sazr
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Raspberry Pi works fine but no red light? Am I doing damage

Sat Feb 25, 2017 12:56 am

I have connected my Raspberry Pi 3 to my laptop through USB. The connection is through a USB hub, ie, I have my laptop connected to the USB hub and the Raspberry Pi is also connected to the USB hub. I am connected to the Raspberry Pi over Wifi using SSH.

The Raspberry Pi is working perfectly fine but the red light is not on. The green light is flashing every so often and SSHing is working fine.

Is there any potential damage I am doing to the Raspberry Pi with the configuration (using the USB hub)? If I take out the USB hub and connect the USB directly to the laptop then the Raspberry Pi red light comes on and stays on.

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Douglas6
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Re: Raspberry Pi works fine but no red light? Am I doing dam

Sat Feb 25, 2017 1:23 am

A Pi may run OK at under-voltage (no red 'power' LED) but it may be flaky and unreliable. Not worth the time trying to figure out if it's your code or a power issue causing problems. Or risking damage to the SD card. Give the Pi its own power supply.

julyjim
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Re: Raspberry Pi works fine but no red light? Am I doing dam

Sat Feb 25, 2017 1:51 am

In the USB 1.0 and 2.0 specs, a standard downstream port is capable of delivering up to 500mA (0.5A); with USB 3.0, it moves up to 900mA (0.9A). The charging downstream and dedicated charging ports provide up to 1,500mA (1.5A). ... It also supports power draw of 1.5A and 3A over the 5V bus.Aug 2, 2016

Check your Pi spec , mine says it can draw max 1 A depending on load .
Your Pi is safe to run , how dependable is the operation is just a guesswork , but your laptop will not provide more that 500 mA ( per spec) on USB 2.0 port.

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allfox
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Re: Raspberry Pi works fine but no red light? Am I doing dam

Sat Feb 25, 2017 11:18 am

It's not worth to risk on power supply problem. Go get a good supply source.

Pi 3 need a 2.5A source. USB can not deliver that much. There could be strange thing happen when under load. It could eat up a lot of time to track down those problem, only to find out we need a new power source.

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Burngate
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Re: Raspberry Pi works fine but no red light? Am I doing dam

Sat Feb 25, 2017 11:24 am

Hang on - red light is off running through the hub, but on direct from the laptop?

So the laptop's usb can provide enough current for the Pi, but the hub can't

Is the hub self-powered? Does it have its own power supply, or does it get its power from the laptop?
If it gets its power from the laptop, it could be that it takes too much itself, so there's not enough left for the Pi.
If it's got its own supply, the manufacturers didn't allow for people like us wanting to power a Pi from it.

alphanumeric
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Re: Raspberry Pi works fine but no red light? Am I doing dam

Sat Feb 25, 2017 1:25 pm

2.5 A is recommended for a PI 3B, but it doesn't have to have that much. By itself it only draws ~400 ma. USB 2.0 can provide that much. Its close to the 500 ma max for USB 2 though. Add in anything connected to the Pi's USB ports and your likely getting close to or maybe exceeding the 500 ma. Normally though, if you exceed the 500ma limit the USB port on a PC shuts down.
I'd say the voltage on the hub is dropping as you get close to that 500 ma limit. Or, its a cheap knock off with poor voltage regulation.
Either way, I'm with the others, get a decent power pack for the Pi and ditch powering it from the hub.

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