# How do I interpret the Volts and Amps on my Raspberry Pi Power Adapter?

I have a Raspberry Pi 1 Model B. I have now bought the Power Adapter so I can finally start using it. But I am wondering how to interpret the information written on my power supply.

The Power Supply is a Belkin Power Adapter model #F8M126cw. It says the following:

Input Rated:

100-240V~ Which I guess is the country voltage used. 110 in the USA and 240 in Norway, Europe. The wavy line is for AC, alternating current.

50-60Hz If alternating current, then this is the positive and negative current which occurs every second.

0.5 Amps Current flow pr. second? What's the difference between this and the output Amps?

Output rated:

5V ... 1A This is where I get confused. Between the 5V and 1A is a continuous top line and below is a dotted line. Direct Current?

So, the Power Adapter has 5V, which is what I interpret as the pressure possible to push the electricity through the wire. 1A is the current, the amount of electricity moving though the wire. And the volts x amps = watts.

What's the difference between the input of 0.5 amps and the output of 1A?

• 1 Amp is sufficient to boot up a Pi, but remember that the USB ports are set up to collectively supply 1.5 Amps to peripherals, so you want to take that 1 Amp and add 1.5 Amps in order to come to the standard Pi power supply which is 2.5 Amps at a nice clean regulated 5 volts. They are very voltage-sensitive. Commented Jan 10, 2017 at 2:33

This is more a question for Electronics.stackexchange.com, but since it's very basic, an answer here is probably fine:

100-240V ~ indeed means the adapter works in all countries which have mains power voltage between 100V and 240V. This covers all countries in the world.

50-60Hz is the frequency with which the voltage alternates. 50Hz is the standard in Europe, 60Hz in the US.

0.5A is the maximum current drawn by this adapter from the mains power. Amperage is a measure describing the number of free electrons moving through a conductor (e.g. the wiring in your house that connects to the outlet in which you have plugged this supply) at a given point in time.

5V=1A means that the power supply turns the input power into an output of 5V, the = with the dotted line is an international symbol denoting direct (non-alternating) current output, with a maximum current of 1 Amp.

Now, assuming (and this is likely not a good assumption as the Amps are peak numbers and provided for rating purposes) the power supply uses 0.5A at 100V to produce 1A at 5V, you can see that with P=V*I 50W is used to deliver 5W in output. The rest will be dissipated as heat, which means the power supply is likely to get hot pretty quickly at this load.

As a side-note: the practical output of this supply is likely less than the 1A peak rating, and you might find it is not strong enough to power your Pi, especially if there are peripheral devices connected. I use 1.5A rated powerplugs for my B/B+ rPi's and 2.2A rated supplies for my rPi 2's.

• I would rather think the 0.5 A input are a not reached even when pulling 1A from the output. A power dissipation of 45 watts would be exteme. This little enclosure would melt in few seconds. I think the manufacturer was to lazy to make tests to find out what input is possible and they want to be sure in any cases so they specify an extreme high value. As you say, 1A is not enough for a RPI. My brother had this problem a few days ago and it took him some time to find out why his PI crashes from time to time. And he had only plugged in a network cable no other periphery. Commented May 24, 2015 at 15:50
• Absolutely right - that's why I put in the "for ratings purposes" comment. My Innogear "made for Raspberry Pi" adapters are 1.5A in peak output, and do not even have an input Amps rating on them. Before I used those, I tried using a cheap HTC phone supply which had 100-240V~ 200mA 50-60Hz input, 5V=1A output (so 20W:5W ratio) ... But it could hardly run the rPi on its own. Commented May 24, 2015 at 17:15