WiFi switch with low power consumption (0.03W) by piotr_go

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Post #1
21778003 11 Dec 2025 16:36

Recently, when building a controller for my cooker, I decided to experiment with something simpler. Admittedly, I'm not keen on WiFi control, but I was curious to see how low the current consumption could currently be. The off-the-shelf solutions I tested ranged from 0.3W to 1W. So I bought some Zigbee modules, a couple of WiFi modules, a couple of different transformerless inverter ICs and bistable relays. A bit of coding and. a pleasant surprise. 0.1W in the first tests, and after a couple of changes to the software + enabling power saving less than 0.05W.... with WiFi... Eeeeee? It didn't stop there. By modifying the power supply a bit I managed to get down to around 30mW. I even assembled my own meter to confirm the results. I was expecting something in the region of 0.1W. I decided not to use the Zigbee version.

I wrote the softwares using ESP-IDF 5.5, without any bytes, apps or clouds. Control from a browser on/off + simple configuration. It is also possible to update the FW.

To make things less rosy, the whole thing took a while. I am completely unfamiliar with web development, some 90% of my programming time was taken up with it.
There was also a bug that was causing all sorts of things to happen, I got stuck until I found it. Reset! Apparently the capacitor + resistor in the module wasn't enough and ESP was able to crash at odd times. I connected a reset to the GPIO and set it to high after startup, helped.

Used WiFi module ESPC2-02 from DOIT, 230v-->5v inverter BP2525D, 5v-->3.3v inverter M3406, bistable relay control GM8023B.

Schedule: 3e2333bd3

Building:

Dimensions: 44x44x22mm

Interior:

Current draw:

Measured with a plug-in meter and an average hourly measurement when powered from 5V.
Consumption measured with the control side running.

WiFi Configuration:

Updating FW:

You can either press and select the file, or drag the file onto the button.

Info:

Various helpful information.

Commercial use prohibited.

Attachments:

switch_0.2.bin Download (763.42 KB) Punkty: 2 for the user

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About Author
piotr_go piotr_go

DIY electronics designer
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Joined: 10 Jan 2003

Posts: 2900

Help: 94

Posts rating: 3316

Points: 13509
piotr_go wrote 2900 posts with rating 3316, helped 94 times. Been with us since 2003 year.
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#2 21778234 11 Dec 2025 20:28

Jawi_P Jawi_P

Level 36

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Post #2
21778234 11 Dec 2025 20:28

Nice it The case is from PLA and the black jumper is a pen?
#3 21778243 11 Dec 2025 20:35

piotr_go piotr_go

DIY electronics designer

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Post #3
21778243 11 Dec 2025 20:35

Jawi_P wrote:
Body is of PLA

PETG, higher softening temperature. Although the chip is unlikely to heat up.

Jawi_P wrote:
the black jumper is a pen?

??? aaaa WZorek, printed in black (on grey film) PETG on the first layer.
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#4 21778398 11 Dec 2025 22:23

krzbor krzbor

Level 28

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Post #4
21778398 11 Dec 2025 22:23

piotr_go wrote:
Modifying the power supply a little, I was able to get down to around 30mW.

Could you write a bit more - how did you manage this? 30mW is usually what the ESP alone draws and that's without a radio, and you have a radio (quite responsive) and an inverter.
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#5 21778405 11 Dec 2025 22:29

chemik_16 chemik_16

Level 26

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Post #5
21778405 11 Dec 2025 22:29

>>21778398
inaccurate gauge
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#6 21778419 11 Dec 2025 22:49

piotr_go piotr_go

DIY electronics designer

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Post #6
21778419 11 Dec 2025 22:49

krzbor wrote:
Could you write something more - how did you get it to work? 30mW is usually what the ESP alone draws and without a radio, and you have a radio (quite responsive) and an inverter.

I initially tested on an ESP32-C3 (I was making a cooker controller on it so it was handy), C2 performed slightly better (can't remember the exact numbers).
R10 I changed to a zener. The original manufacturer of the BP2525D recommended a 1.5k...2k resistor (the voltage at the output increases at low load).
I also tested several 5v--->3.3v inverters, the M3406 performed best at low load.

Upload the binary to the ESP32-C2 if you have one and test.

chemik_16 wrote:
inaccurate meter

While the measurement on the 230V side may be inaccurate (too little current), it should be OK at 5V.
I checked with several USB meters, it came out similar.

