On 02/06/18 01:35, RobH wrote:
> On 06/02/18 09:19, RobH wrote:
>> On 06/02/18 02:19, Kees Nuyt wrote:
>>> On Mon, 5 Feb 2018 13:06:26 -0000 (UTC), Gordon Henderson
>>>  wrote:
>>>
>>>
>>>> If you have a screen connected then you'll see a yellow "lightning
>>>> bolt" icon
>>>> appear if the power is too low (and a red thermometer icon if it's
>>>> too hot)
>>>>
>>>> 99% of issues like this is the power supply. Change it. Try another,
>>>> and if you have one, get your multimeter out and measure it when
>>>> it's powering a Pi.
>>>
>>> I agree, and I'd like to add that many USB cables have very thin
>>> wires and are too long, so they have too much resistence and cause
>>> unacceptable voltage loss. The buffer capacitors in the Raspberry
>>> Pi are too small to even supply short peaks current demands, so
>>> every peak has to be supplied by the power adaptor.
>>>
>>> I replaced those cables with a "charging cable", they just have
>>> thick power wires, no data lines, and haven't had any problems
>>> ever since (RPi 3, with an USB harddisk that draws 500 mA).
>>>
>>> Search on eBay for "Micro B USB Fast Quick Charge Cable 2.1A
>>> Android SmartPhone 18AWG" from Korea (or equivalent).
>>>
>>> Although the offer states 2.1A, they will carry 2.5A with ease.
>>> I prefer a length of 15 cm or 30cm.
>>>
>>> Not cheap, but really good.
>>>
>>
>> I never thought that a USB charging cable would or could power up a
>> pi3. That is really helpful, thank you.
>>
>> I have now attached a charging cable which I already have, and the pi
>> 3 is up and running.
>> At the moment it is drawing 4.84 volts and 1.58 amps, but the red or
>> green leds are not lit up.
>
> I realise that 1.58 amps is not enough power to do what I want it to, so
> I'll get one of those fast charging cables.

you realize that the USB charger spec is 500ma, right?  Although most
USB chargers seem to be able to supply significantly MORE than that, if
you're seeing a voltage drop below 5.0V then it's most likely under-rated.

What are you possibly doing that requires more than 1.5A ?  I suggest
that whatever 'power piggy' device you're trying to power with the RPi
get a separate power supply just for that load...

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