I have a problem with a sensor of pressure anb PBP 2.42

[debutpic]

pbp negative numbers

Hi all

I have a sensor of pressure MPX 2010 DP and a PIC 16F87X, which measures a pressure and a depression.
In the atmospheric pressure ~1013 mb the ADC = 126
with a depression of 2200 mb the ADC=149
I defined one équationressure = (-131) X (value ADC) + 17519
Everything is good in pressure value increases, but in depression under 0
my LCD show 65500 mb,65450 mb etc...

Define LCD_DBIT 4
Define LCD_RSREG PORTB
Define LCD_RSBIT 3
Define LCD_EREG PORTB
Define LCD_EBIT 2
' Define ADCIN parameters
Define ADC_BITS 8
Define ADC_CLOCK 3
Define ADC_SAMPLEUS 50

adval var byte
adval_final var word


TRISA = %11111111
ADCON1 = %00000010

Pause 500
loop: ADCIN 2, adval
adval_final=(adval*(-131))+17519
Lcdout $fe, 1
Lcdout "Value: ", DEC adval_final
Pause 100
Goto loop
End


help me please

 

[Tornado]

pbp negative number

Hi Debutpic how are you?
the equation is giving negative number.

Is the output of the pressure sensor linear?
example 1013mbar = 1.000 volts, 2026mbar = 2.000 volts

If not, you have to get data for various pressure points and built a table lookup.

Regards
Tornado

 

[Sobakava]

lcdout

I finished a project with pressure sensor (custom made) and
PIC18F452 project with CCS. Works fine.
I seems you have problem with size of variables. In CCS
compiler you can use 32bit integers and also floating point
variables.
BASIC is not a language for microcontrollers. (It is just my
opinion) :wink:

 

[Fragrance]

mpx2010 pic18f

hI,

JUST TRY WITH LOOKUP TABLE


REGARDS
FRAGRANCE

 

[Kripton2035]

basınç sensörü pbp

I finished a project with pressure sensor (custom made) and
PIC18F452 project with CCS. Works fine.
I seems you have problem with size of variables. In CCS
compiler you can use 32bit integers and also floating point
variables.
BASIC is not a language for microcontrollers. (It is just my
opinion) :wink:

it's not mine ! basic is a good language for microcontrolers. c is good for computers.
c is good also if you have floating point needs... althought some basics now have floating points.
basic is easier to learn then c
they are both usefull, each one in their own domain.
basic is also often cheaper than c...

I also made a project with on the same card with lcd display a pressure sensor, humidity sensor, light sensor and temperature sensor, all made with picbasic and it works fine too !

 

[para_racer]

picbasic pro lcdout dec 32bits

If you still haven't figured it out you can give this a try. There are lots of ways around this problem and here is one example.

adcin 0, temp 'Reads ambient temperature
IF temp >= 428 THEN 'Checks if temp is greater than
'or equal to 0 deg C
temp1 = (temp-428)/9 'Calculates temp in degrees C
lcdout $FE,1 'Clear LCD
lcdout $FE,$80, "Initializing...."
lcdout $FE,$C0, "Temp = ",DEC temp1, " Deg C"
ENDIF
IF temp < 427 THEN 'Checks if temp is less than 0 deg C
temp1 = (temp-427)/(-15) 'Calculates temp in degrees C
lcdout $FE,1
lcdout $FE,$80, "Initializing...."
lcdout $FE,$C0, "Temp = ","-",DEC temp1, " Deg C"
ENDIF

You can calculate the A/D value that causes the equation to go negative and use IF statements to split the positive and negative parts. The example above splits at the 0 crossing and uses a new equation for the negative value. The new equation devides the negative sign out and then you just display a "-" charactor before the negative number.

Hope this helps.

Wade :idea: