Hey all,
Back in the early '80s I was electrocuted in an industrial accident that knocked me on my a$$, and rendered me unconscious (or maybe kicked me into an alternate universe) for a few seconds. All I remember is the sensation of being hit with a frickin sledge hammer directly in the sternum...and then becoming aware there were several of my coworkers standing around looking down at me, asking if I was OK. I didn't like it.
Which brings us to the here and now...
Due in large part to my story above, I've wanted an isolation transformer for my bench. Well, I found this: AN-104115 - 1000VA 115V Transformer - AnTek Products Corp, and looking at the specs, it should fill the bill, right?
Or is there something I'm forgetting?
Mike
Back in the early '80s I was electrocuted in an industrial accident that knocked me on my a$$, and rendered me unconscious (or maybe kicked me into an alternate universe) for a few seconds. All I remember is the sensation of being hit with a frickin sledge hammer directly in the sternum...and then becoming aware there were several of my coworkers standing around looking down at me, asking if I was OK. I didn't like it.
Which brings us to the here and now...
Due in large part to my story above, I've wanted an isolation transformer for my bench. Well, I found this: AN-104115 - 1000VA 115V Transformer - AnTek Products Corp, and looking at the specs, it should fill the bill, right?
Or is there something I'm forgetting?
Mike
Depends on what bill you want to fill. It ought to cover many situations.
But PLEASE don't tell yourself you cannot be shocked just because you plug something into it.
But PLEASE don't tell yourself you cannot be shocked just because you plug something into it.
Hi Mike,
It looks like a nice transformer and its toroidal construction will have low stray fields.
As added precaution, I suggest Ground Fault Interrupter circuit breakers, sensing imbalance on the load side. I too have had a couple of close calls with lethal power sources. Stay safe!
It looks like a nice transformer and its toroidal construction will have low stray fields.
As added precaution, I suggest Ground Fault Interrupter circuit breakers, sensing imbalance on the load side. I too have had a couple of close calls with lethal power sources. Stay safe!
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1) 4A max on the 120V winding. Fuse it for that to be sure you do not overload. 400VA or maybe 300W max load.
2) Use a GFCI with arc fault if you can. Definately a GFCI.
3) This should not require repeating but make certain you know everything about what you are connecting. Nonconductive bench top, one hand in your pocket etc. Do a basic safety check before plugging in that new creation confirming no shorts or leakage.
2) Use a GFCI with arc fault if you can. Definately a GFCI.
3) This should not require repeating but make certain you know everything about what you are connecting. Nonconductive bench top, one hand in your pocket etc. Do a basic safety check before plugging in that new creation confirming no shorts or leakage.
Um, yeah, I understand that there is still lethal power coming from the transformer. You can put your mind at ease, I am a certified electronics tech, and was a professional wiring tech at a local test equipment manufacturing company before I retired, so I am well aware of standard safety protocols. The idea here is galvanic isolation from the mains. I was just wondering if there would be any practicle limitations anyone was aware of that I'm not, that's all.
Mike
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Be careful the isolation transformer doesnt give you a false sense of security! A L-N connection on the output of it - if it's traveling across your chest - is just as lethal.
Manufacturers of test equipment (Tektronix) went to all lengths to dis-allow operation of a battery powered, isolated input (ch to ch, ch to ground) oscilloscope, unless it was earth grounded. Their legal hated the idea of "floating" an oscilloscope, which customers did all the time - even the AC powered ones. To me, that's like saying you must always earth ground the negative input of your hand-held DMM in order to make a measurement.
I realize the scope has many more ground-potential metal contact opportunities than a hand-held DMM. One would think people that know what their doing (trained techs / engineers) would not touch those when using the instrument "floating". Not when it comes down to a potential liability issue.
So think like a lawyer regarding your isolation transformer!
Manufacturers of test equipment (Tektronix) went to all lengths to dis-allow operation of a battery powered, isolated input (ch to ch, ch to ground) oscilloscope, unless it was earth grounded. Their legal hated the idea of "floating" an oscilloscope, which customers did all the time - even the AC powered ones. To me, that's like saying you must always earth ground the negative input of your hand-held DMM in order to make a measurement.
I realize the scope has many more ground-potential metal contact opportunities than a hand-held DMM. One would think people that know what their doing (trained techs / engineers) would not touch those when using the instrument "floating". Not when it comes down to a potential liability issue.
So think like a lawyer regarding your isolation transformer!
