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LDmicro Forum - pwm output - adc input (servo control) |
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pwm output - adc input (servo control) (by Alex)
Hello, i want to control a servo motor sg90 using 16f88 (with internal oscillator), first of all, i want to use 16f88 as a "driver" like 16f628a for serial lcd, which means that i am using a 16f877a (OUTPUT PWM PIN) connected to an 16f88 (ADC INPUT PIN) ,i tried to use it and got this (watch video please):
https://www.youtube.com/watch?v=F8NPTsgG6uY&feature=youtu.be i have read some information about this connection, it is no accurate, also i have read MGP´s post: http://cq.cx/ladder-forum.pl?a...;parent=8859&tt=1564052315 i watched MGP´s video: https://www.youtube.com/watch?v=qZ92GbxMdN8&feature=youtu.be is there an schematic?
(no subject) (by Alex)
for 16f877a i have used a simple led brightness control program and for 16f88 an example MGP´s gave me in the past which i made some changes, both attach
(no subject) (by Alex)
i need hlep to use it the most accurate possible
(no subject) (by Ziggy)
That is "the most accurate"
What do you actually need?
(no subject) (by Alex)
(no subject) (by Alex)
with my program i can not make an entire turn
(no subject) (by Ziggy)
Alex ,
Ensure the servo driver signal is generated at some lowish frequency at 10 bit resolution. Fool the software by specifying a clock rate in LDmicro but applying some other clock to the micro to ensure signal compliance to drive servo. Make sure the servo driver signal is within the general tolerances of the signaling. Pulse repetition rate and duty cycle range. Servo motors are not meant to turn 360 degrees. Check the specifications of Your motor.
(no subject) (by Alex)
thank for the explenation , my mistake, by "complete turn"i mean that it moves all the way a potentiometer does
(no subject) (by MGP)
It's easy, the servo has 105 - 55 = 50 'steps' (-90 to +90)
And the ADC has 1023 steps. You must divide the ADC (1023) by 1023/55 = 18 See in my program, each 18 units of the ADC is 1 'step' of the servo. If you use the buttons then duty= duty+18. After 50 counts you have the full turn of the servo (-90 +90)
(no subject) (by Alex)
thanks a lot MGP i will try
(no subject) (by MGP)
It's easy, the servo has 105 - 55 = 50 'steps' (-90 to +90)
And the ADC has 1023 steps. You must divide the ADC (1023) by 1023/55 = 18 See in my program, each 18 units of the ADC is 1 'step' of the servo. This is the correct answer, sorry I cant edit my previous answer.
(no subject) (by Alex)
escuseme, about the pin 6 bug in 16f88, has it been fixed?
(no subject) (by MGP)
You can see that for yourself in the program, if you have to choose a PWM pin you can only choose pin9 while pin 6 is the output in this case.
I haven't thought about it anymore and it's just a small bug (?). The latest version of LDmicro is really good. The last project can be seen here, a chronometer and lap counter, the hardware is from Steelwood from the Netherlands and I wrote the program, there is also an MP4 video to see. https://www.circuitsonline.net/forum/view/146222/2
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