Category: measuring equipment

Xiaomi Mijia Bluetooth-compatible Thermometer 2 Electric Humidity Smart Home Wireless Hygrometer LCD Digital Moisture (WHL #91)

Some new gadgets have been sitting here for a while – couldn’t be arsed to write about them last week

It’s pack of three Xiaomi Mijia Temperature + Humidity Monitor 2 (what a name), product number seems to be LYWSD03MMC. They cost me 15.58€ in December, inclusive of shipping and indeed one CR2032 coin cell per unit. Units from German distributors are more like 10 to 15€ each with negligible volume discounts – and shipping cost on top of that.

Anyway, here’s an explosion view from the unit, likely made by Xiaomi and not the seller:

I’ve been using other cheapo thermometer/hygrometer units for the past, well, probably 10 to 15 years, they’re really inexpensive at sub-2€ each and run on LR44 batteries basically indefinitely. […]


CEM DT-9939 multimeter leads (WHL #88)

Just an oddball thing that I discovered this week when lending out the leads of my newest multimeter, a CEM DT-9399. While the unit was an absolute bargain for what it can do, and the only thing to complain about is the slow continuity test mode and the slow Wireless USB (!) data transfer, this post really is about the boring leads. They just happened to be the only ones around in the office, and the boss asked for a spare multimeter that he could take home for the weekend for some rudimentary electrical testing, likely on an AC device. Well, better safe than sorry, don’t hand over the regular (non-safety) 4mm leads with some add-on test prods – give him the leads that came with the 1000V CAT III/600V CAT IV meter, right? […]


Sensirion SGP30 and Bosch BME280 air sensors (WHL #64)

Small air sensor modules for today!

The Bosch BME280 has been in use on my ESP modules across the apartment since I discarded the unreliable DHT sensors, DHT22 in my case. It’s a combined temperature-pressure-humidity sensor, contrary to the much cheaper BMP280 or the predecessor BMP180, which lack the humidity part (pretty much vital indoors, while pressure is just a gimmick). They are sold in many similar versions, I’ve always picked the GY-BME280 module in 3.3V flavour (“GYBMEP”), as the sensor can be operated from 1.71V to 3.6V which is handy for different MCUs. […]


Hiland M644 Multifunctional Transistor Tester LCR Resistance Inductance Diode Capacitance ESR Frequency Meter PWM Signal Generator (WHL #50)

Another component for one of the upcoming projects – a refreshed transistor tester.

I’ve been using these for ages now, I actually built two of them before they got popular (what a hipster thing to say?) and every Chinese seller decided to roll his own. The original thread on mikrocontroller.net dates back to early 2012 and the SVN repository even contains a few fixes of mine to the manual, as I was proofreading this thing at the time.

Times have changed, and the ready made versions are so cheap nowadays that homebrew really doesn’t make any sense any more. […]


16 Bit I2C ADS1115 Module ADC 4 channel with Pro Gain Amplifier RPi (WHL #26)

Meep. We finally have a new product review, after all that editorial, recap and electronic load rubbish ;)

Today’s item in the mail is an I²C ADC on a small PCB, running four channels (or two differential ones) with 16 bit precision. Sounds nice? Well, if it holds the claimed specs, it IS a nice product! I bought it in mid-June on AliExpress for 2.06 USD. Adafruit, by the way, charges 15 bucks for the exact same thing. Do I smell profit margin?

Here’s how it looks straight out of the ESD bag:

Backside is a tad boring (keep the VDD in mind):

(there’s a floating island on the GND plane, boo!) […]


USB detector 3.0 High voltage 4 bit OLED QC 2.0 Digital detector voltmeter ammeter voltage current power capacity tester meter (WHL #17)

New at Wan Hung Lo:

…wait, what?

(I’m pretty sure you’ll be able to find my address if you want to, just making it a little harder for google to index it as an image…)

So, what is it actually? Sure, it’s the USB power meter from the blog title. Who would have thought!
Bloody kids with USB 3 toys! Back in my days, we had…umm, good old RS-232 :lol:

I bought this one month ago at AliExpress for 8,61€ including shipping. As you can see, they decided to use some tracked mailing instead of the “ah, no worries” cheapo variant. […]


New at Wan Hung Lo: Open Source Hardware! Presenting the USB A-to-Micro bridge (WHL #4) (updated)

Oh well, I already announced it’s gonna be fake. But the other way round ;)

A while back, I saw the USB A-to-Micro bridge from youritronics. I already own one of these medium quality USB power meters that display voltage and current in an alternating fashion every few seconds. But complete control over power, data lines and also shielding is new. So I wanted one. In the short comment section however, someone noted that the signal routing probably isn’t the best. I had some spare time after Christmas this year, and I also wanted to test the Platinensammler (PCB aggregator) service from Jakob Kleinen. […]