Reddit reviews SainSmart 2-Channel Relay Module

I've got a relay from amazon connected to some of the GPIO pins, then a simple website I made on the pie that when I press a button on it, it flips the relay. The relay is wired to the door open button and does the same thing as me physically pressing the button in the garage. I also have it monitoring for an amazon dash button press that will also trigger the relay, that is by the front door so I can open the garage on my way out the door if I need.

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However, this has all been running for 4+ years, I tried to review how I pieced it all together about a year ago and couldn't remember or figure out all the pieces, but it still continues to work, so I can't give much more detail than that sorry.

Sure! You'll need a relay to handle the higher voltage from wall outlet, or from the wiring in the strand itself. I have a 4-channel version of this that works great: http://www.amazon.com/SainSmart-2-CH-2-Channel-Relay-Module/dp/B0057OC6D8

If you want a finished solution, Belkin makes WeMo devices you can control from an iPhone or Android, or setup trigger with IFTTT: http://www.amazon.com/Belkin-Automation-Switch-Apple-iPhone/dp/B0089WFPRO

SainSmart 2-Channel Relay Module https://www.amazon.com/dp/B0057OC6D8/ref=cm_sw_r_cp_apa_i_mgsFDbSR97ZA7

And the pi needs to have the pin initialized as an input / output pin. It must be getting a slight amount of current when just powed on but not initialized?

I just setup my temperature control system using a Spark Core and a little relay board. I'll probably do a full posting when I finish some of the control software on the client side (so about three weeks), but I'd be happy to help you with any questions if you have them. Also, should you decide to pick up a Spark Core, I'd be totally willing to share the firmware side of it with you right now.

I looked at BrewPi but it seemed awfully complicated for something that shouldn't be, needing both an Arduino and a Raspberry Pi seems like overkill.

I would use the Raspberry Pi, along with a relay board like this and some DS18b20 temp probes, along with a little breadboard and some plugs and you should be set from the hardware side.

For the software side you should be able to build a quick little python script on the Raspberry Pi to have a web server that would let you type in desired high and low temps. Just remember to have a minimum cycle time to avoid burning out the fridge motor (I use a 120 second delay between any switching on the compressor).

Probably the best way would be with a relay. They're electromagnetic operated switches and as a bonus the two circuits aren't connected so they can't interfere with each other. I bought a 4 relay version of this board and I can control it directly from an Arduino with only a couple of wires.

your standard issue songle. https://smile.amazon.com/gp/product/B0057OC6D8

i took an old 5v straight wired micro usb cable and lopped off the usb end (the other end is part of the power supply not usb-a) and split the +5v into two legs, one powering the esp8266 (it's a nodemcu board) and the other leg providing power to the relays. ground is common to the entire system.

i haven't tested these (https://smile.amazon.com/gp/product/B07CQKMPDP) in the cold but one of them has been the heat "switch" for my esp8266 basement thermostat.

> How did you have the relay connected to the GPIO?

Through this board, which seems to be properly (opto) isolated.

> how were you powering the whole setup?

USB of the Raspberry Pi to a wall wart.

> sounds like latch-up

If you still think it could be a latch-up (given the board I'm using), how would you recommend preventing it?

You can control any AC load within reason using a relay module. For example: http://www.amazon.com/SainSmart-2-Channel-Relay-Module-Arduino/dp/B0057OC6D8/

As for temperature control, you should look in to using PID.

The switch will be connected directly to the pi's GPIO, which will control a relay. The electrical wiring in the walls will be connected to that relay which is connected to the light. I'll be using a 2 channel relay, something similar to the link below. There are also 8 channel relays, so you can control 8 devices with only 1 Pi. I plan on using an 8 channel relay for a Pi controlled thermostat. Also, prices are much cheaper on eBay if you're willing to wait a few weeks for shipping.
http://www.amazon.com/SainSmart-2-CH-2-Channel-Relay-Module/dp/B0057OC6D8

But yes that would also work if you want to wirelessly control the relay, you just have to be connected to your WiFi.

Using your Arduino you can wire a relay and control it from your phone or computer

From what I can tell its rated 5v but can't find anything about running it at a different voltage. This is the relay I have Link. I just tested it with 12v instead and it works with that as well but at the moment it is working again on 5v as well and I can't tell if it will make a difference with the higher voltage.

Ok so looking into SSR's a little more I think I found one I can use. would this be what I want to use to turn on and off the 100W ceramic heating element and the fogger?

I have been using an all-in-one Sainsmart Relay to control my garage door via the Pi.