Pi keeps turning on and off when I have a number of USB devices

Question

So I have a Raspberry Pi B+ - I've had it for several years now, which I think may be the cause of this problem, though I'm not sure how.

Basically, it's fine when I have just a keyboard plugged in, albeit a bit slow, and likewise when I have a keyboard and mouse plugged in, but when I plug in my USB network adapter a little lightning bolt symbol flashes at the top right of the monitor, and power to the keyboard is repeatedly cut off, then turns back on, then gets cut off again, and so on.

When this is happening, the red LED on the PI itself flashing in time with the power to the keyboard (that is, when the keyboard turns off, the light flashes.)

I'm pretty sure it's not the network adapter's fault, since it used to work fine.

If it's relevant, my Pi was overclocked for about a week prior to this, though I didn't use it much in that period. It was overclocked to the turbo setting, and I think this may have been the issue. I've un-overclocked it now, but the issue persists.

So, is it time to get a new Pi? Or is there something else I can do?

Answer 1

Check what output your power adapter is. All power adapters, regardless of USB type or connector are not created equally, power rating wise. Meaning, some phone charges for micro use, or even iPhone stuff etc will be 5v of course, but look at the Amperage. Your amperage power supply will need to be sufficient enough to power the demands of the Pi (and overclocking will put more power load on it). When you plug in more peripherals like keyboard, and especially wifi adapters, you tax out that amperage coming in.

I look at it as showers in a household. The more people you have taking a shower at once across the bathrooms in the house, the less the water pressure coming out. Eventually more and more showers being used, and you only have a set amount of water flow to supply it all, eventually the water pressure will be divided to the point where it's only dribbling out, and nobody can take their showers.

Whats your power adapter amperage rating? Check the wifi amperage rating, keyboards, and your models pi power ratings, and add then subtract from the power supply amperage.

The keyboards don't take up too much, but can offset the power if the wifi adapter is also sucking off the main power running the pi.

If you already checked with sufficient known good power adapters, and they are sufficiently amp'd, then removed all peripherals and test the pi alone.

What pi model you have?

Answer 2

The lightning bolt means that the voltage is going down. So one of the USB devices is taking up too much energy for the power provided.

You can solve this by either using a USB-Hub with external power supply or by using a power adapter with more Ampere (acording to specs USB-B devices should not take more than 0.5A, so using a 2.5A adapter instead of a 2A one might do the trick).