Topics created by Patrik Söderström

Hi i actually did this hack 4 weeks ago, its quite ugly, but here goes: Arduino 5v with external power and the sketch: https://github.com/mysensors/MySensorsArduinoExamples/blob/master/examples/RelayWithButtonActuator/RelayWithButtonActuator.ino Connect the relay to gnd on the little controlboard and the first "long 30-min-spray solderpoint" just Connect some spare wire to test when the motor starts (it start after 15 seconds) tadaa! Use the pushbutton to start the airwick manually. i have a simple timer in domoticz that just shuts off the switch after 20 seconds. This weekend i will build the MQ-2 sensor

@Patrik-Söderström I used this calculator. I entered 3.3V as the input voltage and 1.0 as the output voltage. I set R2 to 330 which is a common resistor value. I pressed "Compute" and got a value of 759 for R1: 759 ohm is not a resistor value that is available, but I looked at the values in the pack on ebay and saw that the nearest was 680. I entered that in R1 and cleared the output field: and pressed Compute again. I now got an output of 1.078V which can be seen as close enough to 1V. This can of course be done by hand, and is a nice educational task if you want to learn the details The important part is the ratio between the two resistors. Try with 680,000 and 330,000 in the calculator and you'll see that you get the same output value. However, there is a third component: The LM393. It also has a resistor value. If the resistors in the voltage divider are small compared to the resistor in the LM393, the calculations will be correct. But if the resistors have about the same value as the resistor in the LM393 the calculations must take the LM393 into account. That's why 330 and 680 ohm probably works better than 330kohm and 680kohm. A caveat with using small resistor values is that they will consume more power. This is important if the sensor is battery powered, but since the NodeMCU generally consumes too much power to run on battery anyway we can ignore the power consumption for now. As long as the resistors are at least 100ohm the used power will be less than what the NodeMCU consumes.

So my current transformers just came. I would like to build the circuit for this and I have one question. For the burden resistor and the voltage divider resistors, can I use 1/8 watt resistors or would I be better with 1/4 watt or higher?

@sundberg84 Yesterday I found you forum post at bygghus.se I was stuck at the phone for a long time reading it all! I´m very impressed and I will for sure order some of your board for the aurdino. @stevebus Great! I´m trying to find a Arduino Uno board, looks like the one in the mysensors hardware is out of stock. I searched on ebay and found this one, is it legit and the real thing? http://www.ebay.com/itm/Arduino-Genuino-UNO-R3-Compatible-ATmega328P-ATmeg-a16U2-with-USB-cable-/252365926607?hash=item3ac22e70cf:g:DR8AAOSw1DtXHD1s

Again, thanks for quick reply. I´m starting to get a better understanding now of how its meant to be used I have ordered some hardware now and will start to test. Thanks once again.