Portable or Plug-in power for RetroPie Gaming setup  - Page 1
Forum section: electronics / projects

author: JBussell
author_rank: Newbie
timestamp: April 03, 2018, 11:06:34 am
content: So I have installed RetroPie on my Raspi. (RetroPie allows you to play retrogames (Nintendo 64, Gameboy etc) on a Raspberry Pi.I would like to make it into a portable gaming device.So I have a Pelican-style case that I used to store my GoPro cameras in and I thought I'd use that. It fits a Raspi in it's case, with a small CPU fan in it and it would fit a 10' screen in the lid, speakers and one or two controllers.The Pi can run off a portable battery pack, like the ones that are used to recharge a phone battery. The screen I was looking at is powered by 12v. I'm using small unpowered desktop speakers.Ideally I'd like it to be portable so I can take it to friends places or play it in my car for whatever reason (when the car is stopped).My issue is I'm not sure how to power everything. If I were to make it plug in, my only thought is having one cable for 12v for screen and 5v for the Pie but that seems illogicalThe other idea would be powering with 24v and using a step down to go to 12v and 5v.The only projects I've seen are using a portable DVD player and building it into a small console using one of the 5' screens. I have one of those screens but haven't worked out how to install drivers for it. It was easy to do on Rasbian OS but I want a bigger screen, at least 8-10".I don't mind the portable DVD player one but trying to use what I already have and building it into a hard case seems like an interesting idea.What are your ideas?

author: Ian.M
author_rank: Super Contributor
timestamp: April 03, 2018, 11:47:28 am
content: I'd lay odds the screen will take more power than the Pi. I would suggest designing your power supply to suit the screen and use a buck converter to get 5V for the Pi.If you use cheap buck converter modules of EBAY, Alibaba etc. remember that Chinese power and current ratings are like 'Sears Horsepower' or Lo-Fi amplifier 'PMPO' (peak music power output) ratings - you have to derate by a large factor to get a realistic rating. I wouldn't expect to get more tham 1.5A from a 3A EBAY buck module without it dying, and anything over 1A would be dodgy for long term reliability. Also, you'll want a crowbar circuit set at 5.5V to protect the Pi if the buck module fails shorted.Another issue is that most 12V LCD screens need 12V in, not the typical 13V to 15V you will get from a car battery. Therefore if you design for 12V in (with a regulated 12V wallwart for use at locations with mains power) and use a simple power lead to run it in the car, the excess voltage is likely to shorten their life and transients may damage them. With the engine and lights off and no electric fans running you'll probably get away with it till the day someone bumps the horn button or starts the engine before you disconnect.If you are going for an internal battery pack, a 4S LiPO pack, with buck modules to get 12V and 5V is probably the best option. Charge it from a 19V netbook or small laptop PSU with a relay that switches the pack over to a DC input balance charging circuit when the PSU is supplying power, and also transfers the buck converters inputs from the battery to the PSU output. If you need in-car charging, use an in-car laptop PSU to boost to 19V.