[Tuya Smart] IoT thermometer and hygrometer

The IoT thermometer and hygrometer based on Tuya Smart adopts a programming-free method and uses the WIFI module XR3 (provided by Tuya Smart), with an additional LED touch dimmer light and IP5306 charging circuit. Assembled into a small desktop lamp, not only do you not have to worry about having no place to put the thermometer and hygrometer, but you also do not have to worry about wasting space.

The power supply part of the Internet of Things thermometer and humidity meter is directly converted from 3.7V of 18650 to 3.3V, using a linear voltage regulator chip (ME6215C33M5G supplier number: C84119)

If you do not want to use 18650 lithium battery for power supply, you can also use the micro usb interface to directly supply power. The micro usb is connected to the charging IC (IP5306 supplier number: C181692). This IC is an integrated charging and discharging IC that can not only charge the lithium battery, but also Boost output (3.7V → 5V). When the battery is not connected, there is voltage and current at the VBAT port, which can directly supply power to the circuit.

The temperature and humidity measurement IC used by the IoT thermometer and hygrometer is SH30T (supplier number: C77361). Because it adopts a programming-free method, the functions are limited. It seems that it only has the temperature and humidity measurement function and anti-tamper alarm, and there is no power detection. If Without a casing, the anti-tamper alarm is generally not used, so the anti-tamper circuit and power detection circuit can be removed.

If you want to add a shell and retain the anti-tamper alarm, you need to slightly modify the anti-tamper circuit (because PA19 alarms when it is high, so you need to connect PA19 to the upper end of KEY2, remove R5:100K, and use the shell to press KEY2 during installation. Just keep it at a low level), modify it as follows:

Although the XR3 WIFI module does not have a power detection function, the IP5306 circuit can display the power and has a charge and discharge protection function.

Implementation function:

The IP5306 charging part and the LED touch dimming lamp (dimming chip: RH6616, supplier number: C78963) are additional circuits. If the LED circuit part does not need to be too bright, the parallel resistance of the LED can be increased. Physical model:

welding:

Notes: 1. Because the low power consumption of the WIFI module will cause the IP5306 charge and discharge IC to enter the low power consumption mode and be unable to boost the output, so the input end of the LDO chip ME6215C33M5G is best directly connected to VBAT (that is, directly powered by the battery) 2. The boost output inductor of IP5306 is recommended to use a 4.7uH power inductor (someone on the open source platform uses 1uH, but I have not tested it, so I don’t know, but please do not use the following inductors. It is not available for personal testing )

Assembly: Just cut and assemble according to the numbers in the PCB. PS: All wires at the cutouts can be removed (it’s not clear whether it can pass the review)……………………

PS: All pads are enlarged. If you need the original package, please modify it yourself (for example: the actual pads of 0603 resistors and capacitors are 0805)

The PCB has been modified and tested with good results.

PS: When the light is turned on, the temperature and humidity measurement will be inaccurate due to the heating of the LED. Appropriate heat insulation measures can be taken (the light will not be turned on all the time, so I don’t think it is necessary)