12v to 5v woes (rainbow square)

[PUTIS1989]

Hello, hope this is the right place to post!

I was working on a project and needed to get 12v DC adapter to the Pi 2, as it is only 5v I used this:



While it does boot and run the OS, I am getting a rainbow square which means there is not enough power, the DC I am using is rated for 12 3A, the USB regulator has an output of 5V 3A, yet this is not enough.

Is there another method? I'm assuming the product is faulty?

Help much appreciated!

[klricks]

Do you have access to a volt meter?
What are you using for the 12V input?

Try a better micro USB cable.
A good quality micro USB cable is just as important as a good power supply. If the wires in the cable are too thin and/or too long and/or the cable end connections are poorly made, then the required voltage will not get through to the RPi.

[PUTIS1989]

Do you have access to a volt meter?

No

What are you using for the 12V input?

A 12v DC Power supply rated at 3A output.

Try a better micro USB cable.
A good quality micro USB cable is just as important as a good power supply.

Micro USB cable is fine, used the same cable I use with a usb power pack and it does not get the rainbow square.


Is there any other ways to power the raspberry pi with 12v?

[davidcoton]

You are using the right approach -- AFAIK there is no other reasonable way to run a Pi (which must have a 5V supply) from 12V.

The RPi spec requires a supply of between 4.75 and 5.25V, or 5V +/- 5%. Without a voltmeter (preferably a digital one, with better than 2% accuracy) it is not easy to establish whether the converter is meeting that or not -- and even if not, whether it is within the manufacturer's spec is a different matter. It may be a combination of a marginal supply and a mediocre cable, such that if either part were improved the other would be okay. Any chance of borrowing a meter, with a friend to work it if necessary? If so, remember that the most important voltage to be measured is that delivered to the Pi when it is running. The voltage at the converter output, with and without a Pi connected, will help to track down any problem.

[PUTIS1989]

You are using the right approach -- AFAIK there is no other reasonable way to run a Pi (which must have a 5V supply) from 12V.

The RPi spec requires a supply of between 4.75 and 5.25V, or 5V +/- 5%. Without a voltmeter (preferably a digital one, with better than 2% accuracy) it is not easy to establish whether the converter is meeting that or not -- and even if not, whether it is within the manufacturer's spec is a different matter. It may be a combination of a marginal supply and a mediocre cable, such that if either part were improved the other would be okay. Any chance of borrowing a meter, with a friend to work it if necessary? If so, remember that the most important voltage to be measured is that delivered to the Pi when it is running. The voltage at the converter output, with and without a Pi connected, will help to track down any problem.

Thanks


I solved the issue by using another female DC Power Plug that was wired to the regulator, it solved the issue.

I might get another PSU with 5a since I am goiing to use all 4 ports.


Thanks again for the responses.!

[klricks]

....
I might get another PSU with 5a since I am goiing to use all 4 ports.

(B+ and 2B models)
There is no point in using a larger power supply. Won't hurt anything but there is no benefit as there is a 'polyfuse' inline with the micro USB power jack which limits the total current into the RPi to 2A. If you attempt to draw more than that the RPi will become unstable or shutdown.

Also the total current out of the USB ports is limited to 2 choices. Default is 600mA or 1.2A by adding a line to the config.txt file. The available USB current is shared by all 4 ports.