CH571F Wireless Thermohygrometer

The program project was created using MounRiver Studio. The program repository address is
[link to Bilibili video] . The video is
on Bilibili . The
project is based on a review of the performance of common major brand AA batteries. The proposed solution is
         to use a single AA alkaline battery to power the circuit by boosting it to 3.3V via an ME2188A33XG power supply. Data from the SHT40 temperature and humidity sensor is read at regular intervals, broadcast, and then the circuit enters sleep mode.
Initially, small-sized CR2477 batteries (Nanfu Chuanying, 12.8 RMB each) or CR2032 batteries (Zimi, 2.58 RMB each) were considered, but due to their high price and small capacity, Zimi Rainbow AA alkaline batteries (1.3 RMB each) were used instead. A 2200mAh battery is roughly equivalent to 11 CR2032 batteries, and is much cheaper. Most of the AA alkaline battery's capacity is around 1.3V, and the system's standby current is relatively high (around 40uA) when boosting a single battery to 3.3V. Fortunately, the large battery capacity compensates for this.
       Many people have probably heard of Sensory, and their SHT40 temperature and humidity sensor is slightly cheaper than the STH30.
       Fixed copper pillars: Dual-channel M2*4 x4, M2*18 x4,
       M2*4 hex screws x8.
       The board uses a 1.6mm thick antenna; if using other board thicknesses, please replace the antenna accordingly.
Program flow:
Broadcast data structure
// Broadcast packet fixed length 31 bytes, automatically padded with 0 if insufficient static uint8_t advertData[] = { 0x02, // AD Structure length 2 GAP_ADTYPE_FLAGS, // Device identifier GAP_ADTYPE_FLAGS_BREDR_NOT_SUPPORTED,
    // Broadcast data 0x0a, // AD Structure length 10 GAP_ADTYPE_LOCAL_NAME_SHORT, // Data type abbreviation device name 0xe6,0xb8,0xa9,0xe6,0xb9,0xbf,0xe8,0xae,0xa1, // Thermometer and hygrometer URL encoding
    0x02, // AD Structure length 2 0x0a, // Transmit power 0, // 0dBm
    0x06, // AD Structure length 6 GAP_ADTYPE_MANUFACTURER_SPECIFIC, // Custom data used to fill temperature, humidity, and battery voltage data 0, 0, // Temperature 0, 0, // Humidity 0 // Battery charge %};
Power consumption test
battery: ZMI No. 5 alkaline battery calculated at 2200mA with an annual self-discharge rate of 2%. The battery capacity under low current discharge is estimated to be close to 2400mA. The following power consumption test is for reference only. 1. Boost voltage is ME2188A33XG, broadcast interval is 5 seconds, signal strength is 0dBm, working days = 2200/(0.08965*24 + 0.12)≈968.5 days.
 
2. The boost converter is XT1861B302MR-G, the broadcast interval is 5 seconds, the signal strength is 0dBm, and the working days = 2200/(0.0818*24 + 0.12)≈1056 days.
 
The program download
uses Qinheng's WCHISPTool (download address), serial port download. The microcontroller needs a cold start to be recognized by the download tool. The attachment provides firmware with a 5-second broadcast interval (it will change to a 100-millisecond broadcast interval in case of abnormal temperature and humidity).

Select the chip series, chip model,
download interface , serial port,
corresponding COM port
, select the firmware,
and click download.

QQ group for discussion: 697752852 (not a hands-on tutorial group) .
 
 
Modification record
: 2023-04-05: Slightly adjusted the wiring.
2023-05-09: Removed the two 10K %1 precision resistors for battery voltage measurement voltage divider.
2023-10-17: Matched components to LCSC Mall and modified the wiring.
2023-11-01: Added an abnormal temperature and humidity alarm function. When the temperature exceeds 60℃ or the humidity exceeds 95%, the broadcast interval was changed from 5 seconds to 100 milliseconds. After the alarm is cleared, the broadcast interval will revert to 5 seconds to save power.
2024-05-14: Retested power consumption and added a version using the XT1861B302MR-G boost converter.
2024-09-08: Changed the battery voltage measurement return value to a battery percentage, divided into 7 levels.