16f84 Switch counter to lcd

[Paul & Lynn Tyrer]

I have to say i am astounded by the reponses.
A bit more information i have an old water meter that i have removed the
broken dial from the middle. Placed a hall effect switch in the cavity and
have it flasheing an led everytime the cylinder turns. Every 50 turns equals
1 gallon. This helped me find a slow leak and fix it. (The new water meter
outside does not have slow flow indicatior until the sun has turned the
display on.)
I then wanted to see how much we use on a typical day - hence this project.
Whilst i whole heartedly thank you for your help. I also am now a little
more cunfused and need to digest my options. I need to look at Input /
output again and whetheri can wait for the whole code to finish before the
switch gets polled, seems like a delay !
Regarding the bounce, i origianally had problems witht he hall switch
bouncing. but i now used a relay for the switch to contact, and have yet no
bounce problems when flashing a led with this setup. However this was before
i put a PIc in the picture.

Once again i thank you.

I will look at other languages too, but i think as my book is all Assembly I
am going to sturggle redesigning the lcd part.


Thanks again

Paul





















Firstly THANK YOU TO ALL.

The book i have demonstrates the Assembly language and each chapter
increases the knowledge depth. However i think i do not understand as much
as i think i do. I am Proud to say i figured the inputs and outputs and
using the data sheet assigned one of the input/output pins for the RB4
Switch and RB5 for the LED. I am currently looking at Interupts to see if i
can make head nor tail of them and hopefully the interupts would then break
into the program and do what it should do if the switch is pressed. If this
works i guess i put my increment count into the interrupt routine and then
when its finished or back to 0 or off then the rest of the program would
continue. Right now the header for the book puts A and B as outputs, do i
just change RB4 to a input or and if so how without setting bank B to all
inputs. This has stumped me for a an hour now. I have a day off and i said
to my wife i would paint but this has been taking me over all day so far.

Thanks again

Paul
























Just to update, I am hopelessly new and lost. I was a VB basic guy years ago
and remember a little of what I need to do but not a lot.
I know I will need a place to store the count, and will have a call list up
to 50 so when the count equals 10 I will have a call to put 1+0 on the
screen.
How do I :
Create a place to store the count.
Increment 1 to this count when the state changes
compare the stored count so when it equals 50 I increment the lcd by 1

I was hoping to find a piece of code out there in Google land to help me but
as of yet I have not been successful. However I do feel a sense of
achievement coming this far.

Any help is of course appreciated.

Thanks

Paul



Hi all.
I am trying to make a switch counter that would put on the lcd screen how
many times /50 the switch has been opened/closed.

I purchased the Book PIC In Practice and have been successful in building
the LCD circuit 2x20 and able to put the words I need to the screen. (after
spending hours trying to get it to work)

What I need and am hopelessly lost at this point, is to count the switch on
A0 and put the amount on to the screen. using the lcd Code in the above
book.

I beg you, this is not for any other purpose than to count the water gallon
usage in my house using a hall effect switch on the meter.

Can anyone help me with code/ suggestions etc

Thanks in advance

Paul

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[Bob Blick-4]

On Fri, 23 Oct 2009 17:35:51 -0500, "Paul & Lynn Tyrer"
<Paul@...> said:

> A bit more information i have an old water meter that i have removed the
> broken dial from the middle. Placed a hall effect switch in the cavity
> and
> have it flasheing an led everytime the cylinder turns. Every 50 turns
> equals
> 1 gallon. This helped me find a slow leak and fix it.

So how about instead of dividing by 50 you just add 2 each time, and put
a decimal place two digits over? That way you can read in 0.02 gallon
increments.

Even better, add 1 each time there is a change of switch state. You can
display down to 0.01 gallon. The 1/50 gallon won't be evenly divided in
two but it will help you spot leaks that much faster, and maybe the code
will be easy since any routine needs to spot changes of state.

Cheerful regards,

Bob

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[Jinx-4]

> origianally had problems witht he hall switch bouncing. but i now
> used a relay for the switch to contact

So using the Hall switch to energise a relay has cured the bounce ?
That sounds like the magnetic inertia of the coil is filtering the bounce
noise, the result being that the contacts don't chatter

If that's correct then adding an RC filter to pre-condition the switch
output would help, although not strictly necessary if the s/w can do
as good a job with a delay or polling routine. For example something
like 10k and 100nF would be a starting point. The 10k and 100n
are joined in series. Their junction goes to the PIC pin. The other end
of the resistor goes to the Hall switch, the other end of the capacitor
goes to 0V

http://en.wikipedia.org/wiki/RC_filter

You may need a discharge resistor (say 100k) across the capacitor if
the Hall switch doesn't drive to 0V, as the high impedance of the PIC
pin may not be low enough to discharge the capacitor between switch
pulses

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[Forrest W Christian-2]

Paul & Lynn Tyrer wrote:
> (The new water meter
> outside does not have slow flow indicatior until the sun has turned the
> display on.)
>  
Flashlight works on mine ... which is inside....
>  I need to look at Input /
> output again and whetheri can wait for the whole code to finish before the
> switch gets polled, seems like a delay !
>  
a 3/4" pipe will likely not do over 40GPM, which means less than 1 pulse
per second.   Shouldn't be a problem.
> Regarding the bounce, i origianally had problems witht he hall switch
> bouncing. but i now used a relay for the switch to contact, and have yet no
> bounce problems when flashing a led with this setup. However this was before
> i put a PIc in the picture.
>  
We're generally talking about bounces down 50 milliseconds...  so as
long as you insert a hundred milliscond delay, you should be ok (1000 ms
in a sec).   If your code takes over 100ms to complete, you can also
just use it as the debouncer....  

