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SuperCap use — Parallax Forums

SuperCap use

steve_bsteve_b Posts: 1,563
edited 2006-10-26 19:20 in General Discussion
Stumbled on this "hack" for using a supercap to give 9volts for 3hours (small loads obviously) and only requires 20seconds to charge.

....might be some remote sensor uses...

handhelds.hackaday.com/2005/12/06/supercap-9v-battery/1

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Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Comments

  • Steve JoblinSteve Joblin Posts: 784
    edited 2006-10-23 17:28
    cool! is there a schematic? seems like a great power source to run simple sensors on a robot!
  • steve_bsteve_b Posts: 1,563
    edited 2006-10-23 19:15
    I'm sure there is, but I didn't see a direct link from that site!

    I'm sure it's not much more than the supercap as the battery source, then running a typical 9Vbattery circuit with some series current protection.

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    Steve

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-10-23 21:59
    The text states there is a switching voltage regulator to pump the 2.3V of the cap upto 9V.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
  • steve_bsteve_b Posts: 1,563
    edited 2006-10-24 12:58
    that would make sense....even in rail-to-rail regulators you need 1% more input than you want output (without buck/pump circuits).

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    Steve

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-10-24 16:08
    10F is huge. I have some 1F @5 or 6V that I was thinking of as temporary power for a BS2. They would only provide 20 seconds a power though -- nothing close to 3 hours.

    Seems like they are assuming an LED light source of some sort.· 3 hours still seems quite dubious for anything useful.

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    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 10/24/2006 4:18:14 PM GMT
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-10-24 17:51
    The capacitor can store 23 Coulombs. Assuming the regulator is 90% efficient and its capable of using all the charge of the capacitor (which it can't), it can deliver 5.29 Amp-seconds at 9V. For a discharge of 3 hours, thats a load of roughly 500 uA.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-10-25 09:52
    Well, one half a millamp for 3 hours is not much. [noparse][[/noparse]or 5ma for 3/10th of an hour = 18 minutes] The BS2 requires 2ma just for operation without output. And of course, the discharge is not a linear rate.

    Still, 10Farads is hefty and really begins to be useful as a backup for BS2's, the SXes, or the Propeller.

    The main problem I had was not the discharge, but the inrush from charging having potentially damaging effects. To a power suplly, it looks like a dead short. In the concept of a backup supply -- One must put a current limiting device on the charge side and blocking diodes to avoid having discharge seek a wrong path. The diode causes a volage drop, so you may either have to provide a voltage that is adequate for the regulators or you have to bypass the regulator. In some cases the regulator won't cause a low-voltage drop out, but the BS2 is set at 4.6volt shut down.

    I guess several could be used in series to up the voltage without a solidstate device. Seems like 3 would be enough as 9V has always been a wasteful alternative, but package of convience.

    My guess is you could get 20ma for a resonable window of time to get power back to the device.

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    "If you want more fiber, eat the package.· Not enough?· Eat the manual."········
    ···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • Tom WalkerTom Walker Posts: 509
    edited 2006-10-25 13:20
    Kramer,
    Also, don't discount the value of a device that can give your project a little extra to perform an "orderly shutdown". I could see something like this even being enough for the Stamp to signal or even "call" (cell phone, land line, packet radio, etc...) its "help me!" message before going into a low-power state...again with a reasonably orderly shutdown...

    hmmm...

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  • Tronic (Greece)Tronic (Greece) Posts: 130
    edited 2006-10-25 14:22
    The full·article can be found here for a cost of £ 1.00... because its from Elektor magazine...

    http://www.elektor-electronics.co.uk/Default.aspx?tabid=28&year=2003&month=-1&art=50470&PN=On&SearchText=


    ...BUT it can be found here also for free!!! jumpin.gif

    http://fussychild.net/2005/precollege_saturday/Spring06/10-2003%2520SuperCap%2520Battery.pdf

    Thanos



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    Post Edited (Tronic (Greece)) : 10/25/2006 2:27:32 PM GMT
  • MacGeek117MacGeek117 Posts: 747
    edited 2006-10-26 02:18
    There are 50F caps out there-they're made with AeroGel.
    RoboGeek

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  • Steve JoblinSteve Joblin Posts: 784
    edited 2006-10-26 19:06
    Yes, but at what cost! They are like $23.00 ... you could buy a lot of duracells for that price!
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-10-26 19:20
    All,

    This circuit is also commonly used with solar cells for battery recharging purposes.
    ...Could also be used with Peltier devices to thermally recharge batteries.

    You can also experiment with different coil ratio's to change the efficiency.

    Google "Hartley oscillator" or "Colpitts oscillator" as this is really the heart of this circuit.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
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