Use a pot to adjust COUNT value

[Sam]

I've been away from programming for a while now and need a little help if you will. I have a 40 watt CO2 laser cutter/engraver that requires water flow to keep the tube cool, the flow is provided by a small "waterfall" pump. If the flow were to stop the tube will be destroyed so I'm installing a flow sensor to monitor the flow. If the flow drops too low or stops, I will have the PIC activate a relay to instantly shut off power to the tube.

The flow sensor I'm using has a turbine with a magnet and a hall sensor on the outside, this of course produces pulses which vary with flow rate. I can program the PIC (12F675) with a COUNT value that will work but I would like to be able to adjust that value with a pot for future uses and I'd just really like to learn how to do this.

I'm using PBP, not sure which version, my manual is copyright 2003 which is when I purchased it.

I have the COUNT working fine and Im using ADCIN to read the pot, (also used it for reading a thermistor I may want to add to monitor temp of the water too). I'll post both codes below, again, I'd like to know how to make them work together using the pot to adjust the "pulse" value in COUNT if anyone can get me on the right track.

Thanks !

COUNT

@ DEVICE pic12F675, INTRC_OSC_NOCLKOUT
@ DEVICE pic12F675, WDT_ON
@ DEVICE pic12F675, PWRT_ON
@ DEVICE pic12F675, MCLR_OFF
@ DEVICE pic12F675, BOD_ON

c var byte

pulse var word
Green var GPIO.2
Red Var GPIO.0

low Red
Low Green

flow:
count GPIO.1, 500, pulse
if pulse > 120 then
high Green            
goto flow
else 
gosub alert
endif
pause 100
goto flow



alert: 
for c = 1 to 4
low Green
high Red
pause 100
low Red
pause 500
next

When flow is good, Green LED is lit, when no flow or too little flow, Red flashes routine. I'll add a relay to another pin.

ADCIN

CMCON=�000111
ANSEL=�000000





@ DEVICE pic12F675, INTRC_OSC_NOCLKOUT
@ DEVICE pic12F675, WDT_ON
@ DEVICE pic12F675, PWRT_ON
@ DEVICE pic12F675, MCLR_OFF
@ DEVICE pic12F675, BOD_ON

define ADC_BITS 8
define ADC_CLOCK 3


rdpot var word
Green var GPIO.2
Red Var GPIO.0
Blue var GPIO.4
Yellow var GPIO.5

low Red
Low Green

flow:
adcin 1,rdpot
if rdpot > 20 then
high Green
else
low Green 
endif 
if rdpot > 80 then
High Red
else
Low Red
endif
if rdpot > 110 then
high Blue
else
low Blue
endif
if rdpot < 20 then
high Yellow
else
low Yellow
endif
goto flow

I did the four LEDs just to see it work.

[mackrackit]

Are you wanting to use the POT to change the COUNT period or the value the count var compares to?

Also, have you looked/thought about PULSIN ?

[Sam]

I started off with trying to use PULSIN, it worked but very strangely and I couldn't get it to adjust properly, COUNT works absolutely perfect for this application.

I want the pot to be able to vary the value not the period. you see in the COUNT code "if pulse > 120 then", that's what I'd like to vary with a pot if possible.

Thanks

[HenrikOlsson]

Hi,
As far as I can see you've already done it.
You have your pot, which you read with ADCIN and get a value in rdpot, then you have your sensor which read with count and get a value in pulse. Then just do

Flow:
  COUNT GPIO.1, 500, pulse
  ADCIN 1, rdpot

  IF pulse < rdpot THEN   ' Compare pulse with rdpot
    ' Flow is under limit
    ' Do what needs to be done.
  ELSE
    ' Flow is OK  
  ENDIF

  Goto Flow

Or you can use a series of IF-THEN to light up the various LEDs or perhaps SELECT CASE, like

' rdpot sets the absolute low limit = red ligtht and stop
SELECT CASE pulse
  pulse is < rdpot
    ' Stop and turn on red LED

  pulse is < (rdpot * 2)
    ' Turn on yellow LED

  pulse is < (rdpot * 4)
     'Turn on Green LED

  END SELECT

Something like that (untested). To be honest, when I think about it I'm not exactly sure how SELECT CASE works in this case. I mean when pulse < rdpot all cases are true and I'm not sure if it only executes the first the one and then exits (which is what we want) or if it continues to evauluate the other cases as well. Worth a try peraps.

/Henrik.

[Sam]

Henrik, you are correct ! I had it close and didn't even realize it. The code below seems to work exactly like I want it to. Just need to add an output for a relay now.

I've been wanting to learn how to use a pot for things like this for a long time, I have other uses for it now too.

Thanks VERY much for your help, I really appreciate it,

Sam

Adjust pot for desired water flow rate

CMCON=�000111
ANSEL=�000000





@ DEVICE pic12F675, INTRC_OSC_NOCLKOUT
@ DEVICE pic12F675, WDT_ON
@ DEVICE pic12F675, PWRT_ON
@ DEVICE pic12F675, MCLR_OFF
@ DEVICE pic12F675, BOD_ON

define ADC_BITS 8
define ADC_CLOCK 3 

rdpot var word
c var byte
pulse var word
Green var GPIO.2
Red Var GPIO.0


low Red
Low Green

PAUSE 50

flow:
count GPIO.4, 500, pulse
adcin 1,rdpot
if PULSE > RDPOT then
high Green
low RED            
goto flow
else 
GOSUB ALERT
endif
pause 50
goto flow



alert: 
for c = 1 to 4
low Green
high Red
pause 100
low Red
pause 500
next