Raspberry Pi Forums

I'm building a mating board and plan to feed the +5 from my board to the rpi via the 40 pin header (rather than micro USB). I will provide a fuse to my pcb. Does anyone (speaking with good authority) know the fuse vendor and part number?

There are references to it holding 0.75A and tripping at 1.1A, but I've not come across a device with exactly those specifications.

Thanks
Barry

iabarry wrote:I'm building a mating board and plan to feed the +5 from my board to the rpi via the 40 pin header (rather than micro USB). I will provide a fuse to my pcb. Does anyone (speaking with good authority) know the fuse vendor and part number?

There are references to it holding 0.75A and tripping at 1.1A, but I've not come across a device with exactly those specifications.

Thanks
Barry

Those numbers are for the old model B not 2B. The 750mA was correct for model B, but I don't think the 1.1A tripping current that was printed on the schematic is correct. I also found that there were no parts that fit those numbers from any makers. The hold current is usually printed on the device in some way. The typical trip current is about 2X the hold current

The B+ and 2B models now use a 2.0A (hold) 'polyfuse'. It is not important that you get the same vendor and part number. Just get one that is 2.0A hold and over 5V.

Note that if you solder a wire to the test points PP1 or PP2 (+5V), then the RPi fuse and other protection circuitry will not be bypassed as it would when powering from the GPIO. This will work just as if you were plugged into the micro USB. PP1/ PP2 are located on the bottom of the board near the fuse. For ground use PP3 or any of the port shield tabs on the bottom of the board.

Thanks much for clearing up my confusion over fuse values for the different versions. The bit about shorting PP1-2 is news to me. I may do that for myself but not sure if that is a good general solution. I'd have preferred a shorting bar that might be cut if NOT desired.
I'll look further at mfgr data and pick something close.
Thanks!

iabarry wrote:Thanks much for clearing up my confusion over fuse values for the different versions. The bit about shorting PP1-2 is news to me. I may do that for myself but not sure if that is a good general solution. I'd have preferred a shorting bar that might be cut if NOT desired.
I'll look further at mfgr data and pick something close.
Thanks!

Sorry I was not clear. The wire to PP1 or PP2 is for you to attach your 5VDC power supply so that power going into the RPi will pass through the onboard fuse and other over-voltage protection circuits. PP1 and PP2 are connected together so you can use either point as a 5VDC power input.

when sodering to pp1 and pp2, which is postive and which is negative?

my_pi wrote:when sodering to pp1 and pp2, which is postive and which is negative?

As mentioned PP1 and PP2 are the same +5V. They are wired together on the board. Use either one for +5V.
For ground use PP3 or one of the port shield hold down tabs on the bottom of the board.