A/D question
Archiver
Posts: 46,084
Hello, everyone! I just joined the BASIC Stamp Group!
I have become very interested in the BASIC Stamp concept. By taining
I am an Electrical Engineer, by 40+ years of experience a Software
Engineer.
I have a project in the planning stage that will require Analog to
Digital conversion. The MAX1270 seems to offer the ideal chip for my
needs.
I have to measure 4 DC current sources which will use 100 millivolt
shunts in the negative (to system ground) line. One of these will be
bi-polar. My question is: What is the best way to amplify the 100 mv
max voltage so that it will be in range for the MAX1270? I presume
that I need to use an op-amp, but it has been a looong time since I've
done this sort of thing (retired now).
Any suggestions/pointers will be welcome!
Oh, and a belated Happy New Year!
Russ Ranshaw
I have become very interested in the BASIC Stamp concept. By taining
I am an Electrical Engineer, by 40+ years of experience a Software
Engineer.
I have a project in the planning stage that will require Analog to
Digital conversion. The MAX1270 seems to offer the ideal chip for my
needs.
I have to measure 4 DC current sources which will use 100 millivolt
shunts in the negative (to system ground) line. One of these will be
bi-polar. My question is: What is the best way to amplify the 100 mv
max voltage so that it will be in range for the MAX1270? I presume
that I need to use an op-amp, but it has been a looong time since I've
done this sort of thing (retired now).
Any suggestions/pointers will be welcome!
Oh, and a belated Happy New Year!
Russ Ranshaw
Comments
Well if you instead use the MAX186 it can measure voltages with 1mV
precision between 0-4.096V. Should work for you. But if you ever need
to go beyond that you'll have to use voltage dividers or the MAX1270
which has higher ranges (at the expense of resolution) of course.
-Dave
--- In basicstamps@yahoogroups.com, "russranshaw" <russranshaw@y...>
wrote:
> Hello, everyone! I just joined the BASIC Stamp Group!
>
> I have become very interested in the BASIC Stamp concept. By
taining
> I am an Electrical Engineer, by 40+ years of experience a Software
> Engineer.
>
> I have a project in the planning stage that will require Analog to
> Digital conversion. The MAX1270 seems to offer the ideal chip for
my
> needs.
>
> I have to measure 4 DC current sources which will use 100 millivolt
> shunts in the negative (to system ground) line. One of these will
be
> bi-polar. My question is: What is the best way to amplify the 100
mv
> max voltage so that it will be in range for the MAX1270? I presume
> that I need to use an op-amp, but it has been a looong time since
I've
> done this sort of thing (retired now).
>
> Any suggestions/pointers will be welcome!
>
> Oh, and a belated Happy New Year!
>
> Russ Ranshaw
I like the TLC2543, for the simple reason it can be set to read directly in
mV, with 1 mV resolution. Max does make chips with 1mV resolution, but I
don't know the part # off hand.
If all of your signals are around 100mV, you could use an external vRef of
100mV or a little above whatever you max input would be. If you need
resolution of more than 1mV, you will need an op-amp.
Jonathan
www.madlabs.info
Original Message
From: "russranshaw" <russranshaw@y...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, January 17, 2004 7:44 AM
Subject: [noparse][[/noparse]basicstamps] A/D question
> Hello, everyone! I just joined the BASIC Stamp Group!
>
> I have become very interested in the BASIC Stamp concept. By taining
> I am an Electrical Engineer, by 40+ years of experience a Software
> Engineer.
>
> I have a project in the planning stage that will require Analog to
> Digital conversion. The MAX1270 seems to offer the ideal chip for my
> needs.
>
> I have to measure 4 DC current sources which will use 100 millivolt
> shunts in the negative (to system ground) line. One of these will be
> bi-polar. My question is: What is the best way to amplify the 100 mv
> max voltage so that it will be in range for the MAX1270? I presume
> that I need to use an op-amp, but it has been a looong time since I've
> done this sort of thing (retired now).
>
> Any suggestions/pointers will be welcome!
>
> Oh, and a belated Happy New Year!
>
> Russ Ranshaw
>
>
>
> 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.
>
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
> http://groups.yahoo.com/group/basicstamps/
>
> To unsubscribe from this group, send an email to:
> basicstamps-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to:
> http://docs.yahoo.com/info/terms/
>
>
>
>
wrote:
> Hello, everyone! I just joined the BASIC Stamp Group!
>
> I have become very interested in the BASIC Stamp concept. By
taining
> I am an Electrical Engineer, by 40+ years of experience a Software
> Engineer.
