On Thursday, May 11, 2017 at 11:32:09 AM UTC-4, Tim Wescott wrote:> On Wed, 10 May 2017 18:13:26 -0400, rickman wrote: > > > On 5/10/2017 1:52 PM, Tim Wescott wrote: > >> On Wed, 10 May 2017 09:57:21 -0700, etpm wrote: > >> > >>> I have an automatic opening trash can in the kitchen that runs off of > >>> batteries. I wanna run it with a wall wart. When the lid opens it > >>> draws more power than the 750 mA wall wart I tried using to power it > >>> could deliver. This makes sense. I don't want to use a bigger wall > >>> wart and I don't want to have betteries in it all the time to provide > >>> the current. I'm thinking instead of using a capacitor. If the current > >>> and voltage draw as well as the duration to open the lid is measured > >>> can that not be used to calculate the minimum size capacitor? And if > >>> not excessive maybe a cap that would open the lid three or four times > >>> in a row could be used in place of the 6 AA cells it uses now. > >>> Reasonable? > >>> Thanks, > >>> Eric > >> > >> This is kind of a repeat of what Rick said, from a different point of > >> view: > >> > >> For the amount of energy stored, caps are BIG. And a capacitor's > >> voltage falls as it delivers energy -- by definition. If it doesn't, > >> it's not a capacitor. > >> > >> Rechargeable batteries are much smaller than caps -- and it's what the > >> thing's designed for anyway. The easiest thing to do, which should be > >> reliable, is to populate the battery tray with rechargable NiMH cells, > >> then put a charger on it that runs at a trickle rate (i.e., 50mA for > >> every 1000mAh of capacity). That _should_ let the batteries last a > >> good long time, but whether it'll stay charged is kind of up in the air > >> (or maybe it'll work fin normally but not on Thanksgiving or > >> Christmas). > >> > >> Make the charger from a wall-wart and a resistor. > >> > >> The only other way I can think of to make this work "better" is with a > >> smart charger -- and then you're messing with some pretty fancy > >> electronics to keep the batteries happy. So -- probably not a good > >> idea. > >> > >> Finally -- have you considered an old fashioned, works just fine, > >> _mechanical_ covered trash can? > > > > I think you have this pretty much backwards. A "smart" battery charger > > is the only real way to go if you want the batteries to last. The > > "trickle" charger may keep the batteries up given that most people don't > > use such a trash can for long periods, but once rechargeables are > > charged, they don't want more current unless they are lead acid. I > > didn't look it up, so do you know that NiMH will take a trickle charge > > without damage? I don't think I've heard of that. > > > > Proper charging electronics doesn't need to be hard to design or use. > > I know Eric from these groups, and I'm assuming that he doesn't want to > run out and design a PCB just for a trash can. > > Eric!! "Accidentally" start a greasy paper towel on fire and toss it in > the trash. Then instead of putting the lid down, freak out and put the > can on the porch where it won't burn down your house. > > Then get a decent freaking garbage can!!!+1 Grin, "Sorry honey, I was trying to fix it and it broke." Eric how much current voltage is it? I've got little Phihong wall warts that do 12V @1.25 A. George H.> > -- > www.wescottdesign.com
Is this scheme reasonable?
