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Simple Low Voltage Shut Down

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  Simple Low Voltage Shut Down Robert Miller <robert.miller@teledyne.com> - 2017-03-30 18:21 +1100
    Re: Simple Low Voltage Shut Down Winfield Hill <hill@rowland.harvard.edu> - 2017-03-30 05:13 -0700
      Re: Simple Low Voltage Shut Down Winfield Hill <hill@rowland.harvard.edu> - 2017-03-30 10:20 -0700
        Re: Simple Low Voltage Shut Down Tim Wescott <seemywebsite@myfooter.really> - 2017-03-30 14:39 -0500
      Re: Simple Low Voltage Shut Down Robert Miller <robert.miller@teledyne.com> - 2017-04-01 07:42 +1100
        Re: Simple Low Voltage Shut Down rickman <gnuarm@gmail.com> - 2017-03-31 18:03 -0400
          Re: Simple Low Voltage Shut Down Robert Miller <robert.miller@teledyne.com> - 2017-04-01 10:35 +1100
            Re: Simple Low Voltage Shut Down rickman <gnuarm@gmail.com> - 2017-03-31 19:49 -0400
        Re: Simple Low Voltage Shut Down Winfield Hill <hill@rowland.harvard.edu> - 2017-03-31 17:56 -0700
          Re: Simple Low Voltage Shut Down Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-04-01 11:17 -0400
    Re: Simple Low Voltage Shut Down John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-30 07:14 -0700
    Re: Simple Low Voltage Shut Down Tim Wescott <tim@seemywebsite.com> - 2017-03-30 12:19 -0500
      Re: Simple Low Voltage Shut Down Winfield Hill <hill@rowland.harvard.edu> - 2017-03-30 13:18 -0700
        Re: Simple Low Voltage Shut Down Tim Wescott <seemywebsite@myfooter.really> - 2017-03-30 15:52 -0500
          Re: Simple Low Voltage Shut Down Winfield Hill <hill@rowland.harvard.edu> - 2017-03-30 14:31 -0700
            Re: Simple Low Voltage Shut Down mike <ham789@netzero.net> - 2017-03-30 15:02 -0700

#454211 — Simple Low Voltage Shut Down

I have a little circuit consisting of an LM358 and BC547 emitter 
follower. It runs off 4 x AAA alkaline batteries and consumes about 50mA.

What is the simplest way, without consuming additional power, of 
disabling the output from the LM358 when the battery voltage drops below 
around 4V?

In other words, I would like to have the circuit deactivate itself 
before a distorted wave form is output.

Prefer all passive components.

Robert Miller

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#454219

Robert Miller wrote...
>
> I have a little circuit consisting of an LM358 and
> BC547 emitter follower. It runs off 4 x AAA alkaline
> batteries and consumes about 50mA.
>
> What is the simplest way, without consuming additional
> power, of disabling the output from the LM358 when
> the battery voltage drops below around 4V?

.
. --+-----E   C----
.   |       B
.  6.2k     |  ZTX718
.   |      470
.   |       |
.   |       K
.   +-----R    TL431
.   |       A  $0.40
.  10k      |
.   |       |
. --+-------+------


-- 
 Thanks,
    - Win

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#454248

Winfield Hill wrote...
>
>Robert Miller wrote...
>>
>> I have a little circuit consisting of an LM358 and
>> BC547 emitter follower. It runs off 4 x AAA alkaline
>> batteries and consumes about 50mA.
>>
>> What is the simplest way, without consuming additional
>> power, of disabling the output from the LM358 when
>> the battery voltage drops below around 4V?
>
>.
>. --+-----E   C----
>.   |       B
>.  6.2k     |  ZTX718
>.   |      470
>.   |       |
>.   |       K
>.   +-----R    TL431
>.   |       A  $0.40
>.  10k      |
>.   |       |
>. --+-------+------

 A little hysteresis would be good.

