NAME
RPi::DHT11::EnvControl - Monitor environment temperature/humidity, and act when limits are reached
SYNOPSIS
Basic usage example. You'd want to daemonize the script, or run it periodically in cron or the like.
use RPi::DHT11::EnvControl;
use constant {
DHT_PIN => 4,
TEMP_PIN => 1,
HUMIDITY_PIN => 5,
ON => 1,
OFF => 0,
};
my $temp_high = 72.8;
my $humidity_low = 25.4;
my $env = RPi::DHT11::EnvControl->new(
spin => DHT_PIN,
tpin => TEMP_PIN,
hpin => HUMIDITY_PIN,
);
my $temp = $env->temp;
my $humidity = $env->humidity;
print "temp: $temp, humidity: $humidity\n";
# action something if results are out of range
if ($temp > $temp_high){
if (! $env->status(TEMP_PIN)){
$env->control(TEMP_PIN, ON);
print "turning on exhaust fan\n";
}
}
else {
if ($env->status(TEMP_PIN)){
$env->control(TEMP_PIN, OFF);
print "exhaust fan turned off\n";
}
}
# humidity
if ($humidity < $humidity_low){
...
}DESCRIPTION
This module is an interface to the DHT11 temperature/humidity sensor when connected to a Raspberry Pi's GPIO pins. This is but one small piece of my indoor grow operation environment control system.
Due to the near-realtime access requirements of reading the input pin of the sensor, the core of this module is written in XS (C).
It allows you to set temperature and humidity limits, then act when the limits are reached. For example, if the temperature gets too high, we can enable a 120/240v relay to turn on an exhaust fan for a time, or enable/disable a warning LED.
The Perl aspect makes it easy to send emails etc.
This module requires the wiringPi library to be installed.
METHODS
new
Parameters:
spin
Mandatory. Pin number for the DHT11 sensor's DATA pin (values are 0-40).
tpin
Optional. Pin number of a device to enable/disable. status() and control() won't do anything if this is not set.
hpin
Optional. Pin number of a device to enable/disable. status() and control() won't do anything if this is not set.
temp
Fetches the current temperature (in Farenheit).
Returns the temperature as either an integer or a floating point number. If any errors were encountered during the polling of the sensor, the return will be 0.
humidity
Fetches the current humidity.
Returns the humidity as either an integer or a floating point number. If any errors were encountered during the polling of the sensor, the return will be 0.
status($pin)
Parameters:
$pin
The GPIO pin number to check.
Returns the current status (bool) whether the specified pin is on (1, HIGH) or off (0, LOW).
control($pin, $state)
Enables the enabling and/or disabling of devices connected to specified Raspberry Pi GPIO pins.
Parameters:
$pin
The GPIO pin number to act on.
$state
Bool, turns the pin on (HIGH) or off (LOW).
Returns false (could be zero, undef or empty string) if the pin is in 'off' state, and true (1) otherwise.
cleanup
Returns all pins to their default status (mode = INPUT, state = LOW).
C TYPEDEFS
EnvData
Stores the temperature and humidity float values.
typedef struct env_data {
float temp;
float humidity;
} EnvData;C FUNCTIONS
c_temp
float c_temp(int spin);Called by the temp() method.
c_humidity
float c_humidity(int spin);Called by the humidity() method.
c_status
bool c_status(int pin);Called by the status() method.
c_control
bool c_control(int pin, int state);Called by the control() method.
c_cleanup
int c_cleanup(int spin, int tpin, int hpin);Called by the cleanup() method, and is always called upon DESTROY().
read_env()
EnvData read_env(int spin);Not available to Perl.
Polls the pin a single time and returns an EnvData struct containing the temp and humidity float values.
If for any reason the poll of the DHT11 sensor fails (eg: the CRC is incorrect for the data), both temp and humidity floats will be set to 0.0.
noboard_test()
bool noboard_test();Checks whether the RDE_NOBOARD_TEST environment variable is set to a true value. Returns true if so, and false if not. This bool is used for testing purposes only.
Not available to Perl.
sanity()
void sanity();If we're on a system that isn't a Raspberry Pi, things break. Every function calls this one, and if sanity checks fail, we exit (unless in RDE_NOBOARD_TEST environment variable is set to true).
Called only from the new() method.
SEE ALSO
- wiringPi
AUTHOR
Steve Bertrand, <steveb@cpan.org<gt>
LICENSE AND COPYRIGHT
Copyright 2016 Steve Bertrand.
This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.
See http://dev.perl.org/licenses/ for more information.