Turning on my robot via the stamp...
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Posts: 46,084
Could I just use a simple switching transistor and the stamp to turn
on the robot. I am not sure if this might be too much stress on the
stamp.
7.2v 3000mAh Ni-MH battery
stamp |
_B2SX_ 2n2222 |
| | xsister /
| | _ /
| |
( |
| | - \
| | \
|
robot circuitry
|
|
ground
on the robot. I am not sure if this might be too much stress on the
stamp.
7.2v 3000mAh Ni-MH battery
stamp |
_B2SX_ 2n2222 |
| | xsister /
| | _ /
| |
( |
| | - \
| | \
|
robot circuitry
|
|
ground
Comments
2N2222. If there is anything inductive in the robot, you need to have
a diode (connected so as to be reverse biased) across the robot.
nestlerv wrote:
> Could I just use a simple switching transistor and the stamp to turn
> on the robot. I am not sure if this might be too much stress on the
> stamp.
>
>
>
>
> 7.2v 3000mAh Ni-MH battery
> stamp |
> _B2SX_ 2n2222 |
> | | xsister /
> | | _ /
> | |
( |
> | | - \
> | | \
>
|
> robot circuitry
> |
> |
> ground
>
>
>
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>
One more question.
What resistance should the resistor be?
And will an led be just as good as a diode for the purpose of
protecting from the inductive elements in the robot?
--- In basicstamps@yahoogroups.com, Bob Reite <bobr@t...> wrote:
> You need to put a series resistor between the stamp and the base
of the
> 2N2222. If there is anything inductive in the robot, you need to
have
> a diode (connected so as to be reverse biased) across the robot.
>
> nestlerv wrote:
> > Could I just use a simple switching transistor and the stamp to
turn
> > on the robot. I am not sure if this might be too much stress on
the
> > stamp.
> >
> >
> >
> >
> > 7.2v 3000mAh Ni-MH battery
> > stamp |
> > _B2SX_ 2n2222 |
> > | | xsister /
> > | | _ /
> > | |
( |
> > | | - \
> > | | \
> >
|
> > robot circuitry
> > |
> > |
> > ground
> >
> >
> >
> > 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.
> >
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http://docs.yahoo.com/info/terms/
> >
> >
for the 2n2222 transistor to switch. I think you'd be better off using
the transistor to drive a relay to switch the power to the load.. Just my
$0.02... [noparse]:)[/noparse]
Vern
--
Vern Graner CNE/CNA/SSE | "If the network is down, then you're
Senior Systems Engineer | obviously incompetent so why are we
Texas Information Services | paying you? Of course, if the network
vern@t... www.txis.com | is up, then we obviously don't need
Cell 507-7851 Desk 328-8947 | you, so why are we paying you?" VLG
nestlerv said:
>
> Could I just use a simple switching transistor and the stamp to turn
> on the robot. I am not sure if this might be too much stress on the
> stamp.
>
>
>
>
> 7.2v 3000mAh Ni-MH battery
> stamp |
> _B2SX_ 2n2222 |
> | | xsister /
> | | _ /
> | |
( |
> | | - \
> | | \
>
|
> robot circuitry
> |
> |
> ground
>
>
>
> 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.
>
>
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> http://docs.yahoo.com/info/terms/
Jonathan
www.madlabs.info
Original Message
From: "Vernon Graner" <vern@t...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, July 26, 2003 7:00 AM
Subject: Re: [noparse][[/noparse]basicstamps] Turning on my robot via the stamp...
> I would be concerned that 3000ma (3amps) would be way too much current
> for the 2n2222 transistor to switch. I think you'd be better off using
> the transistor to drive a relay to switch the power to the load.. Just my
> $0.02... [noparse]:)[/noparse]
>
> Vern
>
> --
> Vern Graner CNE/CNA/SSE | "If the network is down, then you're
> Senior Systems Engineer | obviously incompetent so why are we
> Texas Information Services | paying you? Of course, if the network
> vern@t... www.txis.com | is up, then we obviously don't need
> Cell 507-7851 Desk 328-8947 | you, so why are we paying you?" VLG
>
>
>
> nestlerv said:
> >
> > Could I just use a simple switching transistor and the stamp to turn
> > on the robot. I am not sure if this might be too much stress on the
> > stamp.
> >
> >
> >
> >
> > 7.2v 3000mAh Ni-MH battery
> > stamp |
> > _B2SX_ 2n2222 |
> > | | xsister /
> > | | _ /
> > | |
( |
> > | | - \
> > | | \
> >
|
> > robot circuitry
> > |
> > |
> > ground
> >
> >
> >
> > 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/
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
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>
>
>
bobr@t... writes:
> You need to put a series resistor between the stamp and the base of the
> 2N2222. If there is anything inductive in the robot, you need to have
> a diode (connected so as to be reverse biased) across the robot.