.   4.0-volt low-V shutoff.
.             
.              ZTX718
. --+-----E   C-----+----
.   |       B       |
.  6.8k     |      120k
.   |      470    5% hyst
.   |       |       |
.   +------ | -|<|--'
.   |       K
.   +-----R    TL431
.   |       A  $0.40
.  10k      |
.   |       |
. --+-------+------

 Omit the diode, if a little OFF leakage
 from 127k of resistance can be tolerated.


-- 
 Thanks,
    - Win

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#454262

On Thu, 30 Mar 2017 10:20:54 -0700, Winfield Hill wrote:

> Winfield Hill wrote...
>>
>>Robert Miller wrote...
>>>
>>> I have a little circuit consisting of an LM358 and BC547 emitter
>>> follower. It runs off 4 x AAA alkaline batteries and consumes about
>>> 50mA.
>>>
>>> What is the simplest way, without consuming additional power, of
>>> disabling the output from the LM358 when the battery voltage drops
>>> below around 4V?
>>
>>.
>>. --+-----E   C----
>>.   |       B .  6.2k     |  ZTX718 .   |      470 .   |       |
>>.   |       K .   +-----R    TL431 .   |       A  $0.40 .  10k      |
>>.   |       |
>>. --+-------+------
> 
>  A little hysteresis would be good.
> 
> .   4.0-volt low-V shutoff.
> .
> .              ZTX718 . --+-----E   C-----+---- .   |       B       |
> .  6.8k     |      120k .   |      470    5% hyst .   |       |       |
> .   +------ | -|<|--'
> .   |       K .   +-----R    TL431 .   |       A  $0.40 .  10k      |
> .   |       |
> . --+-------+------
> 
>  Omit the diode, if a little OFF leakage from 127k of resistance can be
>  tolerated.

Hysteresis will just make the thing oscillate slower, at least if you're 
turning the battery off all the way.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

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#454471

On 30/03/17 23:13, Winfield Hill wrote:
> Robert Miller wrote...
>>
>> I have a little circuit consisting of an LM358 and
>> BC547 emitter follower. It runs off 4 x AAA alkaline
>> batteries and consumes about 50mA.
>>
>> What is the simplest way, without consuming additional
>> power, of disabling the output from the LM358 when
>> the battery voltage drops below around 4V?
>
> .
> . --+-----E   C----
> .   |       B
> .  6.2k     |  ZTX718
> .   |      470
> .   |       |
> .   |       K
> .   +-----R    TL431
> .   |       A  $0.40
> .  10k      |
> .   |       |
> . --+-------+------
>
>

That's a neat little circuit, but I was hoping for something passive.

Maybe a dumb question, but, given the low current, would it be possible 
to power the amp through a zener diode?

Robert Miller

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#454489

On 3/31/2017 4:42 PM, Robert Miller wrote:
> On 30/03/17 23:13, Winfield Hill wrote:
>> Robert Miller wrote...
>>>
>>> I have a little circuit consisting of an LM358 and
>>> BC547 emitter follower. It runs off 4 x AAA alkaline
>>> batteries and consumes about 50mA.
>>>
>>> What is the simplest way, without consuming additional
>>> power, of disabling the output from the LM358 when
>>> the battery voltage drops below around 4V?
>>
>> .
>> . --+-----E   C----
>> .   |       B
>> .  6.2k     |  ZTX718
>> .   |      470
>> .   |       |
>> .   |       K
>> .   +-----R    TL431
>> .   |       A  $0.40
>> .  10k      |
>> .   |       |
>> . --+-------+------
>>
>>
>
> That's a neat little circuit, but I was hoping for something passive.
>
> Maybe a dumb question, but, given the low current, would it be possible
> to power the amp through a zener diode?

What would that accomplish other than losing a lot of power and voltage 
to the amp?

