Tech Diary

I have found this interesting board selling on Aliexpress website. It is an Arduino Mega 2650 with a built-in ESP8266 which allows the Mega to connect to wifi. This board has cut down a lot of wiring and bring out interesting possibilities. One of this is to connect up both the microcontrollers using ESP-link firmware. I have an earlier blog post  that described how to wire up an ESP-01 and Arduino Pro Mini. One of the tricky parts in this setup is the sequence of flashing the ESP firmware. Flashing the onboard ESP8266 requires some setting changes to the dip switches. The following are the sequences which I get both the microcontrollers to talk to each other. Set the jumper 5,6,7 to ON and the rest OFF. This will set the ESP to update mode. I am using version 3.0.14  and flashed the ESP using the following parameters: esptool --port com26 --baud 230400 write_flash -fm dio -fs 4MB -ff 80m 0x0 boot_v1.6.bin 0x1000 user1.bin 0x3fc000 esp_init_data_defa...

One of the difficulties I had with the common IR transmitter module block from Arduino kit is it is not powerful. It can only transmit from a distance of about 1 m and the angle is very narrow. I need an effective distance of more than 3m and a wider angle and I wanted to use Tasmota as the bridge so that I can send the IR commands from my PC or another remote non-IR device. The circuit for the super IR transmitter is as follows. On the web, I have found 2 approaches: connect multiple IR LEDs in series or parallel. The parallel configuration will provide more current to the LEDs and the series configuration will provide less current. I chose the series circuit because the resistance in the parallel circuit cannot be matched properly and the LED with the lowest resistance will get more power than the other which may result in 1 IR Led brighter than the other. I managed to find a super bright IR transmitter LED in Aliexpress. The LED has a blueish tint compared to the...

Lately, I have been experimenting on how to DIY a simple WIFI switch which can switch on/off a remote device. I can use OpenHAB to design a screen and use it on my mobile phone to do the job but I wanted a physical switch. I have put together the switch using a Wemos D1 mini and a capacitive touch switch. The capacitive touch switch has a nice blue glow when it is turned on. A NPN transistor is used as a switch to pull the D1 mini GPIO to the ground when activated. Tasmota has a configuration for Switch mode . When a switch is toggled, it will send out a MQTT message. I have made both the Sonoff RF Switch and DIY switch listened to the same queue. When the switch is touched, it will turn on/off the Sonoff RF Switch. Cool !!!