Let's Control It

While searching the forum for "Action store" (a store that i like to visit on a regular base to find new cheap mod stuff), i found this USB charger that already has been modded once by someone else:
https://www.letscontrolit.com/forum/vie ... 71&p=34420

Because i recently said goodbye to all my ESP8266 modules, i wanted to see if an ESP32 would also fit in there. I had my doubts first because the module is bigger than the original Wemos D1 Mini based on ESP8266.

I decided to purchase one and followed most of the instructions provided in the other post.

And indeed, as exptected, i had to use the dremel tool a bit more agressive on this gadget to make it fit. Also had to remove the LED board, so now it is effectively no longer a "nachtlampje". But that wasn't my goal anyway.

In the end, both the ESP32 module and a shield on top will fit the cabinet. And whitout the cap, i can also access the USB port when needed for troubleshooting:

I had to make me a custom angle header to power it because space is too limited for normal headers. I will replace it with a proto shield when things have proven stable:
And the cap still closes: So now we have an ESP32 driven "nachtlampje" that has lost it's primary task. But maybe i can mount some Neopixels inside

When it's stable, i have to find a purpose for it...
(prototyping is fun, but what to do when it finally works???)

Hmm, that looks like some mod that deserves some warnings about safety.
Still a nice and compact mod though, but not all readers may be familiar with the do's and dont's of switching power supplies like these.

martinus wrote: ↑22 Apr 2020, 14:14 (prototyping is fun, but what to do when it finally works???)

• put it in the back of a cupboard

• forget it for a couple of years

• find it again while searching for something totally different

• wonder yourself what the hack* it is, take it apart, and be amazed about the primitive parts found inside

TD-er wrote: ↑22 Apr 2020, 20:30Hmm, that looks like some mod that deserves some warnings about safety.

Agree. It counts for all mods to equipment where live mains is present. So also modding the Sonoff series and the like.

In this case, good isolation between the lower and upper half of the enclosure is important. For the prototype, i used a piece of plastic of 1.2 mm thickness like this, similar to the enclosure thickness itself. But i'm still looking for a piece of hard plastic that can be glued to the enclosure to avoid possible creepage between the edges.

TD-er wrote: ↑22 Apr 2020, 20:30but not all readers may be familiar with the do's and dont's of switching power supplies like these.

Could you elaborate specifically on the don'ts?

I'm not sure if i'll put it into production unless i'm convinced that it's safe enough to use.

If you like, I can also 3D print those parts for you to test. (Remco also has a number of 3D printers, he told me)

I don't know how deep your knowledge of switching power supplies is, so maybe I assume too basic

Basic functionality of such a power supply can be broken down into these steps:

- Turn mains into DC (230V~ => 400V=)
- Create block wave for primary coil (oscillator)
- Rectify voltage from secondary coil
- Provide feedback for oscillator, PWM depending on output voltage



The dangerous parts:
- 400V DC (!!!), when touched, you cannot let go as it is DC.
- Feedback to the oscillator is not always isolated.

Especially on cheap units, the isolation of the feedback loop is sub optimal.
Also these power supplies depend on some minimal load, or else the voltage on the output can rise above the nominal value.
The feedback can only change the PWM signal over some range and often it cannot turn it to 0%.
This means the output capacitor will receive some pulses to charge it, but this will increase the voltage over the capacitor if there is no load.
Another implication of this is that on low loads the ripple will be quite big, especially on cheap units.
Some sensors (e.g. SenseAir S8) will be damaged if the supplied voltage is above 5.2V. With the ripple on some of these cheap USB power supplies, the ripple is over 200 mV.

I'm familiar with the basics of modern PSU devices. And seen some tests of the very cheap ones.
The thing with Chinese Manufacturing is that it can be hard to distinguish between cheap and too cheap.
I definitely stay away from the no-brand 1 euro direct import from ebay versions that according to several reviews make funny noises and tend to go up in smoke during heavy charging.

About the cheap ones available in local dutch stores? Hard to tell without proper testing equipment. They do have CE marking but i guess that only means "China Export" in these cases. It looks like they at least have learned about the 5 mm distance on the PCB between the high and low voltage areas:
The load in my case will be very moderate compared to actually charging a tablet or powerbank.
And i'm feeding the 5 volts only into the onboard regulator on the ESP32 module. So at least there's a second regulator in place and that could help out with the ripple issue if any.

Some more mechanical modding and I've found a possible purpose: Running stable for several days, no false positives. No unexpected reboots.

Second mod, using this standard IR shield:


Attached to the ESP32:


Final solution, wall socket is located opposite of the TV, distance 4 meters.


Using rules like this:
I can now turn on/off the bedroom TV using ESPEasy.

Of course, i could think of programming series of commands like turn on tv, wait a few seconds, select HDMI channel 1, etc
And using the other ESPEasy IRGateway sender in the mediaroom, i can turn on DVD, mediaplayer, PC, etc

When this is stable, it could add to the WAF in my home