This project discusses a Bluetooth-enabled smart mop built using the CY8CKIT-042-BLE-A kit. The smart mop can recognize motion activity using a BMI270 IMU and turn on advertising in its BLE stack. When connected, the mop reports its liquid levels.
While a smart mop doesn't seem practical, some potential applications of this proof-of-concept include:
- Tracking liquids in applications like medical/industrial devices
- Tracking surfaces cleaned with Bluetooth beacons for compliance requirements in places like hospitals, clean rooms etc.
- Automated ordering of refills for the customer by tracking liquid levels
- Automated liquid spray for even application while cleaning surfaces
The following image shows the proof-of-concept stacked on top of a commercially available mop:
A schematic system description of the smart mop is shown in the image below:
A capacitive sensing Flex PCB is attached to the cleaner liquid refill. The Flex PCB is interfaced to the CY8CKIT-022 kit. The liquid levels are measured using the CY8C4248LQI-BL583 MCU on the BLE Pioneer kit.
The device is usually under low power mode until the BMI270 detects significant motion. The MCU wakes up and starts advertising its presence. This enables a mobile device to connect and read the liquid levels.
The prototype measures the liquid levels using CAPSENSE technology about twice a second.
The image below shows the components of the prototype:
The BLE kit is used to report data to the mobile app, track liquid levels and interface an IMU to detect motion.CapSense Liquid Level Sensing Shield
The first step of the prototype is interfacing the BLE pioneer kit to the CapSense shield. The shield is interfaced to the following pins of the MCU:
The prototype is calibrated and tested using the PET bottle that comes with the CapSense liquid level sensing kit (shown in the image below).
The CapSense Slider example is modified to track the liquid levels detected using the CY8CKIT-022 liquid level sensing kit. This enables tracking the liquid levels using the AIROC Bluetooth app from Infineon.
The following video shows the demo of the liquid levels tracked using the app.Power Profile
The BMI270 breakout enables putting the PSOC4 MCU to sleep and wakeup only when a significant motion is detected by the IMU.
The following video shows the power profile of the prototype while the device is under sleep, sampling data and connecting to the mobile device. The average current consumption of the device is about 7 mA. It is fairly high for a battery powered device.
The device wakes up twice a second to sample the capacitive sensors. The high peaks occur when the device is awake and advertising data. The current profile was captured using a Joulescope.Proof-of-Concept Demo
The final step was to put everything together to build the prototype. An off-the-shelf mop was modified to build the prototype. The following video shows the prototype waking up when significant activity is detected by the IMU. When the device starts advertising, it is possible to connect and retrieve the liquid levels of the container.Challenges
There are two challenges that need to be resolved in order to productize this proof-of-concept:
Power Consumption: The average sleep current is 7mA. It is way high for a battery powered device. The device needs to continuously sample the CapSense sensors in order to provide reliable measurements. The alternative is to use the CY8CMBR2044 controller. But the part is currently out of stock.
Material: The capacitance based liquid level measurements were accurate with a PET bottle (#1 plastic). But they were unreliable when measured using an HDPE container (#2 plastic). One possible reason could be the thickness of the container. This could be resolved during productization by choosing a material that provides reliable measurements.Productization
It is fairly straightforward to take this prototype towards a product launch. The product would consist of the following components:
- CYBLE-202007-01 module
- Coin cell / Battery holder
- LLS_CSD_12RX-042 Flex PCB
- Smart Mop PCB
These are the most expensive items that add to the total cost of the mop. A detailed breakdown of the BoM cost is available in the repository. The gerber files for the smart mop are also available in the repository.
The total cost of the product at 1000 units comes to USD 25.75
The BoM doesn't consider the cost of assembly or manufacturing. It is a significant number depending upon the manufacturing volumes.