PWm using 12F675 - Electronic Circuits Projects Diagrams Free

Divs · 11th December 2006, 06:42 AM

hi guys... i've read a lottt of posts on this site and its awesome!

i have a slight problem however.. i need to generate a PWM with 1KHz constant frequency and a duty cycle varying from 5-95% using a PIC12F675..

i cannot use a 12F683..

.. however i did try this using 555. although the duty cycle varies as desired, the frequency does too... any ideas on this would be welcome too...

i dont want a program.. please give me some suggestion on how to go abt it.. i'm new to PIc's and so far all i've done is flash an LED..

thanx in advance.. hoping something would come up..?

akg · 11th December 2006, 07:02 AM

first obtain the delay code from piclist

now define two variables N(on time)

Set a Pin 1 (high)
delay N us
Set the Pin 0
delay 1000-N us
loop

vary N is you require

Divs · 20th December 2006, 12:29 PM

thanx a lot.. i'll try that way

phalanx · 20th December 2006, 01:21 PM

What kind of resolution do you want for your duty cycle? You stated a range of 5-95% but do you want to increment by 1%, 5%, 0.5%, etc.? If the resolution isn't too small, you can use Timer 0 and interrupts to free your PIC up for other processing.

It's too bad that you can't use the 12F683. Ignoring the fact that it has a PWM generator, it also has Timer 2 which has a period register and its internal oscillator can run at 8MHz giving you better resolution if you choose to implement a software PWM setup.

Divs · 20th December 2006, 02:45 PM

hey! thanx so much for your reply...
a 0.5% resolution should do nicely i guess.. i know, but then my boss says no to 12F683.. or any IC which has a CCP module.. so here i am, struggling, cuz all i've managed to learn so far in assembly language programming is to blink an LED..

i've started writing a code tho.. just trial and error, will post it here and someone could lead me on from there...

**Nigel Goodwin** · 20th December 2006, 04:05 PM

Quote:

Originally Posted by Divs

hey! thanx so much for your reply...
a 0.5% resolution should do nicely i guess.. i know, but then my boss says no to 12F683.. or any IC which has a CCP module.. so here i am, struggling, cuz all i've managed to learn so far in assembly language programming is to blink an LED.

Blinking an LED is PWM - you just need to blink it faster!.

SYE · 20th December 2006, 05:13 PM

Quote:

Originally Posted by Divs

my boss says no to 12F683.. or any IC which has a CCP module..

why would he say that ? is he deliberatley trying to make this as difficult as possible ?

**Nigel Goodwin** · 20th December 2006, 07:04 PM

Quote:

Originally Posted by SYE

why would he say that ? is he deliberatley trying to make this as difficult as possible ?

Sounds more like a school project!.

kchriste · 21st December 2006, 03:29 AM

Quote:

Sounds more like a school project!

Or his boss is really cheap and won't spring for an extra 5 cents for the 12F675. It could also be that the company already stocks the 12F675 and wants to minimize inventory. But most likely a school project, since their "engineer" is only flashing LEDs so far.

Divs · 21st December 2006, 03:46 AM

wow!!! how encouraging!!

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

Similar
Title	Starter	Forum	Replies	Latest
A/D with pic 12f675	ndspinney	Micro Controllers	8	23rd December 2006 10:55 AM
12F675 GPIO.3 help.	mramos1	Micro Controllers	8	5th September 2006 12:22 PM
Cannot read 12F675 with ICSP	dprischak	Micro Controllers	4	1st June 2006 03:37 AM
12F675 Problem	brodin	Micro Controllers	10	29th December 2003 10:40 PM
12F675 Calibration?	brodin	Micro Controllers	7	25th December 2003 06:26 PM

11th December 2006, 06:42 AM	#1
Divs	PWm using 12F675 hi guys... i've read a lottt of posts on this site and its awesome! i have a slight problem however.. i need to generate a PWM with 1KHz constant frequency and a duty cycle varying from 5-95% using a PIC12F675.. i cannot use a 12F683.. .. however i did try this using 555. although the duty cycle varies as desired, the frequency does too... any ideas on this would be welcome too... i dont want a program.. please give me some suggestion on how to go abt it.. i'm new to PIc's and so far all i've done is flash an LED.. thanx in advance.. hoping something would come up..?

11th December 2006, 07:02 AM	#2
akg	first obtain the delay code from piclist now define two variables N(on time) Set a Pin 1 (high) delay N us Set the Pin 0 delay 1000-N us loop vary N is you require __________________ Gods own Country Incredible !ndia www.flickr.com/photos/_akg/ "Give a man a fish, and he will eat for a day. Teach that man to fish, and he will eat for a lifetime."

20th December 2006, 12:29 PM	#3
Divs	thanx a lot.. i'll try that way

20th December 2006, 01:21 PM	#4
phalanx	What kind of resolution do you want for your duty cycle? You stated a range of 5-95% but do you want to increment by 1%, 5%, 0.5%, etc.? If the resolution isn't too small, you can use Timer 0 and interrupts to free your PIC up for other processing. It's too bad that you can't use the 12F683. Ignoring the fact that it has a PWM generator, it also has Timer 2 which has a period register and its internal oscillator can run at 8MHz giving you better resolution if you choose to implement a software PWM setup.

20th December 2006, 02:45 PM	#5
Divs	hey! thanx so much for your reply... a 0.5% resolution should do nicely i guess.. i know, but then my boss says no to 12F683.. or any IC which has a CCP module.. so here i am, struggling, cuz all i've managed to learn so far in assembly language programming is to blink an LED.. i've started writing a code tho.. just trial and error, will post it here and someone could lead me on from there...