High Voltage Interface
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Posts: 46,084
Hi,
I need to interface a 100mA 24VDC device with 750 VDC. I was
thinking of making a voltage divider circuit say 30 to 1. Can
someone tell me if this will work or will it go up in smoke?
Thanks,
Chris
I need to interface a 100mA 24VDC device with 750 VDC. I was
thinking of making a voltage divider circuit say 30 to 1. Can
someone tell me if this will work or will it go up in smoke?
Thanks,
Chris
Comments
Please don't take this wrong.....but if you don't know the answer to that
question, you probably should not be messing with a circuit that carries 750
VDC.
It can kill you!!!!!!!!!!!!!!!!!!!!!
---
I need to interface a 100mA 24VDC device with 750 VDC. I was
thinking of making a voltage divider circuit say 30 to 1. Can
someone tell me if this will work or will it go up in smoke?
Thanks,
Chris
[noparse][[/noparse]Non-text portions of this message have been removed]
circuits and even if this shorted it wouldn't matter because it is
fused. I work around these voltages every day and I am extremely
safe. I simply need to know if a voltage divider circuit (30 to 1)
would work in stepping down a voltage of 750 VDC to 25 VDC @100mA?
--- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> Chris,
>
> Please don't take this wrong.....but if you don't know the answer
to that
> question, you probably should not be messing with a circuit that
carries 750 VDC.
> It can kill you!!!!!!!!!!!!!!!!!!!!!
>
>
> ---
>
>
>
> I need to interface a 100mA 24VDC device with 750 VDC. I was
> thinking of making a voltage divider circuit say 30 to 1. Can
> someone tell me if this will work or will it go up in smoke?
>
> Thanks,
>
> Chris
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
> Chris,
>
> Please don't take this wrong.....but if you don't know the answer
to that
> question, you probably should not be messing with a circuit that
carries 750 VDC.
> It can kill you!!!!!!!!!!!!!!!!!!!!!
AMEN!
Sometimes the questions posted here are pretty broad or vague.
This one should not be one of them!
Either be very specific about your "interface" or do not even get
within spitting distance of this project!
Vaclav
Apparently I am not being specific enough for the group. I have a
device that works off of 750 VDC. I need to know when it is turned
on. What is the easiest way to do this?
--- In basicstamps@yahoogroups.com, "aa7ej" <aa7ej@y...> wrote:
> --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > Chris,
> >
> > Please don't take this wrong.....but if you don't know the
answer
> to that
> > question, you probably should not be messing with a circuit that
> carries 750 VDC.
> > It can kill you!!!!!!!!!!!!!!!!!!!!!
>
> AMEN!
> Sometimes the questions posted here are pretty broad or vague.
> This one should not be one of them!
> Either be very specific about your "interface" or do not even get
> within spitting distance of this project!
> Vaclav
rest of the circuit. For example, allow the 750VDC circuit to drive an
electromagnet and then use a reed switch that will draw in when current
flows. You can probably even find relays that work at that voltage and
current. Now you have a pretty safe deal since there is no direct connection
between the two sides. Be sure the relay is overrated for your application.
If you don't want anything mechanical, you could use a hall effect sensor
instead of a reed.
Optical would be another way to go. If you could light a neon or other type
of bulb, you could sense the light from it. Again, very safe.
Regardless of how safe you feel it would be, I would strongly recommend not
using a voltage divider for lots of reasons. There are many very bad failure
modes that would be of nuisance value at 5V but would be disastrous at
750VDC. Also, wiring at 750V requires some care. You need insulation that is
sturdy enough, no sharp points, and a certain distance between anything
exposed. In many states (maybe all of them), you would need to be a licensed
electrician to legally wire something like this.
I would also avoid any scheme involving current sensing torroids or other
transformers. Again, too many failure modes that would be very hazardous.
As the other posters mention, I would urge you to be very careful working
with something like this. If you have any doubt, you should defer to someone
with experience. This is one case where mistakes are not good teachers.
Al Williams
AWC
*New Position Sensor Kit
http://www.al-williams.com/gp5.htm
>
Original Message
> From: christopher41877 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ScNjPYhKA3IfukR07ULoqZrifIL2F8wQBZMgqDw5AqgAgHe88vWDDfH1cPWpStqui2u6lmJz7pd3YMTcuuvjaE_e]CHRIS@R...[/url
> Sent: Thursday, November 20, 2003 10:24 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
>
>
> Ok,
>
> Apparently I am not being specific enough for the group. I have a
> device that works off of 750 VDC. I need to know when it is turned
> on. What is the easiest way to do this?