>
> I have a project in the planning stage that will require Analog to
> Digital conversion. The MAX1270 seems to offer the ideal chip for
my
> needs.
>
> I have to measure 4 DC current sources which will use 100 millivolt
> shunts in the negative (to system ground) line. One of these will
be
> bi-polar. My question is: What is the best way to amplify the 100
mv
> max voltage so that it will be in range for the MAX1270? I presume
> that I need to use an op-amp, but it has been a looong time since
I've
> done this sort of thing (retired now).
>
> Any suggestions/pointers will be welcome!
>
> Oh, and a belated Happy New Year!
>
> Russ Ranshaw
Hi Russ,
One of the questions that comes to mind is the upper and lower end of
the range you need.
Do you need rail to rail or can you use 12V as your power supply ?
Two thoughts here. One is that if you are not going near zero, you
can use a cheaper op-amp that drops out, and if you use 12V power,
you can use an op-amp that that drops out near the upper rail, but
will be fine at 5 volts.
Jon mentioned the 11 channel TI chip that has serial comm to the
Stamp. There is a lot of information on this list and the Parallax
website for this so it is pretty easy to use to get started.
That said, if you use a quad op-amp in an instrument connection, you
can eliminate a lot of the variations due to board temperature on the
signal out of the ap-amp. And the TI chip has internal temperature
monitoring so you can also calculate out for temperature there.
And lastly monitor board voltage. Sid (NewZed) and I had worked on
a project and he realized that all the readings were off ever so
slightly and in his pursuit for excellence, found that board voltage
was off and then figured that by monitoring board voltage and
correcting for that, the readings lined up perfectly.
Also, IIRC Keithly Metrabyte has a book on low voltage signals. Very
interesting read. I didn't find it on therei website so it might
require a phone call.
Dave
Thanks for your rely. Where can I find information/buy the TLC2543?
In addition to the four DC currents, there will be three or four DC
voltages in 0-10v range.
Russ
--- In basicstamps@yahoogroups.com, "Jonathan Peakall" <jpeakall@p...>
wrote:
> Russ,
>
> I like the TLC2543, for the simple reason it can be set to read
directly in
> mV, with 1 mV resolution. Max does make chips with 1mV resolution, but I
> don't know the part # off hand.
>
> If all of your signals are around 100mV, you could use an external
vRef of
> 100mV or a little above whatever you max input would be. If you need
> resolution of more than 1mV, you will need an op-amp.
>
> Jonathan
>
> www.madlabs.info
>
>
>
>
Original Message
> From: "russranshaw" <russranshaw@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Saturday, January 17, 2004 7:44 AM
> Subject: [noparse][[/noparse]basicstamps] A/D question
>
>
> > Hello, everyone! I just joined the BASIC Stamp Group!
> >
> > I have become very interested in the BASIC Stamp concept. By taining
> > I am an Electrical Engineer, by 40+ years of experience a Software
> > Engineer.
> >
> > I have a project in the planning stage that will require Analog to
> > Digital conversion. The MAX1270 seems to offer the ideal chip for my
> > needs.
> >
> > I have to measure 4 DC current sources which will use 100 millivolt
> > shunts in the negative (to system ground) line. One of these will be
> > bi-polar. My question is: What is the best way to amplify the 100 mv
> > max voltage so that it will be in range for the MAX1270? I presume
> > that I need to use an op-amp, but it has been a looong time since I've
> > done this sort of thing (retired now).
> >
> > Any suggestions/pointers will be welcome!
> >
> > Oh, and a belated Happy New Year!
> >
> > Russ Ranshaw
> >
> >
> >
> > 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.
> >
> >
> > Yahoo! Groups Links
> >
> > To visit your group on the web, go to:
> > http://groups.yahoo.com/group/basicstamps/
> >
> > To unsubscribe from this group, send an email to:
> > basicstamps-unsubscribe@yahoogroups.com
> >
> > Your use of Yahoo! Groups is subject to:
> > http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
The TLC sample code is on the Parallax website, and if you do a google
search for "TLC2543" you will find the component spec. sheet in PDF format.
The TLC2543 has a max input of 6.5V. So, to measure higher voltages, you
will need to either use a different chip, or use a voltage divider. A
voltage divider will of course clip your range/resolution.
One way to approach it might be to use an external vRef for the 100mV
inputs, then switch over to internal vRef to measure the 10V inputs with a
volatge divider. The vRef can be set through software on the TLC2543. Note
that you MUST make sure that the divided voltage is less than the vRef.
