Android Hardware

Sonoff Basic


Unfortunately, many of the items linked on this page are from on-line shops. These usually disappear when stock is depleted. I will remove the links when I find they have disappeared.

I was looking for a smart switch to control the heating belt on my fermenter. The belt I have is a pretty basic, it works like the belts used to bake-out high vacuum systems, you plug it into a wall socket and the resistivity gives the heating. The technique with these heating belts is as simple as switching them on and leaving them on for as long as necessary. Unfortunately, with the fermenter belt, I have measured the temperature under the belt to get to around 42C, and this is way too high for beer yeasts, even if the wall of the fermenter is between the belt and the brew.

Showing the heating belt on a fermenter

My idea was to try and control the temperature by limiting the length of time that the heating belt was on, without building a temperature control system. In order to do this, I needed some kind of timer controller. For fun, I was looking for something that could possibly be controlled by Alexa, which would add some value to a device which I currently only use as a streaming radio.

Francois wanted to put in an order with Takealot and was looking for someone to boost the purchases to get free delivery. I decided to get a ready made-up switch using the Sonoff Basic Smart Switch, such as this one from Geewiz. The one I got was from Geewiz, but distributed by Takealot (unfortunately no longer available from Takealot).

The wired Sonoff Basic Switch in a circuit

A close-up of the switch

What is very interesting, is the huge price difference on this device.

Made-up device:

  • Takealot: R385 (12 May)
  • Geewiz: R443 (23 May)

Basic device (prices on 23 May):

Using the device - Android

With the lack of instructions with the device, one had to turn to Google to find out how to operate it. Fortunately, this was as simple as downloading the eWeLink app from the Google Play Store.

As the temperatures are now dropping to below 10C at night here in South Africa, I needed the device working as soon as possible. However, getting the app to make the device do what I wanted it to do took more than a bit of cursing, and is discussed in more detail on my eWeLink app page.

Using the device - Alexa

In order to use the device with Alexa, she first had to be given the eWeLink skill with the necessary credentials. She then immediately picked up the device and I could manually switch the it on and off with voice commands. However, the whole idea behind getting the device was to be able to program it. In order to program one needs to use the Alexa app from a mobile device and build a Routine. Up to now, I have not been able to get this right.

The problem maybe due to the version of the Alexa app that I have. Until I can obtain, and try, a newer version of the Alexa app, which works with at least one of my devices, Alexa remains nothing more than a streaming radio in my household. [Amazon have blocked the download of the Alexa app in South Africa.]

Concluding Remarks

Overall, I am pleased with how the device is working. My one issue is there is no indicator of current flow through the device. As a result, I have a low powered lamp in the circuit so that I can check whether the device is switching on and off when I change the program.

One thing I will do when the current batch of beer is complete, is to extend the cable from the switch to the power outlet. It is too short, so I have to use an extension cable to be able to position the device in order for it to pick up a wifi signal.

(updated: 25 July 2020)

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