Hi

I have the following landscape light:

Better Homes & Gardens Ellis 20 Lumen Solar Powered LED Outdoor Landscape Path Light - Walmart.com

It comes solar powered. I want to modify it so that it is only powered from plug no solar. I am going to use the following adapter to power the lights. The adapter range goes from 3VDC to 12VDC:

Amazon.com: 30W Universal AC/DC Adapter Switching Power Supply with 8 Selectable Adapter Tips, for 3V to 12V Household Electronics and LED Strip - 2000mA Max : Electronics

I am going to change the led in the landscape light to following which is 3VDC 100ma:

Filament Led White Light Bulbs | Led 8 Pcs Filament | Led Filament 10 Leds - 68mm Dc3v - Aliexpress


I am going to use solar panel that the landscape light comes with as my indicator if its night time or day time to turn lights on or off. I measured and determined from solar panel that at 0.5VDC or below it is dark enough so that the lights should turn on. Above solar panel 0.5VDC lights should be off.


Now my next challenge is to build a circuit that meets below all requirements.

Requirement 1. I want a circuit that constant 3 vdc if I put my adapter at 12VDC or 6VDC then I also want the circuit to output constant 3VDC. I would do 12VDC or 6VDC so I don't have to worry about voltage drop in field. I don't want to do resistor divider for the constant voltage because if future the adapter would not only power landscape light but also other items that are not 3VDC. I just don't know voltages right now.


Requirement 2. Turning lights off 0.5VDC or below and turning lights on 0.5VDC and above. Does anyone know how of good circuit I can build from transistor, resistor, diodes etc which can switch the led landscape light on at 0.5VDC or below and light of at 0.5VDC above?

If you do then can you please post it.

Thanks

 

If you are using 12V to avoid the voltage drop in the wiring, and then using a linear regulator to drop the voltage to 3V, then all you have done is increased the losses (by starting with a high voltage) and concentrated them in one device instead of spreading them out across all the wiring.

 

If you are using 12V to avoid the voltage drop in the wiring, and then using a linear regulator to drop the voltage to 3V, then all you have done is increased the losses (by starting with a high voltage) and concentrated them in one device instead of spreading them out across all the wiring.

Zener diode at each landscape light might work

i need circuit that fulfills two requirements post #1

 

Zener diode at each landscape light might work

Wasting more than 3/4 of the energy input. If you use a higher voltage to avoid wiring losses, the only way you win is if you lower the current, which requires an SMPS powering the load.

 

Wasting more than 3/4 of the energy input. If you use a higher voltage to avoid wiring losses, the only way you win is if you lower the current, which requires an SMPS powering the load.

Forget the constant voltage 3bdc from 12vdc or 6vdc due to voltage drop.
By the way its not just for coltage drop. In future i have 6vdc devices or 12 vdc devices. I need voltage for those in future. I need room for voltage. Read post #1 requirements carefully.

Do you know of any circuit that meets requirement #2 post #1?

 

I have the following landscape light:

Requirement 2 is no problem.
How many lamps are you going to use?
How long is the wiring and what guage wire are you using?

 

Requirement 2 is no problem.
How many lamps are you going to use?
How long is the wiring and what guage wire are you using?

2 in parallel. Total would be 200mA 3vdc each landscape light. Wiring is #12 awg copper. Max 40 feet

 

Why not put four of the 3 volt lights IN SERIES across the 12 volts?? If they are identical then each will have three volts and you will not waste any power in any voltage reducing scheme, AND you will not need any additional equipment??? The series scheme avoids the problems completely. The only technical challenge will be keeping the polarity correct.

 

I'd like to see a circuit diagram of what is in the lamp and have you tried to access it? Also consider that you will next have to deal with buried wiring!

 

Why not put four of the 3 volt lights IN SERIES across the 12 volts?? If they are identical then each will have three volts and you will not waste any power in any voltage reducing scheme, AND you will not need any additional equipment??? The series scheme avoids the problems completely. The only technical challenge will be keeping the polarity correct.

Because if one blows all line blows so no series

 

I'd like to see a circuit diagram of what is in the lamp and have you tried to access it? Also consider that you will next have to deal with buried wiring!

Internal circuit would be bypass by the new circuit

 

If you do then can you please post it.

Where you go:

ADDED:

lights are 3vdc not 12vdc. Total each is 200 ma.
How the circuit works?

You drive me crazy...
You should not connect LEDs in parallel
if you want long life for your lamps.

ADDED MORE:

Ok how the circuit work? Can you explain please

We already talked about this circuit:
https://forum.allaboutcircuits.com/...uit-and-how-to-resolve-it.201201/post-1914038
Do not overload your brain.
Simple assemble this circuit and see how it will work with 12 V adapter.

 

Where you go:
View attachment 330262

lights are 3vdc not 12vdc. Total each is 200 ma.

How the circuit works?

 

Does anyone know how of good circuit I can build from transistor, resistor, diodes etc which can switch the led landscape light on at 0.5VDC or below and light off at 0.5VDC above?

2 in parallel. Total would be 200mA 3vdc each landscape light. Wiring is #12 awg copper. Max 40 feet

That's only .127 ohms at 80 ft., less then a 1% loss.

 

Where you go:
View attachment 330262
ADDED:

You drive me crazy...
You should not connect LEDs in parallel
if you want long life for your lamps.

Ok how the circuit work? Can you explain please

 

Where you go:
View attachment 330262
ADDED:

You drive me crazy...
You should not connect LEDs in parallel
if you want long life for your lamps.

ADDED MORE:

We already talked about this circuit:
https://forum.allaboutcircuits.com/...uit-and-how-to-resolve-it.201201/post-1914038

Your circuit is missing dequirement #2 post #1. When i get 0.5vdc or below light turn on and when above 0.5vdc lights turn off. Where is that??

 

Another version using a cmos 555 timer to turn ON and OFF the lights.

 

Requirement 1. I want a circuit that constant 3 vdc if I put my adapter at 12VDC or 6VDC then I also want the circuit to output constant 3VDC

You cannot those LEDs from a constant voltage of 3V. They require current limiting. So this requirement is specious.

Requirement 2. Turning lights off 0.5VDC or below and turning lights on 0.5VDC and above. Does anyone know how of good circuit I can build from transistor, resistor, diodes etc which can switch the led landscape light on at 0.5VDC or below and light of at 0.5VDC above?

I suppose you could build a comparator from discrete parts, but an IC is much simpler. So why this requirement?

 

You cannot those LEDs from a constant voltage of 3V. They require current limiting. So this requirement is specious.

I suppose you could build a comparator from discrete parts, but an IC is much simpler. So why this requirement?

Ok i got it current is important not voltage but why manufacturer say 3vdc if voltage is not important? Can you feed led post #1 with 12vdc and not burn it?

Also do you have circuit for comparator? Not into ics thats all

 

You can use a DC relay powered by the solar cell to switch the LED lights OFF when there is light. NO ELECTRONICS to deal with!
and YOU CAN PUT THE LED LIGHTS IN SERIES BECAUSE LED LIGHTS DO NOT "BLOW" as a failure mode unless you apply way too much voltage, resulting in way too much current.