>
> --- In basicstamps@yahoogroups.com, "aa7ej" <aa7ej@y...> wrote:
> > --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > > Chris,
> > >
> > > Please don't take this wrong.....but if you don't know the
> answer
> > to that
> > > question, you probably should not be messing with a circuit that
> > carries 750 VDC.
> > > It can kill you!!!!!!!!!!!!!!!!!!!!!
> >
> > AMEN!
> > Sometimes the questions posted here are pretty broad or vague. This
> > one should not be one of them! Either be very specific about your
> > "interface" or do not even get within spitting distance of this
> > project! Vaclav
>
>
> To UNSUBSCRIBE, just send mail to:
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> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
>
How about using an inductive pick-up on the AC side of things to tell when
it's sourcing power? This would be the easiest and safest, I should think.
Idea #2 (I'm not sure if it would work, though)... How about using an
inductive pick-up on the DC side? You would only get a signal during turn-on
and turn-off, but I think it might work.
If I'm not being too inquisitive, what the heck do you have that runs off of
750V DC?
- Robert
>
Original Message
>From: christopher41877 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=PX3f8rmgpOkjabcai7PkN8vRNNLlCJvnuK9o0nDAc8nh4U67iuDLz6rJM5-v9XcX-BFppmb6PtLGhW9tNsE5wI-F]CHRIS@R...[/url
>
>Ok,
>
>Apparently I am not being specific enough for the group. I have a
>device that works off of 750 VDC. I need to know when it is turned
>on. What is the easiest way to do this?
First off...A fuse will not blow faster than your heart can stop. Im sure you
don't want to bet your life on it. It takes 150 microamps to stop your heart.
At 750 volts your skin resistance is not as good a protector as it is at 100
or lower. A 750 Volt 100 MA power source is VERY DEADLY.
Also DC is more dangerous than AC as it will paralyze your muscles and make
it difficult if not impossible to let go.
Use great big boat loads of caution, and if in doubt don't do it.
Yes, and no to the voltage divider. If you are just looking for an On/Off
condition I would use an opto-isolator with a big dropping resistor. Actually I
would use 2-3 in series as an added precaution.
Is the 750 VDC clean or noisy?
Use a dropping resistor to allow the current flow you need to trigger the
opto isolator's input LED. If you put 2 to 3 in series then if one shorts out
you
still have others to give you a true indication of On/Off. Do not trust this
indicator before working on the circuit. Check it with a Volt Meter and make
sure the filter caps have bleeder resistors and they work.
I have built voltage dividers to measure 800 Volt DC outputs from Plasma
Cutting Machines (at 1000 amps).
I use lots of filtering and an Analog Opto Isolation Amplifier.
Good luck and be safe.
Alan Bradford
Plasma Technologies
In a message dated 11/20/2003 9:34:35 PM Eastern Standard Time,
CHRIS@R... writes:
Hi,
I need to interface a 100mA 24VDC device with 750 VDC. I was
thinking of making a voltage divider circuit say 30 to 1. Can
someone tell me if this will work or will it go up in smoke?
Thanks,
Chris
[noparse][[/noparse]Non-text portions of this message have been removed]
wrote:
>
> You're bound to have some kind of AC power supply for this thing
(right?).
> How about using an inductive pick-up on the AC side of things to
tell when
> it's sourcing power? This would be the easiest and safest, I should
think.
>
> Idea #2 (I'm not sure if it would work, though)... How about using
an
> inductive pick-up on the DC side? You would only get a signal
during turn-on
> and turn-off, but I think it might work.
>
> If I'm not being too inquisitive, what the heck do you have that
runs off of
> 750V DC?
>
> - Robert
I have to concur that the DC is a result of some AC input. my first
thought was a welder, but those are often extremely low Volts/high
amp jobbs.
a CT or Current Transformer will yield a signal on the AC side that
relates to the current used. so it will change output as the current
changes.
