Have an assortment of capacitors how to charge them - Page 1
Forum section: electronics / beginners

author: ENIAC
author_rank: Contributor
timestamp: January 11, 2015, 04:03:02 am
content: I have one of those big batteries that come with flashlights. I saw a video where someone placed three capacitors in parallel and then place it on the pos and neg terminal of the battery for 5 second then attached the capacitor leads to the side and bottom of a light bulb. He did not say what the capacitor microfarad was or the wattage of the light bulb although it was small. Hence, my question is what capacitor microfarad and light wattage can I use on a smaller scale. I bought a bag of assorted capacitor at Radioshack today and have a 4watt and 6watt light-bulb. What should I do from here?Thank you

author: mariush
author_rank: Super Contributor
timestamp: January 11, 2015, 05:51:58 am
content: Regular capacitors don't store enough energy to keep a regular lightbulb lit for more than a few seconds, maybe. You won't light up 4w or 6w bulbs with regular capacitors.With supercapacitors and high brightness leds, it's possible to light a led for hours if the supercapacitor is big enough. In 5 seconds though, the supercapacitor would probably charge from a battery just enough to keep a led on for a few minutes.The charging speed of a capacitor or a supercapacitor depends on the internal resistance of the battery, the (super)capacitors need time to charge due to this.

author: Evil Lurker
author_rank: Regular Contributor
timestamp: January 11, 2015, 10:43:28 pm
content: Quote from: mariush on January 11, 2015, 05:51:58 amAlso expanding on what he said, supercapacitors are typically low voltage devices, IIRC ~2.5V max rating. That is not enough voltage to overcome the drop of most LEDs so you will either need to rig them up in series or use some sort of boost converter. Also you will not be able to completely convert all of the energy stored in a supercapacitor as IIRC there is saturation voltage of the silicon switching transistors to take into consideration. On top of everything else, a super capacitor has such low internal resistance it essentially acts like a dead short when charging... the same also applies when discharging so it is theoretically possible to blow up your PSU unless there is some sort of current control. Likewise it is possible if you short the terminals of a supercapacitor you could catch something on fire.

author: ENIAC
author_rank: Contributor
timestamp: January 12, 2015, 02:59:39 am
content: What's this guy doing to get this effect at 0:28?Even if I could get a small light-bulb lit for a few seconds that would be pretty coolThanks for the educational and speedy replies!

author: mariush
author_rank: Super Contributor
timestamp: January 12, 2015, 03:16:24 am
content: In the video, he connects 3 1 Farad supercapacitor in series with a maximum voltage of 2.5v each, which creates one single 1 Farad capacitor capable of handling a maximum of 7.5 volts.This makes it possible to connect the supercapacitor directly to the 6v battery terminals and charge it without risking damage to each supercapacitor in the chain. As the supercapacitor was connected to the leads, it quickly charged up probably to about 4-5v because the large battery was capable of pumping so much energy very fast (a regular AA battery may not be able to charge so fast) and then you see the bulb light up. You however did not see what would have happened after another few seconds. you would have seen bulb going orange and then not light up at all, because the supercapacitors discharge fast.Now note that he used 1 Farad capacitors ... what you bought from radioshack are regular capacitors. The capacity for these regular capacitors is measured in microfarads (uF) and a capacitor of same size like the ones in the picture would have less than 1000 uF ...Basically 1 Farad is 1,000,000 uF so understand how much more energy goes into those supercapacitors compared to the energy in regular capacitors.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: January 12, 2015, 03:41:14 am
content: Quote from: mariush on January 12, 2015, 03:16:24 amOne correction: Three 1 Farad capacitors in series is equivalent to a .33 farad capacitor.

author: ENIAC
author_rank: Contributor
timestamp: January 12, 2015, 06:08:03 am
content: In the video is the 1 farad super-capacitor like those hard to come by? where would I find/buy them? Id' really like to preform this type of experiment.

author: mariush
author_rank: Super Contributor
timestamp: January 12, 2015, 12:28:07 pm
content: Excavatoree is correct, when connected in series the total capacitance is1 / Ctotal = 1 / C1 + 1 / C2 + 1/C3So for 3 x 1F capacitors , total capacitance would be 0.33 FaradsAs for where to buy them from, lots of good electronic stores.In US, see digikey.com , mouser.com , newark.com ... in other places see farnell.com or tme.eu or see ebay

author: Skimask
author_rank: Super Contributor
timestamp: January 12, 2015, 01:20:28 pm
content: Quote from: ENIAC on January 12, 2015, 06:08:03 amhttp://lmgtfy.com/?q=1+fara+super+capacitor

author: lapm
author_rank: Frequent Contributor
timestamp: January 12, 2015, 03:40:21 pm
content: Quote from: mariush on January 11, 2015, 05:51:58 amI used to make small led lights like this. 5mm ultrabright led and supercap to keep its powered..

