Stamp as Resistance Meter
Archiver
Posts: 46,084
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
Comments
To display a decimal point in the debug window I use this line of code:
DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
It displays 1 digit behind the decimal point. Ts is 10 times the actual
value, of course. In the rest of the program I keep my integers as large as
needed for this trick.
I guess you could do this with a hundred (two digits). A thousend will
probably cause problems as you may come too close te de size of a word
variable (ca. 65999).
Regards,
Klaus
Oorspronkelijk bericht
Van: Mike Blankenship [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=7RwmF48NG3NYQdEMGJmML_Een9v6bQkfBpX5VWjcACNCH48MKJvgOLDxsqnZ1dl-_gBhooquIG4SSIC8Ruv82dTmbS0]mike_blankenship@s...[/url
Verzonden: zondag 19 oktober 2003 9:12
Aan: basicstamps@yahoogroups.com
CC: mike_blankenship@s...
Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
To UNSUBSCRIBE, just send mail to:
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You need to solve for R2, given the constants R1 and Vin and the
measured value Vout:
R2 = R1 * Vout/(Vin-Vout)
This, involving a variable ratio times a constant, can be done most
easily and accurately on the Stamp using looped long division
calculation:
Vin con 5000 ' supply volts
R1 con 10000 ' reference resistor (1 meg = 10000*100ohms)
Vout var word ' from ADC
R2 var word ' find resistance
D var word ' ditto
J var nib ' ditto
' get Vout, based on unknown R2
Vout=1234 ' for example, millivolts
D = Vin - Vout ' 3766
'
binary division loop
for J=15 to 0 ' 16 bits
Vout=Vout//D<<1 ' remainder*2
R2.bit0(J)=Vout/D ' next bit
next
'
' exits with R2=21474 intermediate result
R2=R2**R1 ' final result, note ** operator
debug dec R2,"00 ohms" ' prints 327600 ohms
' "correct" value is 326668 ohms
Note that the precision of the calculation is about 100 ohms, given
the 10 megaohm reference resistor. Is that good enough? And, the
calculation works for R2 values up to 10 megaohms. There is more info
on the math posted on my web site at
http://www.emesystems.com/BS2math2.htm#longdivision
-- Tracy
>Hello,
>
>Im fairly new to the Stamp but I have had a real cool
>time learning how to use it.
>
>I am building a resistance meter .... On the front end
>of my circuit I have a Fixed resistor R1 (10M) setup
>in a voltage divider configuration with R2 being the
>un known resistance. The out put of my voltage divider
>is going straight to a MAX1202 12 bit A/D converter. I
>ve placed a 10M resistor as R2 and have had very
>stable results after I poll the A/D i receive the
>value 2500 + or - 2 LSB (Im using 5 volts for power).
>Im using the Voltage divider formula and my meter to
>verify accuracy :
>
>Vout = R2/R2+R1 x Vin
>
>5V
>|
>|
>\
>/ R1 10M
>\
>/
>|
>|
> AD > 2500 +- 2 LSB > Debug Screen
>|
>\
>/ R2 10M
>\
>/
>|
>|
>|
>GND
>
>Now I want to display the actual Resistance on my
>debug screen. This is where Im having troubles, the
>Stamp does not deal directlw with Floats only
>Integers.
>
>How do you rewrite Vout = R2/R2+R1 x Vin to solve for
>R2? I guess I still will have an issue because 2500
>needs to be calculated as 2.500 in the formula. Any
>advice would be greatly appreciated.
>
>BTW the thread about the proper setup of the AD helped
>me out ... the 1K resistor in line with the input of
>the AD stabalized my readings .an also a .01 uf cap to
>ground on the input, I seen this on the MAX1202 Eval
>Kit. everyone probally knows this but Maxim gives out
>free samples of parts ... Not the eval Kits though.
>
>mike
DEBUG CLS, DEC Ts/10, ".", DEC1 Ts
When adding a width specifier to DEC (or HEX or BIN) the digits will
come from the LSD side. If, for example, you want to display a value as
x.xx you would do this:
DEBUG DEC x/100, ".", DEC2 x
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=oabwaOzGmz_fklGPtqES4-DFVUsooFXkDzk03c1NE9JCpB24hGKrgEjxV3DjYqR_VH1Vi_UxqCjqSfxcKv7p]Klaus.Jong@n...[/url
Sent: Sunday, October 19, 2003 12:55 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hi Mike,
To display a decimal point in the debug window I use this line of code:
DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
It displays 1 digit behind the decimal point. Ts is 10 times the actual
value, of course. In the rest of the program I keep my integers as large
as needed for this trick.
I guess you could do this with a hundred (two digits). A thousend will
probably cause problems as you may come too close te de size of a word
variable (ca. 65999).