The problem we joke about is that "it's not he volt, but the AMPS
that will kill you"
with 750V, an arc will occur at about 0.001" per each 70 volts, so an
arc may occur at 0.01". this would be a normal and expected thing,
not the oddity or worst case. I get this from the EDM (Electronic
Discharge Machine) used to cut metals and extrapolated it to 750
volts. those machines are used at MUCH lower voltages.
OK, that said, the sense wires will have 750 volts. so they need to
be separated.
normally, I'd point out that the wire used to carry the load will
have a voltage drop and you could get a reading, but still the
voltage is too high.
Putting a resistor near each pick-up might work to drop the sense
line voltage so you never get high voltages near anything or each
other, or ground.
even bringing out the leads for a sensor is kinda scarry.
But, my recommendation is to find another way.
Dave
an electric transit bus in California. Anyway, this is being done
in a controlled environment and I won't even have to go near it when
the power is on. Like I said, I know how to be safe around it just
wasn't sure how to monitor it.
--- In basicstamps@yahoogroups.com, "Dave Mucha" <davemucha@j...>
wrote:
> --- In basicstamps@yahoogroups.com, "Robert Ussery"
<uavscience@f...>
> wrote:
> >
> > You're bound to have some kind of AC power supply for this thing
> (right?).
> > How about using an inductive pick-up on the AC side of things to
> tell when
> > it's sourcing power? This would be the easiest and safest, I
should
> think.
> >
> > Idea #2 (I'm not sure if it would work, though)... How about
using
> an
> > inductive pick-up on the DC side? You would only get a signal
> during turn-on
> > and turn-off, but I think it might work.
> >
> > If I'm not being too inquisitive, what the heck do you have that
> runs off of
> > 750V DC?
> >
> > - Robert
>
> I have to concur that the DC is a result of some AC input. my
first
> thought was a welder, but those are often extremely low Volts/high
> amp jobbs.
>
> a CT or Current Transformer will yield a signal on the AC side
that
> relates to the current used. so it will change output as the
current
> changes.
>
> The problem we joke about is that "it's not he volt, but the AMPS
> that will kill you"
>
> with 750V, an arc will occur at about 0.001" per each 70 volts, so
an
> arc may occur at 0.01". this would be a normal and expected thing,
> not the oddity or worst case. I get this from the EDM (Electronic
> Discharge Machine) used to cut metals and extrapolated it to 750
> volts. those machines are used at MUCH lower voltages.
>
> OK, that said, the sense wires will have 750 volts. so they need
to
> be separated.
>
> normally, I'd point out that the wire used to carry the load will
> have a voltage drop and you could get a reading, but still the
> voltage is too high.
>
> Putting a resistor near each pick-up might work to drop the sense
> line voltage so you never get high voltages near anything or each
> other, or ground.
>
> even bringing out the leads for a sensor is kinda scarry.
>
> But, my recommendation is to find another way.
>
> Dave
Notes. We work with high Voltage daily, up to 100 kV, but usually uner 35
kV.
Resistors have Voltage limits. While it may be simple to put a single 20
Meg Ohm RCR07 resistor on 30 kV to drop the Voltage down, a single RCR07
resistor has a Voltage rating of only 250 Volts, across the single resistor.
Also, make certain that the Voltage divider is complete within the box.
Example, real one. The Tektronix high Voltage oscilloscope probe uses the
oscilloscope itself as a part of the Voltage divider. If one were to
measure 30 kV, and with the probe still attached to 30 kV, remove the probe
from the front of the oscilloscope, then there will be 30 kV snapping in
your hand across the bnc connector on the probe interface, which, by the
way, is rated for less than 1kV<G>.
The opto-isolator is a great idea. They make them which isolate 10 kV, and
are relatively easy to find. Also, wire dress and grounding is extremely
important.
You didn't say which direction you were trying to go? Control the 24 VDC
with the 750 or the other way around.
We generally use FET transistors for less than 1 kV. Turn the fet on with
TTL. If a FET dies, it shorts the 1 kV to ground. Still, there is a small
amount of risk that it may get into the TTL, but never seen it yet<G>.
These boxes are isolated from people<G>.
The opto is an excellent approach.
Original Message
From: plasmastamp@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=I2Jb5fXPc1cg3WNjtvgopX2T2jBKaPPj6GOeoE7AGEG7Eraj_KQt-I0mcWRuyRp6cPXdbVS0H0V_5Q]plasmastamp@a...[/url
Sent: Friday, November 21, 2003 6:22 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] High Voltage Interface
Hi Chris,
First off...A fuse will not blow faster than your heart can stop. Im sure
you
don't want to bet your life on it. It takes 150 microamps to stop your
heart.
