Delay off system using millis()

my original article

    In simple Arduino projects you can use delay command for have few seconds a led on and after that off, but in in this time program is halted. If you use millis() function, Arduino can execute other tests in program, not halt...
   In Arduino IDE program you cam find sketch named BlinkWithoutDelay

  In article Using millis() for timing you can find a good explanations

   I use this schematic for first test, using a push button and pull-up resistor on input

   If you upload delay_button.ino sketch, you will see next cases:
- standby state, led off:

- push buton, led off

- instantaneous, led on, time defined in sketch

- standby state, led off, again, waitting push button.

because I write the sketch using this chart

In Serial Monitor, you can see

   I change button with infrared module, schematic is

   For module sensor with normal state logic output (LOW in standby and HIGH when is triggered) sketch is delay_sensor.ino

and if you use other sensors with negative state logic output (HIGH in standby and LOW when is triggered) sketch is delay_sensor1.ino

    I made movie named delay off using millis()

    For this sketch(es), states are:

- stanfby, led off

- sensor is triggered, led is instant on

- led is on few seconds (selected in sketch), led is on

- after few seconds (selected in sketch), led is off

Also, in Serial Monitor, you can see the states:

Simple alarm system with Arduino

original article

   A simple system alarm can be made with Arduino board, a sensor module (sound, PIR, Doppler, etc) and 2 switch or remote control.
   Base schematic is

If use buttons (switches) for control alarmsystem_0.ino is use without change

but is use remote control (singnal in HIGH) must changed in

Also, if sensor is like mine (infrared sensor) sketch is without change

but it easy to change in

for negative logic comand (active in LOW).
    After powered the system, alarm is in stand-by

and after push ON button (or button from remote control), alarm is in waitting mode

If sensor is activated, sound (yellow led in my case) is intermittently powered 10 second or more, depend value from here

   You can see 2 video:

- alarm system

- alarm system (2)

20.04.2019

   I add a new movie with this alarm system using RCWL-0516 Doppler (radar) sensor (this sensor was tested a few time ago an posted at http://nicuflorica.blogspot.com/2018/02/senzor-de-miscare-tip-radar-doppler.html). 

Movie is named alarm system with Doppler sensor

   Default sketch is for power off the alarm system

but you can change to be armed after powered up dthe alarm system

Unidirectional Communcation between 2 Arduino boards

original article

   I want to send many commands using just 1 wire (and ground) so I use 2 Arduino boards.
   Base schematic for unidirectional communcication between Arduino boards is

and you can test this simple mode communication using info from article Tech Thurday #005: Arduino to Arduino Serial Communication.
   For sender (transmiter) I use a keypad with LCD1602 shield (see https://www.dfrobot.com/

This shield has the schematic

   Test schematic is

and sketch for transmiter is transmiter_v0.ino and sketch for receiver is receiver_v0.ino.
   If you have v.1.1 shield you must have

and for v.1.0

   I made Unidirectional Communication between 2 Arduino boards

  The states for this system are:
- all button are free (not pushed)

- if you push SELECT button

- if you push LEFT button

- if you push RIGHT button

- if you push UP button

- if you push DOWN button