Develop Reference

Moisture detection not resetting

I have a friend setting up an irrigation system at his house. He is telling me it won't detect moisture after the first run-through, regardless of whether there is moisture or not. In his own words:
"I’m trying to figure out how to make my program restarts the detection process. Like say my sensor is in soil and it detects water then after a certain period I need it to run again. My problems is that when I run it again and it’s sitting in a cup of water, it’s doesn’t detect the water. I read something about maybe checking the state of the sensor but I couldn’t get anywhere.
Also would I would the delay function to continuously run it in intervals."
He sent me his code today, and I would like to help him, although I am new to Python. Here is the code.
#!/usr/bin/python
import RPi.GPIO as GPIO
import time
#GPIO SETUP
channel = 20
GPIO.setmode(GPIO.BCM)
GPIO.setup(channel, GPIO.IN)
def callback(channel):
if GPIO.input(channel)==0:
print (" Water Detected!")
else:
print ( 'NO Water Detected!')
GPIO.add_event_detect(channel, GPIO.FALLING, bouncetime=300) # let us know when the pin goes HIGH or LOW
GPIO.add_event_callback(channel, callback) # assign function to GPIO PIN, Run function on change
# infinite loop
while True:
time.sleep(1)
import RPi.GPIO as GPIO # Import Raspberry Pi GPIO library
from time import sleep # Import the sleep function from the time module
GPIO.setwarnings(False) # Ignore warning for now
GPIO.setmode(GPIO.BOARD) # Use physical pin numbering
GPIO.setup(3, GPIO.OUT, initial=GPIO.LOW) # Set pin 8 to be an outputpin and set initial value to low (off)
while True: # Run forever
GPIO.output(3, GPIO.HIGH) # Turn on
sleep(1) # Sleep for 1 second
GPIO.output(3, GPIO.LOW) # Turn off
sleep(1) # Sleep for 1 second

Raspberry Pi 4 output python if else results to LCD: Random characters

I am attempting to make a simple python script that uses a moisture sensor on GOIP 21 and will output text on a display.
What I have:
Raspberry Pi 4 4GB
Arducam 1602 16x2 LCD Display Module Based on HD44780
KeeYees 5 Pcs High Sensitivity Soil Moisture Sensor Module with Female to Female Jump Wires, Sensor Module Watering System Manager for Arduino TE215
Breadboard 830
It's only a learning attempt, after I figure this out I plan on buying better sensors and actually having them display accurate percentages. For not a simple moisture detected vs no-detected is okay with me.
My code seems to work for outputting to the console, however when I try to output to the LCD, it gives some weird characters and stops. Not sure what to do as i'm not a python wiz (you'd think id be more like php, but nah lol).
Here is my code
#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import sys
sys.path.append('/home/pi/lcd')
import lcd
#GPIO SETUP
moist1 = 21
GPIO.setmode(GPIO.BCM)
GPIO.setup(moist1, GPIO.OUT)
def callback(moist1):
if GPIO.input(moist1):
lcd.GPIO.cleanup()
lcd.lcd_init()
lcd.lcd_byte(lcd.LCD_LINE_1, lcd.LCD_CMD)
lcd.lcd_string("Water Is Good", 2)
lcd.lcd_byte(lcd.LCD_LINE_2, lcd.LCD_CMD)
lcd.lcd_string("Don't Add", 2)
lcd.GPIO.cleanup()
else:
lcd.GPIO.cleanup()
lcd.lcd_init()
lcd.lcd_byte(lcd.LCD_LINE_1, lcd.LCD_CMD)
lcd.lcd_string("Add Water Now!", 2)
lcd.lcd_byte(lcd.LCD_LINE_2, lcd.LCD_CMD)
lcd.lcd_string("!!!!!!!!!!!!!!", 2)
lcd.GPIO.cleanup()
GPIO.add_event_detect(moist1, GPIO.BOTH, bouncetime=300) # let us know when the pin goes HIGH or LOW
GPIO.add_event_callback(moist1, callback) # assign function to GPIO PIN, Run function on change
# infinite loop
while True:
time.sleep(1)
I can't figure out what I am doing wrong. Please let me know if you see it. Thanks

Raspberry pi servo doesn't stop

So I'm trying to use a servo (Doman s0306d) with the pi camera, tried running this script I found to test the motor, it starts running but doesn't stop unless I manually unplug it from the breadboard.
import RPi.GPIO as IO # calling for header file for GPIO’s of PI
import time # calling for time to provide delays in program
IO.setwarnings(False) # do not show any warnings
IO.setmode (IO.BCM) # programming the GPIO by BCM pin numbers. (like PIN29 as‘GPIO5’)
IO.setup(19,IO.OUT) # initialize GPIO19 as an output
p = IO.PWM(19,50) # GPIO19 as PWM output, with 50Hz frequency
p.start(7.5) # generate PWM signal with 7.5% duty cycle
time.sleep(4)
for x in range(0,5): # execute loop forever
p.ChangeDutyCycle(7.5) # change duty cycle for getting the servo position to 90º
time.sleep(1) # sleep for 1 second
p.ChangeDutyCycle(12.5) # change duty cycle for getting the servo position to 180º
time.sleep(1) # sleep for 1 second
p.ChangeDutyCycle(2.5) # change duty cycle for getting the servo position to 0º
time.sleep(1) # sleep for 1 second
p.ChangeDutyCycle(0)
p.stop()
IO.cleanup()
Any ideas ? Thank you.