Regards,
Klaus
Oorspronkelijk bericht
Van: Mike Blankenship [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=JFhNBm19jOkRJVNfNiTVEU1HQtEr9wX3Gdoi2v6w37Tz7Cto_r7SstH5JH38EwYK3TJQ4wyDEpWoryZ3LnVf86gIOL9g]mike_blankenship@s...[/url
Verzonden: zondag 19 oktober 2003 9:12
Aan: basicstamps@yahoogroups.com
CC: mike_blankenship@s...
Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
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abuse@p....
It works fine, as expected :-).
Klaus
PS it's in the manual :-))))))).
Oorspronkelijk bericht
Van: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=CgJ_BzLGMeXTCh3nbthtNP8uSMsPlgg9YaagLx-kKSGf5AiWbrgTdK4pVPutwtMETZYY6lRavW4zowmaKb7uK2Q]jwilliams@p...[/url
Verzonden: maandag 20 oktober 2003 13:29
Aan: basicstamps@yahoogroups.com
Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Here's a simplification that won't give you any troubles:
DEBUG CLS, DEC Ts/10, ".", DEC1 Ts
When adding a width specifier to DEC (or HEX or BIN) the digits will
come from the LSD side. If, for example, you want to display a value as
x.xx you would do this:
DEBUG DEC x/100, ".", DEC2 x
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=sQZsDCejHb5tooeDHo1y_XkJYsRZQ7OpepbpyixkVX-Duv2LlF6AmhWRBa1keCulUAA_mobEI9v7n1_s_vY8_Q]Klaus.Jong@n...[/url
Sent: Sunday, October 19, 2003 12:55 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hi Mike,
To display a decimal point in the debug window I use this line of code:
DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
It displays 1 digit behind the decimal point. Ts is 10 times the actual
value, of course. In the rest of the program I keep my integers as large
as needed for this trick.
I guess you could do this with a hundred (two digits). A thousend will
probably cause problems as you may come too close te de size of a word
variable (ca. 65999).
Regards,
Klaus
Oorspronkelijk bericht
Van: Mike Blankenship [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=j-H7buZVB81lZoa6n72cR7VjvaJG2Yw-KIYdz38RXhlVazl_ov-tfQgrnodX6YC-R0mEJrac_69fTo3QMA3Z4q6qpY07Lg]mike_blankenship@s...[/url
Verzonden: zondag 19 oktober 2003 9:12
Aan: basicstamps@yahoogroups.com
CC: mike_blankenship@s...
Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
To UNSUBSCRIBE, just send mail to:
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in the manual? That never happens! <wicked grin>
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZQpj-sqU8U8vHbZ404MYaxg4o76NzVwQuBE7czl2UmXmeGnHWN0Uln2T748sfv-M06SLALhVfFaq3EDBCE5O]Klaus.Jong@n...[/url
Sent: Monday, October 20, 2003 12:31 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Thank you Jon,
It works fine, as expected :-).
Klaus
PS it's in the manual :-))))))).
Oorspronkelijk bericht
Van: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Q95wcl1H_Jy_0bjFdB0E8hxFkFh9vMunZSqlratvY4bGieQla5djTZnPbgJWubjj98srG5C-aQ2J2RLUUE4TsC8]jwilliams@p...[/url
Verzonden: maandag 20 oktober 2003 13:29
Aan: basicstamps@yahoogroups.com
Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Here's a simplification that won't give you any troubles:
DEBUG CLS, DEC Ts/10, ".", DEC1 Ts
When adding a width specifier to DEC (or HEX or BIN) the digits will
come from the LSD side. If, for example, you want to display a value as
x.xx you would do this:
DEBUG DEC x/100, ".", DEC2 x
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZQpj-sqU8U8vHbZ404MYaxg4o76NzVwQuBE7czl2UmXmeGnHWN0Uln2T748sfv-M06SLALhVfFaq3EDBCE5O]Klaus.Jong@n...[/url
Sent: Sunday, October 19, 2003 12:55 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hi Mike,
To display a decimal point in the debug window I use this line of code:
DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
It displays 1 digit behind the decimal point. Ts is 10 times the actual
value, of course. In the rest of the program I keep my integers as large
as needed for this trick.
I guess you could do this with a hundred (two digits). A thousend will
probably cause problems as you may come too close te de size of a word
variable (ca. 65999).
Regards,
Klaus
Oorspronkelijk bericht
Van: Mike Blankenship [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=f7b_AGfx6FzNrqyHlR-oJpff1jp-FWfZTlHyZaO1zbz4W-2k63z8XjfUKsFaJYIrmTDlpFDx_jv_CIXGjaAcTu00Wpx3AlIz]mike_blankenship@s...[/url
Verzonden: zondag 19 oktober 2003 9:12
Aan: basicstamps@yahoogroups.com
CC: mike_blankenship@s...
Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
To UNSUBSCRIBE, just send mail to:
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abuse@p....
