Uno WiFi or MRK1010

Projects General Guidance
1

Hi all,

I have small project to get into the Arduino. My primary purpose is to replace my coffee machine controller (the element relay died, everything else is tested & working); so it has to fit in the (roomy) machine; be splashproof; and operate at a warm temperature.

Secondary purposes are:

  • upgrade the relay to SSR and replace the pressurestat with a temp probe for PID control, but this will be in the future, not now!
  • use WiFi to configure PID settings, view I/O, shot times, basically just play around with the arduino

I thought of either the Arduino Uno WiFi; or MKR1010 WiFi. I'm leaning toward the MKR for the faster CPU and smaller size, however it doesn't have nearly as many shields available. I know there's some UNO2MKR shields, but then that defeats the purpose of being small.

Some options I've considered are:

  • MKR WiFi 1010 with

  • MKR SD proto shield for tweaking; and a separate small 2 channel relay board (for the smaller loads) like this

  • or alternatively with the MKR Relay Proto Shield. This will be a bit larger though.

  • or thirdly, if I can't keep it small, maybe even the MKR carrier. I know this is compatible with Grove, but I think it would do for me. I think it also does 3.3 - 5V level shifting, which would make finding relays easier!

  • Or if I'm going to go larger, maybe just the common-size Uno WiFi rev2, then I can attach the relay shield on top.

Other options are using opto-isolated SSRs for the 2 smaller relays, but I can only find these in 5V so that rules out the standalone MKR.

Whatever I do, I'll need a Fotek SSR-25DA; a case; power supply (something I can wire directly to the 240V, yes danger), etc.

As you can see I'm a bit lost in all the options, so I would appreciate the help. I'm confident I could fit the project in an 8bit architecture and smaller size of the Uno WiFi, but maybe the 32bit Low Power ARM would just be nicer to work with... I don't know!

Your thoughts?

Thanks :slight_smile:
Iain

2

Right! Now I saw the term "WiFi" in the title. :astonished:

That immediately directs you away from Arduinox and to the ESP8266. (Yes, you could use an ESP32 but that would be overkill.) :sunglasses:

thinkOfaNumber:
Other options are using opto-isolated SSRs for the 2 smaller relays, but I can only find these in 5V so that rules out the standalone MKR.

Perhaps you should explain that?

And perhaps you should explain what you are going to use to provide 5 V or 3.3 V power?

3

Hi & thanks for taking the time to reply.

Paul__B:
Right! Now I saw the term "WiFi" in the title. :astonished:
That immediately directs you away from Arduinox and to the ESP8266.

Could you explain that a bit for me as I haven't even looked into this chip? Why immediately, as both Arduinos I mentioned seems to do the job all in one board. Are there complete boards with the ESP8266 on it? Could you recommend one for me to look into further? And is it Arduino compatible & open source?

thinkOfaNumber:
Other options are using opto-isolated SSRs for the 2 smaller relays, but I can only find these in 5V so that rules out the standalone MKR.

Perhaps you should explain that?

Sure. I've found it hard to find 3.3V SSRs, so I thought I would have to get 5V SSRs, which means I would need to level shift. Which means the MKR + level shifting carrier + relays would end up being the same size (or bigger) as the Uno + relays. I'm just making the point that maybe the smaller MKR size won't be any benefit for this project.

And perhaps you should explain what you are going to use to provide 5 V or 3.3 V power?

I haven't calculated total consumption yet but something like RS-15-5 or RS-15-3.3 to power it.

If my mind is all over the place, it's because I've been looking at so many options! My main question is still the same though - MKR1010 or Uno Wifi?

Many thanks,
Iain

4

thinkOfaNumber:
Could you explain that a bit for me as I haven't even looked into this chip?

Which indicates a woeful lack of research. :roll_eyes:

thinkOfaNumber:
Why immediately, as both Arduinos I mentioned seems to do the job all in one board.

Perhaps because the ESP8266 does the job in one chip. Actually, it uses an external EEPROM for general storage, but the point is, the single chip does all the work, avoiding the problems of communication between two devices.

So it is in fact, considerably smaller than the devices you cite.

And by the way, cost one tenth as much or less. Actually, its "bigger brother", the ESP32, is actually what is underused by the MKR1010.

thinkOfaNumber:
Are there complete boards with the ESP8266 on it?

Of course. The ESP-01 is a small one with the least I/O (four pins) but likely to be adequate for your purpose.

thinkOfaNumber:
Could you recommend one for me to look into further?

Probably the most versatile is the WeMOS D1 Mini.

Lousy photo!

thinkOfaNumber:
And is it Arduino compatible & open source?

What is "Arduino compatible"?

You use the Arduino IDE to program it. It is not an Arduino. As I said, the MKR1010 does use its "bigger brother", the ESP32.

It is open source to precisely the same extent as the other devices you mention. The parts you can program are open source.

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Paul__B:
Which indicates a woeful lack of research. :roll_eyes:

OK my bad, sorry. I'm getting confused with all the names. When I looked up the ESP32 and ESP8266 for some reason I didn't find any Arduino results so I thought it wasn't in any of their products, now I see the MRK1010 has the ESP32; and the Uno WiFi Rev1 has the ESP8266.

Probably the most versatile is the WeMOS D1 Mini.

