lrussell
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HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 2:52 am

I needed to get my old VGA monitor to work on my Raspberry Pi, so I bought this:
http://www.ebay.com/itm/271112972705

After changing the settings to these in config.txt:
disable_overscan=0
hdmi_drive=2
config_hdmi_boost=4

It worked. Problem is, it's drawing so much power with NOTHING else plugged in my USB mouse won't work. I unplug the adapter and my mouse instantly comes alive. I ordered a powered USB hub that should partially solve this but is this going to cause any harm to my RPi if I continue to use this adapter? My power adapter is 5v 1amp.

Thanks guys. :)

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johnbeetem
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Re: HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 3:55 am

There's a lot of information about power supply problems at the RasPi Troubleshooting Wiki: http://elinux.org/R-Pi_Troubleshooting# ... r_problems

There are three voltage drops to consider:

1. The power supply itself (a good power supply should be able to produce a full 5V up to its rated current).

2. The Micro USB cable between the power supply and RasPi. Some of those have very thin conductors and result in a large voltage drop at high current.

3. Polyfuse F3 between RasPi's Micro USB power jack and TP1. F3 should be able to carry 1A, but if it's out of spec the voltage drop across it could be enough to make RasPi or peripherals to malfunction. Polyfuses start to increase resistance as they get warmer, so if you're drawing more than RasPi's usual 700 mA max it could start to fail.

Some people have replaced F3 with a shorting wire or a regular fuse, but this voids the warranty. Others have used other ways to bypass F3, which loses the protection of F3 but bypasses its problems.

If you have a multimeter or voltmeter, you might check the voltages across the Micro USB cable and/or polyfuse F3 with and without the HDMI to VGA converter to get a better idea where the voltage drop occurs.

RasPi was never designed to power an HDMI to VGA converter, so some of them have blown diode D1. There's a bunch of information and caveats at the RasPi Hardware Wiki: http://elinux.org/RPi_VerifiedPeriphera ... rter_boxes

Also here: http://elinux.org/RPi_Screens#RGB_analog.2FVGA

lrussell
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Re: HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 3:02 pm

I'm not really savvy when it comes to electronics themselves, I mainly do programming.
The INSTANT I unplug the HDMI to VGA adapter my mouse comes to life.

I purchased my Raspberry Pi on eBay (at a premium, of course) with all the accessories.
The adapter is 5V 1AMP with a fairly sturdy Micro USB cable.

I already saw that page with the Verified Peripherals, and it said this:
"http://www.ebay.com/itm/ws/eBayISAPI.dl ... 0699741793 -- eBay is swarming with $16 converters all like this one."

That's what gave me the idea in the first place to get that adapter. It definitely wasn't plug and play but after some config.txt changes it did work.

I just want to know if it's safe to continue to use the adapter.

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mahjongg
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Re: HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 8:41 pm

probably not, but that is probably what the wiki already told you!

It all depends on how much current the adapter draws, but most similar adapters draw double the acceptable current (400mA) that D1 can handle, so eventually it will burn out, if the polyfuse doesn't go first, but that depends on what else you have connected.

as often is the case your mileage may vary!

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johnbeetem
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Re: HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 8:50 pm

lrussell wrote:I just want to know if it's safe to continue to use the adapter.
My "no warranty expressed or implied" opinion is "probably". It depends on how "safe" you want to be. It's unlikely that the adapter will damage any of the RasPi ICs, since they use 3.3V so as long as RasPi's main 5V line (connected to TP1) is at least 4.3V they'll be fine. However, as I suggested in my last comment if an HDMI->VGA adapter draws too much current it could cause a weak F3 to fail or cause D1 to burn up. Both of these are easy to fix if one's handy with a soldering iron.

It may be that your problem is simply that your mouse requires close to 5V to operate, while a different mouse may work with 3.3V internally so it really only needs 4.3V to operate. For example, I believe wireless mice generally need the full 5V, and they draw a lot more current than a wired mouse.

Sorry if this is unhelpful, but it depends on your particular circumstances. Knowing the voltages at TP1 and at the input to F3 would be useful. A good rule of thumb (or finger-tip in this case) is that if components like F3 and D1 are getting really hot (i.e., you don't want to leave your finger-tip on them for more than half a second) then expect them to fail. If they're cool, you're probably fine.

For more opinions, you might try entering "HDMI to VGA" in the Google search box at the raspberrypi.org home page.

lrussell
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Re: HDMI to VGA adapter - Draws too much power?

Sun Mar 31, 2013 10:13 pm

It is a wired mouse, and it's filled with LEDs.
http://www.dansdata.com/images/moremouses/wmo440.jpg

My keyboard works, but not the mouse. When the adapter is plugged in the LEDs just kinda flash, I unplug the adapter and it springs to life. I read somewhere that Ethernet is USB driven as well and it works. I'm just a bit afraid of blowing something. I'll try to find a self-powered and not bus-powered converter to be safe.

Thanks for all the help. :)

lrussell
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Re: HDMI to VGA adapter - Draws too much power?

Mon Apr 01, 2013 8:12 pm

http://www.ebay.com/itm/190818079460
Should this work? It's self powered.

EDIT: Looks like it should, I just ordered it. If it works, it's an amazing deal. :)

Broniukas
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Re: HDMI to VGA adapter - Draws too much power?

Tue May 07, 2013 6:26 pm

Yes indeed! according to manufacturer, this adapter needs 5V 500mA power from source device, HDMI->VGA adapter without audio input takes less energy, so it is much compatible with raspi. Adapter will use up to 200mA.

There is one big issue using this device. Raspberry have only 50mA output to HDMI. So it is only working for few hours and it will burn D1 diode (you can find ir near HDMI port).

After i got this adapter from ebay, i have tried to connect my projector and it worked fine (some monitors will not accept 1080p, so you must change some values in boot config).

there is a good guide how to fix HDMI power issue: http://imgur.com/a/sLogs#0
Tested and working!

More info: http://www.raspberrypi.org/phpBB3/viewt ... =28&t=9819

(im using 2A power supply, i guess you must have minimum 1,5A to make it work)

Cabral
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Re: HDMI to VGA adapter - Draws too much power?

Sat Feb 01, 2014 10:13 pm

I have a small hub for my PI and I run every thing off it even a small HDD .. I also power a wireless mouse and keyboard. I seen that the RASpi dose not handle well with power so the more I took away from it the better it ran.

Hope it helps

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mahjongg
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Re: HDMI to VGA adapter - Draws too much power?

Thu Jan 22, 2015 10:40 pm

Broniukas wrote:Raspberry have only 50mA output to HDMI. So it is only working for few hours and it will burn D1 diode (you can find ir near HDMI port).
True for models A and B, but fortunately no longer true for a A+ and B+.

it still possible that the extra energy needed cannot be supplied by the Power Supply, or that the total current draw exceeds 1.8A, which is too much for the PI to handle.

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