>
> nestlerv wrote:
> >Could I just use a simple switching transistor and the stamp to turn
> >on the robot. I am not sure if this might be too much stress on the
> >stamp.
> >
> >
> >
> >
> > 7.2v 3000mAh Ni-MH battery
> > stamp |
> >_B2SX_ 2n2222 |
> >| | xsister /
> >| | _ /
> >| |
( |
> >| | - \
> >| | \
> >
|
> > robot circuitry
> > |
> > |
> > ground
A series base resistor is NOT needed. The configuration shown is an emitter
follower. However, this configuration is not likely to be a practical solution
for the following reasons:
1) the maximum voltage to the robot will be one diode drop below the stamp
high voltage, which will give your robot 4.3 volts or less.
2) the 2n2222 will likely "burn up" from too much power. If your robot pulls
one amp and the battery is at 7 volts, the 2n2222 must disspate almost 3
watts.....which means smoke!!!
(7 - 4.3) * 1amp = 2.7 watts
A simple solution assuming you have the space is to use a 2n2222 to ground
the coil of a relay, and the relay contacts will be the voltage/current path to
the robot.
The 2n2222 emitter to ground, base to the stamp via 4.7k ohms, and the
collector to the relay coil. The other end of the relay coil to the + 7.2 volt
battery. A diode MUST also be connected across the relay coil with the cathode
end
(with the line) to the battery positive to supress voltage a voltage spike
that will occur when the relay is turned off.
[noparse][[/noparse]Non-text portions of this message have been removed]
writes:
> I would be concerned that 3000ma (3amps) would be way too much current
> for the 2n2222 transistor to switch. I think you'd be better off using
> the transistor to drive a relay to switch the power to the load.. Just my
> $0.02... [noparse]:)[/noparse]
>
> Vern
Vern is correct here, 3000 ma will ruin your 2n2222. His relay suggestion is
easy, see post from smartdim
[noparse][[/noparse]Non-text portions of this message have been removed]
> In a message dated 7/25/2003 11:11:06 PM Pacific Daylight Time,
> bobr@t... writes:
>
>
>>You need to put a series resistor between the stamp and the base of the
>>2N2222. If there is anything inductive in the robot, you need to have
>>a diode (connected so as to be reverse biased) across the robot.
>>
>>nestlerv wrote:
>>
>>>Could I just use a simple switching transistor and the stamp to turn
>>>on the robot. I am not sure if this might be too much stress on the
>>>stamp.
>>>
>>>
>>>
>>>
>>> 7.2v 3000mAh Ni-MH battery
>>>stamp |
>>>_B2SX_ 2n2222 |
>>>| | xsister /
>>>| | _ /
>>>| |
( |
>>>| | - \
>>>| | \
>>>
|
>>> robot circuitry
>>> |
>>> |
>>> ground
>>
>
> A series base resistor is NOT needed. The configuration shown is an emitter
> follower. However, this configuration is not likely to be a practical solution
> for the following reasons
Even though it's an emitter follower, the base current may still exceed
the rating of the stamp, if indeed the robot draws 3 amps. As pointed
out a 2N2222 can't handle that current. but look carefully... The
battery is rated at 3 Amp/hours, that doesn't say what the robot
circuitry actually draws. That needs to be known.
> Thanks,
>
> One more question.
>
> What resistance should the resistor be?
> And will an led be just as good as a diode for the purpose of
> protecting from the inductive elements in the robot?
>
I don't see the point in using an LED, as it won't light, except briefly
when the robot is turned off. I'm also not sure how LEDs respond to
reverse bias.
In case it wasn't clear, the diode goes in parallel across the robot.
>
> --- In basicstamps@yahoogroups.com, Bob Reite <bobr@t...> wrote:
>
>>You need to put a series resistor between the stamp and the base
>
> of the
>
>>2N2222. If there is anything inductive in the robot, you need to
>
> have
>
>>a diode (connected so as to be reverse biased) across the robot.
>>
>>nestlerv wrote:
>>
>>>Could I just use a simple switching transistor and the stamp to
>>
> turn
>
>>>on the robot. I am not sure if this might be too much stress on
>>
> the
>
>>>stamp.
>>>
>>>
>>>
>>>
>>> 7.2v 3000mAh Ni-MH battery
>>> stamp |
>>>_B2SX_ 2n2222 |
>>>| | xsister /
>>>| | _ /
>>>| |
( |
>>>| | - \
>>>| | \
>>>
|
>>> robot circuitry
>>> |
>>> |
>>> ground
>>>
>>>
>>>
>>>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/
>
>>>
>
>
> 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.
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>
>
bobr@t... writes:
> Even though it's an emitter follower, the base current may still exceed
> the rating of the stamp, if indeed the robot draws 3 amps. As pointed
> out a 2N2222 can't handle that current. but look carefully... The
> battery is rated at 3 Amp/hours, that doesn't say what the robot
> circuitry actually draws. That needs to be known.
You are correct!! ......using a conservative 100 hfe for the 2n2222 and 3
amps for the robot, the stamp would need to provide 30 mA which will exceed its
output current as you have stated.
I think the stamp driving a 2n2222 to ground a relay is likely the simplest
reliable approach.
[noparse][[/noparse]Non-text portions of this message have been removed]
would be more compact and probably less expensive than the relay. Also, the
relay coil would consume battery power, while the MOSFET would not, since it
requires no current to keep it turned on.
Matt Gilliland's books, The Microcontroller Application Cookbook, and The
... Cookbook 2 have many circuit examples like this. They're very handy
when you know what you want to do, but need to see how it's commonly done.
His examples show the IRF9520 p-ch MOSFET in positive side switching
applications like this, but I prefer the IRF9530 which is only a few cents
more and has much higher rated current and lower on resistance. For
example: max continuous current = 14A, max pulsed current = 56A, max
operating voltage = 100, etc. You can get them for under a buck if you know
where to look ;-)
Randy
www.glitchbuster.com
randyjones@w... writes:
> Another good method would be a p-channel MOSFET power transistor, which
> would be more compact and probably less expensive than the relay. Also, the
> relay coil would consume battery power, while the MOSFET would not, since it
> requires no current to keep it turned on.
>
> Matt Gilliland's books, The Microcontroller Application Cookbook, and The
> ... Cookbook 2 have many circuit examples like this. They're very handy
> when you know what you want to do, but need to see how it's commonly done.
> His examples show the IRF9520 p-ch MOSFET in positive side switching
> applications like this, but I prefer the IRF9530 which is only a few cents
> more and has much higher rated current and lower on resistance. For
> example: max continuous current = 14A, max pulsed current = 56A, max
> operating voltage = 100, etc. You can get them for under a buck if you know
> where to look ;-)
>
> Randy
>
> www.glitchbuster.com
Randy brings up excellent points......much cleaner than a relay
[noparse][[/noparse]Non-text portions of this message have been removed]
FYI the 3000 mAh battery lasts about 25 to 30 min on a full charge.
The mosfet stratedy sounds the most advantageous for the reasons you
mentioned, no power consumption of the battery and better able to
handle the current, oh and the cost. As they say, "you da man."
So the mosfet IRF9530 can be controlled with the stamp output?
I will draft a schematic of what Randy described for your critiquing.
--- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> In a message dated 7/26/2003 1:56:08 PM Pacific Daylight Time,
> randyjones@w... writes:
>
> > Another good method would be a p-channel MOSFET power
transistor, which
> > would be more compact and probably less expensive than the
relay. Also, the
> > relay coil would consume battery power, while the MOSFET would
not, since it
> > requires no current to keep it turned on.
> >
> > Matt Gilliland's books, The Microcontroller Application
Cookbook, and The
> > ... Cookbook 2 have many circuit examples like this. They're
very handy
> > when you know what you want to do, but need to see how it's
commonly done.
> > His examples show the IRF9520 p-ch MOSFET in positive side
switching
> > applications like this, but I prefer the IRF9530 which is only a
few cents
> > more and has much higher rated current and lower on resistance.
For
> > example: max continuous current = 14A, max pulsed current =
56A, max
> > operating voltage = 100, etc. You can get them for under a buck
if you know
> > where to look ;-)
> >
> > Randy
> >
> > www.glitchbuster.com
>
>
> Randy brings up excellent points......much cleaner than a relay
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
want to power, with the MOSFET "source" pin to B+ and "drain" pin to the
load. For the MOSFET to be off, its gate must be at the same voltage as its
source pin (B+). To turn on the MOSFET, the gate voltage must be more
negative than the source -- in other words, closer to ground.
If you were switching a +5V power source, you could drive the MOSFET gate
directly from the Stamp pin... When the Stamp pin was high (+5V), the
MOSFET would be off, since the gate and source pins would be at the same
voltage. Remember that the source is connected to B+, which would be 5V in
this case. When the Stamp pin was driven low, the MOSFET gate would be at
0V and the source still at 5V. So the gate would be more negative than the
source by 5V, and the MOSFET would turn on.
Since your battery supply is 7.2V, you can't connect the MOSFET gate
directly to a Stamp pin, because you would never be able to fully turn the
MOSFET off... When the Stamp pin is high at 5V, there is still a 2.2V
difference between B+ and the Stamp pin, which would make the gate 2.2V
negative relative to the source. Fortunately, there is an easy solution...
We will use one more transistor, and it can be a dirt-cheap NPN such as a
2N3904, PN2222, or whatever. First, connect a resistor between the MOSFET
gate and B+ to pull-up the gate voltage so the MOSFET will be normally off
until we turn it on. This is important since the Stamp initially powers up
with all pins as high-impedance inputs, and noise could turn on the MOSFET.
The resistor value isn't critical; lower values provide more noise immunity
but will consume more current when we switch on the MOSFET. Something in
the 10k to 50k range should be fine.
The NPN transistor's base will be connected to the stamp pin through a base
resistor to limit the current. Since the transistor will be switching very
little current, the base resistor can be fairly large -- 10k, or
considerably higher, should work fine. Connect the NPN's emitter pin to
ground and its collector to the MOSFET gate. That's it.
When the Stamp pin is driven high, a small current will flow through the
resistor and the NPN's base, turning it on. This effectively connects the
MOSFET gate to ground, turning on the MOSFET. When the Stamp pin is made
low, there is no current flowing through the NPN's base, and it turns off
(very high resistance). Now the MOSFET's gate is pulled to B+ by its
gate-source resistor, and the MOSFET is turned off.
I would probably start with 10k resistors in both places, which would result
in current consumption of a couple milliamps total for this part of your
circuit. If you wanted to play with larger resistor values, it could
probably be reduced even more. With the amount of power used by the 'bot,
this is just a drop in the bucket and probably not worth worrying about.
Randy
www.glitchbuster.com
Original Message
From: "nestlerv" <nestlerv@a...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, July 26, 2003 11:51 PM
Subject: [noparse][[/noparse]basicstamps] Re: Turning on my robot via the stamp...
> Well thank you to all for your much valued input.
>
> FYI the 3000 mAh battery lasts about 25 to 30 min on a full charge.
>
> The mosfet stratedy sounds the most advantageous for the reasons you
> mentioned, no power consumption of the battery and better able to
> handle the current, oh and the cost. As they say, "you da man."
>
> So the mosfet IRF9530 can be controlled with the stamp output?
>
> I will draft a schematic of what Randy described for your critiquing.
>
>
>
>
>
> --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > In a message dated 7/26/2003 1:56:08 PM Pacific Daylight Time,
> > randyjones@w... writes:
> >
> > > Another good method would be a p-channel MOSFET power
> transistor, which
> > > would be more compact and probably less expensive than the
> relay. Also, the
> > > relay coil would consume battery power, while the MOSFET would
> not, since it
> > > requires no current to keep it turned on.
> > >
> > > Matt Gilliland's books, The Microcontroller Application
> Cookbook, and The
> > > ... Cookbook 2 have many circuit examples like this. They're
> very handy
> > > when you know what you want to do, but need to see how it's
> commonly done.
> > > His examples show the IRF9520 p-ch MOSFET in positive side
> switching
> > > applications like this, but I prefer the IRF9530 which is only a
> few cents
> > > more and has much higher rated current and lower on resistance.
> For
> > > example: max continuous current = 14A, max pulsed current =
> 56A, max
> > > operating voltage = 100, etc. You can get them for under a buck
> if you know
> > > where to look ;-)
> > >
> > > Randy
> > >
> > > www.glitchbuster.com
> >
> >
> > Randy brings up excellent points......much cleaner than a relay
> >
> >
> > [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
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>
>
this web site for schematics and parts to do this with a stamp.
jim
http://www.geocities.com/jimforkin2003/
Original Message
From: smartdim@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=2O_qHiDgrBIvfCb0Wl2YKqjiV2EDoptbbKDPLDcVFdMuy4KQhX6xR36rvFut5Cr4kpmjK5-RRINvhw]smartdim@a...[/url
Sent: Saturday, July 26, 2003 11:55 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Turning on my robot via the stamp...
In a message dated 7/26/2003 7:09:03 AM Pacific Daylight Time, vern@t...
writes:
> I would be concerned that 3000ma (3amps) would be way too much current
> for the 2n2222 transistor to switch. I think you'd be better off using
> the transistor to drive a relay to switch the power to the load.. Just my
> $0.02... [noparse]:)[/noparse]
>
> Vern
Vern is correct here, 3000 ma will ruin your 2n2222. His relay suggestion is
easy, see post from smartdim
[noparse][[/noparse]Non-text portions of this message have been removed]
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