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What’s Inside? — Vol 2: Dropcam Pro

There Is Way More Than Meets The Eye

It’s been about three weeks since the Leap Motion teardown and I’ve been busy working on the next one. Recently we installed a Dropcam in the house to check up on our dog during the day.

So far I’ve been impressed with the ease of setup and its functionality including the night-vision feature. Curious to find out what’s inside this little nifty camera, it became the subject of this post.

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What’s Baker doing in our vegetable box?

Little did I know how many rabbit holes the diminutive gadget would send me down as I tried to understand how it’s put together, details of how it works, and where it’s made.

The process took way longer that I expected, partly because of a surprise feature inside the Dropcam, and partly because of a few improvements I made to the teardown. Read on to find out!

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Dropcam Pro hero shot

Dropcam originally started in 2009 as a software company for streaming and recording live video from existing webcams at home. Since then they’ve successfully transitioned into software + hardware company that provides their own easy to use in-home cameras and cloud-based recording service.

The ease of use and popularity of their service definitely was a big reason why last summer they got acquired by Google owned Nest to bolster the big company’s home automation and monitoring portfolio.

Until recently Dropcam used to offer two camera models; standard and Pro. While the Pro version is a recent addition to their lineup, as of a few weeks go, the company no longer is selling the older version.

The Dropcam Pro has several notable improvements over its retired sibling: A larger image sensor (3MP) for better video quality, wider field of view (130 degrees), dual band Wi-Fi for more reliable streaming, and Bluetooth LE radio for easier setup. Since these upgrades sounded very interesting, I decided to grab the newer model for the teardown. Let’s get to it.

Last summer I pre-ordered the FLIR One thermal camera and it has quickly become one of my favorite tools for hardware development, troubleshooting, and general fun photography. It’s super exciting that this technology is now available at such an affordable price point.

Looking at the thermal signature of electronics and how the heat dissipation is managed by the overall design of the product is a very valuable insight. So from now on I’ll be including thermal scans of the gadgets I take apart. If you’ve seen the Predator movies, I think you’ll get an extra kick out of these:

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Thermal Dropcam Pro

Given the relatively small size of its enclosure, it’s not surprising the Dropcam produces quite a bit of heat. The back side of the device seems to get much hotter than the front side. I’m sure there is an explanation…

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The back cover of the device provides access for the USB port (setup and power), microphone, speaker, and the small hole for a factory reset button. It came off easily by unscrewing the four Philips-head screws.

The top cover is made of plastic and houses the spring loaded mounting pads for the metal stand, as well as the light pipe and the custom RF antenna (black sticker).

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There is a small coax cable that’s connecting the antenna to the main printed circuit board (PCB). This is a standard coaxial RF connector called U.FL — great for space savings. One downside of using an RF connector is the attenuation of the radio signal (versus direct soldering). I’m sure this is a trade-off the designers made for ease of assembly. I’ll be talking about the radio section of the circuit in more detail later on.

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After taking off the top cover, I powered up the device to check out the indicator LED — which turns blue once the device establishes Wi-Fi connection. The LED itself is tucked away deep inside the camera module. The custom light pipe you can see inside the top cover helps channel the light to the front face.

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The main PCB comes off the back cover with an easy nudge using a flat-head screwdriver revealing the microphone, the speaker, and three light blue pads. What are these pads? These are called TIMs (Thermal Interface Material) used as gap fillers that are good thermal conductors. You will typically find them connecting electronic ICs (Integrated Circuit) to heat sinks.

My best guess is these TIMs are made by Saint-Gobain — P/N TC3008 and die-cut to the custom shapes we see here.

It turns out the back cover of the Dropcam is made out of cast aluminum with a soft plastic piece over it. The three TIMs are coupling the main processor, SDRAM, and the FLASH chips to the metal cover.

This group of ICs produce quite a bit of heat during operation especially since the Dropcam compresses its video feed (H.264) which requires lots of computation.

In conclusion, the back cover also acts as a heat sink, explaining why the back of the device is hotter!

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Bottom cover

Another neat component is the speaker itself. It makes electrical contact with the main PCB using two spring loaded legs. You can see the two golden square pads in the photo of the PCB below which the legs of the speaker touch once compressed by the back cover.

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Main PCB with the microphone disconnected
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Next, the camera module disconnects from the main PCB after unscrewing four more Philips-heads. So far dissassembling the Dropcam has been a breeze.