=========== update ===========

Aaaaaa, I completely forgot, in AP mode the current consumption is quite a lot higher.
You can't set it up normally, it's only for the first setup, or after a reset to default settings.
Reset to default settings after holding SW1 for more than a second.
Address: 192.168.2.1
#7 21778587 12 Dec 2025 09:36

gulson gulson

System Administrator

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Post #7
21778587 12 Dec 2025 09:36

Great respect! "The Chinese don't like it, see why".
All in all, Zigbee also consumes 30mW during transmission.
There the standby is implemented a bit better and I think it closes in 1mW ?

But I don't think you're planning on battery power as it's connected to the mains anyway ?
The idea was simply to reduce the electricity bill ?

I was wondering about WiFi switches / remotes with rechargeable batteries.
I heard somewhere about some microWiFi made by a Polish company: https://blebox.eu/
I wonder how they do with consumption, I had a rechargeable remote control that worked for over a year.
Until the cell died
#8 21778723 12 Dec 2025 12:21

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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Post #8
21778723 12 Dec 2025 12:21

I was already waiting for you to post this. Congratulations, it came out great.

Just one thing puzzles me - wouldn't it be possible to optimise the circuit even more? Are there bistable relays on 3 volts?

I ask because although most of the IoT products I review ( list here ) always have a mains voltage -> 5 V inverter and then a separate LDO 3.3 V, then recently I saw that the Chinese have gone one step further and in the plug-in with the LN882H , from what I understand, they have omitted the LDO altogether and will power the Wi-Fi circuit directly from the main inverter - they have put a relay there for 3 V too, albeit a regular one.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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#9 21778840 12 Dec 2025 14:37

piotr_go piotr_go

DIY electronics designer

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Post #9
21778840 12 Dec 2025 14:37

gulson wrote:
But I don't think you're planning battery power

Battery testing will happen, although I don't know when yet.

gulson wrote:
It was simply a matter of reducing electricity bills?

Well baaa, 10pc instead of one

p.kaczmarek2 wrote:
Wouldn't it be possible to optimise the circuit even further? Are there bistable relays for 3 volts?

I suspect I would have to pay quite a bit more for the relay than the inverter cost.
Other than that 5v + inverter is more stable though.
#10 21778943 12 Dec 2025 16:25

Karol966 Karol966

Level 31

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Post #10
21778943 12 Dec 2025 16:25

Apparently a device like many (from majfriends) and yet arouses appreciation, hats off to you for the beautiful, complex workmanship
I am impressed by the ease with which you use Chinese, not necessarily popular electronic components
#11 21779070 12 Dec 2025 18:30

piotr_go piotr_go

DIY electronics designer

» | Topic author Helpful post? (+1)

Post #11
21779070 12 Dec 2025 18:30

Karol966 wrote:
with what ease you use Chinese, not necessarily popular electronic components

The low price is tempting to try.
I remember when I had to pay almost 10zl for a similar 5v-->3.3v inverter at our place, and I could only dream about inductors in 0603/0805. Today at the Chinese ... 2 cents.
Too bad they don't have bp2525d at LCSC, I had to buy on aliexpress (aliexpress has gone completely to the dogs, I put one item in the basket, it shows a rating of 4.9, after paying it turns out to be something else with a rating of 3.2 and comments about fraud).
Create an account, log in here. You will receive points by participating in discussions.
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WiFi switch with low power consumption (0.03W) by piotr_go

FAQ

TL;DR: DIY WiFi mains switch idles at ~0.03 W; “by modifying the power supply a bit I managed to get down to around 30 mW.” [Elektroda, piotr_go, post #21778003] Why it matters: If you hate vampire draw, this build shows how to slash always‑on power while keeping WiFi control.

Quick-Facts

Idle power: Approx. 0.03–0.05 W after PSU tweak and firmware power saving; measured at 5 V side. [Elektroda, piotr_go, post #21778003]
Off‑the‑shelf WiFi switches typically draw ~0.3–1.0 W in standby. [Elektroda, piotr_go, post #21778003]
Size: 44 × 44 × 22 mm enclosure; PETG recommended for higher softening temperature. [Elektroda, piotr_go, post #21778003]
First‑time setup uses AP at 192.168.2.1; AP mode draws more, so use it only for setup. [Elektroda, piotr_go, post #21778419]
Core stack: ESPC2‑02 (ESP32‑C2), BP2525D AC‑DC, M3406 5→3.3 V, bistable relay driver GM8023B. [Elektroda, piotr_go, post #21778003]

Quick Facts

- Idle power: Approx. 0.03–0.05 W after PSU tweak and firmware power saving; measured at 5 V side. [Elektroda, piotr_go, post #21778003]
- Off‑the‑shelf WiFi switches typically draw ~0.3–1.0 W in standby. [Elektroda, piotr_go, post #21778003]
- Size: 44 × 44 × 22 mm enclosure; PETG recommended for higher softening temperature. [Elektroda, piotr_go, post #21778003]
- First‑time setup uses AP at 192.168.2.1; AP mode draws more, so use it only for setup. [Elektroda, piotr_go, post #21778419]
- Core stack: ESPC2‑02 (ESP32‑C2), BP2525D AC‑DC, M3406 5→3.3 V, bistable relay driver GM8023B. [Elektroda, piotr_go, post #21778003]

What is this project and who is it for?

