Teardown Tuesday: Leeo Wi-Fi Carbon Monoxide and Smoke Alarm

In this teardown, we examine the PCBs and the main ICs found inside the Leeo Smart Alert Nightlight.

At a Glance

The Leeo Smart Alert Nightlight is advertised as being a simple-to-use, AC plug-in alarm monitoring system. Its features include:
  • Monitors existing smoke, CO, and water alarms and alerts you if they go off.
  • Alerts you via in-app or push notifications and automated phone calls.
  • Provides your local emergency service phone number in-app or by text.
  • Calls friends and family for backup if you don't respond to alert notifications.
  • Fully adjustable color nightlight design to fit your mood or decor.


Figure 1. Leeo Smart Alert Nightlight packaging (front and back)


Figure 2. Leeo Smart Alert Nightlight device (front and back)

Removing the Leeo Faceplate

The faceplate, with the Leeo marking, was easily removed using a small flat-head screwdriver as a gentle pry bar. Once removed, the PCBs and the microphone become viewable.


Figure 3. Faceplate removed revealing internal PCBs and microphone.

Removing the two Torx screws allowed the white outer metal ring and black plastic insert to be removed. We can now see the primary PCB (round in shape).


Figure 4. Primary/main PCB is visible.

Removing four Phillips screws provides access to the AC/DC power converter module.


Figure 5. The AC/DC power converter module resides in the rear portion of the device.

A Closer Look at PCBs and ICs

Figure 6 below shows the initial items that caught my eye at this point in the disassembly process.


Figure 6. Obvious high-level components associated with the round PCB.

The image below shows some primary components on the AC/DC power supply module.


Figure 7. AC/DC power supply module.

  • The module was most likely custom-made by a 3rd party manufacturer of which, probably, based on the company's name, specializes in power supply designs.
  • The thick copper traces associated with the high-voltage AC lines are derived from UL guidelines—for safety.
  • The bridge rectifier replaces the need for the four diodes of which are required for the conversion of the AC voltage to a DC voltage.
  • The gray-colored foam—glued to the top of the transformer—provides protection to the transformer's internal windings.
  • The big blue capacitor is a Class-Y safety-certified capacitor, p/n AH102M.
  • The isolation transformer is a telltale sign that this is not a transformerless power supply design. Isolation transformers are used for protecting the end-user from the high-voltage AC lines.
  • This board is a multi-layer PCB. It most likely has four layers.

The primary (round) PCB actually has a ring-shaped LED PCB attached to it.


Figure 8. Primary PCB with LED ring-shaped PCB.

Some key features:
  • The Kingston eMMC is mobile and embedded storage solution. It consists of NAND Flash and a Flash management controller.
  • The MSP430 is a microcontroller that, in my experience, is used in many applications. It's a very versatile, low-cost, low-power, and easy-to-use controller. Because it's a general purpose controller, it is really difficult to guess its purpose in this application.
  • The pushbutton is connected to the plastic pushbutton located near the AC prongs (see Figure 2 above)—this is the reset button.
  • The SN74CBTD3306C bus switch provides voltage level shifting and undershoot protection.
  • The layer-to-layer via stitching serves as EMI countermeasures. The idea it that the vias prevent EMI high frequencies from exiting the internal layers.
  • The vias are placed every 4mm on the circumference of the PCB.
  • The round PCB appears to be a four-layer design with the internal layers being copper planes (either ground or some positive voltage).
  • The LED ring-shaped PCB is a two-layer design (only top and bottom layers—no internal layers). This is the best approach for cost savings. However, uniquely-shaped PCB designs, such as this one, may carry a premium tooling/cutting charge. Of course, this all depends on the chosen board house.
  • The four metal stand-offs are used for attaching together—using the screws—the two PCBs.


Figure 9. Primary PCB (bottom side).

  • TLV320AIC3106 stereo audio IC: Connected to the microphone. This IC is designed for low-power stereo audio CODEC for portable audio and telephony.
  • The two EMI metal shield boxes are very efficient, although typically they are not the most cost-effective EMI countermeasures.
  • DDR3 DRAM: This Micron memory part is a 2Gb DDR3 SDRAM device.
  • AM335x Sitara microprocessor: This microprocessor is one of TI's Sitara processors. This device serves as the "brains" of the system.
  • ADBM-A350 optical finger navigator: This device works in conjunction with the moveable/rotational metal ring (see left-side part of Figure 4).
  • TPS65910x power management IC: The multiple (three, in this case) close proximity inductors are a dead giveaway for this IC being a power-related device.


Figure 10. Small PCB.

This small PCB can also be seen in Figure 3 above. It contains the temperature and humidity sensors:
  • SHT20 humidity and temperature sensor: This I2C digital output device is advertised as an industry standard in terms of form factor and intelligence.
  • TMP006 temperature sensor: This is an IR (infrared) thermopile temperature sensor. The thermopile absorbs passive infrared energy allowing the device to measure the temperature of an object without having to be in direct contact with said object.
  • The final device is unknown. It has no markings whatsoever. But what makes it interesting, however, is that its package is transparent. Therefore, it stands to reason that it may be another optical/light sensor.

Summary

This Leeo Smart Alert Nightlight appears to be well designed and manufactured with high quality in mind. As mentioned before, the power supply module looks to be custom designed for this particular system.
Given all the high-quality parts, the high-quality manufacturing details, and the multiple features that this device offers, I'm very surprised of the relatively low purchase price of $50.
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Hi, I`m Sostenes, Electrical Technician and PLC`S Programmer.
Everyday I`m exploring the world of Electrical to find better solution for Automation. I believe everyday can become a Electrician with the right learning materials.
My goal with BLOG is to help you learn Electrical.
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