Pull up resistors..
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Posts: 46,084
Hi,
I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
pull up the inputs from the SRF08 to the stamp by hooking them up to
the 5V power supply with some resistors. I'm just wondering, what
is the point of doing that? I wired it without the resistors and it
seems to be working fine.. Is the actaully a reason to pull up the
inputs? Does it have something to do with accuracy? Because the
results I get are fairly inaccurate...
Thanks
James
I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
pull up the inputs from the SRF08 to the stamp by hooking them up to
the 5V power supply with some resistors. I'm just wondering, what
is the point of doing that? I wired it without the resistors and it
seems to be working fine.. Is the actaully a reason to pull up the
inputs? Does it have something to do with accuracy? Because the
results I get are fairly inaccurate...
Thanks
James
Comments
the I2C buss. Usually 4.7k, though I hear that one customer (in an
electrically noisy robot project) went down to 1K. I've never had to,
I've been able to use 4.7K with BASIC Stamps and Javelin Stamps.
This N&V article may help out:
http://www.parallax.com/dl/docs/cols/nv/vol4/col/99.pdf
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: James Dang [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=baIUV3uqUAxofbD6okiNK4ju-_ostASO9GsDEYoIzcVsMbOS30sAvb3Z8y6P6NfrbbijsePjtCNnDdZsEA]ensignkim113@y...[/url
Sent: Monday, January 26, 2004 5:59 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Pull up resistors..
Hi,
I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
pull up the inputs from the SRF08 to the stamp by hooking them up to
the 5V power supply with some resistors. I'm just wondering, what
is the point of doing that? I wired it without the resistors and it
seems to be working fine.. Is the actaully a reason to pull up the
inputs? Does it have something to do with accuracy? Because the
results I get are fairly inaccurate...
Thanks
James
ensignkim113@y... writes:
> I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
> pull up the inputs from the SRF08 to the stamp by hooking them up to
> the 5V power supply with some resistors. I'm just wondering, what
> is the point of doing that? I wired it without the resistors and it
> seems to be working fine.. Is the actaully a reason to pull up the
> inputs? Does it have something to do with accuracy? Because the
> results I get are fairly inaccurate...
>
The pull up resistors keep you from getting erroneous readings. You should
be using them.
Sid Weaver
W4EKQ
Port Richey, FL
[noparse][[/noparse]Non-text portions of this message have been removed]
ensignkim113@y... writes:
Hi,
I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
pull up the inputs from the SRF08 to the stamp by hooking them up to
the 5V power supply with some resistors. I'm just wondering, what
is the point of doing that? I wired it without the resistors and it
seems to be working fine.. Is the actaully a reason to pull up the
inputs? Does it have something to do with accuracy? Because the
results I get are fairly inaccurate...
Thanks
James
James:
Usually a manufacturer recommends pull up or pull down resistors as a
precaution to prevent inputs and outputs from going into an undefined state
which can
cause problems. Just like the inputs on a TTL or CMOS chip, the chip may
perform flawlessly under many applications with out tying the inputs either high
or low but next time you use that circuit, they very well may not. The same
would be true with your situation, your circuit may work great now but tomorrow
or next week, maybe not. Also, are there resistors elsewhere in the circuit
that may in fact be pulling those inputs/outputs high anyway.
Maybe this will help out.
Randy Abernathy
4626 Old Stilesboro Road
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: cnc002@a...
I[noparse][[/noparse]Non-text portions of this message have been removed]
Pullups keep the pin from floating and being in an undefined logic
level when no input is available, in this case it pulls up to +5V.
There are also pull down resistors which, as you might guess, pull
down a pin to 0V. Regards,
-Dave
--- In basicstamps@yahoogroups.com, "James Dang" <ensignkim113@y...>
wrote:
> Hi,
>
> I'm using the SRF08 (SONAR) with my BS2P. On the example it says
to
> pull up the inputs from the SRF08 to the stamp by hooking them up
to
> the 5V power supply with some resistors. I'm just wondering, what
> is the point of doing that? I wired it without the resistors and
it
> seems to be working fine.. Is the actaully a reason to pull up the
> inputs? Does it have something to do with accuracy? Because the
> results I get are fairly inaccurate...
>
> Thanks
> James
ensignkim113@y... writes:
> I'm using the SRF08 (SONAR) with my BS2P. On the example it says to
> pull up the inputs from the SRF08 to the stamp by hooking them up to
> the 5V power supply with some resistors. I'm just wondering, what
> is the point of doing that? I wired it without the resistors and it
> seems to be working fine.. Is the actaully a reason to pull up the
> inputs? Does it have something to do with accuracy? Because the
> results I get are fairly inaccurate...
>
You should also have a 270 ohm resistor in series with the IR detector pin 3.
Sid Weaver
W4EKQ
Port Richey, FL
[noparse][[/noparse]Non-text portions of this message have been removed]