The remote doorbell battery level is too low. However, it doesn't notify this, it just stops working. This little hack monitors the battery level and sends a little tick sound as a warning to replace or recharge soon.
FindingsThe method described below takes a long time. It could be shortened by using a variable power source and measuring the minimum voltage. However, a drop of 0.02V in two days already gives confidence that a working solution is possible.
First phase: Finding minimum voltageThe first phase is to find out the minimum working voltage. This setup is displayed in the image below. 3 AA batteries are connected through a voltage divider to the Wemos, which sends the voltage value to thingspeak. When the doorbell stops working, read out the last measured voltage and you know the minimum.
- Voltage divider: needed as the maximum input voltage for the Wemos is 3.2V
- Deep sleep: after uploading the value, the Wemos falls into deep sleep to save the external battery. The RST-D0 cable is needed to wake up from deep sleep.
NB: remember to remove this connection when uploading sketches!
- top left: the doorbell
- top right: external power source, rechargeable 9V battery
- bottom left: voltage divider
- bottom right: Wemom D1 R2 (Arduino++: including wifi, ESP8266)
Embedding an attiny85 with a into the doorbell. More info after finalizing phase 1. (still measuring...)
Attiny85Has an analog input of 5V. Three AA rechargeables won't exceed 5V. No voltage divider needed.
PowerDraw power from doorbell? Operating voltage for Attiny85 is 2.7V-5.5V (should be possible). Estimation is that this draws only a little power from doorbell, so just do it.
Deep sleepHow to do this on Attiny85? Read Technoblogy , or RE Innovation, or H2OhNo!.
BuzzerAlready tested with Attiny85 and a buzzer:
void loop()
{
digitalWrite(Speaker, HIGH); // short signal sounds as a tick
delay(3);
digitalWrite(Speaker, LOW);
delay(5000);
}
PerfboardFirst time soldering project. :)
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