PIC16F84A using pulsout and TMR0

[DragonBall_6]

Thanks to the reply.
Solar PV also called photovoltaic cell (direct absord sunlight and generate electricity).

***LCDOUT $fe,$1, #solarvoltage*****

Thus, the LCD only can display the value not above 5 volt,am I right??
If this is the case, if I want to display value above 5v on the LCD then is that possible.

If I'm using 4 Mhz crystal, do I need to have this sentences ***DEFINE ADC_CLOCK 3****?????


Thanks and please advice.

[Archangel]

Thanks to the reply.


Thus, the LCD only can display the value not above 5 volt,am I right??
If this is the case, if I want to display value above 5v on the LCD then is that possible.

.

Hi DragonBall_6,
What the voltage divider does is input voltage based upon the resistors ratio into the pic pin and hopefully limit it's input voltage to TTL levels. You have to write the code to do the math and then output the voltage numbers to suit your purpose. If you store the ADC value in a byte variable then ( and I am going out on a limb here as I am as new to pic programming as you are ) you should be able to express that as a number from 0 to 255. So if 5 v = 255 (input pin at 5 v when solar panel is at 15 volts) then 255 = 15 volts.So with a given voltage divider you can express 15 volts incremented in 255 steps. Anyone out there who is more knowledgable please ring in!
JS

[HenrikOlsson]

Hi,
Just as Joe says, the two resistors forms a voltage divider that "divides" the voltage fed to it by the ratio between the two resistors. The upper one is 2.2 times larger than the lower one so will loose 2.2 times as many volts over that one than over the lower one. Or if you wish to put ohms law to the test:

The total resistance is 3.2k, with a voltage of 15V there will be a current of (I = U / R) 4.6875mA flowing thru the two resistors. Now that current will produce a voltage over the lower resistor of (U = I*R) 4.6875V.

Since the PIC's AD pin is connected in parallel with the lower resistor the PIC will "see" a voltage between 0 and 4.6875V when the voltage from the solar PV is between 0 and 15V.

Now, in the code I showed you we set the ADCON1 register in a way that the ADC uses the PIC's powersupply as a reference voltage. What that means is that whatever the powersupply voltage is at the moment will produce the max reading from the ADC, so for the above to work it's important that the powersupply is stable at 5.0V.

We also said

DEFINE ADC_BITS 10

What that does is set the ADC code to give you a resolution of 10bits, or put another way, the result from the ADC will be between 0 - 1023. That is 0V on the input will give you 0 in SolarVoltage and 5V in will give you 1023 in SolarVoltage. The display will show that value, not the voltage.

To get the display to show actuall volts you need to scale the value. With a powersupply of 5.0V each bit in the ADC result is 0.00488V (5/1024) so if the display shows 958 the voltage at the PIC pin is ~4.67V which in turn corresponds to ~15V from the solar PV. (See the voltage divider)

Are you going to display the "real" voltage or just using the value to decide when to start the motor? If the later then you don't need to scale it at all, just use it as it is.

The DEFINE ADC_CLOCK 3 tells the ADC module inside the PIC what clock source to use. It has nothing to do with the Xtal you are using to drive the PIC.

/Henrik Olsson.

[mister_e]

and '3' comes from the datasheet in the ADCON1 register setting (register 11-2, page 128) ADCS2 table

[DragonBall_6]

Thanks to all the reply.
I really appreciated it. I will try it at lab.
Actually, I would like to receive A/D input from solar PV and after that there are 2 things to be done.
First, IF the A/D input is less that 2 volt then stop the motor ELSE the motor activated.
Secondly, at the same time A/D input from the solar pv is sent to the computer for processing and collected the data for every 15 minute. The result will be calculated and show in graph.
It would need some knowledge of the visual basic as database and link between vb and ms excel.

Somebody can guide me thru this?? Thank and please give advice.

[HenrikOlsson]

Hi,
Just compare the value you get from the ADC with the value that corresponds to 2V, if higher then run the motor, if lower then stop it, you can figure that out. You may need to introduce some hysteresis around the threshold.

Then send the value to the PC using the PBP's SEROUT command, or even better use the USART, a MAX232 level shifter and the HSEROUT command, see the manual. There's many examples on the forum.

For the PC/VB side have a look here: http://www.rentron.com/VisualBasic.htm
Just send the raw value from the PIC and use VB to scale it to volts if you like.

/Henrik Olsson.

[DragonBall_6]

I had try the program that you gave me. It is work.Thank.
Some problem has finding out....



***********'Produce squarewave on PortB.0 period~4.32s, 50% dutycycle.

Loop var Word

Main:
High PortB.0
For Loop = 0 to 2160 'Loop here for ~2.16s, tweak to match.
PauseUs 1000
Next
Low PortB.0
For Loop = 0 to 2160 'Loop here for ~2.16s, tweak to match.
PauseUs 1000
Next
Goto Main**********

The above is the code that you posted to me. Thanks to you again.
I had modify it like the code below:-

********'Produce squarewave on PortB.0 period~4.32s, 50% dutycycle.

Loop var Word
SolarVoltage var word
ADCON1 = %10001110

Main:

High PortB.0
For Loop = 0 to 2160 'Loop here for ~2.16s, tweak to match.
PauseUs 1000
ADCIN 0,SolarVoltage
LCDOUT $FE,$1,#SolarVoltage
If SolarVoltage = 300 then
high motor ' motor stop
ELSE
low motor ' motor run
ENDIF
If update = 1 then
LCDOUT $FE,$C0,DEC2 Hour,":",DEC2 Minute,":",DEC2 Second
ENDIF
Next
Low PortB.0
For Loop = 0 to 2160 'Loop here for ~2.16s, tweak to match.
PauseUs 1000
ADCIN 0,SolarVoltage
LCDOUT $FE,$1,#SolarVoltage
If SolarVoltage = 300 then
high motor ' motor stop
ELSE
low motor ' motor run
ENDIF

If update = 1 then
LCDOUT $FE,$C0,DEC2 Hour,":",DEC2 Minute,":",DEC2 Second
ENDIF
Next
Goto Main

ON INTERRUPT
'
'Time calculation
'
'
Update = 1 'update diaplay after 1 second*************


The display: ****************
0 ' when increase the A/D input, the value
00:00:00 'increase to 0 then 1 then 2 then
**************** 'maximum is 3