Lighting up a 5mm LED using a homemade battery

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Discussion Overview

The discussion revolves around a mini project involving the creation of a homemade battery to power a 5mm LED. Participants explore the effectiveness of different materials and configurations for the battery, as well as the relationship between voltage, current, and LED brightness.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes their attempt to create a coin battery using cardboard, vinegar, aluminum foil, and a coin, achieving a voltage of 6V but only 23 microamps of current.
  • Another participant suggests that the LED might emit a faint glow in darkness and proposes using larger coins or metal sheets to increase the surface area for electrochemistry.
  • There is a suggestion to use a low-power flasher circuit to intermittently drive the LED, potentially allowing it to light up more effectively.
  • After some experimentation, one participant reports that the LED lights up dimly but questions why 5V isn't sufficient for brightness.
  • Several participants discuss the importance of measuring the voltage across the LED when connected to the battery, noting that the unloaded voltage does not reflect the effective voltage when under load.
  • There is a debate about the required voltage for the LED to glow brightly, with suggestions that it should be between 3V and 4V.
  • Participants emphasize that increasing the current is crucial for brightness, and that more metal surface area in the battery could help achieve this.
  • One participant inquires about the effectiveness of stacking coins versus using a different configuration with copper wire and saltwater-soaked tissue, with responses indicating that experimentation is necessary to determine the best approach.

Areas of Agreement / Disagreement

Participants express varying opinions on the relationship between voltage and current in powering the LED, with no clear consensus on the best method to increase brightness or the optimal configuration for the homemade battery.

Contextual Notes

Participants note that the effectiveness of the battery may depend on various factors, including the surface area of the metals used and the specific configurations attempted. There are unresolved questions regarding the precise voltage and current requirements for optimal LED performance.

Joel Kee
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Homework Statement


I'm currently doing a mini project as an assignment in my engineering course. I tried replicating the coin battery, where I stack a piece of cardboard soaked in black vinegar (couldn't find white vinegar), a piece of aluminium foil, then a 20 sen
coin (Malaysian, cupronickel), and continue. I managed to get a stable reading of 6V. However, my 5mm LED did not light up when I tried connecting it. So, I tested the coin battery using the link multimeter and found out that it only produced 23microA. How do I increase the current? Or is that not the problem?

Homework Equations

The Attempt at a Solution

 
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Hi Joel Kee. :welcome:

If you look at the LED at night with the room in darkness you may discover that it is giving a faint glow.

But I see two ways you could go from here. You could try bigger coins or metal sheets, so there'd be larger areas for the electrochemistry to work with. This is equivalent to connecting multiple batteries in parallel.

Or, you could use what you have and drive a low-power flasher, an electronic circuit where a capacitor is slowly charged (over some seconds) by your micropower battery, then its accumulated charge gets dumped through the LED for a brief time, and the charging cycle repeats.
 
NascentOxygen said:
Hi Joel Kee. :welcome:

If you look at the LED at night with the room in darkness you may discover that it is giving a faint glow.

But I see two ways you could go from here. You could try bigger coins or metal sheets, so there'd be larger areas for the electrochemistry to work with. This is equivalent to connecting multiple batteries in parallel.

Or, you could use what you have and drive a low-power flasher, an electronic circuit where a capacitor is slowly charged (over some seconds) by your micropower battery, then its accumulated charge gets dumped through the LED for a brief time, and the charging cycle repeats.

Thanks for the reply! I have almost lost faith in this project, so thanks for replying. I tried using a buzzer with this coin battery, yet no sound is produced. I shall try the LED in a dark room though. Any other advice?
 
UPDATE :
The LED lights up! But it's really dim. Any idea how to make it brighter other than add more coins?

P/s I still don't get why 5v isn't enough to make this LED light up brightly.
 
It's not the unloaded voltage of your battery that is important. If you measure the voltage across the LED when it is connected to the battery you will see that the voltage is nothing like a few volts.

There may be tiny lower-power more-efficient LEDs available.
 
Can you explain more on why? And why does a normal battery make it light up so bright then?
 
NascentOxygen said:
It's not the unloaded voltage of your battery that is important. If you measure the voltage across the LED when it is connected to the battery you will see that the voltage is nothing like a few volts.

And how much voltage do you think I need to make it bright?
 
Joel Kee said:
And how much voltage do you think I need to make it bright?
Across the LED itself when glowing brightly, between 3V and 4V.
 
NascentOxygen said:
Across the LED itself when glowing brightly, between 3V and 4V.
Care to explain why the voltage of the battery doesn't really matter?
 
  • #10
The battery voltage does matter. While powering the LED the battery voltage must of necessity be at least what the LED requires.
 
  • #11
NascentOxygen said:
The battery voltage does matter. While powering the LED the battery voltage must of necessity be at least what the LED requires.
Any idea how much voltage should my battery be in order for the LED to be about 3-4V?
 
  • #12
Joel Kee said:
Any idea how much voltage should my battery be in order for the LED to be about 3-4V?
A battery of that voltage will work. With it connected directly to the LED then the battery voltage becomes the LED voltage.

It's not more volts that is required of your homemade battery; what is needed is more current. The only way for your voltaic pile to supply more current is to provide it with more metal surface for its chemistry to work with.
 
  • #13
NascentOxygen said:
A battery of that voltage will work. With it connected directly to the LED then the battery voltage becomes the LED voltage.

It's not more volts that is required of your homemade battery; what is needed is more current. The only way for your voltaic pile to supply more current is to provide it with more metal surface for its chemistry to work with.
Will having multiple coins on one flat surface, piled on another set of coins on another flat surface on it, work?
 
  • #14
Joel Kee said:
Will having multiple coins on one flat surface, piled on another set of coins on another flat surface on it, work?
You could try that. It will be an improvement.
 
  • #15
NascentOxygen said:
You could try that. It will be an improvement.
Do you think that would work better, or wrapping copper wire with aluminium and salt water soaked tissue together, joined in series?
 
  • #16
You have to try these to find out. It's not as straight-forward as you'd like.
 
  • #17
NascentOxygen said:
You have to try these to find out. It's not as straight-forward as you'd like.
Alright! Any other advice?
 
  • #18
Joel Kee said:
Alright! Any other advice?
Yes, after experimenting come back and tell us the results.
 

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