[Solved] help me to get this circuit working. (Auto On-Off Solar Light Rechargeable)

Thread Starter

John O'C

Joined Mar 22, 2017
55
I wonder if anyone can help me to get this circuit working.

Auto On-Off Solar Light Rechargeable

I am attempting to learn electronics (72 years), and I thought this circuit which I saw on YouTube would be a suitable one for me to make.

Wrong.
Several problems, firstly there was no schematic attached so I have attempted to redraw it.
Next, several of the components mentioned I did not have.
The circuit specified in 18 K resistor, but the nearest I have is 20 K. So I substituted that.
The transistor specified is the BC 547 NPN, I had to substitute a 2N2222.
Also specified was a four volt LED strip which I don't have. (I do have a 12 V LED strip). So I substituted a blue single LED hoping that that would be okay to test the circuit.
And finally the solar panel specified was 6 V, I used a 5.5 V unit which was the nearest I had 150 mA.

I thought all my replacements might be close enough to get the circuit working, but no success.

I'm still hoping it's salvageable, with some help.

Thanks

DIY AUTO ON oFF SOLAR LIGHT (RECHARGRABLE).png
 
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Audioguru again

Joined Oct 21, 2019
1,588
Many videos on You Tube are made by little kids "over there" who know nothing about electronics. You Tube pays them for each hit on the ads.
1) The pins on a 2N2222 are the opposite to the pins on a BC547.
2) The 18k (your 20k) base resistor needs a positive voltage to turn in the transistor. Your transistor is always turned off because the resistor connects to 0V.
3) If the transistor is corrected to work, your blue LED might instantly burn out because it is missing a series current-limiting resistor.
4) If you want the LED to light when the solar panel is dark then you need a second transistor to do it.
 

ericgibbs

Joined Jan 29, 2010
10,195
hi John,
This is your circuit redrawn, it cannot work, the transistor is never On.

Update:
Please post the link to the YouTube video.
E
AAA 386 16.24.gif
 
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Thread Starter

John O'C

Joined Mar 22, 2017
55
Thanks for the prompt response

Many videos on You Tube are made by little kids "over there" who know nothing about electronics. You Tube pays them for each hit on the ads.
:)

1) The pins on a 2N2222 are the opposite to the pins on a BC547.
Yes, I actually knew that (looked it up), hopefully I have taken that into account.

2) The 18k (your 20k) base resistor needs a positive voltage to turn in the transistor. Your transistor is always turned off because the resistor connects to 0V.
Definately base to minus on YT (
)

3) If the transistor is corrected to work, your blue LED might instantly burn out because it is missing a series current-limiting resistor.
I will come back to that - just need to get it working firsto_O
4) If you want the LED to light when the solar panel is dark then you need a second transistor to do it.
Can you suggest how? (apologies, newbe here)
 

dl324

Joined Mar 30, 2015
10,956
I thought all my replacements might be close enough to get the circuit working, but no success.
The base emitter junction of the transistor can never be forward biased, so it won't turn on.

Since you're trying to learn, we prefer for the flow in a schematic to be primarily left to right and top to down. You've drawn your schematic "upside down".

I thought this circuit which I saw on YouTube would be a suitable one for me to make.
There's a lot of crap on YouTube posted by so called "experts".
 

Audioguru again

Joined Oct 21, 2019
1,588
I was almost correct. The video shows the wrinkled skin of an old man (not a kid) who says he is in India.

The video shows the negative of the battery is connected to the emitter of the transistor. Then I guess the solar panel conducts battery current to turn on the transistor when the solar panel has no light and is reverse-biased by the battery.
The LED needs a series current-limiting resistor.
 

Attachments

ericgibbs

Joined Jan 29, 2010
10,195
hi John,
This is a simulation.
Looks a simple circuit, the Solar PV charges the battery when the Sun is shining.
E
The top plot of the simulation shows the Vout of the Solar as the sunshine increases.
 

Attachments

Thread Starter

John O'C

Joined Mar 22, 2017
55
The base emitter junction of the transistor can never be forward biased, so it won't turn on.
So what alterations do I need to make?

Since you're trying to learn, we prefer for the flow in a schematic to be primarily left to right and top to down. You've drawn your schematic "upside down".
Noted. It took me nearly 2 hours to get to that point! (never tried to do schematic before)
 

ericgibbs

Joined Jan 29, 2010
10,195
hi John,
Are the Red and Black your 3.7V battery leads.??
If yes, then the Black wire is in the wrong place, should be other end of the diode.
E
 

Thread Starter

John O'C

Joined Mar 22, 2017
55
Eric, and it is now working.:cool:
Thank you, it feels great to have it working, I feel as though I have just invented penicillin.

Give yourself a pat on the back, or a glass of whiskey, whichever you feel is more appropriate.

But please don't leave me yet, as I have another related question.

What would I need to do to convert this to work with my 12 V LED strip?
 

ericgibbs

Joined Jan 29, 2010
10,195
hi John,
What battery voltage are you planning to use.?
If the LED strip is designed for 12V operation, it would mean a 12V battery and say a 17V Solar panel, unless you are considering a Boost converter.

Update: What is the current requirement of the 12V LED strip.?

E
 
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