Little math help

TC

I am working on a little project that reads the voltage from a ADC0831 I have a working program, but I am looking to save RAM. I would like to use just one variable if i can

here is the math program that works

· FOR index = 1 TO 255
··· HIGH CS_main
··· LOW CS_main
··· LOW CLK
··· PULSOUT CLK, 210
··· SHIFTIN ADCData,CLK,MSBPOST,[noparse][[/noparse]adc\8]
··· ADC_AVG = ADC_AVG + adc
· NEXT

··· ADC_AVG = ADC_AVG / 255
··· v = 15 * ADC_AVG / 255
··· r·= 15 * ADC_AVG //255
··· v2 = 10 * r / 255

· SEROUT VFD, Baud, [noparse][[/noparse]$1F, $24, 0, 0, 0, 0,"Primary· = ", DEC2 v, ".", DEC1 v2,"V" ]

to give a little info on what I am doing. I am measuring a car battery. I am taking the average output from the ADC0831 then converting it to " 00.0 " format. then sending it to a VFD display. I am not a math wiz, but I know there are some amazing people that can fix what I am looking for.

Thanks
TC



Post Edited (TC) : 7/13/2006 2:07:57 AM GMT

Tracy Allen

If the index goes from 0 to 255 (instead of 1 to 255), then there wil be 256 samples:

FOR index = 0 TO 255
' ... as above
NEXT
ADC_AVG = 150 ** ADC_AVG

Note use of the ** operator. This last operation converts ADC_AVG, the whole accumulation, directly to a number 0 to 150. Then display it like this...

SEROUT VFD, Baud, [noparse][[/noparse]$1F, $24, 0, 0, 0, 0,"Primary = ", DEC ADC_AVG/10, ".", DEC1 ADC_AVG,"V" ]

There is no need for the intermediate calculations and variables.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com

TC

Thank you Tracy, I will try it tonight

TC

TC

Tracy,

I tryed your Math Change and there is a 1 tenth of a volt difference from the one I have. The good part is i don't care. the only thing I would like to know is why in laymans terms.

TC

TC

Tracy,

Never mind I did not change the index from 1 to 0. fixed it right up

TC

TC

Tracy,

You killed two birds with one stone for me. I was trying to find a way to calibrate what the output is and now I can. lets say

ADC_AVG = 236 = 13.8 Volts (i think, not at home computer)

but with my Fluke Volt meter, i am getting 14.0 volts, all I have to do is add 2 to the 150

ADC_AVG = 152 ** ADC_AVG

and now the voltage reading is right. see what I an looking for is to read the voltage at a certan part (IE. Battery, Amplifier, ect.) and the ADC0831 can not be at the part, and I was getting voltage drops because of the wire runs. well now I can account for them in the car with out a computer.


READ VOLT_CAL, CAL
ADC_AVG = CAL ** ADC_AVG

I have A programing page that allows me to change things on the fly now I have one more

Thanks

Tracy Allen

Great! glad I could help. The Stamp operators */ and ** are generally very useful for things like this, multiplying by fractions and making calibration constants.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com