ESP8266 Notes

This project connects a PIR motion detector to an ESP8266 but it is especially battery efficient because the ESP8266 is turned off when motion is not present. Adafruit Huzzah ESP8266 board Adafruit PIR motion sensor Batteries, 3xAA Battery PIR     ESP8266 Huzzah ======= ===     ============== POS --- 3-5V -- VBAT NEG --- GND --- GND         DOUT -- LDO cut pull up The PIR maximum voltage is 5V. Four batteries produces 6V which is too high. There is a pull up resistor on the LDO enable pin which is required when nothing is connected to LDO. In this case, the PIR DOUT signal is connected to the LDO pin so the pull up is not needed. To get maximum battery life, the resistor must be disconnected to prevent it from wasting power. In the following photo, the red line shows the trace to cut. LDO is the enable pin for the 3.3V voltage regulator (VR). When grounded, it turns off the VR so everything on the 3.3V side is powered off. When the PIR does not detect motion, it drives DOUT

The TPL5111 timer chip is used to power the ESP8266 board on and off to maximize battery life. This is a better alternative to using ESP8266 deep sleep. Adafruit TPL5111 breakout board Adafruit Huzzah ESP8266 board (not Feather) 3xAA batteries in battery holder. TPL5111     Huzzah  3xAA Batteries -------     ------  -------------- VDD         V+      Pos GND         GND     Neg Delay       n/c ENout       LDO DONE        #13     4.7K Ohm pull down The resistor on the DONE pin ensures it remains LOW while the ESP8266 powers up. In the setup function, GPIO #13 is set to OUTPUT LOW. When the ESP8266 is ready to power off, it sets GPIO #13 HIGH. When the TPL5111 sees the LOW to HIGH transition on its DONE pin, it drives ENout LOW which turns off the LDO voltage regulator on the Huzzah board. Cut trace on top side betweeen R3 and LDO pin. LDO pin connected to LDO EN pin via trace on bottom side. This reduces the current lost through the pull up resistor. Note: The TPL5111