Soldering consumables

Soldering consumables

This cheap "No Clean Flux Dispensing Pen" pen is a bargain. I used one I chose randomly for years, and largely beyond its recommended date. So I was glad to see it still on the market: "951" DJP CW8100 (about ~5€ delivered from banggood).

I also bought this tip "rejuvenator" (about ~7€ delivered from banggood). It works surprisingly well to remove oxidization that could not be "wiped out" with metal sponges. No fumes, no odor, it kinds of "boils dry" instantly when the tip is dipped in it.
The container states it is some common soldering paste but I am glad it is not, as I already have all kinds of solder paste.

Warning/issue with micro-USB ZNTER 1250mAh AA rechargeable batteries

Not-a-deal

These rechargeable AA batteries sold under the ZNTER brand are cool... until they are damn too hot.

Actually, one of mine started to smoke heavily. Too bad, I like the idea for technophilic trekkers like me, as they require no bulky AA charger. I did not use them a lot though, and I bought 4 more lately so one was perhaps only defective on arrival (DOA).

Anyhow, the charging circuit is probably wrong if it can get to this point without shutting down. It even killed the plug from the 4-way micro USB cable.

In the end: do not buy, or at least do not charge without an eye on them!

ZNTER 1250mAh "AA" rechargeable batteries, which have an embedded circuitry powered by a micro-usb plug!

Using PCB rivets vias for homemade double sided PCB

You may remember in a former article the super tiny rivets I bought for double sided prototyped printed circuit boards (these but check those, they are way cheaper!). I realize that I never documented how I used them. So here it is.

The "raison d'être" of these costly rivets is specifically to help doing the vias that route the signals from one side to the other side of the board. The industry does plated holes with a chemical process that deposits a layer of conductive metal on the inside walls. It both conducts the signal but it also really helps making the board sturdier, as the copper rings (well square, here), are bonded together. Without it, the risk to tear apart one of them is much more important. Actually, a few makers do it also but it is both difficult, lengthy, messy and specially risky with a lot of nasty chemicals... not for me since I mill my PCB ;)

So in general, making double sided PCBs at home means there is no such plated holes. So we usually solder a thin wire through the hole on both sides. It is time consuming and it stresses the copper pads a lot, especially when the damn wire falls down when both sides melt again when you just want to solder the other side ;)

Top and bottom layers: making vias by means of PCB rivets on a double-sided milled PCB.
The milling job is quite bad here: the traces were not cut properly on the top layer (left side, check why here),
and the layers were mis-aligned after the board was flipped over to mill the top side... I need more practice.
Also, there are better and expensive tools to fix the rivets, but this prototype worked fine in the end anyway ;)

Now, rivets still help to make more robust single sided PCBs, most notably for the connector holes that will be subject to mechanical stress. Rivets will protect and keep the small copper "rings" tightly bounded to the PCB support material, so they will be less likely torn away.

Most notably, dirt cheap bakelite boards give no second chance in this respect, while fiberglass (FR4) endure more abuse and re-soldering. I guess the bonding is much stronger with the latter.

Which PCB rivets to buy?

I recommend 0.8mm outer diameter (0.6mm ID), because there their heads leave just enough room to route a trace between them. Hence in EAGLE CAD, I make sure to configure my vias to be 0.8mm accordingly, so they fit tightly.

Arducam too unstable to be useful

The costly Arducam Mini 5Mpixel camera module.
Warning, read before you buy, I do not recommend it!

After weeks of fighting I came to the conclusion that the Arducam ecosystem is useless, and even counter-productive to me -- while its original goal was obviously the opposite.

These camera are sold to provide pictures to Arduinos and other microcontrollers. The Arduino does not have enough memory, so these boards embeds enough processing power (FPGA?) and on-board memory to bufferize it and allow for serialized data to be stored and then transferred on demand. This way, the Arduino can store on an SD, or send it over GSM as I needed.

Now, the hardware may be nice and promising, but the software is really bad in my opinion.

This is strange to me as the Arducam is a wellknown project, and it is costly: I paid 43€ on watterott for example!

But it did not help me work faster, on the contrary. I really had all kinds of problems with the software, trying to interface both on a Uno or on a Mega.

