Plz help building a voltmeter on PIC12F683 - Electronic Circuits Projects Diagrams Free

MrSpock · 4th December 2007, 06:07 AM

I'm beginning discovering a PIC world. Trying to build a voltmeter indicator, so it will turn LED on if input voltage drops lower than 3 Volts, and turn it back off it the voltage goes back. It sounds awefully simple, but I'm stuck for couple of day already. I'm using PIC12F683, in MicroCode Studio with PicBasicPro 2.47, and PICKit 2. I'd really appreciate if somebody could give me a code example how to make it work. Thanks in advance.

MrSpock · 6th December 2007, 11:19 AM

Quote:

Originally Posted by MrSpock

I'm beginning discovering a PIC world. Trying to build a voltmeter indicator, so it will turn LED on if input voltage drops lower than 3 Volts, and turn it back off it the voltage goes back. It sounds awefully simple, but I'm stuck for couple of day already. I'm using PIC12F683, in MicroCode Studio with PicBasicPro 2.47, and PICKit 2. I'd really appreciate if somebody could give me a code example how to make it work. Thanks in advance.

Here where I'm so far [see code below]. Conversion seems like working, but I can't make both LEDs go HIGH simultaniously! In other words when Vin somewhere between 86 and 170 both LEDs go into glow or blink. Is there a trick to make both of them go ON at the same time? Or am I doing something wrong?

PIC12F683 connections:
Pin 3 - Input 0-5V
Pin 4 - +5V
Pin 6, 7 - LEDs

Code:

Code:

GrnLED  VAR    GPIO.0   ' Define green pulse-width variable
RedLED  VAR    GPIO.1   ' Define red pulse-width variable
Vin     VAR    BYTE     ' Allocate A/D variable

'A/D Parameters
DEFINE OSC 8
DEFINE ADC_BITS 8		' Use 10-bit A/D as 8-bit A/D

ANSEL.3 = 1				' Set ANS3 as analog input pin
ANSEL.4 = 0				' Set A/D clock
ANSEL.5 = 1
ANSEL.6 = 0
        
ADCON0.0 = 1            ' Turn On A/D
ADCON0.2 = 1			' A/D channel 3
ADCON0.3 = 1            ' ?
ADCON0.6 = 0			' VDD is voltage reference
ADCON0.7 = 0            ' Left Justify result

'GPIO port pins 0, 1 as outputs
TRISIO.0 = 0
TRISIO.1 = 0

PauseUs 100  

start:

    ADCON0.1 = 1        ' Start conversion
    while ADCON0.1 = 1  ' Wait for conversion           
        PauseUs 100   
    wend                    
    Vin = ADRESH
    if Vin < 85 then
        HIGH GrnLED
        'LOW RedLED
    endif
    if Vin > 86 AND Vin < 170 then
        HIGH GrnLED   
        HIGH RedLED
    endif
    if Vin > 171 then
        HIGH RedLED
        'LOW GrnLED    
    endif   
    PauseUs 250
        
goto start

Here is my code:

mramos1 · 6th December 2007, 02:34 PM

Here are 3 things to check.

Are you sure you have enough power for the circuit? Check this first.
Make sure MCLR is handled properly.
Are interrupts turned off?

Pommie · 6th December 2007, 03:35 PM

Looking at your code, you should have both LEDs turned on. If you haven't then I would suspect you are overloading the pic pins and causing a RMW problem. Try placing higher value resistors in series with your LEDs, something like 1K. Alternatively, place a PauseUs(10) after each write to an LED.

Mike.

MrSpock · 6th December 2007, 04:06 PM

Thank you for response, mramos1.

Quote:

Originally Posted by mramos1

Are you sure you have enough power for the circuit? Check this first.

Yes, more than enough. Tried it in Proteus - same result.

Quote:

Originally Posted by mramos1

Make sure MCLR is handled properly.

Tried connecticting MCLR pin through 10K ressistor, no luck.

Quote:

Originally Posted by mramos1

Are interrupts turned off?

I put DISABLE directive, it should turn interrups off, right? Anyway, still blinking.

MrSpock · 6th December 2007, 04:07 PM

Quote:

Originally Posted by Pommie

Looking at your code, you should have both LEDs turned on. If you haven't then I would suspect you are overloading the pic pins and causing a RMW problem. Try placing higher value resistors in series with your LEDs, something like 1K. Alternatively, place a PauseUs(10) after each write to an LED.

Mike.

Tried both, no luck. I'm using Proteus before testing it on a breadboard, so it shouldn't be a problem with power.

mramos1 · 6th December 2007, 04:14 PM

How fast do they blink?

Maybe make the PauseuS 250 to say 2000 and see if the blink rate changes.

Also, can you single step? Halt (breakpoint) at the end of the routine and see if the LEDS stay solid.

EDIT: Not sure what Proteus is. Is it a simulator? Or start PIC kit board?

MrSpock · 6th December 2007, 04:16 PM

Simplified the program to the following, still blinking! Something really wrong with configuration here. Any ideas?

Code:

GrnLED  VAR    GPIO.0   ' Define green pulse-width variable
RedLED  VAR    GPIO.1   ' Define red pulse-width variable

'A/D Parameters
DEFINE OSC 8
DEFINE ADC_BITS 8		' Use 10-bit A/D as 8-bit A/D

ANSEL.3 = 1				' Set ANS3 as analog input pin
ANSEL.4 = 0				' Set A/D clock
ANSEL.5 = 1
ANSEL.6 = 0
        
ADCON0.0 = 1            ' Turn On A/D
ADCON0.2 = 1			' A/D channel 3
ADCON0.3 = 1            ' ?
ADCON0.6 = 0			' VDD is voltage reference
ADCON0.7 = 0            ' Left Justify result

'GPIO port pins 0, 1 as outputs
TRISIO.0 = 0
TRISIO.1 = 0

DISABLE
PauseUs 100  

start:        
    
        HIGH GrnLED
        PauseUs(10)
        HIGH RedLED
        PauseUs(500)
        
goto start

MrSpock · 6th December 2007, 04:21 PM

Quote:

Originally Posted by mramos1

How fast do they blink?