Otherwise, a CMOS lockup can occur that will burn up the chip. And if you
happen to be running it off the Stamp's VDD, you will burn it out too. Don't
ask how I know this to be true ;-P. Ouch! I would also reccomend putting a
10-100k resistor in series with the divided voltage input. This will limit
current should such a lockup occur.
What resolution do you need on the 10V inputs?
Jonathan
www.madlabs.info
Original Message
From: "russranshaw" <russranshaw@y...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, January 18, 2004 8:21 AM
Subject: [noparse][[/noparse]basicstamps] Re: A/D question
> Jonathan,
>
> Thanks for your rely. Where can I find information/buy the TLC2543?
>
> In addition to the four DC currents, there will be three or four DC
> voltages in 0-10v range.
>
> Russ
>
> --- In basicstamps@yahoogroups.com, "Jonathan Peakall" <jpeakall@p...>
> wrote:
> > Russ,
> >
> > I like the TLC2543, for the simple reason it can be set to read
> directly in
> > mV, with 1 mV resolution. Max does make chips with 1mV resolution, but I
> > don't know the part # off hand.
> >
> > If all of your signals are around 100mV, you could use an external
> vRef of
> > 100mV or a little above whatever you max input would be. If you need
> > resolution of more than 1mV, you will need an op-amp.
> >
> > Jonathan
> >
> > www.madlabs.info
> >
> >
> >
> >
Original Message
> > From: "russranshaw" <russranshaw@y...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Saturday, January 17, 2004 7:44 AM
> > Subject: [noparse][[/noparse]basicstamps] A/D question
> >
> >
> > > Hello, everyone! I just joined the BASIC Stamp Group!
> > >
> > > I have become very interested in the BASIC Stamp concept. By taining
> > > I am an Electrical Engineer, by 40+ years of experience a Software
> > > Engineer.
> > >
> > > I have a project in the planning stage that will require Analog to
> > > Digital conversion. The MAX1270 seems to offer the ideal chip for my
> > > needs.
> > >
> > > I have to measure 4 DC current sources which will use 100 millivolt
> > > shunts in the negative (to system ground) line. One of these will be
> > > bi-polar. My question is: What is the best way to amplify the 100 mv
> > > max voltage so that it will be in range for the MAX1270? I presume
> > > that I need to use an op-amp, but it has been a looong time since I've
> > > done this sort of thing (retired now).
> > >
> > > Any suggestions/pointers will be welcome!
> > >
> > > Oh, and a belated Happy New Year!
> > >
> > > Russ Ranshaw
> > >
> > >
> > >
> > > 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.
> > >
> > >
> > > Yahoo! Groups Links
> > >
> > > To visit your group on the web, go to:
> > > http://groups.yahoo.com/group/basicstamps/
> > >
> > > To unsubscribe from this group, send an email to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > >
> > > 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.
>
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
> http://groups.yahoo.com/group/basicstamps/
>
> To unsubscribe from this group, send an email to:
> basicstamps-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to:
> http://docs.yahoo.com/info/terms/
>
>
>
>
> --- In basicstamps@yahoogroups.com, "russranshaw" <russranshaw@y...>
> wrote:
> > Hello, everyone! I just joined the BASIC Stamp Group!
> >
> > I have become very interested in the BASIC Stamp concept. By
> taining
> > I am an Electrical Engineer, by 40+ years of experience a Software
> > Engineer.
> >
> > I have a project in the planning stage that will require Analog to
> > Digital conversion. The MAX1270 seems to offer the ideal chip for
> my
> > needs.
> >
> > I have to measure 4 DC current sources which will use 100 millivolt
> > shunts in the negative (to system ground) line. One of these will
> be
> > bi-polar. My question is: What is the best way to amplify the 100
> mv
> > max voltage so that it will be in range for the MAX1270? I presume
> > that I need to use an op-amp, but it has been a looong time since
> I've
> > done this sort of thing (retired now).
> >
> > Any suggestions/pointers will be welcome!
> >
> > Oh, and a belated Happy New Year!
> >
> > Russ Ranshaw
>
>
> Hi Russ,
>
> One of the questions that comes to mind is the upper and lower end of
> the range you need.
>
> Do you need rail to rail or can you use 12V as your power supply ?
> Two thoughts here. One is that if you are not going near zero, you
> can use a cheaper op-amp that drops out, and if you use 12V power,
> you can use an op-amp that that drops out near the upper rail, but
> will be fine at 5 volts.
