Reddit mentions of JBtek 4 Channel DC 5V Relay Module for Arduino Raspberry Pi DSP AVR PIC ARM

I made this Pi controlled irrigation system. The goal was to make it as user friendly as possible. It is not finished yet. I had to get a working proto going as soon as possible because I moved to a different state and my parents are selling this house. Not to mention fall semester starts on Monday. I plan on working on this as much as possible on my free time and then make a guide and share my code with everyone so others can benefit from my work. If you want my current code and want to improve on it please PM me. Also, I would love it if you shared your version with me as I will implement it into my code. I want to share my best with everyone.

P.S. I did not document my code at all. I mainly hard coded all of this in the past few days since I was limited on time. I am also a noob on Kivy and this is my first big Pi project.

Edit: Below are the hardware

Landzo 7 inch touch panel - 40.88

Raspberry Pi 3 Model B - 39.99

32 GB flash - 15.69

DS3231 RTC Clock Module - 5.99

4 channel relay - 6.99

Uxcell enclosure - 9.99

M2.5 hex spacer screws - 9.98

Modified internal panel - 8.30

Total: 137.81

PS. Definitely could be cheaper. For me it sure was because I had some of the parts already available that came in a some sort of kit.

Yeah, sure. The hardware isn't too difficult to set up, here's the part list I used:

• 3-gang electrical wall box
  
• light switch
  
• 2x dual wall outlet
  
• quad channel relay board
  
• cheap phone charger (for 5V power supply to relay board, this can be omitted if you supply 5V to the relays from the RPi, but too many relays could potentially overwhem the RPi, and I have 12 relays connected right now, so each set of 4 has their own cheap 5V supply)
  
• assorted wires to connect relay board to RPi
  
• assorted wires (of appropriate gauge) to connect AC mains to relays/outlets
  
• if not embedding in the wall, one of these to allow an easy way to supply mains power to the relay box
  
  For wiring any mains power yourself, make sure you know what you're doing. Messing with Arduino/RPi-style hobby electronics is one thing, but making a mistake with wiring mains power can cause property damage, injury, or death. Here's what I did:
  
  AC neutral connects directly to outlets, and one prong of the 5V power supply. AC line connects to switch, and switch connects to 5V power supply, and normally open of relays. Common of relays connects to outlets. Make sure that you don't switch line and neutral. Some people who don't know better will claim that both leads are the same in AC mains, since it's AC, but that's FALSE. Neutral normally connects to earth ground at your main electrical panel, but line obviously does not, as that would be insane. Line is the smaller prong in US-style plugs, and neutral is the larger one. Also, make sure you connect earth ground to everything appropriate (the switches, outlets). All of this applies to the standard 120V, single-phase AC as used in North America.
  
  As for connecting to the PI, each of these relay boxes needs a ground connection, 4 gpios, and a 5V if you're not using a separate power supply for the relays. Then, some software to drive them. My code is at here, where I have a command-line utility called "relays" that I used for scripting and such, and a web interface for controlling them from my phone, tablet, etc.
  
  There's probably better and easier to follow guides out there, just google "rasbperry pi relays' and you should find some stuff. Here's one of the guides that I used as a reference when I was building mine.

https://www.amazon.com/gp/product/B00KTEN3TM/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

The thought of leaving my homebrew printer running while away frightens me, this is a setup to ease my fears of burning the house down.

There are multiple redundancies built in but the basic idea is simple:

• Control a couple relays with the raspberry pi that is running Octoprint.
  
• One relay will have an Arduino that monitors for smoke/fire, so the raspberry pi can shut down power if either is detected.
  
• The other relay controls power to the printer
  
  Yesterday I came up with an easy way to reboot or turn off the Pi using the relay, basically have the Pi ground hooked up to the 4 channel relay using the normally closed side of a channel, then to reset/shutdown simply switch the relay so the ground is no longer connected.
  
  Note: The fans and lights are controlled via SPST switch not SPDT.