-- 

Rick C

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#454514

On 01/04/17 09:03, rickman wrote:
> On 3/31/2017 4:42 PM, Robert Miller wrote:
>> On 30/03/17 23:13, Winfield Hill wrote:
>>> Robert Miller wrote...
>>>>
>>>> I have a little circuit consisting of an LM358 and
>>>> BC547 emitter follower. It runs off 4 x AAA alkaline
>>>> batteries and consumes about 50mA.
>>>>
>>>> What is the simplest way, without consuming additional
>>>> power, of disabling the output from the LM358 when
>>>> the battery voltage drops below around 4V?
>>>
>>> .
>>> . --+-----E   C----
>>> .   |       B
>>> .  6.2k     |  ZTX718
>>> .   |      470
>>> .   |       |
>>> .   |       K
>>> .   +-----R    TL431
>>> .   |       A  $0.40
>>> .  10k      |
>>> .   |       |
>>> . --+-------+------
>>>
>>>
>>
>> That's a neat little circuit, but I was hoping for something passive.
>>
>> Maybe a dumb question, but, given the low current, would it be possible
>> to power the amp through a zener diode?
>
> What would that accomplish other than losing a lot of power and voltage
> to the amp?
>

The amp would be powered through the zener until the supply voltage is 
too low to cause breakdown. Then the zener would stop conducting.

The effect of dynamic resistance may need to be factored in.

I am willing to accept the standard diode voltage drop.

Robert Miller

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#454518

On 3/31/2017 7:35 PM, Robert Miller wrote:
> On 01/04/17 09:03, rickman wrote:
>> On 3/31/2017 4:42 PM, Robert Miller wrote:
>>> On 30/03/17 23:13, Winfield Hill wrote:
>>>> Robert Miller wrote...
>>>>>
>>>>> I have a little circuit consisting of an LM358 and
>>>>> BC547 emitter follower. It runs off 4 x AAA alkaline
>>>>> batteries and consumes about 50mA.
>>>>>
>>>>> What is the simplest way, without consuming additional
>>>>> power, of disabling the output from the LM358 when
>>>>> the battery voltage drops below around 4V?
>>>>
>>>> .
>>>> . --+-----E   C----
>>>> .   |       B
>>>> .  6.2k     |  ZTX718
>>>> .   |      470
>>>> .   |       |
>>>> .   |       K
>>>> .   +-----R    TL431
>>>> .   |       A  $0.40
>>>> .  10k      |
>>>> .   |       |
>>>> . --+-------+------
>>>>
>>>>
>>>
>>> That's a neat little circuit, but I was hoping for something passive.
>>>
>>> Maybe a dumb question, but, given the low current, would it be possible
>>> to power the amp through a zener diode?
>>
>> What would that accomplish other than losing a lot of power and voltage
>> to the amp?
>>
>
> The amp would be powered through the zener until the supply voltage is
> too low to cause breakdown. Then the zener would stop conducting.

The Zener would drop a constant voltage as the supply voltage drops 
leaving very little for the amp to operate from.  As the voltage drops 
to the Zener breakdown voltage the current will tend to zero, but 
largely because the voltage on the amp will tend toward zero.


> The effect of dynamic resistance may need to be factored in.
>
> I am willing to accept the standard diode voltage drop.

What standard diode voltage drop?  Try drawing the circuit and calculate 
the voltages.

-- 

Rick C

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#454530

Robert Miller wrote...
>
>On 30/03/17 23:13, Winfield Hill wrote:
>> Robert Miller wrote...
>>>
>>> I have a little circuit consisting of an LM358 and
>>> BC547 emitter follower. It runs off 4 x AAA alkaline
>>> batteries and consumes about 50mA.
>>>
>>> What is the simplest way, without consuming additional
>>> power, of disabling the output from the LM358 when
>>> the battery voltage drops below around 4V?
>>
>> .
>> . --+-----E   C----
>> .   |       B
>> .  6.2k     |  ZTX718
>> .   |      470
>> .   |       |
>> .   |       K
>> .   +-----R    TL431
>> .   |       A  $0.40
>> .  10k      |
>> .   |       |
>> . --+-------+------
>>
>>
>
> That's a neat little circuit, but I was hoping for
> something passive.

