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Groups > sci.electronics.design > #454518
| From | rickman <gnuarm@gmail.com> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: Simple Low Voltage Shut Down |
| Date | 2017-03-31 19:49 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <obmpp2$4op$1@dont-email.me> (permalink) |
| References | <Nl2DA.428151$fZ.218528@fx41.am4> <obisol016pi@drn.newsguy.com> <dbzDA.285202$2K7.267822@fx18.am4> <obmjib$f0c$3@dont-email.me> <jJBDA.324228$dI6.322446@fx31.am4> |
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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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
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