Maybe make the PauseuS 250 to say 2000 and see if the blink rate changes.

Also, can you single step? Halt (breakpoint) at the end of the routine and see if the LEDS stay solid.

EDIT: Not sure what Proteus is. Is it a simulator? Or start PIC kit board?

They blink about 10 - 50 Hz. The problem is that they can't be ON both. As soon as I put HIGH GPIO.1, GPIO.1 goes LOW. Even with Pauses. Not sure how to use breakpoints. Will research it.

Yes, ISIS Proteus is a simulator.

Pommie · 6th December 2007, 04:37 PM

Is the Watch Dog Timer turned off? If yes then it's something to do with your simulator.

Mike.

blueroomelectronics · 6th December 2007, 04:37 PM

The 12F683 has a comparator module and CVRef, this should be a very simple program.
Comparator mode 3 looks promising, and CVRef can produce very close to 3V

matc · 6th December 2007, 04:57 PM

Got resistors on your leds to limit current?

When you get that working, in your first program remember that values 85,86,170 & 171 will do nothing.
You want to test your ranges more like:
if <85 ...
if >=85 AND <170 ...
if >=170 ...

MrSpock · 6th December 2007, 05:56 PM

Quote:

Originally Posted by Pommie

Is the Watch Dog Timer turned off? If yes then it's something to do with your simulator.

Mike.

I tried to use @ DEVICE PIC12F683, WDT_ON and @ DEVICE PIC12F683, WDT_OFF
Same effect. Not sure it's a correct way of configuring Watch Dog. I tried to program the chip and put on breadboard - it acts exactly like on simulator. Only one LED goes ON.

MrSpock · 6th December 2007, 06:03 PM

Quote:

Originally Posted by matc

Got resistors on your leds to limit current?

Yes. two 300 Ohm resistors between LED cathods and the ground.

Quote:

Originally Posted by matc

When you get that working, in your first program remember that values 85,86,170 & 171 will do nothing.
You want to test your ranges more like:
if <85 ...
if >=85 AND <170 ...
if >=170 ...

The numbers here are for the reference, I'm using a voltage divider potentiometer attached to the input. It changes the input voltage from 0V to 5V. Ideally PIC should turn one LED on at the beginning, both in the middle, and another one at the end of the potentiometer run.

MrSpock · 6th December 2007, 06:05 PM

Quote:

Originally Posted by blueroomelectronics

The 12F683 has a comparator module and CVRef, this should be a very simple program.
Comparator mode 3 looks promising, and CVRef can produce very close to 3V

That is exactly my point! It should be very simple

I believe I'm missing something in configuration.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Title	Starter	Forum	Replies	Latest
Robot Building for Beginners	Souper man	Electronic Books	8	10th August 2008 06:11 PM
Simple 0-120VAC bar voltmeter help	qsiguy	Electronic Projects Design/Ideas/Reviews	8	13th October 2006 10:13 PM
I need a little help building a simple LED voltmeter	joecool85	Electronic Projects Design/Ideas/Reviews	14	2nd February 2006 05:18 PM
Voltmeter using EPROMs	robchava	Electronic Projects Design/Ideas/Reviews	1	17th June 2003 05:49 AM
Building a signal mixer (for music primary)	thec	Electronic Projects Design/Ideas/Reviews	4	3rd October 2002 06:07 PM

4th December 2007, 06:07 AM	(permalink)
MrSpock	Plz help building a voltmeter on PIC12F683 I'm beginning discovering a PIC world. Trying to build a voltmeter indicator, so it will turn LED on if input voltage drops lower than 3 Volts, and turn it back off it the voltage goes back. It sounds awefully simple, but I'm stuck for couple of day already. I'm using PIC12F683, in MicroCode Studio with PicBasicPro 2.47, and PICKit 2. I'd really appreciate if somebody could give me a code example how to make it work. Thanks in advance.

6th December 2007, 02:34 PM	(permalink)
mramos1	Here are 3 things to check. Are you sure you have enough power for the circuit? Check this first. Make sure MCLR is handled properly. Are interrupts turned off?

6th December 2007, 03:35 PM	(permalink)
Pommie	Looking at your code, you should have both LEDs turned on. If you haven't then I would suspect you are overloading the pic pins and causing a RMW problem. Try placing higher value resistors in series with your LEDs, something like 1K. Alternatively, place a PauseUs(10) after each write to an LED. Mike.

6th December 2007, 04:14 PM	(permalink)
mramos1	How fast do they blink? Maybe make the PauseuS 250 to say 2000 and see if the blink rate changes. Also, can you single step? Halt (breakpoint) at the end of the routine and see if the LEDS stay solid. EDIT: Not sure what Proteus is. Is it a simulator? Or start PIC kit board?

6th December 2007, 04:37 PM	(permalink)
Pommie	Is the Watch Dog Timer turned off? If yes then it's something to do with your simulator. Mike.

6th December 2007, 04:37 PM	(permalink)
blueroomelectronics	The 12F683 has a comparator module and CVRef, this should be a very simple program. Comparator mode 3 looks promising, and CVRef can produce very close to 3V __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

6th December 2007, 04:57 PM	(permalink)
matc	Got resistors on your leds to limit current? When you get that working, in your first program remember that values 85,86,170 & 171 will do nothing. You want to test your ranges more like: if <85 ... if >=85 AND <170 ... if >=170 ...