Favorite reverse bias protection for battery circuits [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: Joerg on 16 Mar 2010 16:48

Charlie E. wrote:
> 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.
>

Ah yes, Stephen Hawking:

http://en.wikipedia.org/wiki/Stephen_Hawking

> 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...
>

Once a disabled person masters technology it can add so much to their
abilities.

Same with non-tech skills. A neighbor is deaf and he and his brothers
can "talk" from vehicle to vehicle without any technology, by signing.
It's amazing. But he also uses video phones etc.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: Joerg on 16 Mar 2010 17:32

D Yuniskis wrote:
> Hi Charlie,
>
> Charlie E. wrote:
>> On Tue, 16 Mar 2010 12:15:25 -0700, D Yuniskis
>> <not.going.to.be(a)seen.com> wrote:
>>
>>>> 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...
>
> I take it you aren't making a custom (molded) case?
> Why not purchase COTS battery holder that *is* "keyed"?
>

Anything other than AA cells is expensive. And as Charlie wrote AA cells
are difficult to key without going to precision molding or milling.

>> 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! ;-)
>
> If you go that route, consider how your design can tell the user
> "yes, I am working" vs. absence of that indication so the user
> can deduce "something is wrong with the batteries or their
> installation" (or the device)

Very easy: Oscillator that is connected via a diode so it works only
when batteries are reversed, drives piezo. Battery inserted the wrong
way -> beep ... beep ... beep ...

If you want to also cover the case where only one of the batteries is
reversed use two of those, can drive the same piezo.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: Joerg on 16 Mar 2010 17:33

Jim Thompson wrote:
> 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?
>

Why PMOS?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

From: D Yuniskis on 16 Mar 2010 18:28

Hi Joerg,

Joerg wrote:
> D Yuniskis wrote:
>>>> 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...
>>
>> I take it you aren't making a custom (molded) case?
>> Why not purchase COTS battery holder that *is* "keyed"?
>
> Anything other than AA cells is expensive. And as Charlie wrote AA cells
> are difficult to key without going to precision molding or milling.

Yes. Find a battery holder that someone *else* has incurred
the cost of that molding! Preferably, something that lets
the user access the "battery compartment" without having
to disassemble the device itself.

OTOH, if he is making "one off", a bit of plastic glued on either
side of the '+' holder terminal can do the trick.

I'd also look for those (camera?) batteries (two cells side
by side... 3V?) as I think that is keyed (at the very
least, it eliminates the problem of putting one cell in
correct and one backwards)

>>> 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! ;-)
>>
>> If you go that route, consider how your design can tell the user
>> "yes, I am working" vs. absence of that indication so the user
>> can deduce "something is wrong with the batteries or their
>> installation" (or the device)
>
> Very easy: Oscillator that is connected via a diode so it works only
> when batteries are reversed, drives piezo. Battery inserted the wrong
> way -> beep ... beep ... beep ...
>
> If you want to also cover the case where only one of the batteries is
> reversed use two of those, can drive the same piezo.

You don't need to be that extravagant. Just something in the
*normal* usage of the device that people can count on for
feedback/confirmation. E.g., if the device uses audio
output (synthetic speech or just "tones"), then design
the device so that immediately on turning on, it "chirps"
once.

[I don't recall what he has chosen for his output medium;
personally, I would opt for limited vocabulary speech as
it can be *very* small]

This gives a positive indication to the user in *normal*
operation (i.e., those times when you HAVEN'T just
changed batteries) that the device is, in fact, "on".
And, knowing to expect this, it can be used when replacing
batteries to act as a confirmation that the batteries
are, in fact, installed correctly, aren't "dead", etc.

From: Joerg on 16 Mar 2010 18:29

D Yuniskis wrote:
> Hi Joerg,
>
> Joerg wrote:
>> D Yuniskis wrote:
>>>>> 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...
>>>
>>> I take it you aren't making a custom (molded) case?
>>> Why not purchase COTS battery holder that *is* "keyed"?
>>
>> Anything other than AA cells is expensive. And as Charlie wrote AA
>> cells are difficult to key without going to precision molding or milling.
>
> Yes. Find a battery holder that someone *else* has incurred
> the cost of that molding! Preferably, something that lets
> the user access the "battery compartment" without having
> to disassemble the device itself.
>

Very tough. I had tried that at times in the past and there ain't much
out there. Even the ready-to-go enclosures with built-in compartment
that I came across aren't really good in that respect.

> OTOH, if he is making "one off", a bit of plastic glued on either
> side of the '+' holder terminal can do the trick.
>
> I'd also look for those (camera?) batteries (two cells side
> by side... 3V?) as I think that is keyed (at the very
> least, it eliminates the problem of putting one cell in
> correct and one backwards)
>

I have one, in case of a trip way into the boonies (those are Li
batteries so they'll last longer). Very expensive, not really an option
for everyday use.

>>>> 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! ;-)
>>>
>>> If you go that route, consider how your design can tell the user
>>> "yes, I am working" vs. absence of that indication so the user
>>> can deduce "something is wrong with the batteries or their
>>> installation" (or the device)
>>
>> Very easy: Oscillator that is connected via a diode so it works only
>> when batteries are reversed, drives piezo. Battery inserted the wrong
>> way -> beep ... beep ... beep ...
>>
>> If you want to also cover the case where only one of the batteries is
>> reversed use two of those, can drive the same piezo.
>
> You don't need to be that extravagant. Just something in the
> *normal* usage of the device that people can count on for
> feedback/confirmation. E.g., if the device uses audio
> output (synthetic speech or just "tones"), then design
> the device so that immediately on turning on, it "chirps"
> once.
>
> [I don't recall what he has chosen for his output medium;
> personally, I would opt for limited vocabulary speech as
> it can be *very* small]
>
> This gives a positive indication to the user in *normal*
> operation (i.e., those times when you HAVEN'T just
> changed batteries) that the device is, in fact, "on".
> And, knowing to expect this, it can be used when replacing
> batteries to act as a confirmation that the batteries
> are, in fact, installed correctly, aren't "dead", etc.

Yes, that's usually good enough. No audio feedback -> something must be
wrong with the batteries.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.