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abuse@p....
to Z and had a jumpstart in programming these curious little things.
Take it as the comliment! The manual is superb and I had a nice time reading
it. Especially when you are used to the Microsoft C/C++ and MFC stuff it is
astonishingly clear and I could program right from the manual into the Stamp
;-).
Chapeau!!!
Klaus
Oorspronkelijk bericht
Van: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=IJp_-xBEraZ6jRIto3ayQy5_FLrfGAHWGuB3Q0-X7DOJaR8rVKp-3YdKWixmJuodKiOlzhOhOPLyUKwdA2eEpg]jwilliams@p...[/url
Verzonden: maandag 20 oktober 2003 18:33
Aan: basicstamps@yahoogroups.com
Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
You're kidding, right? You mean you actually found useful information
in the manual? That never happens! <wicked grin>
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=JAvXFuSWgoYXImDvisWvcQiEWkYd7wneH1PBHeA_wBjv_XhCIM-2F-uRo5AnS1dCKNTeYAfSNhiOd8xs8g]Klaus.Jong@n...[/url
Sent: Monday, October 20, 2003 12:31 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Thank you Jon,
It works fine, as expected :-).
Klaus
PS it's in the manual :-))))))).
Oorspronkelijk bericht
Van: Jon Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=IJp_-xBEraZ6jRIto3ayQy5_FLrfGAHWGuB3Q0-X7DOJaR8rVKp-3YdKWixmJuodKiOlzhOhOPLyUKwdA2eEpg]jwilliams@p...[/url
Verzonden: maandag 20 oktober 2003 13:29
Aan: basicstamps@yahoogroups.com
Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Here's a simplification that won't give you any troubles:
DEBUG CLS, DEC Ts/10, ".", DEC1 Ts
When adding a width specifier to DEC (or HEX or BIN) the digits will
come from the LSD side. If, for example, you want to display a value as
x.xx you would do this:
DEBUG DEC x/100, ".", DEC2 x
-- Jon Williams
-- Applications Engineer, Parallax
-- Dallas Office
Original Message
From: K de Jong [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=JAvXFuSWgoYXImDvisWvcQiEWkYd7wneH1PBHeA_wBjv_XhCIM-2F-uRo5AnS1dCKNTeYAfSNhiOd8xs8g]Klaus.Jong@n...[/url
Sent: Sunday, October 19, 2003 12:55 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hi Mike,
To display a decimal point in the debug window I use this line of code:
DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
It displays 1 digit behind the decimal point. Ts is 10 times the actual
value, of course. In the rest of the program I keep my integers as large
as needed for this trick.
I guess you could do this with a hundred (two digits). A thousend will
probably cause problems as you may come too close te de size of a word
variable (ca. 65999).
Regards,
Klaus
Oorspronkelijk bericht
Van: Mike Blankenship [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=iC4se_2KBPMfOfcoBsJxK9OC01Fma_krhTGJSLihjHqDhV1-2X1Ci4F6DbIslhVvmZAMAFMDHhaIcCgWw2LBgLUYUSg]mike_blankenship@s...[/url
Verzonden: zondag 19 oktober 2003 9:12
Aan: basicstamps@yahoogroups.com
CC: mike_blankenship@s...
Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
Hello,
Im fairly new to the Stamp but I have had a real cool
time learning how to use it.
I am building a resistance meter .... On the front end
of my circuit I have a Fixed resistor R1 (10M) setup
in a voltage divider configuration with R2 being the
un known resistance. The out put of my voltage divider
is going straight to a MAX1202 12 bit A/D converter. I
ve placed a 10M resistor as R2 and have had very
stable results after I poll the A/D i receive the
value 2500 + or - 2 LSB (Im using 5 volts for power).
Im using the Voltage divider formula and my meter to
verify accuracy :
Vout = R2/R2+R1 x Vin
5V
|
|
\
/ R1 10M
\
/
|
|
> AD > 2500 +- 2 LSB > Debug Screen
|
\
/ R2 10M
\
/
|
|
|
GND
Now I want to display the actual Resistance on my
debug screen. This is where Im having troubles, the
Stamp does not deal directlw with Floats only
Integers.
How do you rewrite Vout = R2/R2+R1 x Vin to solve for
R2? I guess I still will have an issue because 2500
needs to be calculated as 2.500 in the formula. Any
advice would be greatly appreciated.
BTW the thread about the proper setup of the AD helped
me out ... the 1K resistor in line with the input of
the AD stabalized my readings .an also a .01 uf cap to
ground on the input, I seen this on the MAX1202 Eval
Kit. everyone probally knows this but Maxim gives out
free samples of parts ... Not the eval Kits though.
mike
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I also love the spiral ring very usefule for begginers who need to
flip back and forth back and forth [noparse];)[/noparse]
mike
--- In basicstamps@yahoogroups.com, "K de Jong" <Klaus.Jong@n...>
wrote:
> Well......, to be honest, when I got my first Stamp I read the
manual from A
> to Z and had a jumpstart in programming these curious little
things.
