Today’s Mailbag

I have to say, it felt a little like Christmas today when the Correos post-lady turned up with a plastic container full of packages from China for me.


Among the many items in today’s post were the two you see above – a WEMOS board (i.e.  ESP-12 + power supply) which includes an OLED display. As you’ll know I’ve recently added the SD1306 display to the commands on my ESP8266 code – looks like they’ve done the same but gone a stage further and added the actual display to the board.

(While I’m here – note the site is now https:// rather than http://  – if anyone has issues (despite refreshing the browser) – do please let me know.

To keep costs down they’ve used the raw display and added their own electronics – but it still ends up as an I2c peripheral. I hope later this week to ensure my own software will handle this as the board (AliExpress) is dirt cheap and I can see a bright future for these little displays.

They call the board the Wemos D-Duino and about my only comment up to now is that it arrived with the display a tad loose and not lined up as they’ve used double-sided sellotape to hold it in place. When will people think – that stuff just does not work! So a little Gorilla Glue will be added today.

The second item that turned up was a (supposedly) Wemos uninterruptible supply (we’ve discussed the subject of these supplies and our expectations of them many times).  The battery was NOT included but luckily I had an Ultrafire handy – I also have a wide range of ex-laptop batteries which also do the job.  I had planned to give this board (I have two of them) a good hammering this week and I’ll let you know how that goes but as it turns out I can tell you very quickly and succinctly – it DOESN’T.  The Wemos D-Duino actually powers up in demo mode with the display cycling (and very pretty with it) so with a battery that had been sitting around for months without charge, I didn’t have to wait long for the display to go blank.

With the battery down to 2.89v, nothing was coming out of the power unit.  Without disconnecting the load, I plugged the power unit into USB power (little micro-USB connector on the underside.

I refer you to the AliExpress specification:

LED indicate(Green means full,Red means charging)

The underside red light came on, sure enough but the display did not immediately spring to live –  so I left the board to charge.  No matter what I did, the ESP unit would not spring to life until I disconnected it (at which point charging began) and reconnected it (at which point charging stopped).

I put a meter on the battery and noting that a red light had appeared on the underside of the power board I measured the battery voltage. It did not seem to be rising. Indeed if anything it was going down! I disconnected the load – and reconnected. The Wemos came on for an instant then went off.  The voltage at this point was now down to 2.76v.  Everything was running cold on the power unit. This was not what I was expecting.

I disconnected the load and reconnected. Now the power started to rise. When it got to 3.2v I reconnected the load and the display lit up. I disconnected the input and let the power drop again. At exactly 2.57v the output went off. Of course the battery voltage then shot up to 2.84v– no output.  I plugged the power back in.

The Wemos 1860 Shield (here we see both together) appears to be totally and completely useless, refusing to charge from standby state while the load is connected.  If you turn the load off – it charges.  This is not the first time we’ve seen this on arbitrary battery supply boards – but on a dedicated product?  Is this Candid Camera??  You may have read elsewhere that I HAVE had very cheap boards from China which would ONLY fail to start up from completely flat – something that is easy to get around with a little additional circuitry – in this case however the power cuts out at an entirely reasonable voltage and won’t come back on – so you can’t even circumvent that with an additional circuit.

Read the comments as my testing is down there. Conclusion while waiting to hear from the supplier and up to now they are NOT responding – further my review has failed to appear on AliExpress among the most likely artificial positive comments – AVOID THIS ONE LIKE THE PLAGUE.

There does seem to be an issue here – I’ve not seen ONE of this kind of supply, able to supply 2 amps or more and charge at that rate (otherwise there’s little point in supplying that kind of current) that ACTUALLY WORKS and keeps on working.

More on the rest of today’s rather large postbag later.


32 thoughts on “Today’s Mailbag

  1. Would there be an esp8266 with an e-ink display?

    So that the esp would sleep most of the time, and the e-ink typically does not consume anything.

    1. Not to my knowledge – but it isn’t a bad idea – if you can get significant savings by making the ESP8266 sleep. None of my projects need ultra-low power so it’s not something I’ve investigated.

  2. I’m going to buy some more of the ESP8266 version of this board – my software runs the OLED a treat – the only thing is – they just put the price up!

  3. Anybody knows how to backup/download the original ESP32 firmware that the board are shipped with?

  4. Hi Pete,

    at first i thought we bought the same part – but you got the 8266 version. I got some days ago the follwing parts:

    It works flawless and battery charging works out of the box too.
    I upgraded my arduino ide to the esp32 lib – its longer way than for the esp8266 but its okay.

    You should switch to these modules the display is great too.

    Best regards,

    1. Oh the displays are fine – I have that working on my own code etc… it is the power supply. Sure you can turn it on – and it will charge.. but try this… disconnect the charging input…. and let it run – when it eventually times out and turns off the load – leaving the load connected – plug the power back in – you may be disappointed.

  5. The ESP32 would solve a lot of problems by using Bluetooth LE for indoor sensors.

    Integrating the libraries by hand is still a lot of work. And not really working for me today.

  6. I had the plan of starting without memory struggle, and later switch to cheaper boards with less memory. Yeah, plans.

    I could use the memory for a very cheap surveillance camera. Read the camera buffer into memory and display it as JPG on a webpage. One picture every few seconds. Can’t find a really cheap camera though.

  7. More memory is not always better. I tried a Wemos D1 Pro with 16 MB yesterday but it is not supported by the Arduino IDE. I added the required data to the boards.txt but it is still not fully supported as other people found out.

    Like for the Orange Pi hardware without driver/software support is nothing.

