Flashing led without delay

   I found another solution to made flashing led without delay than example from arduino IDE

   My solution is to use also millis() function but in other style. Millis() function count time from power up the Arduino (microcontroller)

   I use another variable, to made time from power up in seconds.After that I use rest function (%), for odd number led is on, for even number led is off. For example: 7%2=1 => led on, 8%2=0 => led off.

  You can see a simple mobvie with this style for control a led:

   I wrote 2 simple sketches: blink_wo_delay.ino and blink_wo_delay2.ino with same effects but little changes as commands.

  

Consumption measurement for MAX7219 32x8 led display

   For measure the consumption for display made with 4 8x8 led modules drived by MAX7219. I use clock presented in article named ceas animat complex cu date de pe net, whitch use just a development board WeMos D1 Mini and display with 32x8 leds.
   Schematic for a module with 8x8 leds is:

Leds are controlated through muplexing system, so consumption is low.

    First, I removed the display for measure the resistor control for consumption:

I used also a microscope:

Value is 103, so is 10kohmi. You can ckech using an online calculator:

   My display is powered at 3.3V, but I also made measurements at 5V.

   I chose this clock because it can be controlled from a local web page and it's easy to change the intensity.
   We have selected the intensity at 0, the one commonly used at night or when it is cloudy outside and the average consumption is 16mA at 3.3V and 28mA at 5V:

   I selected the intensity at 4, the one commonly used during very bright daytime and the average consumption is 46mA at 3.3V and 66-73mA at 5V:

Bidirectional detection with ultrasonic sensors

   I will made a box with 2 doors and system need to detect movement so I tested a simple system with Arduino board and 2 ultrasonic sensors (HC-SR04).

   I used info from an old project (made a 7 yesrs ago)

   New test schematic is

   My program is bidirectional_detection_ultrasonic.ino and if any sensor detect an object bellow 25cm led is turned on for 3 seconds.

   I made 2 video with this system: