fuses & stamp protection
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Posts: 46,084
What do you mean kicking out? The current that will be given by your
BAsic Stamp will depend on the value of load. Remeber the basic
I=V/R, Ohm's Law. To avoid giving out too much cuurnt try to use
isolators or high side drivers in driving low resistance loads.
Example in your relays, you use transistors. Read the datasheet of
the Stamp if how much current (MAXIMUM) it can drive a load. If your
computation gives an output of more than the maximum, you will surely
get a burned I/O port pin or the worst burned BS2 IC.
Btw, the Voltage peak I think of the BS2 is 5V, so I=5V/R, R is your
load resistance.
Glenjoy [noparse]:)[/noparse]
--- In
basicstamps@yahoogroups.com, "[noparse][[/noparse].......................................
..]" <manwithapipe@y...> wrote:
> I am curious how you more experienced stampers out there protect
your
> stamp from accidentally kicking out too much current? I realize
that
> ideally the program should prevent this from happening, but during
> debugging occasionally I run into the "Oh sh@#" situation when a
Dirs
> command or some piece of logic ends up sourcing all 16 pins at
once.
> I'm considering a fuse on the power supply prior to reaching the
> stamp. Is there a better way?
BAsic Stamp will depend on the value of load. Remeber the basic
I=V/R, Ohm's Law. To avoid giving out too much cuurnt try to use
isolators or high side drivers in driving low resistance loads.
Example in your relays, you use transistors. Read the datasheet of
the Stamp if how much current (MAXIMUM) it can drive a load. If your
computation gives an output of more than the maximum, you will surely
get a burned I/O port pin or the worst burned BS2 IC.
Btw, the Voltage peak I think of the BS2 is 5V, so I=5V/R, R is your
load resistance.
Glenjoy [noparse]:)[/noparse]
--- In
basicstamps@yahoogroups.com, "[noparse][[/noparse].......................................
..]" <manwithapipe@y...> wrote:
> I am curious how you more experienced stampers out there protect
your
> stamp from accidentally kicking out too much current? I realize
that
> ideally the program should prevent this from happening, but during
> debugging occasionally I run into the "Oh sh@#" situation when a
Dirs
> command or some piece of logic ends up sourcing all 16 pins at
once.
> I'm considering a fuse on the power supply prior to reaching the
> stamp. Is there a better way?
Comments
manwithapipe@y... writes:
> I am curious how you more experienced stampers out there protect your
> stamp from accidentally kicking out too much current? I realize that
> ideally the program should prevent this from happening, but during
> debugging occasionally I run into the "Oh sh@#" situation when a Dirs
> command or some piece of logic ends up sourcing all 16 pins at once.
> I'm considering a fuse on the power supply prior to reaching the
> stamp. Is there a better way?
>
I have often read in this forrm users connect a 220 ohm resistor in series
with every pin. In many applications, this will not affect the input or output.
[noparse][[/noparse]Non-text portions of this message have been removed]
be destroyed. A resistor in line with the output to limit current to a safe
value, might be a better choice.
Leroy
Original Message
From: "[noparse][[/noparse].........................................]" <manwithapipe@y...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, August 17, 2003 2:22 AM
Subject: [noparse][[/noparse]basicstamps] fuses & stamp protection
: I am curious how you more experienced stampers out there protect your
: stamp from accidentally kicking out too much current? I realize that
: ideally the program should prevent this from happening, but during
: debugging occasionally I run into the "Oh sh@#" situation when a Dirs
: command or some piece of logic ends up sourcing all 16 pins at once.
: I'm considering a fuse on the power supply prior to reaching the
: stamp. Is there a better way?
:
:
:
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the BS2 pin) is needed to limit current
source/sink should the pin be connected
directly to ground or +5, and then the
pin configured as an output.
If the pin is outputting +5 volts, and is
then connected to a ground, the 220 resistor
limits the resulting current to 22.7 mA,
which won't damage the pin's driver.
Pull-ups or pull-downs provide a 'default'
voltage on the pin -- this should be
'outside' the 220 ohm protection resistor.
Note if you configure a pin as an INPUT,
then the pin goes to a 'high-impedance'
state (10 Meg Ohms?), where it should only
sink micro-amps, if any current at all.
A pin set to an OUTPUT state, then set to
0, will sink current to try to 'pull' the
voltage on its pin to 0. If you attach it
to a non-zero (or non-matching) voltage
source, some current will definitely flow.
--- In
basicstamps@yahoogroups.com, "[noparse][[/noparse].......................................
..]" <manwithapipe@y...> wrote:
> I've done a little more investigating and it seems I may have other
> semi-related questions. (btw thanks to the answers so far).
>
> Part of my earlier issues (not voltage-re;ated) stem from the fact
> that the Opto22 relay boards are logically inverted. Does anyone
have
> a good reason why this is?
>
> Also, if I am toggling one pin at a time, and have all my output
pins
> set, all pins that are not HIGH seem so soak up a little tiny itsy
> bitsy bit of current. I've checked for shorts and the circuit is
> sound. THey're just not completely off; I can see a little glow in
> their LEDs. The thing is, with a 32 channel I/O board and only
using
> one pin at a time, a little bit spread over 32 is hardly detectable
> but a great drain on the stamp. Am I in need of pullups?
>
> In regards to my earlier post, I'm now using a 7805 to regulate V
and
> now working on the other end to make my current load safe. Are
> pullups not needed if I simply put a 220-Ohm on each pin?
>
> (confused semi-noob)