    1. Well Christian – of course – more memory is of very little use for the ESP…. you can’t directly use more than 1MB… but here’s how I’m using the 4MB.. the top of the top meg is used for Espressif stuff – then I have a block for user data which uses Espressif’s checks for duff data (which the Arduino version does not do!!)… the first meg is all mine for programming, the second meg is the swap area for OTA and right now I’m not using the 3rd meg – but I did think it would be nice if I could figure out how to get the environment to shove all my fonts up there…. all in good time. I just don’t see the point of them putting 16MB on the ESP8266 – unless of course you wanted to make some kind of uber-data logger. I’d have thought 1.9MB (third meg and most of 4th meg) would be good enough for most purposes – personally I store very little on the ESPs – I use MQTT to collect up and bang it away on a Raspberry Pi and display graphs etc with Grafana – which today is really very good indeed – well it would be if I didn’t use that InFlux database which won’t let me to math on the data.

        1. Well Julian, it could well be me as my understanding of Grafana would fill, well, maybe 3 lines. So for example if I wish to multiply the field value by 3 – just as an example…. I go to the SELECT – and I have a field value and I attempt to add something from the drop down – one of the options is math… I select that and absolutely nothing happens. That is about as far as ~I’ve been able to get.

          1. Ah, OK. This is more a failing of Grafana rather than InfluxDB which certainly does allow some math in queries. Sometimes it is easier to switch from the handholding version to the raw edit line in the Grafana query editor. There are examples on the InfluxDB site for doing some math in the query.

    2. Yes, I brought a couple of those a while back as they looked like a good bet. It is likely to take a while for the Arduino libraries to catch up. In the meantime, I’m slowly switching to using Homie as my base build which seems to pack loads of features and still leaves plenty of memory left for sensor code.

      1. Personally I rarely use Arduino libraries – as my code is in C (Eclipse, SDK) I certainly take parts I need an un-objectify them – but lots of it is written from scratch – as I have a need for some new peripheral – and now my code handles quite a lot. Still – at some point I’ll have to convert it – right now the ESP8266 does everything I need.

        1. Yes, I know. Unfortunately, some of us don’t have your deep C skills! I’m an IT person not a developer so I need all the help I can get when writing code for microprocessors. 🙂

          Homie seems to have chosen some sensible defaults and I like the fact that they are thinking about the best ways to do OTA (e.g. via MQTT as well as a web site), power management, reconnections, etc.

          Not yet perfect and rapidly changing but I prefer their approach to the Tasmota one that requires tweaking of the Tasmota code to configure for your own environment and so makes it hard to maintain.

  8. Peter, stay away from that UltraFire 18650. It is dangerous crap. Just google it.

    There is already a similar ESP32 available on AE with OLED display: “Lolin ESP32 OLED”.

    I ordered one and will try to use it with a good 18650 battery and maybe without a voltage regulator to the 3V3 input.

    1. Ooooh. I’ve had 2 or 3 of them lying around for ages – never used them – I will indeed look them up – thankfully I’ve quite a few ex-laptop batteries – same size..

      Yes I noticed the ESP32 – not yet got my libraries and code in order to make really good use of the ESP32 and since I walked away from ESP-01 compatibility and shoved the user data right up at the top of the 4MB block I program from 0x1000 upwards and have BAGS of FLASH space left – just wish I had a little more RAM… however – I have an ESP32 board and several OLEDS so in time I’ll start making my code work in the ESP32 – sky will then be the limit not that I’m complaining.

    2. And stay away from batteries left abandoned for a long time discharged to less than 3.5 volts.

    1. Hi Pierre – well I gathered looking at the imagery that they might not be originals – but IMHO that is no excuse for them not doing the job.

      I’ve now returned after a couple of hours out – with the unit on charge and the load plugged in – and there is NO sign of any charging at all.

      I did notice in all of this that while AliExpress has lots of nice comments – most likely written by their staff, there does NOT seem to be a way to add a review – maybe that’s why all the reviews are nice because I cannot for a moment imagine I’m the first to notice this fatal flaw. I’ve written to the supplier.

      The thing is – they all use the same chip sets – I’m beginning to think that all anyone does these days is follow the same manufacturer’s example notes!! How hard can it be to make a supply that can charge from a flat battery to X level and then switch on the load. It isn’t even as if my battery is flat – the unit is successfully switching off the load when the voltage is low – but then utterly STUPIDLY neither charging or switching until the load is removed. It beggars belief.

      I’ll follow this up.

      1. I’m just looking at AliExpress -mostly 5 star reviews…. I managed to leave feedback with 1 star and lo – it does not appear in the reviews.. The instructions are very specific – red light when charging – green when charged – well, I’m looking at a red light right now and is it HELL charging.

        To make sure I wasn’t dreaming – I took the second charger unit (I bought two) and a different battery (ex-laptop). The battery started life at 3.1v and I plugged it in – the Wemos+display powered up and ran for a while. At around the same voltage the unit cut out and before long the voltage crept up to 2.8v (as the output had been shut down) and stayed there. The red light was on – which according to the ad meant the unit was charging – but trust me – it was not. I wondered if it could be my usb supply at fault – so I took the whole assembly over to a powerful USB supply able to fire out over 2 amps per output – no difference.

        No doubt about it – it’s a puppy.

      1. I have one here – arrived in today’s post… doesn’t seem to have enough chips to do both charging and voltage conversion – however this will now have to await the weekend as I have a little seaside travelling to do. Got to get some vitamin D.

  9. This little board including the OLED looks really sweet.
    Thanks for sharing.

    On my search on Aliexpress i didn’t find it with “Wemos D-Duino” but with “nodemcu oled”, just if someone is looking for it too.

Comments are closed.