CHECK OUT OUR SUPER CAPACITOR FLASHLIGHT KICKSTARTER CAMPAIGN:
I recently wrote an instructable on how to make a super capacitor flashlight, but I made it too complicated, and it employed a microcontroller, which many people don't have the means to program. So this one only employs a power supply, a dollar store flashlight, two super capacitors, a switch and a current limiting resistor. I designed this so that my girlfriend (Who has no electronics background) could put it together, which she did. This is her super capacitor flash light based on my design. If you want to modify this design, you only need to follow the very basic arithmetic that I'll be providing. Otherwise, all you need are the parts listed in the parts section (All of which can be found on ebay). See the final product of this very basic flashlight below, then follow on to the circuit theory. Because we're using super capacitors, THIS FLASHLIGHT CAN BE CHARGED 100,000s OF TIMES!
If you like this instructable, please don't be shy! Comment and rate it! This super capacitor flashlight will last for 100,000s of charges, which makes it SO COOL! Below is a video of the final product.
For those of you who are interested, the below video is the final product from my more complicated super capacitor flashlight. I have an instructable for this, so check out my profile if you're interested. It can be found here: https://www.instructables.com/id/The-Super-Capacitor-Flashlight-with-Custom-Charger/
Step 1: Parts List + Tools Required + Notes
1) 2x 50 farad 2.7v super capacitors (Found on ebay for very reasonable prices. Less than $10)
2) 1x Switch. It needs to be a switch capable of supporting more than 2.5A at 5v. You can also consider using the default switch circuitry of your dollar store flash light. Switches can be found on ebay for pennies.
3) 1x 2.5 Ohm 10W power resistor (Found on ebay for a couple of bucks)
4) 1x 5v 3A wall transformer. (Found on ebay for a couple of bucks)
5) 1x dollar store LED flashlight (Found at any dollar store for a buck or two) The bigger the flashlight, the better. It makes for easier placement of the components.
Here is a list of the tools that I used:
1) Soldering Iron
2) Lead Solder (Tin/Silver will work just as well)
3) A Hand Drill
4) A Hot Glue Gun
1) Make sure that the flashlight housing is large enough to fit all of your parts, or you're going to have trouble.
2) DO NOT BUY a bulb flashlight. They consume too much current. Look for a white LED flashlight. It will last much longer each charge.
Step 2: The Circuit
The positive lead of the 5v power supply is connected through a terminal block (Or a DC Jack if you have one) to one side of the 2.5 Ohm 10W power resistor. The terminal block or jack is used so that you can connect and disconnect the wall transformer at any time. The resistor is used to limit the current from the power supply to the capacitors. Without this, you may very well harm your power supply. When charging, this resistor will get hot, but it won't take long to charge your capacitor flashlight using this value, so you're not going to have to worry too much. However, when mounting this resistor in the flashlight, try to keep it insulated from the flashlight plastic.
On the other side of the resistor, you'll see that I have placed two series super capacitors on the line. These capacitors will charge to 5v when the power supply is plugged in. Make sure that you place them in the right way. If you reverse your super capacitors, they will be severely damaged when charging. If you want, you can use a large value of resistor, such as a 5 Ohm 5 Watt resistor, 10 Ohm 2.5 Watt resistor, or a 20 Ohm 1.25 Watt resistor.
In this case, I wanted to charge my capacitor bank very quickly. Since the power supply can handle 5 volts at 3 Amperes of current, I want to charge my capacitors at 2..5 amperes. Ohm's law came into play when I did the design calculations. Follow below.
Charge Voltage = 5V
Charge Current = 2.5A
Resistance = Voltage divided by Current (5V / 2.5A) = 2.5 Ohms
Now, we need to determine the power rating for our resistor
Power = Voltage multiplied by Current (5V x 2.5A = 10 Watts)
Therefore, if we want to charge our bank at 2.5A at 5V, we need a 2.5 Ohm 10 Watt current limiting resistor.
The switch is used to connect power that is stored on the super caps to the LED flashlight module that you've taken out of your dollar store flashlight. This can be turned on during charging, and can be turned on after the charge has been disconnected.
When the switch is off, no power reaches the LED flashlight, and the power on the capacitors will remain stored.
Step 3: Assembly Notes
1) I soldered the circuit together. I then made sure to add long wires in between each component so that placing each component into the flashlight would be easy. I also made sure that the wires from the jack to the resistor, and from the resistor to the capacitors was thick and well insulated. This is because the wires will be hot termporarily during charge.
2) I utilized the on board switch on the flash light to apply/disconnect power from the capacitors to the LED flash light head.
3) I glued the DC back in the battery bank section, so that I could remove the battery cover and plug in my transformer. It just makes the device look more professional.
4) I glued the capacitors together length wise, and placed them in the shaft of the flashlight. I then added some glue in the shaft to secure them in place.
5) I placed my resistor at the top of the shaft.
7) I put the flash light back together.
Then, we both had a beer to celebrate this new fast-charging super capacitor flash light!
Step 4: Considerations
If you're looking for someone to vote for in the instructables MAKE IT GLOW challenge contest, or the MAD SCIENCE FAIR Contest, please consider my instructable =)
If you're interested in super capacitors, see my practical guide to super capacitors here:https://www.instructables.com/id/Lets-learn-about-Super-Capacitors-A-Practical-G/