At 750 volts your skin resistance is not as good a protector as it is at 100
or lower. A 750 Volt 100 MA power source is VERY DEADLY.
Also DC is more dangerous than AC as it will paralyze your muscles and make
it difficult if not impossible to let go.
Use great big boat loads of caution, and if in doubt don't do it.
Yes, and no to the voltage divider. If you are just looking for an On/Off
condition I would use an opto-isolator with a big dropping resistor.
Actually I
would use 2-3 in series as an added precaution.
Is the 750 VDC clean or noisy?
Use a dropping resistor to allow the current flow you need to trigger the
opto isolator's input LED. If you put 2 to 3 in series then if one shorts
out you
still have others to give you a true indication of On/Off. Do not trust this
indicator before working on the circuit. Check it with a Volt Meter and make
sure the filter caps have bleeder resistors and they work.
I have built voltage dividers to measure 800 Volt DC outputs from Plasma
Cutting Machines (at 1000 amps).
I use lots of filtering and an Analog Opto Isolation Amplifier.
Good luck and be safe.
Alan Bradford
Plasma Technologies
In a message dated 11/20/2003 9:34:35 PM Eastern Standard Time,
CHRIS@R... writes:
Hi,
I need to interface a 100mA 24VDC device with 750 VDC. I was
thinking of making a voltage divider circuit say 30 to 1. Can
someone tell me if this will work or will it go up in smoke?
Thanks,
Chris
[noparse][[/noparse]Non-text portions of this message have been removed]
To UNSUBSCRIBE, just send mail to:
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From: "christopher41877" <CHRIS@
> Thanks for all of the replies, especially Al. This voltage is from
> an electric transit bus in California. Anyway, this is being done
> in a controlled environment and I won't even have to go near it when
> the power is on. Like I said, I know how to be safe around it just
> wasn't sure how to monitor it.
A few more specifics please:
Is the current constant? Is it Known?
Is one side of the circuit grounded?
Are you looking for a simple on / off indication?
Or Do you need to know the amount of current flowing, or the voltage present?
Larry
Original Message
From: "christopher41877" <CHRIS@R...>
To: <basicstamps@yahoogroups.com>
Sent: November 20, 2003 8:24 PM
Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
: Ok,
:
: Apparently I am not being specific enough for the group. I have a
: device that works off of 750 VDC. I need to know when it is turned
: on. What is the easiest way to do this?
:
: --- In basicstamps@yahoogroups.com, "aa7ej" <aa7ej@y...> wrote:
: > --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
: > > Chris,
: > >
: > > Please don't take this wrong.....but if you don't know the
: answer
: > to that
: > > question, you probably should not be messing with a circuit that
: > carries 750 VDC.
: > > It can kill you!!!!!!!!!!!!!!!!!!!!!
: >
: > AMEN!
: > Sometimes the questions posted here are pretty broad or vague.
: > This one should not be one of them!
: > Either be very specific about your "interface" or do not even get
: > within spitting distance of this project!
: > Vaclav
:
:
: To UNSUBSCRIBE, just send mail to:
: basicstamps-unsubscribe@yahoogroups.com
: from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
:
:
: Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
:
:
:
many schools, from elementary to high-schools to
junior-colleges. Our audience can be VERY innocent,
and very in-experienced. Plus, the audience for
transit equipment that deals with this kind of
voltage (and BTW, huge currents also) is kind of
small.
Your original question, short as it was, had the
brevity we associate with inexperience -- and all
posters reacted appropriately with dire warnings.
Also, very few of us have dealt with this
equipment, so you had to deal with our innocence
too.
I think you've gotten several good suggestions so
far. If you MUST monitor the 750 VDC line,
isolation is the keyword. A voltage divider does
NOT give you that kind of isolation. Yes, things
can and will explode. Monitoring a 750 VDC lamp
with a light sensor is your best bet.
If you can find some other lower voltage control
point to monitor, that's better. Note that
electric motor voltage/current tends to be VERY
NOISY -- brush arcs, current surges, voltage peaks.
So whatever method you use should filter the noise,
or you'll have to filter it in software.
