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Xiaomi AIoT Wireless Router AX3600 Review

Mon, 13 Jul 2020 00:00:00 +0000

I recently bought the Xiaomi AIoT AX3600 wireless router to experience WiFi 6 (or 802.11ax). This WiFi 6 router has been touted as having very good hardware specs for under US$100. After checking out a few reviews, it looked like you could achieve close to Gigabit speeds over a wireless link, which was pretty exciting. It reminded me of the time I upgraded my home network to Gigabit and could finally copy large files over the network quickly. I decided to get my hands on one and evaluate it with some speed tests around the house.

I don’t have any compatible WiFi 6 devices yet, so I ordered an Intel AX200NGW wireless card to replace the one in my laptop. These cards typically go for US$15 on AliExpress or eBay.

ONV PD3401G PoE Splitter Teardown & Review

Tue, 02 Apr 2019 11:59:00 +0000

Continuing my PoE series, I bought the ONV PD3401G, an active PoE splitter that is capable of extracting up to 60W (24V @ 2.5A) from the PSE. It is housed in a small aluminum extruded case that can be DIN rail mounted. This splitter is comparatively low-cost, about US$35, and more importantly, is capable of passing through Gigabit.

ONV seems to be quite a reputable company, so I believe their products shouldn’t be too badly designed. This unit can also be easily purchased on Aliexpress without having to go through some obscure distributor.

Internally it uses the LT4275A (marking LTGBT) for PD interfacing. The A variant of this chip supports up to 90W of power. On the power supply side, it uses a NCP1034 synchronous buck converter. The NCP1034 is capable of handling up to 100V, which is more than sufficient for PoE.

Looking inside, the in/out Ethernet ports are connected via a transformer, in order extract power from the center taps of each pair. We can see that the PCB traces for the input port pairs are thicker to carry the higher currents. Large beefy diodes form rectifier bridges for the data pairs.

Surrounding the input port on the underside, there are a lot of unpopulated components; those were supposed to offer input protection, probably using some TVS of some kind. these are marked RD1 ~ RD8, one for each Ethernet wire.

PCBWay PCB Review

Sat, 07 Apr 2018 12:47:00 +0000

PCBWay is a PCB manufacturer that prides itself on quick turnaround. You can learn about CNLohr’s sucess story here. They also offer detailed tracking of your order’s progress on their website.

They have reached out to me and kindly offered to sponsor the boards for this particular project, which I will be talking about in the coming weeks. As the cost of these boards were more expensive (compared to their “normal” orders), I had to pay for shipping myself.

With each PCB project, I find more and more methods of testing PCB manufacturers. This time, it’s with a PCB that is inserted directly into your USB socket.

The requirement for such a board is 2 mm thickness. The USB connector size is standard, so the usual 1.6 mm PCB thickness isn’t going to work unless you pad the connector area.

Also, I opted for gold fingers on the USB connector contacts. This is usually done for contacts on the board edge that will be inserted into some mating connector (like PCI cards and USB connectors such as this).

They also offer matte black & matte green colors. I haven’t seen matte colours being offered at other board houses so far. I would have loved to try them out, but that would have bloated the cost beyond my comfort level.

Order Process

The order flow for PCBWay is a bit different because you submit your gerbers without making payment first. This allows their engineers to take a look at the design before you actually pay.

Most other systems I’ve used are largely automated. After you submit your gerbers, they typically don’t expect any problems and so they collect payment from you first.

I uploaded the gerbers on the 8th Aug and I tracked my order progress online. Their website allows you to track the detailed progress of your board as it moves along the manufacturing process. For small runs like this one, it is not crucial but if you were doing a large project with panels of many boards, this would definitely be handy.

They started manufacture 2 days later (on the 10th) and completed everything by 12th. It was not until the 14th that they actually shipped the boards out and provided me with a tracking number.

