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Question concerning power for Raspbery Pi

toxxn

I am making a power supply for the Raspberry Pi I am getting. The reason I am making one rather than using just a standard Micro USB is because I am custom soldering a pcb with a switch to turn on/off the Pi along with a 12v LED to indicate the device is on, and a 4.3 in TFT LCD that is also 12v. Since the LED and TFT LCD I am using both use 12v and the Pi doesnt, I needed to lower the voltage from 12v to 5v so that I can power everything at once with ONE plug. I read up on the the correct voltage to use, which is 5v at 700mA at the least (although some have argued you that barely powers the device and recommend at least 5v 1000mA). My question is, will 5v 500mA work? I have a spare plugin/ car usb charger combo that is AC 100-240v/ DC 12-24v 50/60Hz input to DC 5v 500mA output. I wanted to use this to lower the 12v volts needed for the rest of the project to 5v that is needed for the Pi, however I have no idea if it will work and I dont want to scrap my spare charger if it wont.

 

Any help/ suggestions/ answers would be appreciated.

 

Note: If its any help to the above question, I plan to use ALL usb devices through a hub.

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  • So I was searching around ebay, and I found this:

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=321180084219

     

    It's a KIS3R33S 5V USB 7V-24V to 5V 3A Step-Down Buck Module.

    This would allow me to do away with the 12V to 5V charge I have mentioned in my original post as well as have a more compact setup, and still allow me to jumping down the voltage from 12 to 5.

    I am concerned however. The Raspberry Pi Model B inputs 5V 700mA (3.5W) and it states in the ebay auction it has a continuous output of 3A however it also says: "4A(Spike/Short time)".

    I am concerned that with it spikeing 4A I might fry the Pi. Would this Module be safe to power the Pi?

  • in reply to toxxn

    Don't worry about the continuous 3A and 4A spike. The 3A rating means the regulator can regulate with a 3A continuous load. The 4A spike means that it will regulate with load surges up to 4A. Another way to put it is that the buck module will regulate as long as your load (Raspberry Pi unit) needs less than 3A. You might see 4A when the Raspberry Pi module is turned on or plugged in and the capacitors start charging but normally you will be under 700mA load on the regulator.

  • in reply to tpcipri

    So basically I could go for an even higher miliampere/ampere and the Pi would be uneffected so long as the voltage is 5V as it only draws the current it needs.

    That would be convienant in the case I decide to completely do an all-in-one power supply powering the TFT LCD with 12V and jumping it down to 5V with the Buck Module so I could power the Pi and the USB Hub all with one plug-in rather than 3 seperate ones. I think this may be my goal, I plan to recyle my old iPod box as it seems a perfect fit for what I need. I may use my other iPod box to make a Pi encloser so the power supply and pi encloser realativly match each other.

     

    Thank you for the info!

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  • in reply to tpcipri

    So basically I could go for an even higher miliampere/ampere and the Pi would be uneffected so long as the voltage is 5V as it only draws the current it needs.

    That would be convienant in the case I decide to completely do an all-in-one power supply powering the TFT LCD with 12V and jumping it down to 5V with the Buck Module so I could power the Pi and the USB Hub all with one plug-in rather than 3 seperate ones. I think this may be my goal, I plan to recyle my old iPod box as it seems a perfect fit for what I need. I may use my other iPod box to make a Pi encloser so the power supply and pi encloser realativly match each other.

     

    Thank you for the info!

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