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Using power switch for USB power handling

Hello,

I have been looking for a solution for my use-case and the push-button power switches (https://www.pololu.com/product/2808) seem to fit nicely (not totally, but it seems to be the best solution):

I have a touchscreen Display (https://www.elecrow.com/wiki/index.php?title=5_inch_HDMI_800_x_480_Capacitive_Touch_LCD_Display_for_Raspberry_Pi/_PC/_SONY_PS4) connected to a Raspberry PI 3B+ via HDMI and USB.

To be able to save power (the setup is running from a power bank), I want to be able to turn the display off via a button and programmatically. This can not be done straightforward (and I can not use the power button on the display), so I want to use the power switch.

The plan is to break out the USB and have the power switch control the 5 V USB power line. I know that this is not according to the USB protocol, but I am willing to take that risk.

Now my questions:

  1. USB works at 5V, however the min voltage for the SV version (and up) is 4,5V - should I stick to the LV version?
  2. There are 2 Vin and 2 GND connections. Does that mean I can run two lines through the power switch and control them both at once (or only use either one if the Vin inputs)?
  3. is there another solution? I saw that you have a USB multiplexer also (https://www.pololu.com/product/2596). Can / Should I maybe use that and leave IN2 unconnected and switch to that in order to turn off USB power?

Thanks in advance!

Hello.

I recommend using the LV version of the Mini Pushbutton Power Switch, since with voltages at the low end of their operating range, our pushbutton power switches can be difficult to turn on; you can read more about that in the “Characteristics at limits of operating range” section of the product page. The two VIN pins are connected together, and you can use either one for supplying power to the board, but for applications where you are switching higher currents (more than about 2 or 3 amps), you should consider making connections to both pins.

It sounds to me like the Power Multiplexer Carrier with USB Micro-B Connector might also work in your application, although depending on what you do with your Raspberry Pi, the multiplexer might limit your current. If you decide to use the power multiplexer, I recommend connecting your power to IN1 and bringing the EN pin high when you want to disconnect power from the output.

-Tony

Hi,

thanks for your help. i ordered the LV version and it should arrive tomorrow. It will take some time to get everythign together, but I will post about my efforts.

So, now I fell completely stupid and you please must excuse this very basic question, btu I feel unsure and do not want to break everything right from the start:

There is only one hole to connect Ground, do I need to connect the ground of Vin, Vout or both (or none)?

The Out-Part of this will be connected to a USB connection, so there is a ground there.

While drawing this correctly, I realized just HOW stupid my question was. Sorry about that.
Unless I am making a collossal mistake and will be buying new componentes soon :smiley:

Hello.

It sounds like you probably already figured this out, but in general, electronic devices should share a common ground (i.e. ground on one device should connect to ground on the others). So, for your situation, both the ground from your USB break out and your touch screen display should connect to the mini pushbutton power switch LV. The most reasonable/appropriate way to ground your 5V USB power is to connect ground from it to one or both of the ground pads beneath VIN on the LV. Likewise, the most reasonable/appropriate way to ground your touch screen display is to connect ground from it to one or both of the ground pads beneath VOUT on the LV.

-Tony