anyone have good circuit for solar power garden light

[hhsting]

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

 

[Tony Stewart]

You will run into thermal losses and excessive temperature rise in your plan. I suggest you fix that by using a much lower voltage less than 5V with a current limiter and not CV.

 

[hhsting]

You will run into thermal losses and excessive temperature rise in your plan. I suggest you fix that by using a much lower voltage less than 5V with a current limiter and not CV.

I dont follow what you are saying. Voltages are less than 5v

 

[Tony Stewart]

https://www.amazon.ca/LIFKOME-Ediso...pcontext&ref_=fplfs&psc=1&smid=A2466VW74JWMT4

With a 3V LED 120 mA , at 25 'C you can use your adjustable 3V supply with an NPN switch for the current limit then use the PV with a resistor to turn off the base.

Your values will vary. https://tinyurl.com/2b7q4zdl

 

[hhsting]

https://www.amazon.ca/LIFKOME-Ediso...pcontext&ref_=fplfs&psc=1&smid=A2466VW74JWMT4

With a 3V LED 120 mA , at 25 'C you can use your adjustable 3V supply with an NPN switch for the current limit then use the PV with a resistor to turn off the base.

Your values will vary. https://tinyurl.com/2b7q4zdl

View attachment 146923

 

[hhsting]

I dont have adjustable 3V supply.

My 3V supply is constant and it is power source for the led lights.

I have second supply that varies from 0V to 1.5v. I want light to turn on when that adjustable supply is equal to or below 0.5V and turn off when above 0.5.

 

[Tony Stewart]

Well you can choose taps 3 , 4.5 and add series R to limit power dissipation. or just use 3V and no adjustment.

Then just use a transistor switch with suitable gain, threshold and current limit. or a comparator active low drive.

 

[hhsting]

Well you can choose taps 3 , 4.5 and add series R to limit power dissipation. or just use 3V and no adjustment.

Then just use a transistor switch with suitable gain, threshold and current limit. or a comparator active low drive.

I dont follow.

My adjustable voltage is from 0V to 1.5vdc which is coming from solar lanel.

My constant voltage is 3bdc which is coming from plug.

I want to turn lights off above 0.5vdc and on below 0.5vdc.

Can you show me circuit?

 

[Tony Stewart]

Some tolerances included

https://tinyurl.com/229aqd26

How precise must it be ? and what is source resistance at 500 mV?

 

[hhsting]

View attachment 146935
Some tolerances included

https://tinyurl.com/229aqd26

How precise must it be ? and what is source resistance at 500 mV?

How does this circuit work? Meaning in terms of microelectronics meaning getting values of resistor and what type of transistor you are using NPN but what model? Also where does the led light fit into all this?