I have a problem when I am debuging. My PWM generate circuit can not adjust the duty cycle to 10%! It just 46% when I modulate Rp_Potentiometer.
But I have checked the circuit by a software called EWB and the follow images are test result.
1 R_potentiometer =100k Ohm 100%
Duty cycle=10%
2 R_potentiometer =100k Ohm 50%
Duty cycle=50%
3 R_potentiometer =100k Ohm 0%
Duty cycle=90%
Why? Can anyone tell me why!
You could always try using a PICAXE 08M micro to generate your PWM. These are good for 0% - 100% and are adjustable by simple basic programing.
Effectively you would put your pot between 0V and +V with the wiper connected to Pin 6 (ADC 1) and use Pin 5 (PWM2) to generate your pulses, this can be isolated via a mosfet if more drive is required. Apart from a 5V regulated supply thats all you need!
Program the micro with the code along the lines of....
;INPUT PIN 6 (ADC1)
;OUTPUT PIN 5 (PWM2)
SYMBOL ADCVALUE = W1 ;ASSIGN WORD 1
MAIN:
READADC10 1,ADCVALUE ;Reads the Voltage off the pot and assigns a number 0-1024
PWMOUT 2,150,ADCVALUE ;The PWM period (150 IN THIS CASE) = (period + 1) x 4 x resonator speed (1/4000000) effectively = the number + 1 in uS
GOTO MAIN
;THE DUTY CYCLE IS DETERMINED BY THE 'ADCVALUE FIGURE' 0 = 0% AND 1024 = 100%
;SCALING CAN BE DONE VIA CALCULATION WITHIN THE PROGRAM
;E.G LABEL PWMVAL =W2
;AFTER READING THE ADCVALUE IT CAN BE MANIPULATED
;LET PWMVAL = ADCVALUE/2 (EFFECTIVELY A 0-50% PWM)
Picaxe chips, software (free) etc can be obtained from www.picaxe.co.uk
Cheers
Warren.
You could always try using a PICAXE 08M micro to generate your PWM. These are good for 0% - 100% and are adjustable by simple basic programing.
Effectively you would put your pot between 0V and +V with the wiper connected to Pin 6 (ADC 1) and use Pin 5 (PWM2) to generate your pulses, this can be isolated via a mosfet if more drive is required. Apart from a 5V regulated supply thats all you need!
Program the micro with the code along the lines of....
;INPUT PIN 6 (ADC1)
;OUTPUT PIN 5 (PWM2)
SYMBOL ADCVALUE = W1 ;ASSIGN WORD 1
MAIN:
READADC10 1,ADCVALUE ;Reads the Voltage off the pot and assigns a number 0-1024
PWMOUT 2,150,ADCVALUE ;The PWM period (150 IN THIS CASE) = (period + 1) x 4 x resonator speed (1/4000000) effectively = the number + 1 in uS
GOTO MAIN
;THE DUTY CYCLE IS DETERMINED BY THE 'ADCVALUE FIGURE' 0 = 0% AND 1024 = 100%
;SCALING CAN BE DONE VIA CALCULATION WITHIN THE PROGRAM
;E.G LABEL PWMVAL =W2
;AFTER READING THE ADCVALUE IT CAN BE MANIPULATED
;LET PWMVAL = ADCVALUE/2 (EFFECTIVELY A 0-50% PWM)
Picaxe chips, software (free) etc can be obtained from www.picaxe.co.uk
Cheers
Warren.
