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1100D battery hack USB connection fault.


Stargazer33

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An interesting if not frustrating fault arose the other night when I wanted to do an imaging session with my newly modified 1100D.

I have done the Canon battery hack on an old spare battery to allow me to power the camera from a mains feed via an AC/DC converter giving me an output of 8v dc. This works fine and I get a full battery icon on the camera and in EOS Utilities and APT when I run those programs.

In my power distribution box I have also fitted a genuine HP Compaq mains power supply giving 18.5v dc output for the laptop. This again works fine and I have run the laptop for many hours via this power supply.

My problem occurs when I have both my laptop and my camera running from my power distribution box. When I have them both plugged into the power distribution box the laptop says that it cannot recognise a USB device connected. If I unplug the laptop and run it on battery the fault disappears. If I put a battery in the camera with the laptop on the power supply the problem disappears. It only occurs when the laptop and camera are plugged in at the same time.

I am really stumped as to what might be causing this problem. If anyone has any ideas or similar experience I would love to know how to rectify this fault.

Thanks in advance!

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I think there might be a grounding problem. The two power supplies should be isolated from each other.  

Check with an ohm meter if there is a connection between the two minus (or plus) poles.

Be careful and switch off the power first!

/T 

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Sounds like you have a ground loop - basically the camera and the laptop have different voltages for their '0V/Ground' pin on the USB port and when you connect them a current flows along the USB cable and mucks up the USB communication. As soon as you unplug one from the mains, the ground voltage on that item floats to match the ground voltage on the other. It's more common with audio signals - never personally heard of it with USB before.

Try measuring the voltage between the -ve of the laptop PSU and the -ve of the camera PSU using a multimeter - I expect there will be an offset. Usually the -ve pin is the outside of the plug and the +ve the inside.

If it is a ground loop type problem (and I'm only making an educated guess here), then there seem to be USB isolators available to buy for about £35 - search 'olimex usb isolator'. I think I might be tempted to get a second opinion from someone else before splashing out that sort of cash though :)

cheers,

Robin

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As above but also most power adaptors have floating outputs the laptop one could have anything approaching 70V on the -ve connector, the DC-DC convertor may have its -ve connected to the source (i am assuming that this is a battery) you could try grounding the laptop -ve to a common ground in your distribution box through a 1-10 ohm resistor.

Alan

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Thanks for the replies, I was leaning to this sort of thing myself.

Both supplies come from the same 240v mains supply. On the back of my switched kettle socket I have taken one feed off to the laptop power supply - effectively just cut the plug off and wired it to the kettle socket. The other feed goes to a 240v AC to 12v DC SMPS. This then feeds the 12v to 8v DC/DC regulator which powers the camera through a modified battery (Li-ion pack removed and wires soldered onto the B+ and B- connectors.)

It's very Heath Robinson as it grew and grew and rather out grew its original box!

post-21511-0-73651700-1409677016.png

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Hi

Hi Bryan

Your camera supply wires aren't screened and could easily pick up a lot of noise. Um, I know it's not DIY, but couldn't you just use one of these instead? http://www.amazon.co.uk/Fotga-ACK-E10-Power-Adapter-Coupler/dp/B00CDFTO9I/ref=sr_1_3?ie=UTF8&qid=undefined&sr=8-3&keywords=canon+1100d+power+adaptor

In any case, make sure you keep the usb camera cable well away from the psu/power leads.

Louise

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I do like that i did notice that the laptop supply has an earth connection it would be interesting to see if the earth is connected to the output ground some of my psu`s do some dont, i also cant see a chassis earth that is vital for safety and should help with any interference too.

Alan

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Hi Louise,

I did get one of those with my camera from the seller. As I had already put the power supply in the box I was hoping to use that. Also I would only require one lead trailing across the patio to my mount/power box. If I can't rectify the problem I will have to use it as the batteries run out during an imaging session.

Hi Alan,

The laptop output ground is connected to the earth according to my DMM. I'm sorry but I am not sure what you mean about chassis earth. The power box is plastic so doesn't require/have a ground point. The SMPS has an earth wire running to it from the mains supply so I assumed that this was grounding the chassis. Am I missing something?

Thank you both for your help.

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My mistake i assumed the case was metal however if the front and rear panels are then they should be grounded with an earth wire too the main point is though that the camera and laptop -ve outputs should share a common ground.

Alan

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I have exactly the same problem with my 1100 and a "battery" and adapter that I bought of Ebay,the exact one in Thalestris link.  In my case I am using it with a desktop and it does the same thing.  I put it down to the psu giving slightly too much voltage.

I hadn't thought about a ground loop. Will test with my lappy and report back.

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Hi Alan,

No, the back and front plates are plastic too so no problem there. If I understand you correctly can I just run a link wire from the -ve on the camera power feed to the -ve on the laptop power feed and then take it back to the ground pin on the mains power supply?

ctorpey: I would be interested to hear what you find.

Thomas: I have done a continuity test -ve to -ve and +ve to +ve through the dc/dc converter and there is continuity on the -ve feed and output through the pcb.

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Alan, you're a STAR (no pun intended)!

I was too impatient to try out your suggestion, so got a piece of wire and connected the -ve solder tag on the back of the camera power feed socket to the -ve solder bucket on the back of the laptop LEMO socket and everything is working perfectly. As I said in answer to Thomas's question the -ve feed/output from the dc/dc converter for the camera feed goes straight through the pcb; so connecting this output to the output -ve of the laptop power has commoned the grounds (the -ve laptop feed/output are isolated in the converter).

Thanks again for everyone's help and suggestions.

Why can't the rest of the World work together like the members of this forum do? :undecided:

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Hi Bryan im glad it worked, i have a box to power all my kit from either a battery or a mains adapter plugged into a wall socket with 12V cable running outside it uses 4 DC-DC converters to power the mount (6v on mine) the camera and a 5v for running the mobile used as an intervalometer plus a spare output, and all grounds are connected together and i have had no issues.

I have also heard of people having problems when kit is connected to a mount which being metal can induce ground currents flowing through the wiring so i include an M5 bolt with nuts and washers on the PSU so that i can run a separate ground to the mount.

Alan

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Must admit I haven't tried it all connected up to the mount yet! Better do that before I try another imaging session.

As Robin said earlier I have come across ground loops within audio circuits in my job - I service/repair aviation communication equipment - but I wasn't aware of it on power circuits.

Just goes to show a little knowledge is/can be a dangerous thing!

Thanks again for your help, much appreciated. :icon_salut:

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