A mains‑powered WiFi switch optimized for ultra‑low standby draw. It serves makers who want browser control without clouds or apps. It uses ESP‑IDF 5.5, offers simple on/off, config pages, and firmware update from the web UI. [Elektroda, piotr_go, post #21778003]

How did you reach ~30 mW standby with WiFi?

The author swapped R10 for a zener to stabilize the BP2525D at light load and chose an M3406 for efficient 5 V→3.3 V conversion. ESP32‑C2 performed slightly better than C3 in tests. Quote: “C2 performed slightly better.” [Elektroda, piotr_go, post #21778419]

Which parts does the build use?

Key parts: ESPC2‑02 WiFi module, BP2525D 230 V→5 V inverter, M3406 5 V→3.3 V regulator, and GM8023B bistable relay control. This mix enables low idle current and robust mains operation. [Elektroda, piotr_go, post #21778003]

How do I perform first‑time setup in AP mode?

Hold SW1 for >1 s to reset to defaults.
Connect to the device’s AP.
Open 192.168.2.1 in a browser and enter your WiFi credentials. AP mode draws more power, so exit after configuration. [Elektroda, piotr_go, post #21778419]

Why does AP mode consume more power?

Running the ESP as an access point keeps the radio active continuously. That raises current versus STA mode. Use AP only for initial configuration or after a settings reset. Then let it rejoin your WiFi network. [Elektroda, piotr_go, post #21778419]

How were power measurements taken and how accurate are they?

The author used a plug‑in meter and averaged hourly at 5 V. They verified results with several USB meters on the low‑voltage side. Accuracy at 230 V can degrade at very low current, but the 5 V readings aligned. [Elektroda, piotr_go, post #21778419]

How do I update the firmware (OTA)?

Open the web UI and use the Update FW page. Click to select the file or drag‑and‑drop onto the button. The device hosts its own configuration pages and supports updates without cloud services. [Elektroda, piotr_go, post #21778003]

What are the enclosure dimensions?

The printed enclosure measures 44 × 44 × 22 mm. This compact footprint helps fit wall boxes and appliance cavities while keeping wiring short. [Elektroda, piotr_go, post #21778003]

What material is the case and what is the black stripe?

The enclosure is PETG for a higher softening point. The black “jumper” is a first‑layer pattern printed in black PETG over gray film, not a marker line. [Elektroda, piotr_go, post #21778243]

Is Zigbee lower power than WiFi here?

A commenter notes Zigbee transmits around 30 mW and can reach about 1 mW in standby. The author tested Zigbee but chose WiFi for this build. Quote: “Zigbee also consumes 30 mW during transmission.” [Elektroda, gulson, post #21778587]

Any reliability gotchas and fixes I should know?

A reset‑circuit weakness caused occasional crashes. Wiring reset to a GPIO and driving it high after startup fixed instability. Expert tip: “Reset!” was the culprit until the GPIO fix. [Elektroda, piotr_go, post #21778003]

How do I restore factory defaults later?

Press and hold SW1 for more than one second. The device resets, starts in AP mode, and serves the config portal at 192.168.2.1 for setup. [Elektroda, piotr_go, post #21778419]

Can I power this project from batteries?

The design targets mains supply and uses an AC‑DC stage. Discussion centers on wired power, not battery operation. One comment explicitly assumes mains rather than battery use. [Elektroda, gulson, post #21778587]

What software stack runs on the device?

ESP‑IDF 5.5 with a lightweight web interface. No vendor apps, accounts, or clouds. You control on/off and configuration directly from a browser. OTA updates are built in. [Elektroda, piotr_go, post #21778003]

Which ESP variant worked best here?

Tests compared ESP32‑C3 and ESP32‑C2. The C2 “performed slightly better” on consumption for this use. You can flash the provided binary to an ESP32‑C2 module. [Elektroda, piotr_go, post #21778419]

Why use a bistable relay driver?

The GM8023B driver controls a latching (bistable) relay, which needs power only during switching. That helps minimize standby draw versus a continuously powered coil. [Elektroda, piotr_go, post #21778003]

WiFi switch with low power consumption (0.03W) by piotr_go

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