Teardown: WeMo Switch is highly integrated

-November 10, 2015

I've written a lot about home automation systems over the years, mostly those based on the Insteon powerline protocol. More recently, Belkin has come up with a Wi-Fi-based approach called WeMo, which I've been testing in conjunction with Amazon's Echo voice-activated virtual assistant. After you associate a WeMo device with your wireless network via an Android or iOS application, you're subsequently able to control that device via the same application while on your LAN, or optionally even through a WAN connection.

Hands-on evaluation results will be published soon; for now I'd like to share my hands-on disassembly results, specifically on a WeMo Switch. The more advanced Insight Switch, which supports both control and power-consumption monitoring functions, was previously discussed on EDN last year.

Here's what my particular unit looks like from the back, along with a closeup of the product-info sticker:

The two halves of the chassis are held together with four screws, whose heads are of the triangular anti-tamper flavor:

Two of the four are visible; the others are underneath the sticker:

Fortunately, my 30-in-one screwdriver set was up to the task. This is what the inside of the back shell looks like after removal, with the two sticker-obscured screws still poking through it. The mechanical assembly for the factory-reset button, normally at the top of the device, is visible on the left side of the photo:

Opposite it is the "guts" of the device; the digital subsystem is on the left-side PCB, with the power subsystem to the right of it:

Here's a close-up of one side of the digital PCB, still mounted in the chassis:

At top is the aforementioned factory-reset switch. To the left of it is the PCB-etched Wi-Fi antenna. At the bottom is a five-pin connector and cable, which interconnects the two PCBs. And in-between them at the PCB's center is its processing "heart," Ralink's MIPS-based RT5350 Wi-Fi SoC. The RT5350 is also found in 802.11b/g routers, access points, and the like ... the value of its routing capabilities becomes understandable when you understand how the WeMo Switch is initially configured.

If you haven't already noticed, the WeMo Switch doesn't include an Ethernet port, USB interface, or other system connection. How then do you initially configure it with your Wi-Fi network's SSID, encryption key, and other parameters? As is the case with Google's Chromecast, the WeMo Switch initially creates its own private Wi-Fi network, which the configuring Android or iOS device temporarily connects to. Via the configuration utility, the desired end Wi-Fi network attributes are sent to the WeMo Switch, which then reboots to complete the setup process.

Here's a closeup of one side of the power PCB:

Remove two screws from the power PCB, along with loosening two retaining clips holding the digital PCB in place, and the two-board assembly lifts away.

Let's first look more closely at the underside of the power PCB:

The HF3FA relay switches the "live" wire of the three-prong AC outlet set; the ground and neutral connections pass through the input-to-output chain unaltered.

Finally, let's look at the underside of the digital PCB:

Near the bottom is the switch used to manually switch the output outlet via the front-panel button. Above and to the right of it is an Etron Technology EM63A165TS (PDF) 256 Mbit 166 MHz SDRAM. And at the top is a Macronix MX25L12835EMI serial NOR flash memory.

As is the case with many consumer electronics devices, the hardware implementation is highly integrated and low cost from a bill-of-materials standpoint. Given that the product ASP is $49.99, Belkin is presumably making a decent profit margin on a per-unit basis. Unknown, however, is how much it cost the company to develop the WeMo Switch and its product line companions, as well as the costs of maintaining the WeMo "cloud" server infrastructure that supports both initial device activation and ongoing WAN access.

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