P.S. I'm glad you don't have to be near it when
the power is on. You WILL have to be near whatever
monitor equipment you build to indicate it IS on.
We don't want you to couple that voltage into
your monitor.
--- In basicstamps@yahoogroups.com, "christopher41877" <CHRIS@R...>
wrote:
> Thanks for all of the replies, especially Al. This voltage is from
> an electric transit bus in California. Anyway, this is being done
> in a controlled environment and I won't even have to go near it
when
> the power is on. Like I said, I know how to be safe around it just
> wasn't sure how to monitor it.
>
>
> --- In basicstamps@yahoogroups.com, "Dave Mucha" <davemucha@j...>
> wrote:
> > --- In basicstamps@yahoogroups.com, "Robert Ussery"
> <uavscience@f...>
> > wrote:
> > >
> > > You're bound to have some kind of AC power supply for this
thing
> > (right?).
> > > How about using an inductive pick-up on the AC side of things
to
> > tell when
> > > it's sourcing power? This would be the easiest and safest, I
> should
> > think.
> > >
> > > Idea #2 (I'm not sure if it would work, though)... How about
> using
> > an
> > > inductive pick-up on the DC side? You would only get a signal
> > during turn-on
> > > and turn-off, but I think it might work.
> > >
> > > If I'm not being too inquisitive, what the heck do you have
that
> > runs off of
> > > 750V DC?
> > >
> > > - Robert
> >
> > I have to concur that the DC is a result of some AC input. my
> first
> > thought was a welder, but those are often extremely low
Volts/high
> > amp jobbs.
> >
> > a CT or Current Transformer will yield a signal on the AC side
> that
> > relates to the current used. so it will change output as the
> current
> > changes.
> >
> > The problem we joke about is that "it's not he volt, but the AMPS
> > that will kill you"
> >
> > with 750V, an arc will occur at about 0.001" per each 70 volts,
so
> an
> > arc may occur at 0.01". this would be a normal and expected
thing,
> > not the oddity or worst case. I get this from the EDM
(Electronic
> > Discharge Machine) used to cut metals and extrapolated it to 750
> > volts. those machines are used at MUCH lower voltages.
> >
> > OK, that said, the sense wires will have 750 volts. so they need
> to
> > be separated.
> >
> > normally, I'd point out that the wire used to carry the load will
> > have a voltage drop and you could get a reading, but still the
> > voltage is too high.
> >
> > Putting a resistor near each pick-up might work to drop the
sense
> > line voltage so you never get high voltages near anything or each
> > other, or ground.
> >
> > even bringing out the leads for a sensor is kinda scarry.
> >
> > But, my recommendation is to find another way.
> >
> > Dave
voltage is connected directly to a resistor that is about 5KW, 1.4
ohms. I found an easy, simple and safe method to do this. We just
need to know when voltage is present so my meter has a peak hold on
it and when there is voltage then the meter will beep.
--- In basicstamps@yahoogroups.com, "FalconWireless Tech Support -
KF4HAZ" <techsupport@f...> wrote:
>
>
From: "christopher41877" <CHRIS@
> > Thanks for all of the replies, especially Al. This voltage is
from
> > an electric transit bus in California. Anyway, this is being
done
> > in a controlled environment and I won't even have to go near it
when
> > the power is on. Like I said, I know how to be safe around it
just
> > wasn't sure how to monitor it.
>
> A few more specifics please:
> Is the current constant? Is it Known?
> Is one side of the circuit grounded?
> Are you looking for a simple on / off indication?
> Or Do you need to know the amount of current flowing, or the
voltage present?
a clip on amp meter.
Original Message
From: "christopher41877" <CHRIS@R...>
To: <basicstamps@yahoogroups.com>
Sent: November 21, 2003 7:27 AM
Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
: The polarity will swing both ways depending on the situation. The
: voltage is connected directly to a resistor that is about 5KW, 1.4
: ohms. I found an easy, simple and safe method to do this. We just
: need to know when voltage is present so my meter has a peak hold on
: it and when there is voltage then the meter will beep.
:
:
: --- In basicstamps@yahoogroups.com, "FalconWireless Tech Support -
: KF4HAZ" <techsupport@f...> wrote:
: >
: >
From: "christopher41877" <CHRIS@
: > > Thanks for all of the replies, especially Al. This voltage is
: from
: > > an electric transit bus in California. Anyway, this is being
: done
: > > in a controlled environment and I won't even have to go near it
: when
: > > the power is on. Like I said, I know how to be safe around it
: just
: > > wasn't sure how to monitor it.
