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Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
magnet18 wrote ...
Okey Dokey Could an isolation transformer be used before rectification, or would that limit the power too much? (HV hobbyist fears death by 120/170V :P)
An isolation transformer is not going to protect you from getting zapped. It can be useful when using a oscilloscope though, to isolate the oscilloscope from mains voltage so you can scope live circuits being powered directly from mains.
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Goodchild wrote ...
magnet18 wrote ...
Okey Dokey Could an isolation transformer be used before rectification, or would that limit the power too much? (HV hobbyist fears death by 120/170V :P)
An isolation transformer is not going to protect you from getting zapped. It can be useful when using a oscilloscope though, to isolate the oscilloscope from mains voltage so you can scope live circuits being powered directly from mains.
You'll still get zapped, but I thought having galvanic separation from the mains was supposed to be safer than a direct connection?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
magnet18 wrote ...
Goodchild wrote ...
magnet18 wrote ...
Okey Dokey Could an isolation transformer be used before rectification, or would that limit the power too much? (HV hobbyist fears death by 120/170V :P)
An isolation transformer is not going to protect you from getting zapped. It can be useful when using a oscilloscope though, to isolate the oscilloscope from mains voltage so you can scope live circuits being powered directly from mains.
You'll still get zapped, but I thought having galvanic separation from the mains was supposed to be safer than a direct connection?
It isn't safer if you touch both terminals, but since the secondary of an isolation transformer is floating, if you touch one terminal, no matter which one it is, you will not be electrocuted if you are grounded. If you are grounded and you touch the live wire of direct mains, you will be electrocuted.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
An isolation transformer won't hurt anything. I used one initially when I was testing out the circuit. I always use one when troubleshooting "hot chassis" equipment like this, otherwise if you connect a scope probe to "ground" on the PCB, BOOM. There shouldn't be any significant voltage loss through an isolation transformer, if there is, your transformer is too small for the load.
Sorry I missed the request for secondary specs. I used the specs Steve listed for his, 10" of 4.5" OD (4" PVC) pipe wound with #30 wire. I've tested the circuit with a couple of other vastly different secondaries and it worked ok with those too so there is really nothing critical. You could probably wind any wire you have on a paper towel tube or empty plastic bottle and still get decent sparks. I would say aim for a Fres below 600kHz and add a modest topload if you have one. A 8" aluminum pie tin did make the sparks an inch or so longer but it was rather ugly.
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
Posts: 624
Arcstarter wrote ...
It isn't safer if you touch both terminals, but since the secondary of an isolation transformer is floating, if you touch one terminal, no matter which one it is, you will not be electrocuted if you are grounded. If you are grounded and you touch the live wire of direct mains, you will be electrocuted.
James wrote ...
An isolation transformer won't hurt anything. I used one initially when I was testing out the circuit. I always use one when troubleshooting "hot chassis" equipment like this, otherwise if you connect a scope probe to "ground" on the PCB, BOOM. There shouldn't be any significant voltage loss through an isolation transformer, if there is, your transformer is too small for the load.
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