Hi, new guy asking a stupid question here.
I'm a senior software developer, so coding's my strong suit, electronics is definitely not.
I have read dozens of threads but haven't found an answer.
I'm trying to make a visual metronome that lets a few leds blink to midi clock and also has an lcd display to show bpm and rhythm.
It worked great with 5 leds at the same time (used a transistor so they draw the current from the 5V pin).
But now that I connected the display (16x2), the slight flickering backlight every time the leds light up tells me that together it draws too much current. It didn't burn anything, I'd say it's not much over the limit, with only 3 leds the flickering's gone, but that's not enough for my project.
So, my current idea:
I really just started to begin to understand capacitor, so I probably am very wrong, but... The leds blink at max. 4 times a second. Couldn't I use a capacitor that could supply more than 200mA for those short time periods?
That's worth trying. Might only need a couple, who knows. Remember to put them in parallel, between 5V & GND, close to the transistor/LEDs.
But 5 LEDs @ 20mA is only 100mA, which is not that much. How are you powering the circuit? Even a 0.5A 5V PSU connected to the USB should be more than enough. What else except the LEDs and LCD are connected? Have you checked your circuit for faulty cables? Are any cables long and/or use thin conductors?
Powering it via the barrel jack by a 5V/1A* PSU instead of USB did the trick (I'm leaving the capacitors on, though). But now I'm confused. Why shouldn't I do that?
Edit: I know it should be 7-12V. But still, seems to be better than USB... Since I'll switch to a nano later on, I guess I'll use the PSU directly on the 5V/GND.
Precisely what have you got connected to where? To what is the display connected, to what power are the LEDs connected, to what power is the UNO connected?
Tell me 'bout it
I finally found a 12V/1A PSU which I'm now using on the Arduino UNO external power jack. Everything (LEDs and Display) is connected to the 5V/Gnd on the Arduino and it does the job. It seems that the USB PSU didn't supply enough amps. Case closed, thank you
No, that doesn't add up. USB can normally supply about 500mA, and you were not close to that. 100mA for the LEDs, 50mA for the Uno, 30~40mA for the display. Plus, the LEDs are only flashing a few times per second, so on for perhaps 25% of the time. The caps should help to smooth that to an average of only around 25mA. So your circuit is probably only pulling 100~150mA of the 500mA that usb can supply. So something else is wrong. Perhaps your usb socket isn't able to supply the normal 500mA, or the usb cable is poor quality with thin conductors, causing a voltage drop in the cable
Supplying the Uno with 12V through the barrel socket is a bad idea, as already pointed out. More than half the power is wasted as heat in the 5V regulator, which could easily cause it to overheat and shut down. You mentioned a 5V 1A supply? That's a much better idea. You can't connect it to the barrel socket, but you can split the cable and connect it to the 5V pin as well as supplying the other components.
