abrown
Posts: 1
Joined: Fri Apr 27, 2012 11:41 am

Re: Power from TV?

Fri Apr 27, 2012 1:42 pm

When I finally get my RasPi I'm hoping to use the 5v power supply that my TV provides via it's UHF antenna connection (I think it does this for TV mast signal boosters). I want to do this as I only have 1 mains power socket behind my TV and don't want to have any more mess there (it's wall mounted).

Has anyone managed to do this? I'm guessing if the TV can provide enough current @ 5v then I should just be able to hack together a UHF connector and an old micro USB connector. Any thoughts?

bredman
Posts: 1415
Joined: Tue Jan 17, 2012 2:38 pm

Re: Power from TV?

Fri Apr 27, 2012 1:55 pm

Please measure the voltage carefully, you need a well-regulated voltage between 4.85v and 5.25v.

You will need to build your own filter to extract the DC component. DO NOT connect the UHF directly to the RPi.

It's very strange to see 5v on a UHF connector. Most boosters use 12v or 24v.

All in all, it's very risky for little benefit.

User avatar
cnxsoft
Posts: 191
Joined: Sat Oct 15, 2011 2:33 pm
Location: Chiang Mai, Thailand
Contact: Website

Re: Power from TV?

Fri Apr 27, 2012 2:19 pm

If your TV is new enough to have a USB connector then your problem should be solved.

Powering the Pi using the antenna connection seems risky to me.

User avatar
mahjongg
Forum Moderator
Forum Moderator
Posts: 12117
Joined: Sun Mar 11, 2012 12:19 am
Location: South Holland, The Netherlands

Re: Power from TV?

Fri Apr 27, 2012 11:03 pm

There is a big risk that the 5V isn't stabilized, and the voltage fluctuates heavily under load, which makes it totally unuseable for the R-PI which needs exactly (to 5% precise) 5 Volt.

At least test if the unloaded voltage, and the loaded with 750mA voltage doesn't vary beyond 4.75 and 5.25 volt.

User avatar
rew
Posts: 423
Joined: Fri Aug 26, 2011 3:25 pm

Re: Power from TV?

Sat Apr 28, 2012 9:10 am

It is difficult to measure properly. If the voltage drops to 3V for a milisecond, then your raspberry pi will crash. So if you measure a proper 5V without load and with load, you might still run unto power problems.
Check out our raspberry pi addons: https://www.bitwizard.nl/shop/

Return to “Beginners”