Here’s a summary of the timeline:

08: Gerber files submission
10: start of PCB manufacture
12: boards completed
14: boards shipped (via registered post)
24: boards received

Seeedstudio Fusion PCB Review

Wed, 01 Feb 2017 23:58:00 +0000

Fusion PCB is a PCB service from Seeedstudio. They have been offering PCB prototyping service since I made my first board in 2011. It has recently been revamped a little, tweaking prices and options, as well as integrating an online Gerber viewer from EasyEDA. I was invited to give Seeedstudio’s revamped Fusion PCB service a try, and since I had some boards in the pipeline for manufacture, I thought why not?

You can configure various options for the PCB, such as board thickness, copper pour and surface finish. You can also make flex PCBs or aluminium for better heat sinking, as opposed to regular FR4. These options will of course come at a price. However, you can select various colours for your PCB at no additional cost.

The Boards

I ordered 2 sets of boards in total. I’ve decided to opt for an ENIG finish for the TIL311 display boards, just because it looks nicer in gold. The boards are manufactured with black solder mask, making the gold pads stand out better.

I’ll describe the display board in a separate post after I’ve assembled it. For now, here’s what 4 of the boards look like, component side up:

Like most PCB prototyping services, they track your order by printing some kind of order identifier onto each PCB. Usually they try to put this identifier underneath a component like an IC so it gets hidden when the board is fully populated, but sometimes they put it somewhere prominent, like under your product name. On this board, the identifier sits under IC4 but for the other board, it was under the product name.

The PCBs arrived in a shrink-wrapped bubbly packaging to protect the boards. There was also a desiccant thrown in for one set of the boards to keep it dry.

CXG 936d Temperature-Controlled Soldering Iron

Mon, 28 Dec 2015 00:09:00 +0000

A few weeks ago, I watched a Mike’s Electric Stuff video in which he was talking about options for portable soldering irons:

[youtube https://www.youtube.com/watch?v=sDMhh3p2nuM]

The first soldering iron he talked about seems to be interesting. It’s a soldering iron with temperature control, but everything is built into the form factor of a regular soldering iron. He also showed the insides of the iron, which uses a triac to control the supply, hence eliminating the need for the bulky 24V transformer found in most soldering stations.

Ever since my temperature-controlled soldering station died, I was left without one and fell back to using my cheap 20W iron. I was previously using the Duratool D00673 from element14, which is actually just a re-branded Zhongdi ZD-916. It was really expensive (S$120), so when it died after very infrequent use, I didn’t think it was worth it to get a replacement unit.

The 24V transformer is quite heavy and accounts for most of the weight of this unit, so trying to ship it from overseas was also not worth it. After it died, I tore it down and found that its construction was pretty crappy:

[tweet https://twitter.com/zxcvgm/status/468787841204375552]

If you want to see more teardown photos and a review of sorts, check out this EEVBlog forum thread. Of course I have verified that this crappy connector job wasn’t the cause of failure. My preliminary troubleshooting found that the power supply seemed to be working, but there was nothing on the LCD display nor was it responding (no beeps on keypresses).

Thanks to this video, I realized that there are alternative products that combine the best of both worlds.

The Cost of Fixing an Old iPod

Thu, 03 Jul 2014 01:43:00 +0000

My decade-old 4th generation iPod decided to blue screen on me, literally.

I love old stuff and I’m rather attached to this very first Apple product that I purchased 10 years ago. So I decided to turn to iFixit, the well-known DIY repair store for Apple products, for a replacement LCD screen.

Logic Analyzer Software Review

Sun, 08 Jan 2012 23:00:00 +0000

I was looking into the Openbench Logic Sniffer (OLS) client, an open source logic analyzer software to be used with the Logic Sniffer from Dangerous Prototypes and Gadget Factory, so I thought it might be worthwhile to look at other alternatives, including commercial products. In the next few posts, it will probably become obvious why I’m doing this.

Since I do not have any of the hardware, I must make it clear that I am only reviewing the software that is meant to be used with their analyzers. Good logic analyzer products will usually make their software available free, with either some demo files or a means to generate random or test waveforms.