Pi3 B+ to 8 channel relay CODING HELP

Question

Hello, I will be blunt and honest, This is my first time looking at a Linux system let alone trying to learn to code in python and I'm struggling big time trying to learn this all. I need a coding mentor who is willing to communicate with me and help me get this done. Ahead of time, I apologize for my lack of vocabulary and my unorthodox techniques and perspective and thank you for your everlasting patients and I really appreciate any and all time you invest into helping me!

Question: Will you look over my project (posted below) and help me get it coded? ideally, i would be able to have an interface that would allow ease of use programmable on//off cycle on each outlet (all 8) and also in addition to, a simple toggle on//off of all 8 as well. ( example: [OUTLET 1] on=15 minutes off=45 minutes * repeat*

[OUTLET 2] on= 16 minutes off=44 minutes *repeat*

[OUTLET 3] on=2pm off=11pm

[OUTLET 4] ON

etc....etc......)

Here's where i am so far the best i can sum it up;

Pi3

Relay Diagram of relay

CanaKit GPIO to Breadboard Interface Board

This is how i wired the relay to the main power source

Below is a how I wired the breadboard to the relay. (Picture is visual rep of it written out)

Relay | Gpio#

JD=Vcc 5v

GND GND

Vcc 5v

1n1 GPIO 17

1n2 GPIO 27

1n3 GPIO 22

1n4 GPIO 23

1n5 GPIO 24

1n6 GPIO 26

1n7 GPIO 12

1n8 GPIO 16

what do you think? Can you tailor some code for me? I'm sure the code is out there some where, I most likely just need some guidance on how to fine tune it to my wiring/setup.

Anxiously and hopefully awaiting a response

~Mathew

* WORKING WITH ELECTRICITY IS EXTREMELY DANGEROUS. DO NOT TRY THIS. THIS IS A HYPOTHETICAL PROJECT NOT MEANT TO BE DUPLICATED OR REPRODUCED BUT FOR EDUCATION PURPOSES ONLY. ALWAYS USE ALL SAFETY STANDARDS WHEN WORKING WITH ELECTRICITY PER YOUR AREAS LAWS AND REGULATIONS*

Message was edited by: Mathew Rawlings THANKS PETER

Robert Peter Oakes · Accepted Answer

Looking at what your doing with the GPIO etc and also the scheduling of the GPIO, I think using Node-Red would greatly simplify the design of the solution.

Node-Red is a graphical Design environment and is fully supported on the Raspberry PI... And it is Free and with the latest versions of Raspbian, it is also part of the image.

There are nodes designed to directly interact with the GPIO of the PI and you can also script in Java or call python if you want.

This is what a design could look like

,

this produces a WEB UI like this (I took 3 pics as I scrolled down)

and for output to GPIO there are design elements like this

Note the set of Raspberry PI nodes on the left and the great big BIGTIMER below that. BIGTimer is a node that can handle scheduling for you and was written by a good friend of mine.

Also note the light blue node second in that is used to automatically handle a DS18B20 temperature sensor.

So in summary... Node Red can provide the interface to the hardware for you in an easy to use way, it can provide a WEB based UI for you to interact with your project from any smart device, it can schedule tasks. It is free and runs on Linux.

Hope this helps

phoenixcomm · Answer

I will add my 2cents in as well you kind of have it right. but you have one huge error:

The language does not accept whitespace in a variable name!

Variable names in C are made up of letters (upper and lower case) and digits.
The underscore character ("_") is also permitted.
Names must not begin with a digit.

Also, remember that this variable outlet1 is not the same as Outlet1 or outlet_1. As C is case sensitive!! (common bobo)

Oh yes please stay away from full caps on names. And please don't do this _Outlet1 As names that start with the underscore are normally reserved for system calls and libraries.

And one last comment and that is to comment by using // after a variable to describe what is or used for.

And BTW use a good IDE!! Personally, I love Eclipse! you should go to https://yoxos.eclipsesource.com/ use their installer and you are always you will be up to date.

Cris Harrison

rew · Answer

The fact that this runs on Linux means you can split the project into easily manageable parts.

First you like to refer to the relays as relay 1-8. So I recommend you create a directory "relays" that has a symlink "relay1" that links to the proper gpio. You could also use more useful names like "water" and "fan" (things that apply to what you're switching).

You could also automatically generate those from a configuration file.

Next instead of having one program do everything, you should create separate programs tthat do just one thing. I would make a program called "PWM" and call it using PWM <relay> <ontime> <offtime>. Writing this in bash is for me much easier than in python. So here goes in bash:

#!/bin/sh
relay=$1
ontime=$2
offtime=$3
while true ; do
   echo 1 > $relay
   sleep $ontime
   echo 0 > $relay
   sleep $offtime
done

call it with PWM /home/pi/relays/water 960 2640 to run the water for 16 minutes and then turn it off for 44 minutes.

Another simple program should "turn on a relay". So you can put "on at 11PM" in a crontab.

Breaking things down this way makes the bigger project several smaller projects that are all easily managed.

Robert Peter Oakes · Answer

Logically, everything looks good.

Electrically ti are not following safe standards and while it is up to you if you do this on your projects, you need to consider that others will follow your example

The relay board should be in a safe housing. It has mains on it and as such should be correctly protected from people sticking their fingers into it.

Using standard and approved power outlets is a good thing, especially if they are in the approved enclosure and with the right covers in place.

You need to add words of wisdom indicating to viewers that if they are not familiar with working with mains then they should get help from someone that is., add the fact that not doing this can lead to death or worse.

You need to add that Electrical Code is different for each country and province so people should be aware and follow their local codes of practice or dont do this.

Hope this helps

Peter