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Topic: Sun Powered spotlights (Read 5564 times) previous topic - next topic

AntroxEv

May 18, 2020, 02:19 pm Last Edit: May 18, 2020, 02:21 pm by AntroxEv
Hello,
I have 3 out of 4 sunpowered spotlights that are not working anymore.
Usually this is due to the corrosion as you can see in the pics although these spotlights are sold for exteriour use.

I am trying to understand the schematics to reproduce it with a breadboard and then use it in a larger project with Arduino:

The red and yellow wires are the positive and negative poles of the solar pannel.
The white wire is the negative pole attached to the battery.
The positive wire of the battery that is now detached was soldered to the pcb where you can see a circle  with a + and it was in series with a latching pushbutton.
The LED wires were attached to S+ and S- in the pcb (maybe)
The resistor should be connected in series with the power and the anode of the LED.

Before drawing an attempt of sckematics, what I am missing is how the LED become powered when it is dark. It is like when the sun pannels are not providing any voltage, then the rechargable battery are powering the LED. It is like the flow of current change path if a voltage is provided or not.
Or am I missing a component?

Thanks




AntroxEv

#1
May 19, 2020, 03:11 pm Last Edit: May 19, 2020, 03:12 pm by AntroxEv
I have attempted this schematics below.
I imagined that the solar panel should have a voltage higher than the battery when it is lit by the sun.
Therfore, there are 2 circuits in parallel; one with resistance 2komh connect to the LED and one with low/nill resistance.
When the voltage of the solar panel is higher than the battery voltage, the current is flowing to the battery only due to the low resistance offer by the circuit while no enough current is flowing to the LED keeping it off.
When the voltage of the solar panel is either lower than the battery or zero, the solar panel can be assimilated to  a high resistor or a break in the circuit (?) and the current flows to the LED.
But my attempt seems wrong since with no battery I should have the LED lit during the day
Any ideas?
thanks


Paul_KD7HB

How much current will your LED draw from a 2 volt battery when it has to go through a 2k Ohm resistor?


Paul

AntroxEv

How much current will your LED draw from a 2 volt battery when it has to go through a 2k Ohm resistor?


Paul
Yes, nothing. But I am not sure why that resistor is there. Maybe I cannot see well the colours on the photo but it seems a 1k or 2k resistor.
The fact I am not sure what is the working principle of this spotlight.
How can it turn on when it is dark?






jremington

#4
May 19, 2020, 08:24 pm Last Edit: May 19, 2020, 08:32 pm by jremington
The blue green component is an inductor, not a resistor. The circuit is actually a step up voltage converter, as described here, with an IC under a black blob.

More about that chip here.

AntroxEv

The blue green component is an inductor, not a resistor. The circuit is actually a step up voltage converter, as described here, with an IC under a black blob.

More about that chip here.
Thanks for the links.
It was completely new to me.

The Joule thief theory is nice but I am now wondering if I can use the YX8018 to activate an auto power off circuit (practically replacing the physical push button) or to trigger a relay?


kionokitse

Hi AntroxEv,
Yes you can totally use the YX8018 to control when the light turns on. If the solar cell is providing no charge it is possible to detect this situation and turn on the LED. Here is a site that explains it fairly clearly.

https://ez.analog.com/adieducation/university-program/b/blogs/posts/hacking-an-led-solar-garden-light

AntroxEv

#7
May 26, 2020, 02:16 pm Last Edit: May 26, 2020, 02:17 pm by AntroxEv
Hi AntroxEv,
Yes you can totally use the YX8018 to control when the light turns on. If the solar cell is providing no charge it is possible to detect this situation and turn on the LED. Here is a site that explains it fairly clearly.

https://ez.analog.com/adieducation/university-program/b/blogs/posts/hacking-an-led-solar-garden-light
Hi kionokitse,
Yes, thanks for your message.
What I would like to do is to use the YX8018 to either:
1) as interrupt (falling mode) to wake up arduino when the solar cell is on/off by using the Joule thief circuit with inductor to boost the voltage to activate the arduino pin
2) to replace the physical pushbutton for an autopower off circuit such as:
here

In option 1 a RTC can do the job but  this system assures that the operation will be carrying out at the dusk that occurs every day at different time
In option 2, it is a way to save energy without using pro mini and removal of several components

kionokitse

Option 1 sounds really good but I have no experience with this so I couldn't comment on if it's possible. Option 1a would probably work really well. Since sunset changes every day, you could have a variable that increases by (x) min per day until the height of summer (y) number of hours then starts decreasing by (z) min per day. You could look up these variables by looking at the sunrise/sunset times for where you are living. 

jremington

#9
May 27, 2020, 03:48 am Last Edit: May 27, 2020, 03:51 am by jremington
Quote
1) as interrupt (falling mode) to wake up arduino when the solar cell is on/off
If the solar cell puts out > 2.5V with no load, just use a level interrupt. That works in all sleep modes, including power down.

You will probably need a resistor across the cell to set the light level that triggers the interrupt.

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