Stable ADC readings

[HankMcSpank]

Excellent.....many thanks, I shall use that code gratuitously.

[Ioannis]

Have you tested this fast averaging with Hysterisis by Darrel:

http://www.picbasic.co.uk/forum/cont...ith-hysteresis

Ioannis

[HankMcSpank]

Yes I have (& very good it is too) , but I'd rather have this jittery AtoD values 'cleaned up' at the source (rather than putting averaging in place to address unstability caused by avoidable factors)

[Bruce]

Just include an RC filter on the A/D input, and put the PIC to sleep just before enabling the A/D conversion. This returns very stable readings in most applications with a stable power supply or Vref.

[fratello]

Nice subject !
I use a similar code for reading the over-current of one DC motor :

check:           
 vt  =0
 vs  =0
 grup=0
 cnt =0
 pause 50					
 for cnt = 1 to 10
 	adcin 3, adval
 	vt=adval * 5000
 	vt=div32 1023
 	grup=vt+grup
 	pause 5
 next cnt
 vs=grup / 10
      if (vs > checkin) or (T1Count > 50) then 		   
  	     	gpio.0=0
           	gpio.5=0
      endif

If the averge of 10 readings it's bigger than checkin value (or time exceed 5 seconds) then gpio.0 and gpio.5 goes low.
It's one good ideea to use ADCON instead ADCIN ? How to do this and keeping average of 10 readings ?

[fratello]

It's this correct ?
In header of code I add :

    ADCON0 = %10001101      ' ADC input on GPIO.4/AN3/pin3 (page 41)
                            ' MSB 1 = Right Justify                   "1"    
                            '     0 = Vdd as voltage reference        "0"
                            '     0 = n/a                             "00"
                            '     0 = n/a
                            '     1 = select channel 03 (bit 2 of 2)  "11"
                            '     1 = select channel 03 (bit 1 of 2)
                            '     0 = conversion status (see routine) "0"
                            ' LSB 1 = A/D converter module is on      "1"

And I modify the "check" subroutine like that :

check:           
 vt  =0
 vs  =0
 grup=0
 cnt =0
 pause 50			
 for cnt = 1 to 10
      ADCON0.1 = 1
      NOT_DONE:
		if ADCON0.1 = 1 THEN NOT_DONE
            Pause 10
            adval.highbyte = ADRESH
            adval.lowbyte = ADRESL
 PAUSE 10
 	vt=adval * 5000
 	vt=div32 1023
 	grup=vt+grup
 PAUSE 10
 next cnt
 vs=grup / 10
      if (vs > checkin) or (T1Count > 50) then 		   
  	     	gpio.0=0
           	gpio.5=0
      endif

The hardware it's in picture.
Thanks !

[fratello]

I've tested the code ; it's OK.