# Small, simple way to generate 500 Joules in 15 minutes

• PraAnan
In summary, you are looking for a small, fast, human powered generator that can generate 500 Joules in a span of 30 seconds.
PraAnan
Hey everyone,

I'm looking to build a simple generator that can either produce 500 Joules and then store it in a capacitor so it can be used up over 15 minutes or something that can generate the needed 500 Joules in the span of 15 minutes so you wouldn't need to store it. The thing that needs to be powered for 15 minutes is a 5V 100mA LED

I can't use solar or wind so was thinking of either using human power or gravity power but ruled the latter out because both the mass needed and the height will be too much. If it's human power the person will need to generate that in less than 30 seconds.

How would you do it?

Bicycle wheel driving a small DC motor to charge a large cap.

russ_watters
Competitive cyclists routinely generate hundreds of watts for hours at a time. It's pretty easy to generate 50 Watts on a bicycle. 50 Watts for 10 seconds is 500 J. So hook a generator up to a stationary bicycle and you're there. Can you elaborate on what you're trying to do? I assume you can't plug it into the wall. Note that 500J of electrical power is about 0.0001 kWh and costs much less than 1 cent.

russ_watters
phyzguy said:
Competitive cyclists routinely generate hundreds of watts for hours at a time. It's pretty easy to generate 50 Watts on a bicycle. 50 Watts for 10 seconds is 500 J. So hook a generator up to a stationary bicycle and you're there. Can you elaborate on what you're trying to do? I assume you can't plug it into the wall. Note that 500J of electrical power is about 0.0001 kWh and costs much less than 1 cent.

I'm trying to build a light (with a 5V 100mA LED) that can run for 15 minutes and can be recharged really quickly. I didn't want to use a cycle generator because I wanted the generator to be a little small.

Why don't you list ALL the attributes needed in the system and its construction, along with any material, costs, size, time, fit, form, feel, function restraints we should be aware of, so we don't keep picking at this thing?

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I don't know why you ruled out gravity light. Please don't hold back your requirements and make us guess. How small? How fast? What size?

anorlunda said:
I don't know why you ruled out gravity light. Please don't hold back your requirements and make us guess. How small? How fast? What size?

The problem with the gravity light for my case is that even a 20kg load over a height of 2m (which is already too heavy and too high) doesn't have enough energy to produce the 500J unless you 'reload' the mass.

For the size, something that can fit in a box that is 15cm x 15cm x 15cm. Cost to build should be under $50 and I guess the material / construction really depends on what the actual generator type will be right? PraAnan said: The problem with the gravity light for my case is that even a 20kg load over a height of 2m (which is already too heavy and too high) doesn't have enough energy to produce the 500J unless you 'reload' the mass. For the size, something that can fit in a box that is 15cm x 15cm x 15cm. Cost to build should be under$50 and I guess the material / construction really depends on what the actual generator type will be right?
Can it use fuel? What do you expect the ultimate energy source to be? It sounds like the only source that is acceptable to you is muscle power. I think a hand-cranked generator would fit in that size. 500J in 30 seconds is about 17W, and you can probably do this with a hand crank. Here's one you could buy that looks like it would meet your needs.

russ_watters
Another thing to think about. If you want to store 500J in a capacitor at 5V, E = CV^2/2 gives C = 40 Farads. This is a lot of capacitance, but I guess supercapacitors like https://www.mouser.com/Passive-Components/Capacitors/Supercapacitors-Ultracapacitors/_/N-5x76s?P=1ypvpvvZ1ykkebw&Keyword=190963940&FS=True&Ntk=P_MarCom could fill the bill.

You could make a primary battery, like a pair of Daniel Cells. Then use this to charge a lead acid battery.

PraAnan said:
I wanted the generator to be a little small.
Which part of the generation system are you calling the generator? The requirement seems pretty modest but you need to provide Fuel or Mechanical Effort input. If you are considering anything at all then the mechanism will take up some room. Without some details, we are working and thinking in the dark. With that approach, most of our suggestions and answers will be totally irrelevant.

I suggest that you look at electrically powered model aircraft for some ideas. Their Lion batters charge very fast and their systems have all been designed for you. The only difference is that they use a motor and you want to use a light.

Asymptotic
@PraAnan are you still there? Do any of these suggestions meet your needs?

The solution costs about \$10. and includes the generator, capacitor and LED.
Search ebay for 'wind up hand crank LED torch'

## 1. How can I generate 500 Joules in just 15 minutes?

There are several small and simple ways to generate 500 Joules in 15 minutes. One method is to use a hand-cranked generator, which converts mechanical energy from your hand into electrical energy. Another option is to use a battery-powered device, such as a portable power bank or a rechargeable battery, and charge it using a wall outlet or a solar panel.

## 2. Is it possible to generate 500 Joules without using any special equipment?

Yes, it is possible to generate 500 Joules without using any special equipment. One way to do this is by using a simple pulley system and a weight, such as a heavy book or a bag of sand. By lifting the weight and allowing it to fall, you can convert potential energy into kinetic energy, which can then be measured as Joules.

## 3. How long does it take to generate 500 Joules using a hand-cranked generator?

The time it takes to generate 500 Joules using a hand-cranked generator will depend on the efficiency of the generator and the speed at which you crank the handle. However, on average, it would take approximately 15-20 minutes to generate 500 Joules using a hand-cranked generator.

## 4. Can I use renewable energy sources to generate 500 Joules in 15 minutes?

Yes, you can use renewable energy sources, such as solar or wind power, to generate 500 Joules in 15 minutes. However, the amount of energy produced will depend on the size and efficiency of the renewable energy system you are using.

## 5. What can I power with 500 Joules?

The amount of power that 500 Joules can provide will vary depending on the device or appliance you are trying to power. For example, 500 Joules can power a small LED light for several hours, but it may only power a laptop for a few minutes. It is important to consider the energy requirements of the device you are trying to power before attempting to use 500 Joules.

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