There is a board-to-board connector attaching the main PCB to the camera module which is made up of multiple assemblies including the IR LEDs, wide-angle lens assembly, the image sensor, and a component I’ve never seen before. There is also a two-wire connector that I originally thought supplied the current for driving the IR LEDs. [I was badly mistaken]

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Camera module — image sensor, lens assembly, and IR LEDs

This time around for the teardown, I did quite a bit of research on the components and investigated the operation of the electrical circuitry. I spent time probing various points of interest on the PCBs with my oscilloscope and voltmeter in order to make better educated guesses at how the design works.

Let’s take a look at some of the notable components and what their functionalities are:

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Main PCB — Top Side

Atheros AR6233X — Provides dual band Wi-Fi and Bluetooth Low Energy radio link for the system. The Bluetooth LE radio makes the setup process much easier by letting the user enter his Wi-Fi network credentials using a smartphone instead of physically connecting the camera to a computer by cable. Atheros was acquired by Qualcomm a while back and continues to make innovative radio chips.

Texas Instruments TPS65053 — Generates multiple voltage rails for the system — 3.3V, 2.8V, and 1.8V (measured on the PCB). These are typical voltages used by a digital system like the Dropcam.

Wolfson WM8974 — This chip is used by the main processor to acquire ambient sound from the microphone and drive the speaker. Essentially it’s a digital audio system on chip (SoC) that abstracts away the analog parts of interfacing with audio components. Wolfson was also recently acquired by Cirrus Logic who also provides audio ICs for several notable Apple products.

Hirose FH34SRJ — My best guess is this flex cable connector is used for programming / debugging the firmware. I happened to recognize this part because I used the 12-pin version of this connector for the Structure Sensor.

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Main PCB — Bottom Side

Ambarella A5s IP Camera SoC — This IC is the brains of the whole system. It’s a system on chip designed for this very specific application. The A5s takes care of acquiring video from the image sensor, compressing the video, and streaming it over Wi-Fi. It also orchestrates the setup and audio features of the device. An interesting trivia about Ambarella is that GoPro also uses the A5s and other Ambarella processors in their popular Hero products.

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Now it’s time to dive into the camera module. There is a stamped metal component that’s used for scaffolding the assembly. I think it’s also used as shielding for the image sensor which needs to be protected from electrical noise on the main PCB (i.e. power supplies, processor, etc). Also, I’m sure it acts as a heat sink for the image sensor clued by the TIM.

Four more Philips-heads and a copper tape (grounding?) keeps the IR LED assembly and the image sensor assembly together.

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IR LED Assembly

The IR LED assembly is fairly straightforward; made up of a PCB on which the eight individual LEDs are soldered and a plastic molded piece to hold the LEDs in the right orientation. These LEDs provide the illumination for the night-vision feature. Once the Dropcam detects low ambient light conditions, it turns on these LEDs and switches to night-vision mode.

This assembly is connected to the image sensor assembly with the two-wire connector you can see in the above photos. Probing the PCB, I can see that the IR LEDs are wired in series and driven by ~10V which equates to a ~1.25V drop for each LED, which is fairly typical for IR LEDs.

Also, I noticed that the drive voltage comes from the board-to-board connector that attaches to the main PCB. I was wrong to think that the yellow+white wire pair provided the power for the LEDs.

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Image sensor assembly

At last, we’re left with the image sensor assembly with the wide-angle lens mounted on top of the small image sensor PCB.

Wait a minute! What the heck is the yellow & black component right underneath the lens? I can see copper wire coils exposed on each side and it directly connects to the main PCB.

My first guess was that this component is a relay for turning the IR LEDs on/off since I’ve noticed that the Dropcam makes a clicking sound when it switches in and out of night-vision mode.

I was wrong. By carefully reconnecting the assemblies and the RF antenna I powered up the device. The web/mobile interface lets you manually override the night-vision mode. Indeed, I could hear the clicking sound coming from the mystery part every time I switched the mode.

Next, I disconnected the part from the main board. I expected the clicking sound to stop and the IR LED’s not turn on. Nope! The LEDs still turned on, but no clicking sound. This part is not a relay.

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Image sensor PCB and the wide-angle lens assembly

Let’s keep the disassembly going. The stamped metal and the wide-angle lens came off with two screws revealing another TIM. It’s hard to say who put the lens assembly together — Sunnex perhaps?

At this point, I’m very much distracted by the mystery part right on top of the image sensor.

