Searching for the right board and accessoires

I’m startting a new project and was told arduino is best for making my own micro-controlled stuff :slight_smile:
It’s basically a countdown-clock, and it’ll be started by supplying power and shut down by stopping the power supply, is that okay for an arduino board, or does it need a proper shutdown?

Additionally there are four seven segment displays needed (I found this one: and a couple of control elements.
I’m still searching for a “wheel” to set the time and also a small button to start the countdown.
The clock should also feature about 20 LEDs which show the time left.

So I’m searching for the control elements and the right board to get started, please help me :slight_smile:

(I’m sorry for any cases of bad spelling, german-autocorrect is not exactly helping)

Uno and some extra bits, like MAX7219 to control common cathode LED display - Check that you purchase Common Cathode - and LEDs wired up as common cathode array (3 columns of LEDs - anodes connected in parallel across the rows - A,B,C,D,E,F,G,DP - and cathodes connecte in parallel down the column (digit0, digit1, digit2, etc).

That will leave you plenty of pins for a “control wheel” (rotary encoder?) and control elements/buttons.

Simple power removal is sufficient, unless you are writing to EEPROM while power is lost - provide a signal to users to not remove power when EEPROM writes are occurring (requires 3.3mS (0.0033 seconds) per byte, so it happens pretty quick.

Thank you very much for the quick answer :D

As I'm very new to this, I'd be great to have some recommendations for a big four segmant display (for time) and the "control wheel" as well as a button. Also for shops, shipping to europe (germany) is needed.

The kingbright parts are good parts, I'd have no problem recommending those and a MAX7219 to drive them. Rotary encoder, any mechanical encoder with say 12 or 24 detente positions will work okay. www.taydaelectronics is one source of inexpensive parts, VAT and all that to Europe may be a factor. Shipping to the US is very inexpensive. If there is a German forum, I would ask for sources there as well.

Many thanks again, I haven't even thought about a german Forum :)

Would you recommend a board or something like that for easy wiring?

Why don't you use Arduino Mega?Less and easy wiring

thereyouare: Why don't you use Arduino Mega? Less and easy wiring

Not such a good suggestion actually. Generally, one uses multiplexing to drive multiple-digit seven segment displays - and these are large displays - so that you then run into problems supplying the necessary currents for the common lines.

The MAX7219 is specifically designed to drive such displays, making the wiring much simpler, and in addition, provides the segment decoding making the programming much simpler and performs all the multiplexing for you.

A UNO is more than sufficient. It's pretty much a done deal.

Isigiel, if I was doing a one-time build, I would assemble the parts onto a protoboard, with socket pins for the displays, and wirewrapping directly to the legs of the individual LEDs. I find wirewrapping to be faster and a lot more forgiving and easy to correct mistakes with than point to point soldering.
Here’s an example with some 8x8 matrices, MAX7219, resistor/caps, and a female header to accept male-male wires over to an Arduino.