Hi,
I'm sure this has been asked before but all the keywords combinations I can think of lead me to posts unrelated to my problem...
As far as I remember my board used to supply a steady 5V (that is steady enough to produce a constant 1023 reading), but now it just seems to flicker between 4.8V and 5V. Is that normal or is my board too tired? Is there something I can do or should I get a new one?
Thanks and apologies if this has been asked before.
What model of Arduino?
How is it powered? Have you measured that power source?
Since the "+5V" power rail is used as the analog reference it will read 1023 even if the "+5V" rail is 4.8V.
yan_g:
Hi,I'm sure this has been asked before but all the keywords combinations I can think of lead me to posts unrelated to my problem...
As far as I remember my board used to supply a steady 5V (that is steady enough to produce a constant 1023 reading), but now it just seems to flicker between 4.8V and 5V. Is that normal or is my board too tired? Is there something I can do or should I get a new one?
Thanks and apologies if this has been asked before.
Many of my Arduinos do NOT supply a constant/stable 5V from the 5V rail. It is usually between 4.8-5.0, if this is critical to your project you could simply purchase a 5v regulator which supply a very stable 5.0v output.
rep8:
Many of my Arduinos do NOT supply a constant/stable 5V from the 5V rail. It is usually between 4.8-5.0, if this is critical to your project you could simply purchase a 5v regulator which supply a very stable 5.0v output.
Well, it depends on the power source. If the USB supply isn't stable, then of course the Arduino can't do anything about that.
If on the other hand the on-board regulator is being used, it would be expected for that to be a bit more stable.
johnwasser:
What model of Arduino?How is it powered? Have you measured that power source?
Since the "+5V" power rail is used as the analog reference it will read 1023 even if the "+5V" rail is 4.8V.
It's a UNO, I haven't measured the power source (USB - which computer I plug it into doesn't make a difference).
yan_g:
johnwasser:
What model of Arduino?
How is it powered? Have you measured that power source?It's a UNO, I haven't measured the power source (USB - which computer I plug it into doesn't make a difference).
You should check the USB power. The Arduino uses the USB power directly, without a regulator, and will run fine on any power within the USB specification:
USB 1.x and 2.0: 4.75-5.25 V
USB 3.0: 4.45–5.25 V
Are you measuring a voltage from some external device?
You could always supply external power. If you apply more than about 6.6V to the power jack or Vin pin the UNO will use its 5V regulator instead of USB power. You could also provide clean 5V power to the +5V pin directly but if the USB power goes above 5V you will get those peaks,
johnwasser:
You should check the USB power. The Arduino uses the USB power directly, without a regulator, and will run fine on any power within the USB specification:USB 1.x and 2.0: 4.75-5.25 V
USB 3.0: 4.45–5.25 VAre you measuring a voltage from some external device?
You could always supply external power. If you apply more than about 6.6V to the power jack or Vin pin the UNO will use its 5V regulator instead of USB power. You could also provide clean 5V power to the +5V pin directly but if the USB power goes above 5V you will get those peaks,
I've done my measurements again...
My USB cable carries a steady +5.07V.
The +5 pin slowly alternates between 4.97 and 4.98.
Unsurprisingly the reading varies between 1023 and 1022, it seems it's actually my breadboard/components that fail isn't it? 
Anyway I learnt a few things in the process (among which double check my measurements before looking for help) so thank you for that!