: >
: > A few more specifics please:
: > Is the current constant? Is it Known?
: > Is one side of the circuit grounded?
: > Are you looking for a simple on / off indication?
: > Or Do you need to know the amount of current flowing, or the
: voltage present?
:
:
: To UNSUBSCRIBE, just send mail to:
: basicstamps-unsubscribe@yahoogroups.com
: from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
:
:
: Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
:
:
:
Most of the Stamp (or similar) users only deal with harmeless low
voltage circuits. Do not realize the dangers of dealing with high
energy systems.
UL defines 32 volts as the limit between low energy and high energy
systems.
Some body sugested the use of a current transformer to sense current
in a DC circuit. Are you kidding?.
Galvanic isolation should be a safety concern.
To sense currents in a relatively high voltage circuit, a Hall effect
device is good alternative.
a proper dropping resistor (a known technology that easily works with a 700
volt feed) pointing into a 6" length of black plastic pipe with a
phototransistor on the other end. That would isolate you from anything short
of a lightening strike. I would concur with the rest of the group that you
don't want a direct electrical connection between a 700 volt supply and any
low voltage circuitry. Too many things to go wrong with potential
life-threatening results.
BTW: I was very stupid in my youth while working on a tube guitar amp with a
600-volt DC supply 30 years ago. My left hand was on the chassis and my
right hand on the screwdriver which slipped and touched the power supply
cap. Last thing I remember was my arm flying past my head and me flying into
the corner as the blackness descended. I woke up what could have been a few
seconds or few minutes later feeling like I had been kicked in the chest.
Two important lessons from this... Always keep one hand in your pocket while
working with any lethal voltages (yes, 120 Volts AC is lethal). This
minimizes the chance of a hand-to-hand shock which can stop your heart. And
secondly, never ever work by yourself on any high voltages. Always make sure
someone else is close by that can dial 911, at least. A few lessons in CPR
would be a good thing as well. I was EXTREMELY lucky, and could have been in
fibrillation on the floor and then died. My unlucky parents would have found
me dead the next day. I think about this every time I dive into a
high-voltage
circuit, which is probably what keep me from electrocuting myself over the
following 30 years.
Mike Sokol
www.modernrecording.com
mikes@m...
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: "Albert Catano" <acatano2002@y...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, November 21, 2003 1:57 PM
Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
> You hit the nail right on the head.
> Most of the Stamp (or similar) users only deal with harmeless low
> voltage circuits. Do not realize the dangers of dealing with high
> energy systems.
> UL defines 32 volts as the limit between low energy and high energy
> systems.
> Some body sugested the use of a current transformer to sense current
> in a DC circuit. Are you kidding?.
> Galvanic isolation should be a safety concern.
> To sense currents in a relatively high voltage circuit, a Hall effect
> device is good alternative.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
On Fri, 21 Nov 2003, christopher41877 wrote:
> Ok,
>
> Apparently I am not being specific enough for the group. I have a
> device that works off of 750 VDC. I need to know when it is turned
> on. What is the easiest way to do this?
>
> --- In basicstamps@yahoogroups.com, "aa7ej" <aa7ej@y...> wrote:
> > --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > > Chris,
> > >
> > > Please don't take this wrong.....but if you don't know the
> answer
> > to that
> > > question, you probably should not be messing with a circuit that
> > carries 750 VDC.
> > > It can kill you!!!!!!!!!!!!!!!!!!!!!
> >
> > AMEN!
> > Sometimes the questions posted here are pretty broad or vague.
> > This one should not be one of them!
> > Either be very specific about your "interface" or do not even get
> > within spitting distance of this project!
> > Vaclav
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Sean T. Lamont, CTO / Chief NetNerd, Abstract Software, Inc. (ServNet)
Seattle - Bellingham - Vancouver - Portland - Everett - Tacoma - Bremerton
email: lamont@a... WWW: http://www.serv.net
"Do not fear mistakes, There Are None" - Miles Davis
in a DC circuit. Are you kidding?.
That would be me! guess I did not read the part about it being DC, thought
he wanted it to be dc to read with his meter?