The examples are half-baked, the API code source and the entire library is bloated with tens of variants of boards (28MB zipped just for the Arduinos!). Even the links to source code examples on some product page are broken. All in all, I consider that this somehow expensive camera is barely usable as it produces way too often invalid JPEG streams.

Cheap plastic boxes and enclosures that are just plain good

Below is is a collection of many of the sizes I found on Banggood, mostly to give me a real life feel of the stuff and to have them ready for future projects. I never have the proper box and I often revert to 3D-printing. But they do not look always as neat or they are not as weatherproof as a regular box for some outdoor projects... and it takes a long time to print in any case.

Probably not comprehensive, but a first-hand evaluation of many of the boxes found on Bangood.

Power IoT devices with solar energy, the $1.50 cheap way!

Had to find an easy solution to power some of my low-power device, like the one on the right (it is a minimalist 433MHz receiver).

A long time ago I bought a bunch of solar flashlight keyrings specifically for scavenging the parts.

They proved to be better than my expectations, with a very convenient 37×22×1.1mm solar cell which gives 7V unloaded, and up to 8mA for tested loads of 1 and 100 ohms (it "rains fire" as we often say here in summer: specs are only 5.2mA~6.3mA at 3.4V~4.5V loaded).

Admittedly, it is not much, but it is enough for a great lot of IoT devices, and given the size, it is just GREAT.

Measuring tiny currents to assess power consumption

The original EEVblog µCurrent (David Jones).
Way cheaper than real industrial probes,
but still too expensive for my needs ($80+)
It is open source btw (see here).

Optimizing power needs requires power tools that can read tiny currents (nano or pico amperes)...

Nothing happened like I wanted to the last N days and had to work on unexpected stuff, like a remote water level alarm for our swimming pool after more leakages (the liner is 14 year old). So I made an RF alarm, which is powered by a small ultracapacitor (0.47F) backed by a tiny 3x2cm solar panel I scavenged from a led keychain.

I wanted it to be small, so I can duplicate the project and put sensors all around (I should end up at around 3x2x2 cm all included). But small means low power.

Review: tiny Arduino Nano-based CNC shield

"Keyes_CNC" Arduino Nano shield for 4 axes CNC machines

The Keyes_CNC controller embarks an Arduino Nano

This little board is an "inverse" shield, on which an Arduino Nano must be plugged to provide functionality. It offers the same functionality as a regular Arduino Uno or Duemilanove CNC shield, with the same power.

But the result is both extremely compact and cheap: less than 7€ for the naked shield (or here), and about 22€/$25 for a complete setup: the shield plus an Arduino Nano and basic Pololu stepper drivers (here or there if you want ebay -- but the latter seems to be a reseller). And for once, it seems to come from a Chinese seller who designs and makes its own boards, which I tend to like.


Add a few Dupont wires (well, Jump wire is the generic name) and you are ready to go!
Fifteen years ago it would have cost thousands of euros!

Review: microscope for electronics (three Andonstar USB microscopes)

Here: fixing a board (0805 SMT resistors near a µSD socket, 0.6 mm wires).
A microscope is a much needed tool to inspect electronics, or to work at small scales.

(shot on my $160 workhorse, a very good Andonstar ADSM302)

This post shows the microscopes I have been using so far, sorted in historical order. This is also sorted by price, not surprisingly: with time my gear tend to get more expensive...
I am using microscopes all the time to inspect PCBs, read SMT component values, work at small scales, or whenever my (ageing) eyes are tired... And it feels like being in another world when you end up raising your eye back to the reality after a few hours :)

Review: arduino mega pro mini (aka Meduino)

This is a smaller variant of the Arduino Mega, and it is like what the Pro is to the Uno. It is even smaller than regular Arduino Uno boards, and costs about the same (less connectors, eh). And yes, it has all of what the Mega provides: extra memory & extra pins. And extra stuff to have in stock :)

Ref: check for "meduino" on ebay, or "mega2560 pro mini". There is also the "Mega2560-CORE mini" which needs and FTDI cable (no USB), and which is slightly cheaper. I bought the one below for $16 S&H included, and it took only 9 days from china to FR with tracking, impressive.

The Arduino Mega 2560 Pro Mini (aka Meduino) is a small factor regular Arduino Mega.