Electronic Toy Safety
November 13, 2018
Background

The global toys and games market is projected to grow at a compound annual growth rate of 4.9% during the period 2017–2021. Toy sales in the United Sates, the world’s largest toy market, grew to $20.8 billion in 2017. In addition to the conventional role of companionship and education, modern toys provide comprehensive engagement for children to interact with their surroundings, both indoors and outdoors. With the increasing complexity of toys, safety needs to be built into every step of the production process, from the initial concept to the final product available in retail. According to the U.S. Consumer Product Safety Commission (CPSC), “All children’s toys manufactured or imported on or after February 28, 2018, must be tested and certified to ASTM F963-17.” Standards aim to reduce the risks to kids playing with a toy; unfortunately, toy-related injuries are common. In 2016, there were an estimated 240,000 toy-related injuries for all ages treated in U.S. hospital emergency departments. In some cases, recalls are issued to notify the public of the danger and to remove the potentially hazardous products from the market as soon as possible. For example, a recent recall issued by CPSC in May 2018 involves a spin art kit with a battery compartment that can overheat, posing fire and burn hazards. This recall affects about 110,000 units.

Potential Hazard

As electronic toys utilize electricity to drive their functions, they present risks besides more common mechanical and choking hazards if designed poorly, including electrical shock and burns. When electronic toys draw power from batteries or wall plugs to operate, any malfunction in the path of the electrical current could alter the desired functions. For example, if the circuit board carries current higher than the design limit, excessive heat dissipation is likely to be induced. Increasing temperature in the circuit board, motor, or battery compartment could cause surface overheating, which subsequently poses a burn hazard to consumers upon contact. Furthermore, many toys are made with plastic or fabric enclosure. This creates a fire hazard in the event of overheating. In the following paragraph, a few areas regarding concerns with toy safety are discussed in detail.

Battery

Battery safety is a top priority when it comes to consumer electronics. Lithium-ion or lithium-ion polymer batteries incorporated into or included with toys must comply with one of the following standards: ANSI C18.2M Part 2 , UL 2054, or IEC 62133. The standards outline a series of electrical and mechanical tests that the sample battery must pass, including but not limited to short-circuit tests, abnormal charging tests, abusive overcharge tests, forced-discharge tests, limited power source tests, short tests, crush tests, impact tests, vibration tests, etc. A battery safety review, however, shall evaluate the battery as an integral part of the entire toy, and its specifications need to meet the performance requirement of the toy design. The battery protection mechanism shall be consistent with its specifications. For instance, a lithium-ion battery can only safely work within a certain voltage and temperature range due to its electrochemistry. Overcharge or over-discharge could lead to cell damage, such as loss of capacity, venting, or, in the worst-case scenario, thermal runaway. A protection circuit module (PCM) is built in place to monitor battery conditions. Customary experiments are designed to simulate possible battery operating conditions and faulty scenarios and to evaluate whether the toy battery safety system has adequate protection. A proper PCM will measure the battery voltage, current, and/or temperature and take actions in the event of abnormal battery behavior. In Figure 1, a battery cell went into thermal runaway during testing.



Figure 1. A lithium-ion battery went into thermal runaway during testing.

Circuit Board

A circuit board controls the various functions of a toy, such as motion, sound, and lighting. Toys integrate an electronic system of microprocessors, motors, sensors, input devices, output devices, and memory. Potential faults in the circuit, if not properly mitigated, could cause failure propagation along the entire board. For example, an electronic component failure in the circuit board can create a short path between the positive power supply and negative ground. In turn, a large amount of power dissipates at this location and can result in a hot spot on the device. With just a few watts of electrical power, the device surface temperature can reach so high that a burn or fire hazard is likely. Testing under all possible failure modes by identifying the weak points in the product schematic provides an effective approach to assess the consequence of any circuit board failure.

In Figure 2, an electronic component failure was simulated on a prototype device. Without a protection mechanism to stop excessive current under fault, the device surface temperature rose to 99°C. Touching a surface this hot could cause third-degree burns in just a few seconds.

Toy Fig2

Figure 2. The surface temperature of a device rose to about 100°C when a fault occurred on the device circuit board.

Toy Malfunction

Toys are designed for proper usage; nevertheless, children may invent uses for their toys not necessarily considered proper. When a toy is mishandled, the device needs to have built-in mechanisms to control the damage and prevent it from developing into more severe situation. For example, many toys utilize DC motors to drive their moving parts. The spinning fans of a toy helicopter, the rotating wheels of a toy car, and the body movements of a doll are all driven by motors. When a motor malfunctions, a higher-than-normal current could pass through the toy and lead to a temperature rise in the motor area, which poses a risk of overheating. Depending on the specific function of a toy, different malfunction scenarios need to be simulated. Controlling measures established for possible malfunction can be an indispensable safety feature during toy design, and their correct implementation needs to be reinforced. Figure 3 illustrates an example of how a motor temperature reached almost 100°C when a toy malfunctioned. The temperature stopped rising only after the battery died.

Toy Fig 3

Figure 3. A motor surface temperature rose to about 100°C during device malfunction.

Conclusion

To identify potential risk and devise solutions to mitigate risk, proper product safety and risk assessment is essential to preventing faulty products from going to market or initiating effective recalls when necessary. It is critical to incorporate design safety review, prototype failure analysis, battery evaluation, hazard identification and risk assessment into the product-development life cycle. With the increasing complexity of products in the toy industry, safety assessment is essential to protecting consumers, manufactures, and retailers against any potential harm or loss.

References

  • Global Toys and Games Market 2017-2021 by Infiniti Research 
  • The NPD Group / Retail Tracking Service, January-December 2017 
  • Toy Safety, U.S. consumer product safety commission, https://www.cpsc.gov/Business--Manufacturing/Business-Education/Toy-Safety
  • Toy-Related Deaths and Injuries Calendar Year 2016, US Consumer Product Safety Commission
  • https://www.cpsc.gov/Recalls/2018/Michaels-Recalls-Spin-Art-Kits-Due-to-Fire-and-Burn-Hazards#
  • ANSI C18.2M Part 2 for Portable Rechargeable Cells and Batteries
  • UL 2054, Standard for Household and Commercial Batteries
  • IEC 62133 Secondary Cells and Batteries Containing Alkaline or Other Non-acid Electrolytes—Safety Requirements for Portable Sealed Secondary Cells, and for Batteries Made From Them, For Use in Portable Applications or Equivalent Standards
  • Degrees of burns includes first-degree burn (superficial burn), second-degree burn (superficial/deep partial thickness burns), and third-degree burn (full thickness burn). The burn degree assessment was done by comparing the measured skin temperature with the burn threshold provided in ASTM C1055-03, Standard Practice for Heated System Surface Conditions that Produce Contact Burn Injuries.

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