>
> Jon mentioned the 11 channel TI chip that has serial comm to the
> Stamp. There is a lot of information on this list and the Parallax
> website for this so it is pretty easy to use to get started.
>
> That said, if you use a quad op-amp in an instrument connection, you
> can eliminate a lot of the variations due to board temperature on the
> signal out of the ap-amp. And the TI chip has internal temperature
> monitoring so you can also calculate out for temperature there.
>
> And lastly monitor board voltage. Sid (NewZed) and I had worked on
> a project and he realized that all the readings were off ever so
> slightly and in his pursuit for excellence, found that board voltage
> was off and then figured that by monitoring board voltage and
> correcting for that, the readings lined up perfectly.
>
>
> Also, IIRC Keithly Metrabyte has a book on low voltage signals. Very
> interesting read. I didn't find it on therei website so it might
> require a phone call.
>
> Dave
Who would I call to find out about Keithly's book? Do you know it's
exact title?
Russ
the gain by software to get an optimal voltage for readout, so you can use
the full resolution of your adc.
Oorspronkelijk bericht
Van: russranshaw [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=I_dWOgncyWb9fzxeuasFGcrhRTToKiC_zvY2ZWk3FRzs0RZV9vBOBvOaYyhCINuAc4rYqnmA6Pm6]home.rr@c...[/url
Verzonden: zondag 18 januari 2004 23:40
Aan: basicstamps@yahoogroups.com
Onderwerp: [noparse][[/noparse]basicstamps] Re: A/D question
--- In basicstamps@yahoogroups.com, "Dave Mucha" <davemucha@j...> wrote:
> --- In basicstamps@yahoogroups.com, "russranshaw" <russranshaw@y...>
> wrote:
> > Hello, everyone! I just joined the BASIC Stamp Group!
> >
> > I have become very interested in the BASIC Stamp concept. By
> taining
> > I am an Electrical Engineer, by 40+ years of experience a Software
> > Engineer.
> >
> > I have a project in the planning stage that will require Analog to
> > Digital conversion. The MAX1270 seems to offer the ideal chip for
> my
> > needs.
> >
> > I have to measure 4 DC current sources which will use 100 millivolt
> > shunts in the negative (to system ground) line. One of these will
> be
> > bi-polar. My question is: What is the best way to amplify the 100
> mv
> > max voltage so that it will be in range for the MAX1270? I presume
> > that I need to use an op-amp, but it has been a looong time since
> I've
> > done this sort of thing (retired now).
> >
> > Any suggestions/pointers will be welcome!
> >
> > Oh, and a belated Happy New Year!
> >
> > Russ Ranshaw
>
>
> Hi Russ,
>
> One of the questions that comes to mind is the upper and lower end of
> the range you need.
>
> Do you need rail to rail or can you use 12V as your power supply ?
> Two thoughts here. One is that if you are not going near zero, you
> can use a cheaper op-amp that drops out, and if you use 12V power,
> you can use an op-amp that that drops out near the upper rail, but
> will be fine at 5 volts.
>
> Jon mentioned the 11 channel TI chip that has serial comm to the
> Stamp. There is a lot of information on this list and the Parallax
> website for this so it is pretty easy to use to get started.
>
> That said, if you use a quad op-amp in an instrument connection, you
> can eliminate a lot of the variations due to board temperature on the
> signal out of the ap-amp. And the TI chip has internal temperature
> monitoring so you can also calculate out for temperature there.
>
> And lastly monitor board voltage. Sid (NewZed) and I had worked on
> a project and he realized that all the readings were off ever so
> slightly and in his pursuit for excellence, found that board voltage
> was off and then figured that by monitoring board voltage and
> correcting for that, the readings lined up perfectly.
>
>
> Also, IIRC Keithly Metrabyte has a book on low voltage signals. Very
> interesting read. I didn't find it on therei website so it might
> require a phone call.
>
> Dave
Who would I call to find out about Keithly's book? Do you know it's
exact title?
Russ
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.
Yahoo! Groups Links
To visit your group on the web, go to:
http://groups.yahoo.com/group/basicstamps/
To unsubscribe from this group, send an email to:
basicstamps-unsubscribe@yahoogroups.com
Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
wrote:
> Russ,
>
> The TLC sample code is on the Parallax website, and if you do a google
> search for "TLC2543" you will find the component spec. sheet in PDF
format.
>
> The TLC2543 has a max input of 6.5V. So, to measure higher
voltages, you
> will need to either use a different chip, or use a voltage divider. A
> voltage divider will of course clip your range/resolution.
