Hi All,

Can someone please help in my project? I have a laptop power supply which I would like to use to power a raspberry pi and a LCD screen. The raspberry pi takes 5v/1A and LCD screen controller board takes 12v/2A. I would like to power both using only one power supply, so will need to reduce the voltage down the line before it goes to respective devices.

I checked switching controllers and voltage converter ICs but my knowledge about these things is very basic. Also, I heard it generates lot of heat.

Can someone please advice if I can achieve step-down of voltage using good old color coded resistors? if yes, how can I calculate which resistor I need?

 

Can someone please advice if I can achieve step-down of voltage using good old color coded resistors? if yes, how can I calculate which resistor I need?

No, you will need voltage regulators. In addition, your power requirements seem too large for the devices. The RP model A needs 300mA or less, and I am doubtful about an LCD that requires 12V at 2A.

 

Thanks for your reply.

The power requirements are confirmed. The LCD controller board powers up a 15.6" laptop screen and requires min of 2A current. Also, RPi needs min of 750mA current otherwise it starts hanging on applications.

 

Hi All,

Can someone please help in my project? I have a laptop power supply which I would like to use to power a raspberry pi and a LCD screen. The raspberry pi takes 5v/1A and LCD screen controller board takes 12v/2A. I would like to power both using only one power supply, so will need to reduce the voltage down the line before it goes to respective devices.

I checked switching controllers and voltage converter ICs but my knowledge about these things is very basic. Also, I heard it generates lot of heat.

Can someone please advice if I can achieve step-down of voltage using good old color coded resistors? if yes, how can I calculate which resistor I need?

http://www.ebay.com/itm/PM7-HOT-DC-...ravel_Adapters_Converters&hash=item35c9b76af5

http://www.ebay.com/itm/AC-100V-240...=US_Server_Power_Supplies&hash=item3a7a976151

 

Thanks bounty hunter ut i would like to supply power using one power supply. Two power supply for a tablet wont be practical

 

Tablet? Like an iPad? They run on batteries and have touchscreens.

 

I agree but my project is to put a old laptop screen in a photo frame and power it using raspberry pi and use it as a digital photo frame or media device to play songs or other media content.......the device will sit on a desk or may be above a fireplace as a traditional photo frame

 

Something like this....http://m.instructables.com/id/How-to-Make-a-Raspberry-Pi-Media-Panel-fka-Digita/

Also....the aim is to use old laptop parts like screen....power supply and keep costs low..

 

I agree but my project is to put a old laptop screen in a photo frame and power it using raspberry pi and use it as a digital photo frame or media device to play songs or other media content.......the device will sit on a desk or may be above a fireplace as a traditional photo frame

Then why would you care if you plugged one cord or two into the wall?

There are dual output supplies out there. Here's one for $6

http://www.coolerstars.com/actodc12duou1.html

 

You can buy 2 of these from eBay to convert your 20V 3.25A supply to the voltage and current you want.

http://www.ebay.com/bhp/dc-dc-converter-adjustable

Choose wisely so the input and output voltage and current is within its limits.

Allen

 

Or, you can buy the one I posted for $6 that's a fully sealed plug in unit that has both converters in it.