>
> Take it as the comliment! The manual is superb and I had a nice
time reading
> it. Especially when you are used to the Microsoft C/C++ and MFC
stuff it is
> astonishingly clear and I could program right from the manual into
the Stamp
> ;-).
>
> Chapeau!!!
>
> Klaus
>
>
Oorspronkelijk bericht
> Van: Jon Williams [noparse][[/noparse]mailto:jwilliams@p...]
> Verzonden: maandag 20 oktober 2003 18:33
> Aan: basicstamps@yahoogroups.com
> Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
>
>
> You're kidding, right? You mean you actually found useful
information
> in the manual? That never happens! <wicked grin>
>
> -- Jon Williams
> -- Applications Engineer, Parallax
> -- Dallas Office
>
>
>
Original Message
> From: K de Jong [noparse][[/noparse]mailto:Klaus.Jong@n...]
> Sent: Monday, October 20, 2003 12:31 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
>
>
> Thank you Jon,
>
> It works fine, as expected :-).
>
> Klaus
>
> PS it's in the manual :-))))))).
>
>
Oorspronkelijk bericht
> Van: Jon Williams [noparse][[/noparse]mailto:jwilliams@p...]
> Verzonden: maandag 20 oktober 2003 13:29
> Aan: basicstamps@yahoogroups.com
> Onderwerp: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
>
>
> Here's a simplification that won't give you any troubles:
>
> DEBUG CLS, DEC Ts/10, ".", DEC1 Ts
>
> When adding a width specifier to DEC (or HEX or BIN) the digits
will
> come from the LSD side. If, for example, you want to display a
value as
> x.xx you would do this:
>
> DEBUG DEC x/100, ".", DEC2 x
>
> -- Jon Williams
> -- Applications Engineer, Parallax
> -- Dallas Office
>
>
>
Original Message
> From: K de Jong [noparse][[/noparse]mailto:Klaus.Jong@n...]
> Sent: Sunday, October 19, 2003 12:55 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
>
>
> Hi Mike,
>
> To display a decimal point in the debug window I use this line of
code:
>
> DEBUG CLS, DEC Ts/10,".",DEC Ts-((Ts/10)*10)
>
> It displays 1 digit behind the decimal point. Ts is 10 times the
actual
> value, of course. In the rest of the program I keep my integers as
large
> as needed for this trick.
>
> I guess you could do this with a hundred (two digits). A thousend
will
> probably cause problems as you may come too close te de size of a
word
> variable (ca. 65999).
>
> Regards,
>
> Klaus
>
>
>
>
>
Oorspronkelijk bericht
> Van: Mike Blankenship [noparse][[/noparse]mailto:mike_blankenship@s...]
> Verzonden: zondag 19 oktober 2003 9:12
> Aan: basicstamps@yahoogroups.com
> CC: mike_blankenship@s...
> Onderwerp: [noparse][[/noparse]basicstamps] Stamp as Resistance Meter
>
>
>
> Hello,
>
> Im fairly new to the Stamp but I have had a real cool
> time learning how to use it.
>
> I am building a resistance meter .... On the front end
> of my circuit I have a Fixed resistor R1 (10M) setup
> in a voltage divider configuration with R2 being the
> un known resistance. The out put of my voltage divider
> is going straight to a MAX1202 12 bit A/D converter. I
> ve placed a 10M resistor as R2 and have had very
> stable results after I poll the A/D i receive the
> value 2500 + or - 2 LSB (Im using 5 volts for power).
> Im using the Voltage divider formula and my meter to
> verify accuracy :
>
> Vout = R2/R2+R1 x Vin
>
> 5V
> |
> |
> \
> / R1 10M
> \
> /
> |
> |
> AD > 2500 +- 2 LSB > Debug Screen
> |
> \
> / R2 10M
> \
> /
> |
> |
> |
> GND
>
> Now I want to display the actual Resistance on my
> debug screen. This is where Im having troubles, the
> Stamp does not deal directlw with Floats only
> Integers.
>
> How do you rewrite Vout = R2/R2+R1 x Vin to solve for
> R2? I guess I still will have an issue because 2500
> needs to be calculated as 2.500 in the formula. Any
> advice would be greatly appreciated.
>
> BTW the thread about the proper setup of the AD helped
> me out ... the 1K resistor in line with the input of
> the AD stabalized my readings .an also a .01 uf cap to
> ground on the input, I seen this on the MAX1202 Eval
> Kit. everyone probally knows this but Maxim gives out
> free samples of parts ... Not the eval Kits though.
>
> mike
>
>
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Subject
> and Body of the message will be ignored.
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