9 ms·

From what I've experienced, most power supplies are just awful and don't hold up at all to their specs, especially current in excess of 500mA. I've been workin

by tibbon 10y ago

From what I've experienced, most power supplies are just awful and don't hold up at all to their specs, especially current in excess of 500mA. I've been working with LEDs recently (APA102s), and I attempted just doing some testing with 4 meters (60 LEDs/m) and a cheap old 5VDC laptop power supply that in theory was rated for 5A+. Didn't work so well. Overheating, not providing enough current to keep the LEDs acting stable, power on spike, etc... To solve my problem, I've purchased two 5V 90A Meanwell power supplies, and those seem to work pretty well. But needless to say, I cannot imagine cheap/small power adapters working well at all. At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while.

andmarios 10y ago
With a quick look, APA102 LEDs draw 0.04-0.2A. Even at minimum intensity, we have 4m × 60 LED × 0.04A = 9.6A for the best case scenario.
Gibbon1 10y ago
> we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies I've been doing this for 30 years now. My rule is. Power supplies? Derate by 50% or you will be sorry. That power IC that says it's good for 1.2A? Yeah read that as 600ma. Capacitors are the same way, rated for 16 volts? Try 10 volts. If you look at capacitors specs you'll often see MTBF at rated voltage and temperature of 2000 hours which is three months.
- gh02t 10y ago
  Usually I see a big voltage sag when you get near the rated voltage on most wall wart type supplies. I try and stick to 50% or maybe 75% if I think it's quality.
digi_owl 10y ago
> At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while. What you could be running into there is a charger OEM that thinks Apple way is the proper way. Thing i that Apple uses a couple of resistors on the data pins to give slightly different V between them this indicates to an Apple device that they can go 1A or higher. But the USB spec says to basically short the data pins. Depending on the device OEM you may have the device think it is dealing with a normal computer port rather than charging port when encountering the Apple setup, and dropping back down to .5A.

by tibbon 10y ago

andmarios 10y ago

With a quick look, APA102 LEDs draw 0.04-0.2A. Even at minimum intensity, we have 4m × 60 LED × 0.04A = 9.6A for the best case scenario.

Gibbon1 10y ago

> we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies I've been doing this for 30 years now. My rule is. Power supplies? Derate by 50% or you will be sorry. That power IC that says it's good for 1.2A? Yeah read that as 600ma. Capacitors are the same way, rated for 16 volts? Try 10 volts. If you look at capacitors specs you'll often see MTBF at rated voltage and temperature of 2000 hours which is three months.

gh02t 10y ago
Usually I see a big voltage sag when you get near the rated voltage on most wall wart type supplies. I try and stick to 50% or maybe 75% if I think it's quality.

digi_owl 10y ago

> At my day job, we have some hardware that requires 800mA at peak to run. Even many 1A USB supplies we've found to offer nowhere near that current capacity. And if they do, they frequently fail after a while. What you could be running into there is a charger OEM that thinks Apple way is the proper way. Thing i that Apple uses a couple of resistors on the data pins to give slightly different V between them this indicates to an Apple device that they can go 1A or higher. But the USB spec says to basically short the data pins. Depending on the device OEM you may have the device think it is dealing with a normal computer port rather than charging port when encountering the Apple setup, and dropping back down to .5A.