Favorite reverse bias protection for battery circuits
in [Design]
|
Prev: ESD and surge Protection
Next: Investment Analysis and Portfolio Management Reilly 9th Edition complete Solution manual is available for purchase at affordable prices. Contact me at alltestbanks11[at]gmail.com to buy it today.
From: Jim Thompson on 16 Mar 2010 15:51 On Tue, 16 Mar 2010 12:43:08 -0700, Charlie E. <edmondson(a)ieee.org> wrote: >On Tue, 16 Mar 2010 12:15:25 -0700, D Yuniskis ><not.going.to.be(a)seen.com> wrote: > >>Hi Charlie, >> >>Charlie E. wrote: >>> Still working on my color reader, and getting close. Biggest problem >>> is that now I have almost TOO much drive on my LEDs, but that I can >>> deal with! >>> >>> Now, to the latest problem. My system is for the visually impaired. I >>> just put the batteries in one of my prototypes backwards, and it >>> didn't last very long. While I expect this device to have very long >>> battery life, since it normally doesn't operate but for a second or >>> two, it looks like the MC1253's don't like getting reversed biased >>> very long. So, for my design question of the day - What is your >>> favorite circuit for preventing reverse bias from the batteries? The >>> old diode trick drops too much voltage, so wondered if there are any >>> clever FET tricks to block backwards voltages. >> >>Solve this problem *mechanically*. You need to prevent the >>batteries from being *installed* wrong, in the first place. >>E.g., any sort of circuit that protects (the rest of) the >>circuit from reversed battery won't do anything to tell the >>VI user *why* your device isn't working. Are the batteries >>*dead*? Installed wrong? Corroded terminals? Or is the >>*device* broken?? >> >>"Key" the battery holder so the user can feel the correct >>orientation for the batteries *and* so it prevents the >>cells from making electrical contact if not oriented >>properly. >> >>Think of how the *user* is going to interact with your device. >>Close your eyes and "figure out" why it doesn't work :-/ > >Would be the best result, but these are standard AA cells, no way to >key them without using expensive custom battery packs. Not the way to >go for inexpensive... > >Will be looking for a good PMOS FET that will still conduct with two >low AA batteries, probably around 1.8VDC, if they make one! ;-) > >Thanks All! > >Charlie Called a PNP :-) What's the load current? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Hammy on 16 Mar 2010 16:17 On Tue, 16 Mar 2010 12:42:56 -0700, Joerg <invalid(a)invalid.invalid> wrote: >>> That renders the unit dead and a blind or almost blind person will have >>> a hard time finding or buying the proper fuse and installing it. >> Thats what they have seeing eye dogs for:-) Jokeing. >> > >Ok, I'll ask our new Labrador when she is back :-) > >She went through the first three phases of guide dog training and then >had to be discharged for a medical condition (soft trachea, happens a >lot with guide dog Labs). Are you a foster dad for pups? You must dread having to give them up? I just took my Golden Retriever to the vet. He started to develop a sunken eye. The vet doesn't know the cause yet. I'm hoping its nothing to serious. > >> Of course your right for a blind person either #3 or a keyed battery >> connection. With a brail instruction manual >> > >It's actually even better these days. A nearly blind relative has a >Casio watch that talks. That's nothing look at Hawkins chair that dude is wired for sound and then some. :-) >>> Charlie: Solution #3 is the ticket (look on Hammy's link). But make sure >>> that the FET is guaranteed to be fully turned on at the lowest allowed >>> battery voltage, IOW the point where an UVLO comes on.