I can only help with first point. A relay like this will work: https://www.amazon.com/gp/aw/d/B00KTEN3TM/ref=mp_s_a_1_7?ie=UTF8&qid=1523803746&sr=8-7&pi=AC_SX236_SY340_FMwebp_QL65&keywords=Relay

It depends on what the wire connects. If it's low voltage, like a 3v audio signal, you can use a small relay which can be controlled with a switch or raspberry pi. https://www.amazon.com/JBtek-Channel-Module-Arduino-Raspberry/dp/B00KTEN3TM

They make relays like this for lots of applications. Just make sure you're not sending too much voltage.

By relay boards, I'm assuming you're talking about a relay board off of Amazon like this one? I'd actually recommend that relay over a 12V relay simply because this will save you from having to do voltage conversions. Keep in mind that the relay board and your controlled device can operate on different voltages. I have a Raspberry Pi with this board that controlls various aspects of a 12V 3D printer. This board is especially advantageous as it is already wired to interface with the Arduino directly, just give the board GND, +5V, and a digital signal pin. Be aware that this board uses inverted signalling, which means that the relays are "ON" by default, or when the I/O pin is 0(low), and turn "OFF" when the I/O pin is 1(high).

A relay consists of two parts: A coil that is energized or de-energized according to the input power on the I/O pin, and a switch of some sort. These particular relays have single pole double throw switches which means this will allow you to switch one flow of power (single pole) to one of two states (position 1, or position 2).

Relay pins are usually designated with three values "NC" (for Normally Closed), "NO" (for Normally Open), and "C" (for Common) and are determined by the switch's contacts at rest (the relay is not energized). If you put power to the C pin and put your load on NC, when the relay is energized, that connection will be opened and will turn your load off. The inverse is true if you put your power on the C pin and you put your load on the NO pin, the relay will energize and the connection will be closed, turning your load on.

In your application, I would imagine that using the relays to control +12V to your solenoid valves would be a good use of the board because it's already wired up with the correct I/O protection and isolation that you'd have to be worried about if you attempted to drive the solenoid valves directly from the Arduino.

Remember the inverted thing? Well, you could do one of two things with your code. Either write 1's to each of the I/O pins you're using on the relay board to turn off the relays, or you could use the NC pins to wire to your solenoids. Each has their pros and cons:

If you write 1's to the relay board as one of the first steps in your program, there's a chance a little bit of whatever you're controlling with the valves would drip out when the arduino is restarted/reset. If you use the NC pins to your relay board, your relays would always be engaged until they are needed which might cause extra wear. If the relay were to fail and the switch goes to "rest", the relay would direct your solenoid valves to open causing a significant spill. You're going to have to figure out which is right for you.

So you're thinking of something like this?

Use the relays to electronically close the circuit?

basically, the relay will act as a switch. You need to wire the phase and ground to the back of the receptacle and the neutral wire to the output side of the relay. The other end of the output from the relay should go to the neutral

Thanks!

I am using this relay which I believe will be able to handle the current, right?

Is there any extra precautions I can take to make sure I wont have any problem with arcing? Or are you saying that 110V shouldn't arc?

I think I'm getting what you're saying but if you have any kind of diagram so I could confirm that would help.

I can use this to control 4 power outlets correct?

https://www.amazon.com/gp/product/B00KTEN3TM/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Following a guide like this:
https://www.sparkfun.com/tutorials/119

I'm not technically "using" them yet, so I can't say whether they work, but here's what I bought:
position sensor
relay board

I've used a 12V power supply for a motorized curtain project. Something like this should suffice depending on your motor (though if you're using a motor that draws too much current for that power supply it's probably way overpowered). You can run the arduino off of it too, just run the 12V to Vin and ground to ground. You could also use something like this to control the motor, might be easier than making a circuit out of transistors.

It doesn't sound like this is your problem, but how many relays are you switching at any given time? Your relay module looks similar to this one.

Those relay coils draw about 70mA when activated, so if you have your VCC of the relay board hooked up to your +5VDC Arduino power, having multiple relays on at the same time might pull too much current from the Arduino and cause it to reset. This can be resolved by removing the VCC - JD-VCC jumper, wiring your +5V Arduino power to VCC (for logic reference), and wiring a secondary +5V power supply to the JD-VCC pin.

Like I said, probably not what you're experiencing, just wanted to throw that out there in case anyone else has had problems with relays resetting their Arduinos.