan on connecting about 6 to 8 leds, the voltage on the packages states that they are 3.2 to 3.8 volts and draw 25 ma, I plan on connecting the LEDs in parallel.

 

[ericgibbs]

I plan on connecting about 6 to 8 leds, the voltage on the packages states that they are 3.2 to 3.8 volts and draw 25 ma, I plan on connecting the LEDs in parallel.

You cannot connect LED's of different voltages in parallel, using a common resistor.

 

[jakethepup]

Maybe I am missing something but the LED's are the same voltage, the voltage I quoted are the operating voltages on the packages, they are all the same size. Sorry like I said I don't know much about electronics just trying to learn as I go.

 

[ericgibbs]

Maybe I am missing something but the LED's are the same voltage, the voltage I quoted are the operating voltages on the packages, they are all the same size. Sorry like I said I don't know much about electronics just trying to learn as I go.

hi jake,
You say the LED's are in a pack marked 3.2V to 3.8V, the LED's are not matched.

I would suggest that you get a 150R resistor with the 6Vbty and check the voltage across each LED. You may be able to get a matched set. OK.

I have looked at some circuit options using the photo cell, its not the best choice of light/dark detector when using a battery power source, there is only a 100R change from light to dark.

I would suggest you look as some light dependant resistors LDR's or phototransistors instead of the photocell.

 

[Hero999]

In the sunlight the photocell tests at 152.6 and with my finger over it while inside it measures 45.8

Hope that helps some.

Thanks a bunch

I don't believe that, the resistance should be higher with your finger covering it, not lower.

 

[jakethepup]

Ok on the photo cell I used another one out of the package and here are the results I got in the light measures 4k with my finger over the cell it measures 36k I am guessing that are better results.

 

[ericgibbs]

Ok on the photo cell I used another one out of the package and here are the results I got in the light measures 4k with my finger over the cell it measures 36k I am guessing that are better results.

hi jake,
So you are confirming that light=4K and dark=36K.?

Thats a better choice, a 32K change is much better than 100R.!

Do you want me to draw up a circuit.?

Did you test each LED's voltage drop as I suggested, it is important.

Do you have a part number for that photo-cell.?

 

[aljamri]

Ok on the photo cell I used another one out of the package and here are the results I got in the light measures 4k with my finger over the cell it measures 36k I am guessing that are better results.

These are possible readings, while the first two has a missing kilo or Miga.

While measuring a resistance try not to touch the multimeter leads because it will measure your body resistance along with the resistor.

 

[jakethepup]

I would love for you to draw up the circuit, the part number for the photocell, is from Radioshack and the part number is 276-1657

 

[ericgibbs]

I would love for you to draw up the circuit, the part number for the photocell, is from Radioshack and the part number is 276-1657

hi,
Eventually found the part.
They call it a photo-cell, which is not quite correct, a photo-cell actually generates a voltage when illuminated,
thats what threw me a curve.

Its really a Cds photo-resistor.

For the circuit I must know how many matched LED's you are going to have to light.

 

[aljamri]

I would love for you to draw up the circuit, the part number for the photocell, is from Radioshack and the part number is 276-1657

Sorry, i have no circuit for this specific photocel, instead you may benefet of this circuit ( got some where on web )

 

[ericgibbs]

Sorry, i have no circuit for this specific photocel, instead you may benefet of this circuit ( got some where on web )

hi aljamri,
The problem is the OP wants to use a 6Vbty, I suspect he wants to keep the current drain to a minimum.
Driving a relay would put an extra burden on the battery.