Low Voltage Battery Shutoff Circuit
Archiver
Posts: 46,084
I have a 9 volt battery connected to a motor. When the voltage drops down
to 5 volts, I want the motor to shut down.
I have tried using a relay between the battery and the motor. When it gets
close to the point where there is not enough
voltage to keep the contact pin connected, it starts chattering and spitting
out arcs.
I thought about using a 339 comparator, but how would I set my reference
voltage using the single power supply.
So, I am at a loss. If anyone has some suggestions, I would appreciate the
help.
to 5 volts, I want the motor to shut down.
I have tried using a relay between the battery and the motor. When it gets
close to the point where there is not enough
voltage to keep the contact pin connected, it starts chattering and spitting
out arcs.
I thought about using a 339 comparator, but how would I set my reference
voltage using the single power supply.
So, I am at a loss. If anyone has some suggestions, I would appreciate the
help.
Comments
> I have a 9 volt battery connected to a motor. When the voltage
drops down
> to 5 volts, I want the motor to shut down.
>
> I have tried using a relay between the battery and the motor. When
it gets
> close to the point where there is not enough
> voltage to keep the contact pin connected, it starts chattering and
spitting
> out arcs.
>
> I thought about using a 339 comparator, but how would I set my
reference
> voltage using the single power supply.
> So, I am at a loss. If anyone has some suggestions, I would
appreciate the
> help.
Just a thought for ya..
Maybe a really simple way of doing this would be to shut down the
entire circuit and not just the motor. Since the stamp resets at low
power levels, your first few lines of code could be out of the normal
program loop to verify if a port is high, you could do this easiest
by adding a switch from a port to +V, and holding it down when you
turn it on initially so it would be set high and therefore be allowed
to continue running the program, if not, jump to end or something.
That when it reaches low power and the stamp resets, the switch won't
be held down and it will jump to end. Pretty crude but hey...I guess
it depends on the application.
I might be able to help you out here.
Quoting Bryan Smith <bsmith@w...>:
> I thought about using a 339 comparator, but how would I set my
> reference
> voltage using the single power supply.
You've got the first part of the solution with the comparator. The way you get
your reference voltage is by using a voltage divider. This is two resistors
between VCC and GND with values choosen so that if you take the voltage between
the two it is your reference voltage. Then you just need to feed this value and
the actual output value of the battery into the comparator and feed the result
of this into the stamp.
Hope this helps you,
kind regards,
James Fitzsimons
relay connected to form a latching relay. You just need a button or
switch to start it.
Once its running it will continue to run until the voltage drops to the
coil dropout voltage
and the contacts open and the motor stops.
On Thu, 22 Nov 2001 00:46:32 -0000 cbielek@y... writes:
> --- In basicstamps@y..., Bryan Smith <bsmith@w...> wrote:
> > I have a 9 volt battery connected to a motor. When the voltage
> drops down
> > to 5 volts, I want the motor to shut down.
> >
> > I have tried using a relay between the battery and the motor.
> When
> it gets
> > close to the point where there is not enough
> > voltage to keep the contact pin connected, it starts chattering
> and
> spitting
> > out arcs.
> >
> > I thought about using a 339 comparator, but how would I set my
> reference
> > voltage using the single power supply.
> > So, I am at a loss. If anyone has some suggestions, I would
> appreciate the
> > help.
>
> Just a thought for ya..
>
> Maybe a really simple way of doing this would be to shut down the
> entire circuit and not just the motor. Since the stamp resets at low
>
> power levels, your first few lines of code could be out of the
> normal
> program loop to verify if a port is high, you could do this easiest
> by adding a switch from a port to +V, and holding it down when you
> turn it on initially so it would be set high and therefore be
> allowed
> to continue running the program, if not, jump to end or something.
> That when it reaches low power and the stamp resets, the switch
> won't
> be held down and it will jump to end. Pretty crude but hey...I guess
>
> it depends on the application.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
a latching relay
This would keep the motor running until the dropout voltage is reached .
Once the contacts open for even a fraction of a second the coil would
drop out and the motor would stop.
On Thu, 22 Nov 2001 00:46:32 -0000 cbielek@y... writes:
> --- In basicstamps@y..., Bryan Smith <bsmith@w...> wrote:
> > I have a 9 volt battery connected to a motor. When the voltage
> drops down
> > to 5 volts, I want the motor to shut down.
> >
> > I have tried using a relay between the battery and the motor.
> When
> it gets
> > close to the point where there is not enough
> > voltage to keep the contact pin connected, it starts chattering
> and
> spitting
> > out arcs.
> >
> > I thought about using a 339 comparator, but how would I set my
> reference
> > voltage using the single power supply.
> > So, I am at a loss. If anyone has some suggestions, I would
> appreciate the
> > help.
>
> Just a thought for ya..