From: Joerg on 16 Mar 2010 16:24 Hammy wrote: > On Tue, 16 Mar 2010 12:42:56 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > > >>>> That renders the unit dead and a blind or almost blind person will have >>>> a hard time finding or buying the proper fuse and installing it. >>> Thats what they have seeing eye dogs for:-) Jokeing. >>> >> Ok, I'll ask our new Labrador when she is back :-) >> >> She went through the first three phases of guide dog training and then >> had to be discharged for a medical condition (soft trachea, happens a >> lot with guide dog Labs). > > Are you a foster dad for pups? > You must dread having to give them up? > No, we are puppy sitters. So we jump in when a family goes on vacation or visits a sick relative where they can't take the guide dog puppy. Even then it's tough when they have to go back to San Rafael, especially for my wife since she sees them every week during trainings. But when you see them paired up with a blind person you know it's all worth it. We used to also sit the one that came home now. She instantly remembered our other dogs, where everything is in the house, etc. > I just took my Golden Retriever to the vet. He started to develop a > sunken eye. The vet doesn't know the cause yet. I'm hoping its nothing > to serious. Hopefully not. Our Rottweiler is now at an age where it's just a matter of time :-( >>> Of course your right for a blind person either #3 or a keyed battery >>> connection. With a brail instruction manual >>> >> It's actually even better these days. A nearly blind relative has a >> Casio watch that talks. > > That's nothing look at Hawkins chair that dude is wired for sound and > then some. :-) > No idea what a Hawkins chair is. <scratching_head> [...] -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Charlie E. on 16 Mar 2010 16:31 On Tue, 16 Mar 2010 13:24:00 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Hammy wrote: >> On Tue, 16 Mar 2010 12:42:56 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >> >>>>> That renders the unit dead and a blind or almost blind person will have >>>>> a hard time finding or buying the proper fuse and installing it. >>>> Thats what they have seeing eye dogs for:-) Jokeing. >>>> >>> Ok, I'll ask our new Labrador when she is back :-) >>> >>> She went through the first three phases of guide dog training and then >>> had to be discharged for a medical condition (soft trachea, happens a >>> lot with guide dog Labs). >> >> Are you a foster dad for pups? >> You must dread having to give them up? >> > >No, we are puppy sitters. So we jump in when a family goes on vacation >or visits a sick relative where they can't take the guide dog puppy. >Even then it's tough when they have to go back to San Rafael, especially >for my wife since she sees them every week during trainings. But when >you see them paired up with a blind person you know it's all worth it. > >We used to also sit the one that came home now. She instantly remembered >our other dogs, where everything is in the house, etc. > > >> I just took my Golden Retriever to the vet. He started to develop a >> sunken eye. The vet doesn't know the cause yet. I'm hoping its nothing >> to serious. > > >Hopefully not. Our Rottweiler is now at an age where it's just a matter >of time :-( > > >>>> Of course your right for a blind person either #3 or a keyed battery >>>> connection. With a brail instruction manual >>>> >>> It's actually even better these days. A nearly blind relative has a >>> Casio watch that talks. >> >> That's nothing look at Hawkins chair that dude is wired for sound and >> then some. :-) >> > >No idea what a Hawkins chair is. > ><scratching_head> > >[...] He's talking Stephen Hawkins (sp?) the physicist with MS. Well, my wife's computer talks to her, she has two watches that talk (one red, one blue) a talking calculator that includes a calendar and timer function, and another talking calculator that just does math... Charlie
From: Hammy on 16 Mar 2010 16:38
On Tue, 16 Mar 2010 13:24:00 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> I just took my Golden Retriever to the vet. He started to develop a >> sunken eye. The vet doesn't know the cause yet. I'm hoping its nothing >> to serious. > > >Hopefully not. Our Rottweiler is now at an age where it's just a matter >of time :-( Mine just turned 9. My last one was 11 when he died. > >>>> Of course your right for a blind person either #3 or a keyed battery >>>> connection. With a brail instruction manual >>>> >>> It's actually even better these days. A nearly blind relative has a >>> Casio watch that talks. >> >> That's nothing look at Hawkins chair that dude is wired for sound and >> then some. :-) >> > >No idea what a Hawkins chair is. > ><scratching_head> > >[...] He's that British theoretical physicist who came up with a theory for the origin of the universe among other things. http://en.wikipedia.org/wiki/Stephen_Hawking He has amyotrophic lateral sclerosis. So he uses a chair with all sorts of gadgets on it. |