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What the heck is this part?

At first I was hesitant to try to take this part off the image sensor PCB fearing that it may be irreversible. No guts, no glory! Off with it.

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Image sensor completely exposed. Don’t do this at home!

Seeing the exposed image sensor gave me a big clue! I’ve got to put the system somewhat back together and observe what’s going on when the night-vision kicks in and out. This time though I leave our mystery part off the image sensor assembly.

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Right away, I noticed something peculiar with the video feed in the regular mode (no night-vision). All the colors are quite washed out… And once I engage the night-vision mode I can see something moving inside the part.

I think this is a swappable IR cut filter!

Let me explain: In order to get good color information from image sensors, most consumer cameras use a filter that blocks IR light which is normally present in the regular light spectrum. (better explanation here)

Unfortunately, this same filter would make it impossible to use IR LED illumination for night-vision mode. So Dropcam designed this part to literally change the filter that’s on top of the image sensor depending on the mode of the device!

So how does it work!?

While probing the circuit, I noticed a pulse (4V) on the two-wire connector when the night-vision mode is activated. This pulse reverses polarity (-4V) when switching into the regular mode. Yes, this part is an electromagnet that swaps filters which are arranged on a moving tray. Check out the bonus magnification section for a close look.

Electromagnetic filter!

So happy to have figured out this component!

Next up, let’s see what the microscope reveals.

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RF block magnified

This is a closer look at the RF section of the circuit featuring the dual band Atheros AR6233X chip. Notice the two relatively wide traces coming out of the top-side of the part.

One of them is going into the black rectangular IC. This is the 5GHz RF signal for the dual band Wi-Fi link. The black IC is a FEM (Front End Module) that provides signal amplification and RX/TX switching.

The other trace out of the Atheros part is the 2.4GHz RF signal for both the Wi-Fi and Bluetooth LE links. This trace first goes through a low-pass filter (part with the “C” on it”).

Finally, both the output of the FEM and the 2.4GHz signal go into the part called a diplexer which is the small white rectangular part at the very top of the image. Simply put, the diplexer combines the 2.4GHz and 5GHz signals into a single trace so it can be output on a single RF connector.

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Image sensor magnified

Great close-up look at the bare image sensor itself. The darker rectangular section on the surface of the sensor is the active optical section.

Can we figure out the exact part number for the image sensor?

The Dropcam website states this is a 3-Megapixel sensor. Scouring the internet, I found this article suggesting that it’s a 1/3 inch image sensor made by Aptina — a well known manufacturer.

These clues lead us to the Aptina AR0330 sensor. The package and active region dimensions from the data sheet collaborate. I’m pretty sure the Dropcam Pro is using the AR0330.

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Image sensor package specification

Sticking with the acquisition theme, it turns out Aptina was also recently acquired by ON Semiconductor.

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Filters on magnitized tray magnified

Here is the electromagnetic filter system in all its glory. You can see the two filters are glued onto a tray that slides on a rail. Each filter glass has a small rectangular piece of metal next to it. Depending on the coil that’s magnetized by the electric pulse fed into the part, the tray moves to that side bringing the corresponding filter directly over the image sensor. The purplish glass is the IR cut filter.

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The parting shot of the Dropcam Pro completely disassembled — minus the screws.

I think you’ll agree there is more to this small camera than meets the eye. My favorite part by far has been discovering and figuring out the filter system.

The teardown didn’t reveal any obvious clues about the CM and manufacturing location for the Dropcam Pro. I haven’t given up so easily though.

Global supply chains leave behind a lot of breadcrumbs. Any time goods are imported into the USA, there is documentation about the cargo.

Here is a bill of lading that tells us quite a bit about Dropcam’s supply chain.

It looks like the Dropcam Pro is manufactured by Chicony Electronics based in Taiwan. This batch of Dropcams were made at their plant in Dongguan City just northwest of Shenzhen and shipped out of Hong Kong. It was shipped to the port in Oakland, CA on a cargo ship named Mol Courage. This is a very typical route for goods manufactured in the Shenzhen area.

In fact, the cargo was delivered to Great World Logistics who seems to be taking care of storage and fulfillment for Dropcam at least in the USA.

In line with the tradition I was able to put the whole device back together. Despite getting a few specks of dust on the image sensor, this Dropcam is back working completely fine!

I hope you enjoyed this teardown as much as I did!

Next up, I’ll look inside one of Baker’s favorite toys — a robot!

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