How much current can I put into my RPi?

Using a larger source curent capable supply will not cause any problem, as the PI will draw only the current that it needs.

The usb ports are current limited, so the problem there is that you WILL need a powered hub if you need to use power hungry devices.

The power supply you use MUST be regulated as the voltage must be 5.0V +/- 0.2V.

Millard Watson II wrote:

 

Using a larger source curent capable supply will not cause any problem, as the PI will draw only the current that it needs.

 

The usb ports are current limited, so the problem there is that you WILL need a powered hub if you need to use power hungry devices.

 

The power supply you use MUST be regulated as the voltage must be 5.0V +/- 0.2V.

If this is the case, how come the documentation that came with the Raspberry Pi says specifically a "maximum" of 700mA for model A and 1200mA for model B? Please don't take this as an attack, I am a newb.

The Max. current is the design max draw of the PI not the max capabilaty of the supply. In fact this could be read as a minimum spec. for the supply

The Max. current is the design max draw of the PI not the max capabilaty of the supply. In fact this could be read as a minimum spec. for the supply

So what does this mean in terms of maximum current draw?

If I use a 2.1A power supply and then using the 5v GPIO pin want to draw 500mA for a motor, what will happen?  Will it be safe?

That is going off the wiki which states:

     Power consumption of the Raspberry Pi device is

• • Board A: 5V, 500 mA (2.5W) without any devices connected (e.g. USB, Ethernet, HDMI)
  • Board B: 5V, 700 mA (3.5W) without any devices connected (e.g. USB, Ethernet, HDMI)

     The maximum permitted current draw from the 3.3 V pin is 50 mA.

     Maximum permitted current draw from the 5 V pin is the USB input current (usually 1 A) minus any current draw from the rest of the board.^[13]

• • Model A: 1000 mA - 500 mA -> max current draw: 500 mA
  • Model B: 1000 mA - 700 mA -> max current draw: 300 mA

Change the 1A above to 2.1A and you end-up with max current draw = 1400mA

Can someone please clarify this.

Fergus Byrne wrote:

 

So what does this mean in terms of maximum current draw?

 

If I use a 2.1A power supply and then using the 5v GPIO pin want to draw 500mA for a motor, what will happen?  Will it be safe?

 

That is going off the wiki which states:

 

     Power consumption of the Raspberry Pi device is

• • Board A: 5V, 500 mA (2.5W) without any devices connected (e.g. USB, Ethernet, HDMI)
  • Board B: 5V, 700 mA (3.5W) without any devices connected (e.g. USB, Ethernet, HDMI)

    

     The maximum permitted current draw from the 3.3 V pin is 50 mA.

     Maximum permitted current draw from the 5 V pin is the USB input current (usually 1 A) minus any current draw from the rest of the board.^[13]

• • Model A: 1000 mA - 500 mA -> max current draw: 500 mA
  • Model B: 1000 mA - 700 mA -> max current draw: 300 mA

 

Change the 1A above to 2.1A and you end-up with max current draw = 1400mA

 

 

Can someone please clarify this.

If you are powering an unmodified RasPi through its Micro USB connector S1 you are limited to 1A by polyfuse F3.  If you try to draw more than 1 A (e.g., 700 mA for RasPi + 500 mA for your motor = 1.2A total), the fuse may trip.  However, before it does so the voltage drop across your Micro USB cable and through F3 may cause 5V0 to fall below 4.75V, causing other problems such as your monitor and/or attached USB devices malfunctioning.  F3's trip current and time delay depend on temperature and vary from one polyfuse to the next.  The voltage drops across the Micro USB cable and F3 are also variable.

There are various ways to solve this.  Some people have powered their RasPis through the GPIO connector P1, bypassing F3.  However, by doing so they have lost all protection from F3 so if they accidentally hook up the wrong voltage or reverse their voltage leads they can easily destroy their RasPis and any attached peripherals.  Another solution is to provide separate 5V cables for RasPi and for your motor, perhaps using an externally-powered hub as the common power source.  Make sure that 5V to the motor doesn't have a sneak path back to the RasPi through P1 or you've lost F3's protection.

John Beetem wrote:

 

Fergus Byrne wrote:

 

So what does this mean in terms of maximum current draw?

 

If I use a 2.1A power supply and then using the 5v GPIO pin want to draw 500mA for a motor, what will happen?  Will it be safe?

 

That is going off the wiki which states:

 

     Power consumption of the Raspberry Pi device is

• • Board A: 5V, 500 mA (2.5W) without any devices connected (e.g. USB, Ethernet, HDMI)
  • Board B: 5V, 700 mA (3.5W) without any devices connected (e.g. USB, Ethernet, HDMI)

    

     The maximum permitted current draw from the 3.3 V pin is 50 mA.

     Maximum permitted current draw from the 5 V pin is the USB input current (usually 1 A) minus any current draw from the rest of the board.^[13]

• • Model A: 1000 mA - 500 mA -> max current draw: 500 mA
  • Model B: 1000 mA - 700 mA -> max current draw: 300 mA

 

Change the 1A above to 2.1A and you end-up with max current draw = 1400mA

 

 

Can someone please clarify this.

If you are powering an unmodified RasPi through its Micro USB connector S1 you are limited to 1A by polyfuse F3.  If you try to draw more than 1 A (e.g., 700 mA for RasPi + 500 mA for your motor = 1.2A total), the fuse may trip.  However, before it does so the voltage drop across your Micro USB cable and through F3 may cause 5V0 to fall below 4.75V, causing other problems such as your monitor and/or attached USB devices malfunctioning.  F3's trip current and time delay depend on temperature and vary from one polyfuse to the next.  The voltage drops across the Micro USB cable and F3 are also variable.

 

There are various ways to solve this.  Some people have powered their RasPis through the GPIO connector P1, bypassing F3.  However, by doing so they have lost all protection from F3 so if they accidentally hook up the wrong voltage or reverse their voltage leads they can easily destroy their RasPis and any attached peripherals.  Another solution is to provide separate 5V cables for RasPi and for your motor, perhaps using an externally-powered hub as the common power source.  Make sure that 5V to the motor doesn't have a sneak path back to the RasPi through P1 or you've lost F3's protection.

Thank you for explaining this.