Power requirements


#1

Hello there,

Just got my BrickPi here, (normal, no power upgrade, which I never ordered because I didn’t even understand what it meant)

Connected this to a 9v 500amp adaptor, the red light on the pi comes up, and the green blinks, but I get nothing on the other lights

Connecting the pi directly via the usb power made the image you supplied work (I wonder why you cut out the screen output, but does not matter that much)

I have no 6 aa to 9v adaptor yet, so I didn’t do that

I have read on the forums here about people powering the pi directly, about people using 6v 2amp PSU, and many other answers.

So what I would like to know, is what will officially work, what psu should I buy (for immobile setups), and what is the voltage variance and amps needed, as I don’t want to fry this just yet :wink:

Thanks


#2

Hi !

I would suggest to try to get the original Lego Battery Box. It is able to deliver 800 mA which is sufficiant to drive some motors a while. Also it has a protection circuit for current above 800 mA.

The 6 Volt 2 Ampere power supply works without a problem here. And it is not disspating so much heat on the LM7805.

Please see here:

http://dl6kbg.blogspot.de/2013/10/brickpi-power-solutions.html

Good luck, Oliver


#3

Hello oferwald,
Can you share some more information about how you connected the 9V adapter?

And for your question about which power solution you should buy: you should have something that’s around 9V and it should be able to provide at least 2 Amps.


#4

Hi,

Its a rathar standard wall socket adaptor that has variable voltage selection, and a few different output sockets, rated at 500ma. Used the cable you have provided to connect directly to it.

Looks very much like:
http://www.alibaba.com/product-gs/479451932/3_12V_adjustable_voltage_ac_adapter.html

I will try looking for a suitable adaptor (with some more juice), will update.

Can you explain the power upgrade and if it should make any difference? (I am not upgraded, I assume)


#5

If you are going to use a mains power supply, it’s very important to remember that unless it’s regulated, the actual voltage will be significantly different than what it says.

For example, if you use an unregulated power supply that’s rated 9V 1A, with no load (or very little load) the output voltage will likely be more like 12V to 15V. With a heavy load, the voltage might go down to 7V.

If you intend to power it using a mains power supply, I highly recommend using a switching power supply (regulated) rather than a transformer power supply (almost always unregulated).

The power upgrade version of the BrickPi uses a different 5V regulator to regulate the 5V for itself and the RPi, from the 9V input of the BrickPi. The standard power version uses a 5V linear regulator (LM7805) and the power upgrade version uses a switching regulator (LM2576). The linear regulator wastes a lot more power, turning it into heat. The switching regulator is a lot more efficient, and wastes very little power as heat.


#6

Sorry if these are very basic questions but I’m new to electronics.
I have the standard power version of the BrickPi. I’d like to attach it to a power adapter connected to the mains power supply while I work at my desk.
What are the specs of the power supply I should be looking for ?

  • regulated
  • 9-10V
  • how many Amps?

    #7

    A RPi model A is rated to require 300ma, and a model B 700ma. A WiFi USB dongle will use a fair bit of power (maybe a few hundred ma?). NXT motors can draw up to 2A stalled, and should each have at least 700ma-1A available. If only used very lightly, 400-600ma is probably okay.

    With no motor use, something like 1A should be enough to power the BrickPi with a running Raspberry Pi Model B and a USB WiFi dongle.

    I’d say ideally 1A plus 1A per motor, but 800ma plus 500-700ma per motor will probably be adequate.


    #8

    Apologies for waking up an old post but are there any major headaches replacing the LM7805 with an LM2576? The circuit diagram, from a quick glance, seems pretty clear, but I wonder if this change is actually practical. Is the BOM accurate? Anyone done this and able to provide feedback?

    My basic board I have is getting a little brown around the LM7805. It has mostly just be sitting around with very little activity. Powered by a 10.5V (actually 11.15V) power supply.


    #9

    I can’t answer all of your questions (I think some folks have done it but I’ll let them speak up).

    Basically you’ll want to first snip out the LM7805 to avoid heat sinking. You also might need an air rework gun to heat the LM7805 off. It’s not trivial, but it’s actually pretty easy with the right tools.


    #10

    What’s holding the LM7805 down? If I could (non-destructively) get that off the board, a possible interim solution could be just heatsinking that.


    #11

    The LM’s are both soldered to the board into the heat-sink, as well as the connector pins are soldered into the board.