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Old 29-09-2007, 07:30 PM
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[1ponders] (Paul)
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I just got "tickled" by my camera. What's going on.

I'm out imaging atm using my 300D and when I bent over to look through the viewfinder my nose touched the body and I felt as though there was a sharp edge rubbing against my nose. I checked and it was smooth. I then tried my nose on other parts of the camera and received the same sharp tickle. I also noticed a smell.

I then got out my multi meter, placed one prob on my nose and the other on the camera body. The maximum voltage reading I got was 54V. Now I thought this can't be right. I then took out the battery (AC Adapter type) and put in a normal battery and there was no tickle. Checked it with the multimeter, 0 V.

Can anyone tell me WTH is going on?
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  #2  
Old 29-09-2007, 07:54 PM
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Is the ground you're standing on damp, dewy etc?
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Old 29-09-2007, 07:58 PM
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acropolite (Phil)
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There's obviously a bit of mains leakage from the AC adapter, could be a danger to the electronics of the camera, as well as yourself. It's common to get leakage from power supplies, the foil lining buildings often has quite a high potential induced from surrounding wiring and TV feeds and is now required to be earthed in new buildings. If you have more than one supply involved (e.g. one for the camera, one for the G11) that could also be the cause of the problem. You could try earthing one side of the supply to ground, but be aware that some switchmode supplies don't like having their output's earthed. I would also measure each side of the output of the Plugpack to ground to see how high the voltage is.
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Old 29-09-2007, 08:18 PM
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Paul I had the same problem with the Dew Controller recently, each time i touched it I got exactly what you experienced.

I was getting my supply through a heavy duty extension lead plugged into my shed, which i had done myself.

I had the shed properly wired by a professional and the problem is gone, although i still use that heavy duty lead.

leon
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Old 29-09-2007, 08:19 PM
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[1ponders] (Paul)
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I have the AC pack velcroed to the legs of the G11 normally. I'm going to see what happens when I have it seperate from the G11.

There are a number of 240-12V power feeds to the mount but the camera one is the only one that has the adapter on the mount.

I'll have to find a translator to explain the rest of it
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Old 29-09-2007, 08:20 PM
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Leon, everything runs through a powerpack with a safety switch, but I don't know if that would make a difference.
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Old 29-09-2007, 08:21 PM
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Quote:
There are a number of 240-12V power feeds to the mount but the camera one is the only one that has the adapter on the mount
You've answered your own question then, run everything from the same source and I'll bet the problem is gone.
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Old 29-09-2007, 08:28 PM
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What do you mean by running everything from the same source? The camera output is 7.8V whereas the mount is 12-18, the powered USB is 5-30 (not sure what the adapter is, I'll have to check).

Anyway I just tried the camera and adapter on their own and there was no tickle and the multimeter showed less than 1V between my nose and the camera body.
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Old 29-09-2007, 09:08 PM
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Paul, your just a ball of potential difference aren't you

you havent answered the main question - is it really dewy?

are the plug packs wet?
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Old 29-09-2007, 09:09 PM
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I didn't realise that they were all different voltages, it may be that one of the supplies is the culprit and changing only one will cure the problem. It may also be possible to simply join all the offending gadgets together with an earth strap, but I would do so with caution; I've seen equipment go up in smoke due to different earth potentials. The easiest solution may be to just run the camera from batteries. On the other hand, Sir h0ugh may be right, it may be leakage caused by dew.
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Old 29-09-2007, 09:24 PM
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Quote:
Originally Posted by acropolite View Post
I didn't realise that they were all different voltages, it may be that one of the supplies is the culprit and changing only one will cure the problem. It may also be possible to simply join all the offending gadgets together with an earth strap, but I would do so with caution; I've seen equipment go up in smoke due to different earth potentials. The easiest solution may be to just run the camera from batteries. On the other hand, Sir h0ugh may be right, it may be leakage caused by dew.
yes Phil one must always know their potential

sorry.

had to while waiting for Paul to reply
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Old 29-09-2007, 09:53 PM
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At Qld Astrofest in 2002, I had a power supply (mains to 12V 4A DC) where an internal heat sink (live) became loose and ended up touching the external metal case of the power supply and as a result, I got circulating currents in other cables connected to my Skysensor 2000 controller, making the auto guider cable become quite warm to the touch.

Reanto diagnosed this for me, re-seated the heat sink and the problem went away. I was extremely fortunate that no damage was done.

Cheers

Dennis
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Old 29-09-2007, 10:03 PM
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Sure you haven't got a groundloop, could be generating one with the different voltages.

Just my 0.02 cents worth.

Cheers
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  #14  
Old 30-09-2007, 07:25 AM
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No dew at all guys, lovely and dry. I've never experienced this before and I've used the same setup quite a few times now. As I said above though, isolating the AC adapter from the mount seems to have done the trick but I still don't know what caused it, being an electro-techno-neanderthal and all
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Old 30-09-2007, 09:35 AM
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Quote:
Originally Posted by [1ponders] View Post
I have the AC pack velcroed to the legs of the G11 normally. I'm going to see what happens when I have it seperate from the G11.
I'm wondering whether having the AC pack velcroed onto the metal legs of the G11 has induced some sort of current onto the unit.
Were you holding another part of the G11 or a controller at the time that was also attached to the G11, when it happened ?

Either way don't strap the unit onto the legs since it's fixed the problem.
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Old 30-09-2007, 02:32 PM
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Quote:
I'm wondering whether having the AC pack velcroed onto the metal legs of the G11 has induced some sort of current onto the unit
My thoughts as well, if it's switchmode there's going to be high DC voltages switched through small transformers and inductors, that could induce currents in to the metal legs.
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Old 30-09-2007, 02:35 PM
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Would that come through the camera body?
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Old 30-09-2007, 03:39 PM
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what sort of surface was your mount sitting on?
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  #19  
Old 30-09-2007, 03:59 PM
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G11 sitting on concrete.
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  #20  
Old 30-09-2007, 04:43 PM
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do you normally have it sititng on concrete? or is it normally out in the yard somewhere on some grass?

just thinking it could be that this potential difference has always been there, but only by removing its normal earth path that it's become apparent to you.
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