I recently started building a large “busy box” for kids. I’m using a multiplexer to connect up to 16 buttons and switches (at the moment I have 9 push buttons and 1 toggle switch), and I’m using a PCA9685 to control up to 16 LEDs (currently I have 9 LEDs connected). I also have a rotary encoder wit…

I used a 5v 5A power supply like below. It uses a barrel plug to bring 5v to the circuit. [IMG_4434]

before I make any fireworks - I must not connect the arduino to the computer while I’m powering it from the 5V pin, right? when I first powering the circuit and until the arduino is starting there is a brief moment of 1 2 sec that all LED are ON. I guess there is nothing to do regarding it with the…

OK I understand the confusion. This part is for the “game” that connecting a dc cable will lit the led on. this is not the circuit power input. [image] this is the circuit power input: (I made it two pin terminal for the moment because I still not sure if I will use 5v PSU or power bank. [imag…

[image] hk_jh: I must not connect the arduino to the computer while I’m powering it from the 5V pin, right? All the NANOs I have seen have a blocking diode on 5v therefore plugging in the PC to the NANO is not a problem. The UNO is different though.

To keep our sketches responsive we avoid using blocking code. Remember, delay(. . .) stops normal program execution for the delay time amount. Avoid delay(. . .) ! Learn to make non-blocking TIMERs using the millis() funtion. You should also look into how a State Machine can make your code e…

[image] hk_jh: when I first powering the circuit and until the arduino is starting there is a brief moment of 1 2 sec that all LED are ON. I guess there is nothing to do regarding it with the current configuration, right? If this is unwanted, you can use the circuit below to keep the PCA LED…

Further to Post #44. The schematic below needs just a 100uF capacitor and 10k resistor on OE to prevent your LEDs from flashing at power up time. setup() in the following sketch has code to enable Hi-Z outputs when OE goes to 5V during powerup. This allows the capacitor and resistor can do the…

Thanks - I try those modification but I still having this 1 sec flash. just to say - I could be nice without but it is also not so bad with.

Busy box with multiple LEDs and buttons

Projects General Guidance

LarryD February 21, 2026, 6:09pm 56

One of my favourite DIY tools is the magnetic hold down clamp.

Front panels.

DIY spring clamp.

1 Like

Topic		Replies	Views
MIDI Controller PART 3 Deutsch	651	2622	February 14, 2026
Fancy Dog Bed w/ FastLeds and Rotary Encoder General Guidance	27	146	April 12, 2026
Hallo, wieder ein Neuling am Start Deutsch	80	653	January 28, 2026
Un primo progetto semplice Generale	115	657	December 11, 2025
Einsteiger benötigt Hilfe (Wahlbox) Deutsch	71	746	January 8, 2025

Busy box with multiple LEDs and buttons

Front panels.

DIY spring clamp.

Related topics