Started by ●May 10, 2017
Reply by ●May 11, 20172017-05-11
Reply by ●May 11, 20172017-05-11
On Wed, 10 May 2017 13:50:05 -0700, etpm@whidbey.com wrote:>On Wed, 10 May 2017 11:31:40 -0700, John Larkin ><jjlarkin@highland_snip_technology.com> wrote: > >>On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >> >>>I have an automatic opening trash can in the kitchen that runs off of >>>batteries. I wanna run it with a wall wart. When the lid opens it >>>draws more power than the 750 mA wall wart I tried using to power it >>>could deliver. This makes sense. I don't want to use a bigger wall >>>wart and I don't want to have betteries in it all the time to provide >>>the current. I'm thinking instead of using a capacitor. If the current >>>and voltage draw as well as the duration to open the lid is measured >>>can that not be used to calculate the minimum size capacitor? And if >>>not excessive maybe a cap that would open the lid three or four times >>>in a row could be used in place of the 6 AA cells it uses now. >>>Reasonable? >>>Thanks, >>>Eric >> >>A conventional cap, no. Maybe a super expensive supercap. >> >>I wouldn't want an electronic trash can. All that cheap, badly >>programmed microprocessor/LCD appliance junk will break in a couple of >>years, and be annoying meanwhile. >> >>*SIX* AA cells? How long do they last? >Thanks for the quick responses everyone. It looks like rechargeable >cells are really the best way to go. The regular cells last about 3 >months. I hate the garbage can. I hate throwing batteries in the >recycle bin. I hate the garbage can. It was advertised as motion >sensitive. It is not. It senses reflected IR, not motion. So if the >damn sensor is covered with IR reflective material the lid stays open. >Did you know that some clear plastic sheet reflects IR? Did I say I >hate the garbage can? Unfortunately for now it is the best solution. >Though a foot operated model is in the future right now it just won't >work. >Thanks Again, >EricWe have a nice kitchen trash can that opens when you step on a little pedal thing. Would someone there have a problem with the mechanical version? Wheelchair or something? For a serious engineering project, throw away the electronics and drive the lid motor yourself. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 11, 20172017-05-11
On Wed, 10 May 2017 18:42:05 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 05/10/2017 02:31 PM, John Larkin wrote: >> On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >> >>> I have an automatic opening trash can in the kitchen that runs off of >>> batteries. I wanna run it with a wall wart. When the lid opens it >>> draws more power than the 750 mA wall wart I tried using to power it >>> could deliver. This makes sense. I don't want to use a bigger wall >>> wart and I don't want to have betteries in it all the time to provide >>> the current. I'm thinking instead of using a capacitor. If the current >>> and voltage draw as well as the duration to open the lid is measured >>> can that not be used to calculate the minimum size capacitor? And if >>> not excessive maybe a cap that would open the lid three or four times >>> in a row could be used in place of the 6 AA cells it uses now. >>> Reasonable? >>> Thanks, >>> Eric >> >> A conventional cap, no. Maybe a super expensive supercap. >> >> I wouldn't want an electronic trash can. All that cheap, badly >> programmed microprocessor/LCD appliance junk will break in a couple of >> years, and be annoying meanwhile. >> >> *SIX* AA cells? How long do they last? >> >> > >A couple of supercaps in series might work fine. For instance, >SCMT22C505MRBA0 AVX CAPACITOR 5F 20% 5V 0.065ohms $5.23000 in onesies >from Digikey.That's pretty good. At 1 amp, they will droop 0.4 volts/second, which should get the thing open.> >Two of those in series, with a TL431 across each one (set for 4.8V or >so) to equalize the voltage, plus a charger with about a 50 mA current >limit ought to work, I should think.Or 5 volt zeners. Or maybe they will just equalize on their own.> >Cheers > >Phil Hobbs-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 11, 20172017-05-11
On 5/11/2017 3:49 PM, George Herold wrote: ...> Eric how much current voltage is it? I've got little Phihong wall warts > that do 12V @1.25 A. >...12V, 2A on eBay for less than $5. More than 2A also there.
Reply by ●May 12, 20172017-05-12
On 2017-05-12, Bob Engelhardt <BobEngelhardt@comcast.net> wrote:> On 5/11/2017 3:49 PM, George Herold wrote: > ... >> Eric how much current voltage is it? I've got little Phihong wall warts >> that do 12V @1.25 A. >>... > > 12V, 2A on eBay for less than $5. More than 2A also there.I've got some here. performance does not match the label, 250mA at 11V from a 120V supply 350 at 11V from a 240V supply. -- This email has not been checked by half-arsed antivirus software
Reply by ●May 12, 20172017-05-12
On 11/05/17 00:42, Phil Hobbs wrote:> On 05/10/2017 02:31 PM, John Larkin wrote: >> On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >> >>> I have an automatic opening trash can in the kitchen that runs off of >>> batteries. I wanna run it with a wall wart. When the lid opens it >>> draws more power than the 750 mA wall wart I tried using to power it >>> could deliver. This makes sense. I don't want to use a bigger wall >>> wart and I don't want to have betteries in it all the time to provide >>> the current. I'm thinking instead of using a capacitor. If the current >>> and voltage draw as well as the duration to open the lid is measured >>> can that not be used to calculate the minimum size capacitor? And if >>> not excessive maybe a cap that would open the lid three or four times >>> in a row could be used in place of the 6 AA cells it uses now. >>> Reasonable? >>> Thanks, >>> Eric >> >> A conventional cap, no. Maybe a super expensive supercap. >> >> I wouldn't want an electronic trash can. All that cheap, badly >> programmed microprocessor/LCD appliance junk will break in a couple of >> years, and be annoying meanwhile. >> >> *SIX* AA cells? How long do they last? >> >> > > A couple of supercaps in series might work fine. For instance, > SCMT22C505MRBA0 AVX CAPACITOR 5F 20% 5V 0.065ohms $5.23000 in onesies > from Digikey. > > Two of those in series, with a TL431 across each one (set for 4.8V or > so) to equalize the voltage, plus a charger with about a 50 mA current > limit ought to work, I should think. > > Cheers > > Phil Hobbs >Is there data on leakage or self-discharge of these beasts? The datasheet just says "low leakage current" and this could just mean anything... Pere
Reply by ●May 12, 20172017-05-12
On Fri, 12 May 2017 10:47:54 +0200, o pere o <me@somewhere.net> wrote:>On 11/05/17 00:42, Phil Hobbs wrote: >> On 05/10/2017 02:31 PM, John Larkin wrote: >>> On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >>> >>>> I have an automatic opening trash can in the kitchen that runs off of >>>> batteries. I wanna run it with a wall wart. When the lid opens it >>>> draws more power than the 750 mA wall wart I tried using to power it >>>> could deliver. This makes sense. I don't want to use a bigger wall >>>> wart and I don't want to have betteries in it all the time to provide >>>> the current. I'm thinking instead of using a capacitor. If the current >>>> and voltage draw as well as the duration to open the lid is measured >>>> can that not be used to calculate the minimum size capacitor? And if >>>> not excessive maybe a cap that would open the lid three or four times >>>> in a row could be used in place of the 6 AA cells it uses now. >>>> Reasonable? >>>> Thanks, >>>> Eric >>> >>> A conventional cap, no. Maybe a super expensive supercap. >>> >>> I wouldn't want an electronic trash can. All that cheap, badly >>> programmed microprocessor/LCD appliance junk will break in a couple of >>> years, and be annoying meanwhile. >>> >>> *SIX* AA cells? How long do they last? >>> >>> >> >> A couple of supercaps in series might work fine. For instance, >> SCMT22C505MRBA0 AVX CAPACITOR 5F 20% 5V 0.065ohms $5.23000 in onesies >> from Digikey. >> >> Two of those in series, with a TL431 across each one (set for 4.8V or >> so) to equalize the voltage, plus a charger with about a 50 mA current >> limit ought to work, I should think. >> >> Cheers >> >> Phil Hobbs >> > >Is there data on leakage or self-discharge of these beasts? The >datasheet just says "low leakage current" and this could just mean >anything... > >PereThe caps I'm using give the leakage at .16 ma. http://www.illinoiscapacitor.com/ic_search/super_products_detail.aspx?icpartnumber=700020
Reply by ●May 12, 20172017-05-12
On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote:>When the lid opens it >draws more power than the 750 mA wall wart I tried using to power it >could deliver.You can use both cap and battery/wart. Common enough trick we used servicing 8 tracks back in the day. The solenoids they used for ejecting the tape were designed to suck power from the car's 12V system fused at 30 amps... Bench power supplies couldn't always make it work so we wired in a 30,000 uf /25V cap across the output to the supply and it would work every time. A trick model rail road enthusiasts and others use to conserve power on solenoids, relays and actuators, is to wire a resistor in series with the coil to lower the average current then wire a cap across the resistor to deliver the high current to get it moving.