>
> Maybe a really simple way of doing this would be to shut down the
> entire circuit and not just the motor. Since the stamp resets at low
>
> power levels, your first few lines of code could be out of the
> normal
> program loop to verify if a port is high, you could do this easiest
> by adding a switch from a port to +V, and holding it down when you
> turn it on initially so it would be set high and therefore be
> allowed
> to continue running the program, if not, jump to end or something.
> That when it reaches low power and the stamp resets, the switch
> won't
> be held down and it will jump to end. Pretty crude but hey...I guess
>
> it depends on the application.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
Panasonic. They are three terminal devices that trigger at specified
voltages, the highest range they detect is between 4.6 and 4.9V.
Presumably that means that a particular device will trigger at a constant
voltage somewhere in that range, depending on manufacturing variations,
not that it will trigger at 4.6V one day and another voltage later. I
first encountered them at the solarbotics site, they have schematics
available for some of the kits they sell, which I found informative.
www.solarbotics.com, then go to the link for kits -- I found the schematic
for kit 5 useful -- the circuit turns on above the threshold, turns off
below it.
They were originally designed for low battery voltage detection, come in a
TO-92 package (ie look like a switching transistor), and have built in
voltage references and comparators. It might be just what you want. I
have been planning on using them, but haven't had time to put things
together yet... As a bonus, they are only about a dollar.
There is more information about them at the Digikey webpage:
http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=9&M=MN13822-U(TX)
I hope this is useful and that everyone is having a happy turkey-day.
Nick
>
> If the motor is uncontrolled you can use a DP/DT relay connected to form
> a latching relay
> This would keep the motor running until the dropout voltage is reached .
> Once the contacts open for even a fraction of a second the coil would
> drop out and the motor would stop.
>
> On Thu, 22 Nov 2001 00:46:32 -0000 cbielek@y... writes:
> > --- In basicstamps@y..., Bryan Smith <bsmith@w...> wrote:
> > > I have a 9 volt battery connected to a motor. When the voltage
> > drops down
> > > to 5 volts, I want the motor to shut down.
> > >
> > > I have tried using a relay between the battery and the motor.
> > When
> > it gets
> > > close to the point where there is not enough
> > > voltage to keep the contact pin connected, it starts chattering
> > and
> > spitting
> > > out arcs.
> > >
> > > I thought about using a 339 comparator, but how would I set my
> > reference
> > > voltage using the single power supply.
> > > So, I am at a loss. If anyone has some suggestions, I would
> > appreciate the
> > > help.
http://www.emesystems.com/images/bs2/BVcutoff.gif
described in:
http://www.emesystems.com/BS2power.htm#Brownout
The circuit adds additional hysteresis.
cbielek, The fact that your motor+relay circuit chatters when it hits
the relay threshold probably means that there is feedback as follows:
- battery voltage drops due to motor+relay load
- low voltage makes relay open
- battery voltage rises as soon as the load is removed
- relay closes due to voltage increase
- voltage drops due to load
- .... repeat over and over.
If you want it to stay off, you need to include the power to the
relay in the _output_ circuit of the relay. That would also need a
"push to start" switch in the circuit.
-- Tracy
>Another option would be a voltage trigger, such as the MN1380 series by
>Panasonic. They are three terminal devices that trigger at specified
>voltages, the highest range they detect is between 4.6 and 4.9V.
>Presumably that means that a particular device will trigger at a constant
>voltage somewhere in that range, depending on manufacturing variations,
>not that it will trigger at 4.6V one day and another voltage later. I
>first encountered them at the solarbotics site, they have schematics
>available for some of the kits they sell, which I found informative.
>www.solarbotics.com, then go to the link for kits -- I found the schematic
>for kit 5 useful -- the circuit turns on above the threshold, turns off
>below it.
>
>They were originally designed for low battery voltage detection, come in a
>TO-92 package (ie look like a switching transistor), and have built in
>voltage references and comparators. It might be just what you want. I
>have been planning on using them, but haven't had time to put things
>together yet... As a bonus, they are only about a dollar.
>
>There is more information about them at the Digikey webpage:
>http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=9&M=MN13822-U(TX)
>
>I hope this is useful and that everyone is having a happy turkey-day.
>
>Nick
>
> >
> > On Thu, 22 Nov 2001 00:46:32 -0000 cbielek@y... writes:
> > > --- In basicstamps@y..., Bryan Smith <bsmith@w...> wrote:
> > > > I have a 9 volt battery connected to a motor. When the voltage
> > > drops down
> > > > to 5 volts, I want the motor to shut down.
> > > >
> > > > I have tried using a relay between the battery and the motor.
> > > When
> > > it gets
> > > > close to the point where there is not enough
> > > > voltage to keep the contact pin connected, it starts chattering
> > > and
> > > spitting
> > > > out arcs.
> > > >
> > > > I thought about using a 339 comparator, but how would I set my
> > > reference
> > > > voltage using the single power supply.
> > > > So, I am at a loss. If anyone has some suggestions, I would
> > > appreciate the
> > > help.