 In engineering terms, passive means no transistors.
 Really?  How could that work?  My simple circuit is
 passive in the sense that no other power is required.
 But I do suggest the hysteresis version, with more
 hysteresis to force shutoff after the battery dies.


-- 
 Thanks,
    - Win

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#454606

On 03/31/2017 08:56 PM, Winfield Hill wrote:
> Robert Miller wrote...
>>
>> On 30/03/17 23:13, Winfield Hill wrote:
>>> Robert Miller wrote...
>>>>
>>>> I have a little circuit consisting of an LM358 and
>>>> BC547 emitter follower. It runs off 4 x AAA alkaline
>>>> batteries and consumes about 50mA.
>>>>
>>>> What is the simplest way, without consuming additional
>>>> power, of disabling the output from the LM358 when
>>>> the battery voltage drops below around 4V?
>>>
>>> .
>>> . --+-----E   C----
>>> .   |       B
>>> .  6.2k     |  ZTX718
>>> .   |      470
>>> .   |       |
>>> .   |       K
>>> .   +-----R    TL431
>>> .   |       A  $0.40
>>> .  10k      |
>>> .   |       |
>>> . --+-------+------
>>>
>>>
>>
>> That's a neat little circuit, but I was hoping for
>> something passive.
> 
>  In engineering terms, passive means no transistors.
>  Really?  How could that work?  My simple circuit is
>  passive in the sense that no other power is required.
>  But I do suggest the hysteresis version, with more
>  hysteresis to force shutoff after the battery dies.
> 
> 

Since this is a battery-powered circuit, maybe a BSS209 PFET ($0.07 @
1000 pcs) and a TLV431 ($0.16 @ 1000 pcs, 80 uA min), with 33k or so
between source and gate?  Still equally impassive, of course. ;)

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

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#454228

On Thu, 30 Mar 2017 18:21:15 +1100, Robert Miller
<robert.miller@teledyne.com> wrote:

>I have a little circuit consisting of an LM358 and BC547 emitter 
>follower. It runs off 4 x AAA alkaline batteries and consumes about 50mA.
>
>What is the simplest way, without consuming additional power, of 
>disabling the output from the LM358 when the battery voltage drops below 
>around 4V?
>
>In other words, I would like to have the circuit deactivate itself 
>before a distorted wave form is output.
>
>Prefer all passive components.
>
>Robert Miller

What does the emitter follower do? If it's a linear circuit and the
emitter follower has a passive pull-down, that might waste a lot of
power.

Got a schematic?


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#454247

On Thu, 30 Mar 2017 18:21:15 +1100, Robert Miller wrote:

> I have a little circuit consisting of an LM358 and BC547 emitter
> follower. It runs off 4 x AAA alkaline batteries and consumes about
> 50mA.
> 
> What is the simplest way, without consuming additional power, of
> disabling the output from the LM358 when the battery voltage drops below
> around 4V?
> 
> In other words, I would like to have the circuit deactivate itself
> before a distorted wave form is output.
> 
> Prefer all passive components.

First, there's a lot of useful energy you can get from an alkaline cell 
between 1V an 0.9V (NiMH, too, but not as much).

Second, you want some hysteresis, or at a certain level of charge the 
thing will start madly turning on and off.  Without hysteresis the 
current will get shut off, the battery voltage will rebound, the circuit 
will turn on, the battery voltage will get pulled low, and the cycle will 
repeat.

I'd design the circuit to work well down to 0.9V/cell, and I'd design the 
turn-off circuit to latch off -- maybe design the thing with an "on" 
pushbutton and an "off" pushbutton, with "off" coming either from the 
user or from the low-voltage cutout.

-- 
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work!  See my website if you're interested
http://www.wescottdesign.com

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#454267

Tim Wescott wrote...
>
>Second, you want some hysteresis, or at a certain level of charge the 
>thing will start madly turning on and off.  Without hysteresis the 
>current will get shut off, the battery voltage will rebound, the circuit 
>will turn on, the battery voltage will get pulled low, and the cycle will 
>repeat.

 True, but a 1-volt battery with no load doesn't
 rebound very much.  If the hysteresis is, say,
 0.25V, it should stay off.


-- 
 Thanks,
    - Win

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#454269

On Thu, 30 Mar 2017 13:18:33 -0700, Winfield Hill wrote:

> Tim Wescott wrote...
>>
>>Second, you want some hysteresis, or at a certain level of charge the
>>thing will start madly turning on and off.  Without hysteresis the
>>current will get shut off, the battery voltage will rebound, the circuit
>>will turn on, the battery voltage will get pulled low, and the cycle
>>will repeat.
> 
>  True, but a 1-volt battery with no load doesn't rebound very much.  If
>  the hysteresis is, say, 0.25V, it should stay off.

An Internet acquaintance of mine who used to be a battery engineer for GE 
claimed that nearly-fully-discharged NiCd cells would rebound to 1.2V if 
you gave them enough time, even if they couldn't deliver any significant 
charge.

But -- I'd have to test that theory on alkalines.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

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#454275

Tim Wescott wrote...
>
>On Thu, 30 Mar 2017 13:18:33 -0700, Winfield Hill wrote:
>
>> Tim Wescott wrote...
>>>
>>>Second, you want some hysteresis, or at a certain level of charge the
>>>thing will start madly turning on and off.  Without hysteresis the
>>>current will get shut off, the battery voltage will rebound, the circuit
>>>will turn on, the battery voltage will get pulled low, and the cycle
>>>will repeat.
>> 
>>  True, but a 1-volt battery with no load doesn't rebound very much.  If
>>  the hysteresis is, say, 0.25V, it should stay off.
>
>An Internet acquaintance of mine who used to be a battery engineer for GE 
>claimed that nearly-fully-discharged NiCd cells would rebound to 1.2V if 
>you gave them enough time, even if they couldn't deliver any significant 
>charge.
>
>But -- I'd have to test that theory on alkalines.

 Alkalines are rather different, in a useful way.
 Their open-circuit voltage drops from 1.55V to
 1.0 or 0.9V, etc, as they're depleted, providing
 a convenient way to evaluate their condition.


-- 
 Thanks,
    - Win

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#454287

On 3/30/2017 2:31 PM, Winfield Hill wrote:
> Tim Wescott wrote...
>>
>> On Thu, 30 Mar 2017 13:18:33 -0700, Winfield Hill wrote:
>>
>>> Tim Wescott wrote...
>>>>
>>>> Second, you want some hysteresis, or at a certain level of charge the
>>>> thing will start madly turning on and off.  Without hysteresis the
>>>> current will get shut off, the battery voltage will rebound, the circuit
>>>> will turn on, the battery voltage will get pulled low, and the cycle
>>>> will repeat.
>>>
>>>   True, but a 1-volt battery with no load doesn't rebound very much.  If
>>>   the hysteresis is, say, 0.25V, it should stay off.
>>
>> An Internet acquaintance of mine who used to be a battery engineer for GE
>> claimed that nearly-fully-discharged NiCd cells would rebound to 1.2V if
>> you gave them enough time, even if they couldn't deliver any significant
>> charge.
>>
>> But -- I'd have to test that theory on alkalines.
>
>   Alkalines are rather different, in a useful way.
>   Their open-circuit voltage drops from 1.55V to
>   1.0 or 0.9V, etc, as they're depleted, providing
>   a convenient way to evaluate their condition.
>
>
Is there a simple explanation for why this happens?
It's a chemical reaction with voltages determined by
chemistry/physics.  I can understand why the series
resistance would increase as the reagents are "used up".
But, why does the open-circuit voltage change?

I don't mean to hijack the thread, just a few words in
layman's terms or a link will suffice.
Thanks,

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