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dark sensor using a kit

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Hmm.. lower value for R1 - even though thats what came with the Kit...?

the LED series has the these stats:

=========
current: 20mA
typ. Voltage: 3.4V
luminosity: 20,000 mcd.
==========

there is a 120 Ohm resistor to run 3 LEDs (when complete will have 18 leds with 6 resistors)

Are you saying that R1 in the kit doesn't suit the Kit or just doesn't suit my LED series?

Also if it is wrong, should it not have worked the first few times?

Thanks again
 
Hmm.. lower value for R1 - even though thats what came with the Kit...?

the LED series has the these stats:

=========
current: 20mA
typ. Voltage: 3.4V
luminosity: 20,000 mcd.
==========

there is a 120 Ohm resistor to run 3 LEDs (when complete will have 18 leds with 6 resistors)

Are you saying that R1 in the kit doesn't suit the Kit or just doesn't suit my LED series?

Also if it is wrong, should it not have worked the first few times?

Thanks again

Hi David,
I think hero means the variable resistor P1, have you adjusted it for the best dark/light response.

What are you powering the circuit from.?
 
Wow - responses up the Wahzoo (thanks to all)

Ok....

1) Battery still has about 6v left
2) tried adjusting P1 (but it stopped working before I touched it anyway)
3) R1=330k, R2=3k 3 (not sure why it has extra '3' orr-org-red-gld), R3=10k, P1=22k

also, I swear I tested the battery an hour ago and it was still over 9v - is it possible this thing is draining my battery faster then it should?
 
1) Battery still has about 6v left

Hi,
If the 12V SLA is reading 6V on load, its not acceptable.
Thats why the circuit worked and now it dosnt.

The SLA should never be less than 10.8V or you will ruin it..
 
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Right then... recharge the battery and pat myself on the back?

it sounds like with a full battery this will work fine....

Now, when Im done the whole thing will run 18 LEDs at 20mA each (360 total) - according to the it Kits information that should only consume less the 100mA.

so in theory, the whole thing should only consume about 460mA.

With a fully charged 12v 7ah battery, I should get about 15 hours use out of it, right?

my next question (which, I should possibly open a new thread for) is do I need 2 batteries to see it through the night, until the solar panel (which I have not added yet) can recharge it, ready for the next night ? or will it be ok with just the one battery?

Thanks to all - you guys Rock.
 
Right then... recharge the battery and pat myself on the back?

it sounds like with a full battery this will work fine....

Now, when Im done the whole thing will run 18 LEDs at 20mA each (360 total) - according to the it Kits information that should only consume less the 100mA.

so in theory, the whole thing should only consume about 460mA.

With a fully charged 12v 7ah battery, I should get about 15 hours use out of it, right?

my next question (which, I should possibly open a new thread for) is do I need 2 batteries to see it through the night, until the solar panel (which I have not added yet) can recharge it, ready for the next night ? or will it be ok with just the one battery?

Thanks to all - you guys Rock.

hi David,
Ref the solar charging, where is your location.?

BTW, whats it lighting up. ?:)
 
I kid you not, the thing just came on as I pressed submit - and with it plugged in, it now shows 8.6v with leds off - cover the sensor and they come and the battery shows 7.5v

Why is it randomly working... ghost in the machine ?
 
I kid you not, the thing just came on as I pressed submit - and with it plugged in, it now shows 8.6v with leds off - cover the sensor and they come and the battery shows 7.5v

Why is it randomly working... ghost in the machine ?

Its the battery recovering slightly when off load..

DONT damage your battery, charge it up PDQ...:)
 
what about the amount of batteries? If Im not supposed to let it drop below 10.8 then wont it go below that before the sun can get to it the next morning?
 
what about the amount of batteries? If Im not supposed to let it drop below 10.8 then wont it go below that before the sun can get to it the next morning?


hi David,
The battery performance depends upon the AHr capacity of the battery, the current drawn from the battery and the general state of the battery.. its age and how well its been maintained and also the state of the 'charged capacity' when you start to drive your circuit.

Recharge your battery, upto 13.8V [14V absolute max.!]
Connect the circuit, cover the sensor so the leds are ON, observe the fall off of the battery voltage, STOP the discharge at 10.8V,,, note the running time.

To charge up the battery, using a solar panel you need to put the same current in for the same time * 1.5.

EDIT:
Obviously if you increase the recharge current the time comes down, but allow only 60% for the conversion efficiency.
 
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https://www.futurlec.com/Solar_Charge_Controller.shtml

This is a charge controller, also has a built in timer, and switches on after dark. It's exactly what you are looking for to charge your battery and turn on the lights. Will shut off when the battery gets below a safe level. The solar panel should produce 20v no load, and about 750 mA, for your 7.5 Ah battery. $26 and about 3 weeks, plus shipping. Not too bad, been working well for me.

Your relay probably consumes as much current as the LEDs, might be able to remove it, and drive the LEDs in it's place.

120 mA worth of LEDs, perhaps NiMh battery pack would be a better choice. Less worries about maintaining its charge level, and smaller solar panel.
 
are you saying that little gizmo will also swith on my LEDs at night? So I all have to do is plug my LED array in to it, plug in the right solar panel, turn it all on, and walk away?

Forgot the battery, but yes it's exactly what you are trying to build. I've got one, and works fine. Can't say if it will last all night though, but still going strong at 2:00 AM. I've got a 10 Ah battery, but going to get a boat battery eventually. Doing this for emergency lighting when the power goes out during hurricane season, maybe the coffee maker...
 
Anything that makes heat like a coffee maker uses a very high current.

Then you will need a huge and expensive solar panel, a huge and expensive battery and continuous sunshine every day without any hurricanes.
 
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