Mainly what you don't want to have happen is you read the pin, determine
it is high, then read it too soon again - because there is a chance that
it will turn on and off a whole bunch of times within the first few
milliseconds of turning it on.   Thus getting false counts.
> I will look at other languages too, but i think as my book is all Assembly I
> am going to sturggle redesigning the lcd part.
>  
The mikroe basic compiler I suggested has LCD part built in...   Plus
the basic might free you up to play with things like metering on a
last-minute, last-hour, and last day basic (think about creating a small
array in memory of buckets)... want ideas for this later, shoot me or
the list a ide...

Sample code for your application, assuming bits as described below:

Program Meter

'Adjust the following
dim LCD_RS as sbit at RB4_bit
    LCD_EN as sbit at RB5_bit
    LCD_D4 as sbit at RB0_bit
    LCD_D5 as sbit at RB1_bit
    LCD_D6 as sbit at RB2_bit
    LCD_D7 as sbit at RB3_bit
    LCD_RS_Direction as sbit at TRISB4_bit
    LCD_EN_Direction as sbit at TRISB5_bit
    LCD_D4_Direction as sbit at TRISB0_bit
    LCD_D5_Direction as sbit at TRISB1_bit
    LCD_D6_Direction as sbit at TRISB2_bit
    LCD_D7_Direction as sbit at TRISB3_bit

    hallsensor as sbit at RB6_bit

dim lasthall as bit
dim thishall as bit
dim hundreths as byte
dim gallons as word
dim hundrethsstring as string[2]
dim gallonsstring as string[4]


main:

     ' Adjust the following as needed for your processor and wiring.
     TRISB = 0
     PORTB = 0xff
     TRISB = 0xff


    Lcd_Init()                                  'Initialize display
    Lcd_Cmd(_LCD_CLEAR)      ' Clear Display
    Lcd_Cmd(_LCD_CURSOR_OFF)    'Turn cursor off

    lasthall=0
    hundreths = 0
    gallons = 0
    while TRUE
       thishall=hallsensor ' capture so if it bounces quickly, we don't
have logic errors

   

       if thishall<>lasthall then
           delay_ms (50) ' adjust as needed to eliminate bounces
           hundreths=hundreths+2;  // add 2 hundredths
           if hundredths>99 then
              hundreths=hundredths-100
               gallons=gallons+1
           end if
           ByteToStr(hundreths, hundrethsstring)
           if hundredthsstring[0]=' ' then hundrethsstring[0]='0'  '
Handle single digits correctly
           WordToStr(gallons, gallonsstring)
           Lcd_Out(1,5,gallons)
           Lcd_Chr(1,10,'.')
           Lcd_Out(1,11,hundrethsstring)

       if thishall then
          Lcd_Chr(1,1,'H')   'show status of hall sensor at 1,1
       else
          Lcd_Chr(1,1,'L')   'show status of hall sensor at 1,1
       end if
         

    wend
end.

The above should (besides the fact I never tested it in mikro basic, and
I likely have typos and the like) do exactly what you are asking for.  
Other thank the mikro-basic that should be mostly what you need.
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[Barry Gershenfeld-2]

I don't recall seeing this tidbit, so I thought I'd comment.

Regarding the bounce, i origianally had problems witht he hall switch
> bouncing. but i now used a relay for the switch to contact, and have yet no
> bounce problems when flashing a led with this setup. However this was
> before
> i put a PIc in the picture.
>

Don't be fooled by watching an LED.  Switch bounce is way faster than your
eye can see.  You would need an oscilloscope to see it.  Or...a fast
processor...!  If you have contact bounce, you will get tens of counts with
each switch closure.  And that's why everyone is talking so enthusiastically
about it.

Barry
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[SME-2]

> Regarding the bounce, i origianally had problems witht he hall switch
>> bouncing. but i now used a relay for the switch to contact, and have yet no
>> bounce problems when flashing a led with this setup. However this was
>> before
>> i put a PIc in the picture.

Note that a Hall switch tends to provide a degree of inbuilt
debouncing due to hysteresis in its response to a magnetic field. This
is often quite a significant amount compared to what may be needed.
For bounce to occur the field must rise to the trigger point and then
drop by the hysteresis amount and then rise to the trigger point
again. Also, in a rotating system where a Hall switch detects a
magnet, "bounce" tends to suggest axial vibration (to and fro around
the axis of rotation. In a rotating system the mechanical slop tends
(only TENDS) to be preloaded by windage and other forces and so reduce
such contributors to bounce. However, Murphy can make anything bounce
if the situation demands it.


    R
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