Raspberry Pi - Step-Down Power Supply - USB Shield

[blackfox]

A Raspberry Pi and a Master Brick is in many situations a very useful combination. But unfortunately there is a serious voltage drop of ±20% in the Raspberry USB.

 

Adding a Step-Down Power Supply solves that problem but adds more cables.

 

My idea was that a Step-Down Power Supply Shield for the Raspberry would make this much neater. And adding a USB port to that shield would give the options to have a properly powered Master Brick local on the shield or remote via USB to keep it compact, or a second Master Brick via USB.

[Cathodion]

If I understand you correctly you could simply solve this by using a powered USB hub. That's the way I do it:

 

Raspberry Pi --> Powered USB Hub --> Master Brick.
                                 --> Wifi Dongle.
                                 --> RFID Reader.

 

This way the Master brick doesn't draw power from the Raspberry Pi. The powered USB hub costed me about 6 euro's. Cheapest solution I know!

[blackfox]

You are 100% correct and I use this setup as well, but it's a messy and far from compact solution.

 

But besides those objections, the main advantage of using a step-down power supply is that you could use a 12V or 24V PS and with those PS's I can power devices that require those voltages and use Tinkerforge bricklets to read the values of the sensors of those devices and power the RPi, all in one compact setup.

 

A powered USB setup works, but than I would need two PS's one of 5V and a bulky powered USB hub and another PS of let's say 12V or 24V to power my device.

 

I proposed this because the RPi is a very popular board and I saw that a lot of people were using them with Tinkerforge, but in the mean time I stopped using them and I switched to the more powerful and versatile beaglebone black.

 

 

[photron]

AFAIK you can power the Raspberry Pi via the 5V pins in its extension header. So this would allow this Step-Down Power Supply Shield to power the Raspberry Pi. This would allow to get rid of the cable from the Step-Down Power Supply to the Raspberry Pi.

 

And adding a USB port to that shield would give the options to have a properly powered Master Brick local on the shield or remote via USB to keep it compact, or a second Master Brick via USB.

 

Do you suggest to have an USB hub on this Step-Down Power Supply Shield? One problem with this is that the extension header of the Raspberry Pi does not include USB pins. So you would need an USB cable between the shield and the Raspberry Pi and another USB cable between the shield and the Brick that is stacked on top of the shield, because there are no USB pins in the stack connectors.

 

For just one Brick this doesn't make much sense. You could just connect it directly via USB and power it with this Step-Down Power Supply Shield.

 

To inject 5V from the Step-Down Power Supply Shield into an USB host connector to power a Brick via USB, this would require an USB device connector on the Step-Down Power Supply Shield to connect it to the Raspberry Pi's USB port. If you want to run more than one Brick from this you need extra logic and will end up with a crossbreed of a Step-Down Power Supply and an active USB hub that happens to be powered by the Step-Down Power Supply.

[blackfox]

Hi photron,

 

Yes you're right about the USB part. The reason why I suggested it was to make the shield commercially more attractive by adding some features to it.

 

Things that could be added to the shield are a Real Time Clock and a SD Card Reader/Writer.

 

The reasoning behind the SD Card Reader/Writer is the following: On the RPi the operating system is the IPE – Industrial Perennial Environment a special blackout-proof flavor of Raspbian – a Debian-based Linux Distribution for the Raspberry PI. See http://nutcom.hu/?page_id=108

 

This solution keeps the SD card on the RPi intact for a very long time and the SD card on the shield is used for writing data.

 

With these two features and Tinkerforge bricks, a simple standalone data logger can be created.

 

But I guess that this could also be achieved with a Brick or Bricklet(s) that have an RTC and a SD Card Writer. This makes really sense when power consumption is a factor because the RPi's power consumption is fairly high compared to i.e. an Arduino.

 

 

 

 

[Trevis]

My idea was that a Step-Down Power Supply Shield for the Raspberry would make this much neater. And adding a USB port to that shield would give the options to have a properly powered Master Brick local on the shield or remote via USB to keep it compact, or a second Master Brick via USB.