That actually looks pretty cool... cheaper, smaller, however I'm uncertain about the ease of getting started with this. The personal posted projects & community didn't quite seem as big.

I'm also really put off by soldering on my own connectors. It's not something I'm good at. Sure I could learn eventually but I don't want to have too much to do on this project!

There aren't so many shields either, but I guess the basic board does most of what I want, and the relays just require 3.3V digital pins.

Thanks for your help.

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thinkOfaNumber:
When I looked up the ESP32 and ESP8266 for some reason I didn't find any Arduino results so I thought it wasn't in any of their products, now I see the MRK1010 has the ESP32; and the UNO WiFi Rev1 has the ESP8266.

Well, the ESP8266 and ESP32 are not Arduinos, and those Arduinos avoid programming the ESPs, so it is not surprising there are no overlaps.

thinkOfaNumber:
That actually looks pretty cool... cheaper, smaller, however I'm uncertain about the ease of getting started with this. The personal posted projects & community didn't quite seem as big.

Which is just as likely a good thing! Many projects posted - notably "instructables" - are misleading. In fact, there are plenty of discussions here (various forums) regarding using the ESPs.

thinkOfaNumber:
I'm also really put off by soldering on my own connectors. It's not something I'm good at. Sure I could learn eventually but I don't want to have too much to do on this project!

Sorry, it is most unlikely you can achieve the project you propose without soldering. End of story.

thinkOfaNumber:
There aren't so many shields either, but I guess the basic board does most of what I want, and the relays just require 3.3V digital pins.

Another bad guess! :astonished: There are a variety of "shields" offered for the WeMOS D1 Mini, including a relay shield.

The variety of "shields" is always very restrictive - there are overall, few situations in which they are useful. :roll_eyes:

As to the relays, the relay shield uses a 5 V relay switched from the 3.3. V signal by a transistor - which is always required to control a relay. And the commonly available opto-isolated active-LOW relay modules (operating on 5 V) require you to connect the "Vcc" (input side of the opto-isolator) common to 5 V, not 3.3 V even though the "IN" pins are switched by 3.3 V logic.

7

Paul__B:

however I'm uncertain about the ease of getting started with this. The personal posted projects & community didn't quite seem as big.

Which is just as likely a good thing!

That's rather elitist. In my experience it's not a good thing. You're always going to get unhelpful advice rising with the amount of helpful advice. The size and attitude of the community is a good indicator of how easy it is to get started.

Sorry, it is most unlikely you can achieve the project you propose without soldering. End of story.

There are pre-soldered arduino's and shields with screw terminals or single wires with female headers. There are plenty of other PLCs and single board computers that require no soldering. Let's not argue about the pointless stuff.

Another bad guess! :astonished: There are a variety of "shields" offered for the WeMOS D1 Mini, including a relay shield.

Let's leave the insults and eye-rolls out eh? I'm not guessing. I've looked into the WEMOS shields that I can find & purchase online easily; and there are less available than all the brand or aftermarket arduino uno shields.

The variety of "shields" is always very restrictive - there are overall, few situations in which they are useful. :roll_eyes:

Well perhaps I'm one of the few situations then. As I said, it looks like the available shields do most of what I want. I could get a multi-channel arduino relay shield if I was going to use a Uno, but it's just as easy to get a multi-channel relay board to work with the WEMOS. It's not a problem either way.

As to the relays, the relay shield uses a 5 V relay switched from the 3.3. V signal by a transistor - which is always required to control a relay. And the commonly available opto-isolated active-LOW relay modules (operating on 5 V) require you to connect the "Vcc" (input side of the opto-isolator) common to 5 V, not 3.3 V even though the "IN" pins are switched by 3.3 V logic.

OK now we're getting to useful information, and I honestly thank you for these bits of advice. So one like this for example, would use 3.3V for both the Vcc and DIN?

Please don't feel obliged to reply if this is tedious for you. I'm not expecting you to. You've given me much useful advice for which I'm thankful, but I find your negative-yet-helpful attitude confusing, and I'm not sure what your point is with it. If you choose not to reply, you've given me much helpful advice already and probably enough to go on alone, so thanks again.

8

thinkOfaNumber:
So one like this for example, would use 3.3V for both the Vcc and DIN?

That one, being designed to work on a 3.3 V system would clearly do the job, ignoring the nonsense description as "Optocoupler Isolation" which is meaningless in this context as it clearly provides no isolation. I am unable to figure out the actual circuit but the presence of two 1k resistors suggests that it requires no more than 2 mA to actuate but this is somewhat inconsistent with the relay's requirement for 120 mA to operate as the transistor would not have sufficient gain - unless it is perhaps, a FET. The zero Ohm resistor is rather suspicious.

The design looks dodgy! In any case, it is more logical to use a relay "shield" for the WeMos D1 Mini:

(Note the one I cite is the safer design. :astonished: )

I suppose you can make do with "screw shields".

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The Wemos D1 mini (esp 8266) using the Arduino IDE is likely the way to go. Loading the Arduino core and using the IDE is well documented. Using the D1 mini is very well supported through this forum.

I've looked into the WEMOS shields that I can find & purchase online easily; and there are less available than all the brand or aftermarket arduino uno shields.

Where are you located. The D1 mini shields look widely available for between 1 and 2 dollars US.