This is actually a H/W snippet...
I made a clock which runs on Wemos D1 and get the time from TimeNist module (thanks to Erel), displaying the data on LCD 1602.
Then I added a temperature sensor (tmp36) to show the room temperature.
Then I wanted to control the 1602 led intensity by measuring the room light intensity and turn the display intensity to low when I go to sleep. The problem is that this sensor (a resistor) is read by A0 also and Wemos has only one analog sensing pin...
I had two options:
1. Wait till I get the DS18B20 temperature sensor which works on another pin, or
2. Use a relay to measure one sensor after the other. I didn't want to use a solenoid relay because it ticks when changing position so I created an optical switch using two 4n35 opto cuppler and few resistors. There is a voltage reduction due to the transistor so a re-calibration of the sensors data is required.
The opto cuppler has a diode on the left side, when ON it shines light on the light sensitive transistor on the right and makes it connect the two pins in-out.
When the control signal is false the bottom ic will connect and the top one disconnects, and vice versa when the signal is true.
I made a clock which runs on Wemos D1 and get the time from TimeNist module (thanks to Erel), displaying the data on LCD 1602.
Then I added a temperature sensor (tmp36) to show the room temperature.
Then I wanted to control the 1602 led intensity by measuring the room light intensity and turn the display intensity to low when I go to sleep. The problem is that this sensor (a resistor) is read by A0 also and Wemos has only one analog sensing pin...
I had two options:
1. Wait till I get the DS18B20 temperature sensor which works on another pin, or
2. Use a relay to measure one sensor after the other. I didn't want to use a solenoid relay because it ticks when changing position so I created an optical switch using two 4n35 opto cuppler and few resistors. There is a voltage reduction due to the transistor so a re-calibration of the sensors data is required.
The opto cuppler has a diode on the left side, when ON it shines light on the light sensitive transistor on the right and makes it connect the two pins in-out.
When the control signal is false the bottom ic will connect and the top one disconnects, and vice versa when the signal is true.