author: ENIAC
author_rank: Contributor
timestamp: January 12, 2015, 04:22:48 pm
content: So I could wire three of these 1.0F caps together in parallel and it would keep a charge for around 5 seconds?Here is what I am considering buying:https://www.sparkfun.com/products/10068Or this one comes with 4PCS is 1.0F but 2.7V is the voltage too much?http://www.ebay.com/itm/4PCS-1F-2-7V-KAMCAP-Farad-Super-Capacitor-Ultra-Capacitor-High-Power-EDLC-/351030159432?pt=LH_DefaultDomain_0&hash=item51bb072848Thanks for the input guize

author: katzohki
author_rank: Frequent Contributor
timestamp: January 12, 2015, 05:09:06 pm
content: So it seems like you are learning electronics, right? I don't think repeating the experiment is going to tell you anything new, I think what you need to do is work on understanding and learning more about how capacitors work.

author: mariush
author_rank: Super Contributor
timestamp: January 12, 2015, 05:13:03 pm
content: If you connect the capacitors in parallel, the voltage rating remains the same but the amount of energy adds up. So 3 x 1F capacitors = 3 F , 2.5v max.If you connect the capacitors in series ( + lead goes to - of next capacitor) , voltage rating increases but capacitance drops .. so 2 x 1f 2.5v capacitors = 0.5F , 5v ,,, 3x1f 2.5v = 0.33F 7.5vIf you fully charge the capacitors with energy, as soon as the bulb is connected the voltage drops - think of it like a glass of water and the lightbulb makes water pour out. As soon as the voltage goes down a particular level, your bulb won't light up anymore. Supercapacitors don't behave like batteries which keep the voltage between a particular range (1.1 - 1.35v for a rechargeable AA battery for example) until they can't give energy anymore.Use proper stores, skip ebay and forget about Sparkfun because they're expensive.Have a look for example at Digikey:http://www.digikey.com/product-search/en?FV=fff40002%2Cfff8000c&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&quantity=2&ptm=0&fid=0&pageSize=25I forced the quantity to 2 pcs so that you won't see products with minimum orders of 100 pcs or something like that - you can order 1 or as many as you want, but the prices shown are for 2Ignore the capacitors that look like coin cells (the batteries that go in watches or on pc motherboards), they're designed for things that use very little power but have to run 24/7, like a clock for example.A better experiment for you would be to buy a few resistors and maybe a couple of leds as well .. for example get some red and green leds, because those can operate starting from about 1.7v.negative -[ capacitor ] - positive ----> resistor -----> positive -[ led ]- negative ----> to capacitor negative wire.If you want, put two supercapacitors in series just to make it easier for you to charge them, without worrying about damaging them. Two in series will handle 5v maximum, so you could use 2 AA batteries in series to charge the capacitors to about 2.5-3v.So you can charge a supercapacitor with energy and connect a led to it but with a resistor in series with the led to limit the amount of current going into the led because otherwise the led will take as much energy as its available and would burn up.If you use a high value resistor like let's say 1000 ohm, little current will go through the led so it will not light up very bright but the energy from supercapacitor will discharge much slower, so the voltage will go down from 2.5-3v slowly down below 1.7v-1.9v, at which point the led will stop working at all.If you use a lower value resistor, like let's say 100 ohm, the led will be very bright but it will stay lit for way smaller time.You can find resistors and leds on the same site, so you could add them to basket and buy all at onceresistors :http://www.digikey.com/product-search/en?FV=fff40001%2Cfff80482%2C142c0685%2C142c0bf1&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&quantity=2&ptm=0&fid=0&pageSize=25leds :http://www.digikey.com/product-search/en?FV=fff40008%2Cfff801b9%2C1140050%2C114016f%2C11402b2%2C1140343&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&quantity=2&ptm=0&fid=0&pageSize=25

author: ENIAC
author_rank: Contributor
timestamp: January 12, 2015, 06:49:27 pm
content: Mariush thank you sooooo muchyour tips and advice are helpful beyond words! I will take your advice and build something smaller first and work my way up from there!