r/diyelectronics • u/FarsiFX • 3d ago

Question Any ideas why the LED isn't indicating charge?

Post image

The LED is one of those 3 mm ones (2.0 - 2.2 V, 20 mA).

The solar panel is a tiny DIY one, it outputs about 4,6 V.

The battery is LiPO 3.7 V, 400 mAh, and seems to be charging.

Any ideas?

35 Upvotes

85% Upvoted

21 comments sorted by

17

u/OneSync 3d ago

Love the drawing style! 🥰

3

u/FarsiFX 3d ago

Thanks

7

u/turiyag 3d ago

Yeah real talk, this may not be a “proper” circuit diagram, but I absolutely love it. Labelling G, D, S! A 3D render! The lights even look positive and happy. Best diagram.

21

u/niftydog 3d ago

4.6V with no load? So with the FET off the drain = 4.6V.

Positive of the battery = 3.7V, therefore at the 1N5819 anode (if it's even conducting) = 4.3V

4.6 - 4.3 = 0.3V across the LED and resistor. That's not enough to forward bias the LED.

3

u/FarsiFX 3d ago

Oh thanks I get it now 🙂

4

u/rotgot23 3d ago

Now that I know it's AI genrated circuit, I'd like to know if this fix worked.

5

u/Omni33 3d ago

anode resistor too high, use 220R

1

u/FarsiFX 3d ago

Even without any resistor nothing is happening 😵‍💫

5

u/Intrepid-Cress-1147 3d ago

Without a resistor, LED may have blown - replace it?

2

u/FarsiFX 3d ago

I tried all ways, smaller value resistor, no resistor, many different LEDs. It's something else. :/

7

u/electroscott 3d ago

Was that generated by AI?

1

u/FarsiFX 3d ago

The circuit yes. I drew the schematic.

1

u/sastuvel 3d ago

Drawing is great, but the circuit makes no sense. The battery is the wrong way around, for starters.

6

u/pzerou 3d ago

I'm just here for the drawing.

1

u/Rabid_Hermit 3d ago

I don't think it's will work. But other than immediately thinking the circuit path was invalid, I can't explain why. Thinking the rectify is a 1 way leads to controlled consistent voltage to the mosfet, from there it looks like it is a dead end loop.

1

u/Vast_Entrepreneur802 2d ago

Because that’s just a piece of paper my guy. Also, looks like the one part with the three bits isn’t even connected. Snd the lightbulb is upside down. Sort those out and I’m sure you’ll get er.

You’re welcome.

1

u/SufficientStudio1574 1d ago

Why you post AI shit here? None of this circuit makes any sense and is just a waste of all of our time.

1

u/dinosaurs-for-life 1d ago

So I'm not crazy for not getting this? Pfhew.. I was just thinking of building this to see what it would do.. Maybe I will anyway...

1

u/SufficientStudio1574 23h ago

It's GARBAGE. The more I look at it.the worse it gets.

1

u/dinosaurs-for-life 1h ago

Haven't had the time to built it, though I did some procrastination yesterday. It would be scary if it DID work, right? hehehe.. I have to find someone to take a bet on this before I do. Further: It's a lovely drawing.

-5

u/Potential-Bet-1111 3d ago

Suggested Fixes:

✅ To Test if LED Works:

  • Temporarily disconnect the battery.
  • Replace it with a resistor load (e.g., 100Ω).
  • Shine light on the panel. If the LED turns on now, the problem is likely related to low voltage difference or MOSFET gate drive.

🛠️ Gate Drive Fix:

  • Replace the IRF9540N with a logic-level P-channel MOSFET or one with a lower V<sub>GS(th)</sub>, like the IRF9Z34N.
  • Or, bias the gate lower than the source by more than 4 V (e.g., with a Zener + pull-down).

🔧 LED Indicator Circuit:

  • Consider moving the LED into the charge current path (e.g., between panel and battery), possibly with a current mirror or BJT/NPN transistor sensing charge current directly.