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Given that the RPi Zero consumes about 1A, and I have a power adapter that gives 2.4A of DC output - I'd like to use the spare ~1.4A to power up some stuff on the throughhole board.

Will that be sufficient if I will simply solder the single micro-USB female socket onto the board, and then route the parallel connection for RPi USB (using male socket for simplicity - don't want to screw up the RPi) and power rails om my board?

Any precautions, like including some resistors in the power tracks to prevent overloading?

The desired result - I will have the single power input for everything, and still be able to use the data OTG mode at my pi, if necessary.

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You could add a fuse.

Its probably better to create a power budget so you don't go over the 2.4A mark.

(Fake numbers)

Device 1 =1a
Device 2: 50ma
Device 3: 100ma
Device 4: 200ma

Total them up, and you know won't go over because you totaled the maxes.

You could add some kind of voltage sensor, and if they voltage drops significantly say more than 5% your overloading it.

I did some more poking around and found a current limiter.

https://www.maximintegrated.com/en/products/power/protection-control/protection-ics/MAX14575AL.html

Check that out.

  • What fuse would you recommend? Most of those I know are about 100V, and I can't find anything for 5V/2A. – jdevelop Jan 17 '18 at 3:41
  • Thanks for the link, the website you've listed offers the quantities starting from 1000 :) Anyway I've got the idea of what to look for, thanks! – jdevelop Jan 17 '18 at 4:42
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    Each MAX14575AL is $1.88 and is in TDFN package (non-through hole). A PTC fuse will be more cost effective. – Chetan Bhargava Jan 17 '18 at 7:26
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I doubt that "the RPi Zero consumes about 1A" and also that the "power adapter that gives 2.4A", but putting that aside you can power devices from the 5V pins on the Expansion Header. See Raspberry Pi Power Limitations No one really knows how much current the traces on the Pi will carry.

Using a fuse, or worse a resistor will not help; indeed a resistor would cause problems.

It is unclear exactly what you are proposing, but the simplest solution is to power the Pi through the 5V pins on the Expansion Header and connect your external circuitry to the same power supply. I CERTAINLY would NOT be attempting to solder anything to the Pi, except through the solder pads provided for the purpose.

  • I'm not going to solder anything on the Pi itself. I want to solder the micro-usb female socket on the throughhole board. Then I route a small cable with male micro-use header from this socket to the micro-usb on the Pi. And I make a fork on this cable to get plus/ground for the power rail on the through-hole board. I was thinking whether I need some fuse before Pi. – jdevelop Jan 17 '18 at 4:16
  • Essentially I'd like to off-load the power from the pi, and use the "single" power inlet to power separately Pi and the board. – jdevelop Jan 17 '18 at 4:44
  • @jdevelop You COULD do this, but presumably you are planning to connect some GPIO to the board, so it is cleaner to just use the 5V pin. I wouldn't use a µUSB socket unless I had to. The pin spacing is small, and they are a bugger to solder. – Milliways Jan 17 '18 at 4:49
  • I want to use Mifare RFID reader and LCD display, it will draw too much power from Pi, keeping in mind that I have USB2Ethernet adapter attached as well. So I need separate the power for RFID&LCD, and I don't want to have another USB inlet for this. So the plan was to have single microusb port that will power RPi and the board. – jdevelop Jan 17 '18 at 13:14
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I would say that don't mess with the pi board or alter it in any way. It could induce more problems.

You are correct that Raspberry Pi Zero takes under 1A but if your other gadget (throughhole board) draws more power, the output voltage of the adapter will drop and your pi will either become unresponsive or may restart due to under volt condition.

There is also a chance that if your other gadget has inductive load, it can cause spikes on the Raspberry Pi power line.

It is recommended to keep the power separate. Unless you have an adapter that provides two USB sockets like one below. These power adapters are cheap. Also would like to add that not all adapters deliver the power as marked.

enter image description here

If you still are too desperate and want to use one USB power port to power you Pi and your through hole board, you can also use a power splitter cable like below; there won't be any need to modify anything, just add a micro USB connected to your through hole board: enter image description here

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