In my opinion, before dreaming of transformer, a quality earth with sensistive differential breaker is the first step to security.(lowest resistance value)
a link to a product I use for protection of mobiles units
https://catalog.block-trafo.de/prodvardatasheet/393231-983068_EN
A shield like in this transformer may be usefull for noisy lines.
a link to a product I use for protection of mobiles units
https://catalog.block-trafo.de/prodvardatasheet/393231-983068_EN
A shield like in this transformer may be usefull for noisy lines.
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Whats the advantage of this isolation other than floating your scope etc? Which is more dangerous.
But there's two of those, and a couple minor windings. The data shows 9.6A from both 120V windings at 110V output (<10% drop). There may be few audio chores which need >1000VA isolated for long enough to heat a 18 pound lump. If we need an all-night 750 Watt stress test, do it hands-off.
Mike, did you want to describe how an isolation transformer would have averted your earlier shock, in lieu of other standard safety practices?
Did you want to describe how you would use a new isolation transformer for a particular test setup where you have determined there is no other way to make the test environment safe?
Did you want to describe how you would use a new isolation transformer for a particular test setup where you have determined there is no other way to make the test environment safe?
Are you referring to the capacitance acting to pass noise (ie. not a safety related issue), or acting to pass parasitic current that could be sufficient to cause a safety incident (tingle followed by jerk movement, or actual fibrillation)?
I note the linked Antek model does not include a protective safety screen between primary and secondary windings, which would be a better safety aspect from galvanic isolation, as well as alleviate capacitive coupling from mains to secondary.
It isolates one, and one's equipment from a direct connection to the mains...what do I win? 😀
Oh yeah...the fun I had was a malfunctioning operator pedal on an industrial machine, the internal switch broke apart and allowed the hot side of the mains contact the pedal housing...meanwhile, a malfunctioning ground connection on the pedal housing failed to do it's job...I didn't like it. If the foot pedal had been isolated, I wouldn't have been electrocuted.
Mike
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I'm about safety and noise. That capacitance wan't cause fibrilation but can make some excessive mains-frequency noise currents.
One would hope that the malfunctioning protective earth connection would be identified nowadays by regular periodic PAT testing.
I guess many of us would consider using a floating mains supply as an absolute last resort for a specific technical issue that could not be managed by the many and various means of applying safety barriers/trips and other risk and hazard reduction measures to a test/use situation.
In 1980 I was studying electronics on a course.
I was quite a bit ahead so asked if I could make a valve pre amp.
I built it up and it didnt work so powered down and touched the power cap and got a huge belt. My tutor suggested discharging the cap before touching the circuit. So next time I duly discharged the cap and touched the circuit and got a huge belt again, I had forgotten to turn it off !
Remarkably that was 40 years ago and I am still alive.
On high voltage systems I now add a LED and resistor across any high voltages to indicate they are on/charged.
I tend to now attach scope/meter probes when system is off.
And turn off before moving probes to next stage.
I also use a isolation transformer.
I was quite a bit ahead so asked if I could make a valve pre amp.
I built it up and it didnt work so powered down and touched the power cap and got a huge belt. My tutor suggested discharging the cap before touching the circuit. So next time I duly discharged the cap and touched the circuit and got a huge belt again, I had forgotten to turn it off !
Remarkably that was 40 years ago and I am still alive.
On high voltage systems I now add a LED and resistor across any high voltages to indicate they are on/charged.
I tend to now attach scope/meter probes when system is off.
And turn off before moving probes to next stage.
I also use a isolation transformer.
In the 1980s I recall having these metallic guitar picks, so I naturally soldered a wire onto one. I think I had some mini-korg synth at the time which triggered its ADSR envelope generator with a low-going pulse. I was able to pipe my bass through the synth and have it trigger every time I touched the string with the pick. Survived that one.
Then I remembered my favorite thing to do as a kid with my father's battery charger was strike sparks off the end of the cable connectors. Used to love to scare my friends that way. I thought sparks coming off the bass guitar strings would be a blazing effect as you played, but luckily canned the idea before ever executing on it. (Yes, both DC and an amplifier's output of the pickups were considered for "touch feedbacks", with independent cabling to keep the return current out of the normal cord shield)
Then I remembered my favorite thing to do as a kid with my father's battery charger was strike sparks off the end of the cable connectors. Used to love to scare my friends that way. I thought sparks coming off the bass guitar strings would be a blazing effect as you played, but luckily canned the idea before ever executing on it. (Yes, both DC and an amplifier's output of the pickups were considered for "touch feedbacks", with independent cabling to keep the return current out of the normal cord shield)