Reply by ●May 12, 20172017-05-12
On 05/12/2017 04:47 AM, o pere o wrote:> On 11/05/17 00:42, Phil Hobbs wrote: >> On 05/10/2017 02:31 PM, John Larkin wrote: >>> On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >>> >>>> I have an automatic opening trash can in the kitchen that runs off of >>>> batteries. I wanna run it with a wall wart. When the lid opens it >>>> draws more power than the 750 mA wall wart I tried using to power it >>>> could deliver. This makes sense. I don't want to use a bigger wall >>>> wart and I don't want to have betteries in it all the time to provide >>>> the current. I'm thinking instead of using a capacitor. If the current >>>> and voltage draw as well as the duration to open the lid is measured >>>> can that not be used to calculate the minimum size capacitor? And if >>>> not excessive maybe a cap that would open the lid three or four times >>>> in a row could be used in place of the 6 AA cells it uses now. >>>> Reasonable? >>>> Thanks, >>>> Eric >>> >>> A conventional cap, no. Maybe a super expensive supercap. >>> >>> I wouldn't want an electronic trash can. All that cheap, badly >>> programmed microprocessor/LCD appliance junk will break in a couple of >>> years, and be annoying meanwhile. >>> >>> *SIX* AA cells? How long do they last? >>> >>> >> >> A couple of supercaps in series might work fine. For instance, >> SCMT22C505MRBA0 AVX CAPACITOR 5F 20% 5V 0.065ohms $5.23000 in onesies >> from Digikey. >> >> Two of those in series, with a TL431 across each one (set for 4.8V or >> so) to equalize the voltage, plus a charger with about a 50 mA current >> limit ought to work, I should think. >> >> Cheers >> >> Phil Hobbs >> > > Is there data on leakage or self-discharge of these beasts? The > datasheet just says "low leakage current" and this could just mean > anything... > > PereWell, they wouldn't open the bin more than once or twice per charge, so I'd just leave it plugged in. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 13, 20172017-05-13
On Fri, 12 May 2017 06:47:01 -0400, default <default@defaulter.net> wrote:>On Fri, 12 May 2017 10:47:54 +0200, o pere o <me@somewhere.net> wrote: > >>On 11/05/17 00:42, Phil Hobbs wrote: >>> On 05/10/2017 02:31 PM, John Larkin wrote: >>>> On Wed, 10 May 2017 09:57:21 -0700, etpm@whidbey.com wrote: >>>> >>>>> I have an automatic opening trash can in the kitchen that runs off of >>>>> batteries. I wanna run it with a wall wart. When the lid opens it >>>>> draws more power than the 750 mA wall wart I tried using to power it >>>>> could deliver. This makes sense. I don't want to use a bigger wall >>>>> wart and I don't want to have betteries in it all the time to provide >>>>> the current. I'm thinking instead of using a capacitor. If the current >>>>> and voltage draw as well as the duration to open the lid is measured >>>>> can that not be used to calculate the minimum size capacitor? And if >>>>> not excessive maybe a cap that would open the lid three or four times >>>>> in a row could be used in place of the 6 AA cells it uses now. >>>>> Reasonable? >>>>> Thanks, >>>>> Eric >>>> >>>> A conventional cap, no. Maybe a super expensive supercap. >>>> >>>> I wouldn't want an electronic trash can. All that cheap, badly >>>> programmed microprocessor/LCD appliance junk will break in a couple of >>>> years, and be annoying meanwhile. >>>> >>>> *SIX* AA cells? How long do they last? >>>> >>>> >>> >>> A couple of supercaps in series might work fine. For instance, >>> SCMT22C505MRBA0 AVX CAPACITOR 5F 20% 5V 0.065ohms $5.23000 in onesies >>> from Digikey. >>> >>> Two of those in series, with a TL431 across each one (set for 4.8V or >>> so) to equalize the voltage, plus a charger with about a 50 mA current >>> limit ought to work, I should think. >>> >>> Cheers >>> >>> Phil Hobbs >>> >> >>Is there data on leakage or self-discharge of these beasts? The >>datasheet just says "low leakage current" and this could just mean >>anything... >> >>Pere > >The caps I'm using give the leakage at .16 ma. > >http://www.illinoiscapacitor.com/ic_search/super_products_detail.aspx?icpartnumber=70002050.625 watt hours???!!! -- John Larkin Highland Technology, Inc lunatic fringe electronics