>
> One way to approach it might be to use an external vRef for the 100mV
> inputs, then switch over to internal vRef to measure the 10V inputs
with a
> volatge divider. The vRef can be set through software on the
TLC2543. Note
> that you MUST make sure that the divided voltage is less than the vRef.
> Otherwise, a CMOS lockup can occur that will burn up the chip. And
if you
> happen to be running it off the Stamp's VDD, you will burn it out
too. Don't
> ask how I know this to be true ;-P. Ouch! I would also reccomend
putting a
> 10-100k resistor in series with the divided voltage input. This will
limit
> current should such a lockup occur.
>
> What resolution do you need on the 10V inputs?
>
> Jonathan
>
> www.madlabs.info
>
>
>
>
>
>
Original Message
> From: "russranshaw" <russranshaw@y...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, January 18, 2004 8:21 AM
> Subject: [noparse][[/noparse]basicstamps] Re: A/D question
>
>
> > Jonathan,
> >
> > Thanks for your rely. Where can I find information/buy the TLC2543?
> >
> > In addition to the four DC currents, there will be three or four DC
> > voltages in 0-10v range.
> >
> > Russ
> >
> > --- In basicstamps@yahoogroups.com, "Jonathan Peakall" <jpeakall@p...>
> > wrote:
> > > Russ,
> > >
> > > I like the TLC2543, for the simple reason it can be set to read
> > directly in
> > > mV, with 1 mV resolution. Max does make chips with 1mV
resolution, but I
> > > don't know the part # off hand.
> > >
> > > If all of your signals are around 100mV, you could use an external
> > vRef of
> > > 100mV or a little above whatever you max input would be. If you need
> > > resolution of more than 1mV, you will need an op-amp.
> > >
> > > Jonathan
> > >
> > > www.madlabs.info
> > >
> > >
> > >
> > >
Original Message
> > > From: "russranshaw" <russranshaw@y...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Saturday, January 17, 2004 7:44 AM
> > > Subject: [noparse][[/noparse]basicstamps] A/D question
> > >
> > >
> > > > Hello, everyone! I just joined the BASIC Stamp Group!
> > > >
> > > > I have become very interested in the BASIC Stamp concept. By
taining
> > > > I am an Electrical Engineer, by 40+ years of experience a Software
> > > > Engineer.
> > > >
> > > > I have a project in the planning stage that will require Analog to
> > > > Digital conversion. The MAX1270 seems to offer the ideal chip
for my
> > > > needs.
> > > >
> > > > I have to measure 4 DC current sources which will use 100
millivolt
> > > > shunts in the negative (to system ground) line. One of these
will be
> > > > bi-polar. My question is: What is the best way to amplify
the 100 mv
> > > > max voltage so that it will be in range for the MAX1270? I
presume
> > > > that I need to use an op-amp, but it has been a looong time
since I've
> > > > done this sort of thing (retired now).
> > > >
> > > > Any suggestions/pointers will be welcome!
> > > >
> > > > Oh, and a belated Happy New Year!
> > > >
> > > > Russ Ranshaw
> > > >
> > > >
> > > >
> > > > 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.
> > > >
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > > To visit your group on the web, go to:
> > > > http://groups.yahoo.com/group/basicstamps/
> > > >
> > > > To unsubscribe from this group, send an email to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > >
> > > > 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.
> >
> >
> > Yahoo! Groups Links
> >
> > To visit your group on the web, go to:
> > http://groups.yahoo.com/group/basicstamps/
> >
> > To unsubscribe from this group, send an email to:
> > basicstamps-unsubscribe@yahoogroups.com
> >
> > Your use of Yahoo! Groups is subject to:
> > http://docs.yahoo.com/info/terms/
> >
> >
> >
> >
Jonathan,
The DC voltages are arbitrary. I can scale them to any needed range,
as the actual voltages are much higher (50 to 100 volts). So this
isn't really a problem.
I just ordered a TLC2543 plus a box full of other goodies. I did find
the TLC2532 data sheet as was suggested, even found a suppler. Never
found it on the Parallax site.
I'd like to discuss the project with you off-line if you wouldn't
mind. I'm not quite ready to discuss it on an open forum. I think
you might be interested in the application.
Russ
>the TLC2532 data sheet as was suggested, even found a suppler. Never
>found it on the Parallax site.
Try this URL:
<http://www.emesystems.com/OL2tlc2543.htm>
-- Tracy