using pin 2/4 to supply 5v Pi Zero specifically

[pootle]

I'm doing a little project to run a couple of micro servos from a Pi Zero. They draw around 200mA running, but up to 600mA stalled (should that occur!).

I'm trying to track down exactly what is happening on pin 2 and pin4. I've seen schematics for some models that show 2 & 4 are identical, I've also seen info (which now I can't find *sigh*) that suggests pin 2 goes direct to the usb power socket and pin 4 is after the 5v rail polyfuse protection - which itself may not be present on the Pi Zero.

What is the proper answer to this?

If both pins are after any sort of protection, then it looks like I'll need to break into the usb cable and spur out 5v to the servos.

(and yes I already have some capacitors right next to the servos to tame the noise they might introduce.)

[joan]

Pin 2 is 5V. Pin 4 is 5V.

It's the same on all the Pis with the 40 pin expansion header.

They are the same point electrically and are both after any protection circuitry which may be present.

[bensimmo]

Are the pads still present on the Pi Zero like they are on the A+ ? So you could just solder to the pads near the USB power connector?
Some are before and some after the fuse iirc. I use them on the A+ to power it before the fuse.

[rpdom]

There are pads on the Zero. There is no fuse to worry about.

[pootle]

There are pads on the Zero. There is no fuse to worry about.

Ah! many thanks. hardly had time to make a cup of tea there!

On other models there are fuses between usb power and the pins, so the pad option should be used I assume?

[joan]

You haven't actually mentioned how you plan to power the Pi or the servos. We (at least I) am guessing at what you are planning to do.

[pootle]

just found viewtopic.php?f=100&t=83820, so it seems recent models have a much higher value polyfuse, so on 2's and 3's it's safe to take a lot more current from the pi.

[pootle]

Ah! sorry, overall plan is:

hi power wart (2A) to supply pi through micro usb power port as usual

2 sg90 servos with power from pins 2 & 6, controls from pins 11 & 12 (gpio 17 / 18 for those that don't already have the pinout wired into their brains).

I'm just doing a write up...

[pootle]

here's the write up

http://morepootling.blogspot.co.uk/2016 ... amera.html

[bensimmo]

You haven't actually mentioned how you plan to power the Pi or the servos. We (at least I) am guessing at what you are planning to do.

I guessed powering the servos from the gpio header pins hence tapping in the pads as an alternative to splicing/spkitting the cable if the power gpio pins cannot provide the current.

[bensimmo]

here's the write up

http://morepootling.blogspot.co.uk/2016 ... amera.html

Having a read now

OK other than having to search for what a wart is (other than something on the skin)
I see it's a PSU/ Plug adaptor.