[EDIT] The servo you are using is a "continuous" servo - so you need to give it the zero speed or "STOP" setting pulse width of 1500us (according to the website http://www.domanrchobby.com/content/?150.html). I haven't used PWM on the pi but if the percentages are of the 50Hz pulse rate (20ms interval) then that should be your 7.5% centre value. You need to make sure the servo gets that pulse before your code exits.
[Original] You are setting the duty cycle to 0 when you exit, which will probably mean the servo doesn't get any pulses. Some servos will stop sometime after they don't get pulses, but some servos (particularly digital servos, but not all) will continue to try achieve the setting from the last pulse they received. Suggest you leave the setting at the mid range 7.5 which you know the servo can achieve and delay for a little while before cleaning up.

How can keep a timed count of user input (from a button)?

I'm using a Raspberry Pi 2 and a breadboard to make a morse code interpreter. The circuit is a simple button that lights up an LED when pressed. How could I use functions to count how long the button is held down?

You haven't given sufficient details of your circuit to pin this down to your particular use case, so I'll suggest the following (on which I'll base my code):
Connect the LED (with series resistor) to GPIO 12
Connect a 10k resistor between GPIO 11 and the 3.3V rail (acts as a pull-up)
Connect the push-button between GPIO 11 and Ground (0V).
I'd then write the code to monitor the pin and log the time for each press into a list. You can read out the values in the same order which allows you to process the times and interpret the code from them.
import RPi.GPIO as GPIO
import time
# set up an empty list for the key presses
presses = []
# set up the GPIO pins to register the presses and control the LED
GPIO.setmode(GPIO.BOARD)
GPIO.setup(12, GPIO.OUT)
GPIO.setup(11, GPIO.IN)
# turn LED off initially
GPIO.output(12, False)
while True:
# wait for input to go 'low'
input_value = GPIO.input(11)
if not input_value:
# log start time and light the LED
start_time = time.time()
GPIO.output(12, True)
# wait for input to go high again
while not input_value:
input_value = GPIO.input(11)
else:
# log the time the button is un-pressed, and extinguish LED
end_time = time.time()
GPIO.output(12, False)
# store the press times in the list, as a dictionary object
presses.append({'start':start_time, 'end':end_time})
You'll finish up with a list that looks something like this:
[{start:123234234.34534, end:123234240.23482}, {start:123234289.96841, end:123234333.12345}]
The numbers you see here are in units of seconds (this is your system time, which is measured in seconds since the epoch).
You can then use a for loop to run through each item in the list, subtract each end time from the start time, and of course subtract the start of the next press from the end of the previous one, so that you can assemble characters and words based on the gaps between presses. Have fun :-)

Lighting program - GPIO on/off on raspberry pi runtimewarning

Hello i have been trying to work this one out by myself for over a week now but i think its time to ask the question.
This is my first program with python and i intend to control my aquarium with various functions.
The first function i am programming is a lighting schedule (shortened the code a bit for this post)
The code executes okay but the GPIO pin 2 isnt turning on and off properly. and im also getting a "runtimewarning this channel is already in use"
Can i please have a bit of guidance, im sure its something simple and noob :)
here is my code
#Lighting Program
import RPi.GPIO as GPIO
import datetime
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
#Declare Lighting On/Off Times
on_time_Monday = 600
off_time_Monday = 2330
rest of the days here
#Find out what day of the week it is
day = datetime.datetime.now()
day_of_week = day.isoweekday()
#find out what time it is
Current_time = datetime.datetime.strftime(datetime.datetime.now(),'%H%M')
#convert the time to an int so it can be compared
Current_time_INT = int(Current_time)
#Schedule on / off
if (day_of_week == 1) and (Current_time_INT > on_time_Monday and Current_time_INT < off_time_Monday) :
Light_on_off = 'on'
Using 'elif' for tues wed etc etc
else :
Light_on_off = 'off'
Now enable the outputs
#CALL OUTPUTS ON / OFF
GPIO.setup(2, GPIO.OUT)
if Light_on_off == 'on':
GPIO.output(2, GPIO.HIGH)
else:
GPIO.output(2, GPIO.LOW)
GPIO.cleanup()

In my experience "runtimewarning this channel is already in use" comes up when you have previously setup the GPIO pin, but haven't called
GPIO.cleanup().
I see that in your code, but I would suspect that for some reason it is not actually running.
Sometimes it is helpful to test out a GPIO pin in the terminal by running the python interpreter. It is especially useful to test if you have wired your circuit correctly.
>>>import RPi.GPIO as GPIO
>>>GPIO.setmode(GPIO.BCM)
>>>GPIO.setwarnings(False)
>>>GPIO.setup(2, GPIO.OUT)
>>>GPIO.output(2, GPIO.HIGH)
>>>GPIO.input(2)
True
>>>GPIO.output(2, GPIO.LOW)
>>>GPIO.input(2)
False
>>>GPIO.cleanup()
If your circuit is wired correctly you should be able to turn your light on and off this way. When you call GPIO.input(2) the interpreter responds with the current state of the pin. This enables you to make sure the pin is working even without a working external circuit. Once you know that it is working you can move on from there.
One simple way to flip a light switch on and off would be to use cron jobs. I have used this method successfully in the past.
You can write two short scripts, one that turns the light on, and one that turns it off.
Example: lightOn.py (replace 'HIGH' with 'LOW' for lightOff.py)
#!/usr/bin/env python
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(2, GPIO.OUT)
GPIO.output(2, GPIO.HIGH)
GPIO.cleanup()
Now you can create a crontab to automatically run the script at the times you want.
For example:
0 6 * * * /home/pi/lightOn.py
0 18 * * * /home/pi/lightOff.py
Would turn the light on everyday at 6AM and off at 6PM