So yea I was Kidding
Larry
Original Message
From: "Albert Catano" <acatano2002@y...>
To: <basicstamps@yahoogroups.com>
Sent: November 21, 2003 10:57 AM
Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
: You hit the nail right on the head.
: Most of the Stamp (or similar) users only deal with harmeless low
: voltage circuits. Do not realize the dangers of dealing with high
: energy systems.
: UL defines 32 volts as the limit between low energy and high energy
: systems.
: Some body sugested the use of a current transformer to sense current
: in a DC circuit. Are you kidding?.
: Galvanic isolation should be a safety concern.
: To sense currents in a relatively high voltage circuit, a Hall effect
: device is good alternative.
:
:
: To UNSUBSCRIBE, just send mail to:
: basicstamps-unsubscribe@yahoogroups.com
: from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
:
:
: Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
:
:
:
<acatano2002@y...> wrote:
> You hit the nail right on the head.
> Most of the Stamp (or similar) users only deal with harmeless low
> voltage circuits. Do not realize the dangers of dealing with high
> energy systems.
> UL defines 32 volts as the limit between low energy and high energy
> systems.
> Some body sugested the use of a current transformer to sense
current
> in a DC circuit. Are you kidding?.
I think the CT's were offered for the AC, before it became DC,
assuming of course, there is an AC line that feeds the Dc.
Dave
wrote:
> I think the most straightforward and safe way to do this is a neon
bulb with
> a proper dropping resistor (a known technology that easily works
with a 700
> volt feed) pointing into a 6" length of black plastic pipe with a
> phototransistor on the other end. That would isolate you from
anything short
> of a lightening strike. I would concur with the rest of the group
that you
> don't want a direct electrical connection between a 700 volt supply
and any
> low voltage circuitry. Too many things to go wrong with potential
> life-threatening results.
>
> BTW: I was very stupid in my youth while working on a tube guitar
amp with a
> 600-volt DC supply 30 years ago. My left hand was on the chassis
and my
> right hand on the screwdriver which slipped and touched the power
supply
> cap. Last thing I remember was my arm flying past my head and me
flying into
> the corner as the blackness descended. I woke up what could have
been a few
> seconds or few minutes later feeling like I had been kicked in the
chest.
> Two important lessons from this... Always keep one hand in your
pocket while
> working with any lethal voltages (yes, 120 Volts AC is lethal). This
> minimizes the chance of a hand-to-hand shock which can stop your
heart. And
> secondly, never ever work by yourself on any high voltages. Always
make sure
> someone else is close by that can dial 911, at least. A few lessons
in CPR
> would be a good thing as well. I was EXTREMELY lucky, and could
have been in
> fibrillation on the floor and then died. My unlucky parents would
have found
> me dead the next day. I think about this every time I dive into a
> high-voltage
> circuit, which is probably what keep me from electrocuting myself
over the
> following 30 years.
>
> Mike Sokol
> www.modernrecording.com
> mikes@m...
Interesting, anyone know what it takes to make a Jacobs ladder ?
Not THAT would be a really COOOL ! circuit monitor.
heck, you could monitor that with an AM radio from a long distance.
Or a Tesla coil ?
why be stuck with a boring meter display when you can have huge arcs ?
and as a note, on high voltage stuff, a friend who worked for the
power company told me he firmly plants his hand on the box and passes
his thumb over the contacts before doing any work.
if said that if the meter was faulty, he would rather suffer damage
to one hand than have power pass thru his body.
Guess, it was his final go/no-go test.
And I think his idea was that BEFORE he risked his own hand, he darn
well made sure everything was safe. I know I would !
Dave
usual Stamp related, low-voltage, topics. I suggest dropping it.
Dennis
Original Message
From: Dave Mucha [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=YHmgY7_XnV_LSDQitdrLCEysP_sTaWt0qN5adiwHOgAVwkNJqcGVbFbLR4OQeqhKOd_D7RarxrHz6kk]davemucha@j...[/url
Sent: Friday, November 21, 2003 5:18 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: High Voltage Interface
--- In basicstamps@yahoogroups.com, "Mike Sokol" <mike.sokol@m...>
wrote:
> I think the most straightforward and safe way to do this is a neon
bulb with
> a proper dropping resistor (a known technology that easily works
with a 700
> volt feed) pointing into a 6" length of black plastic pipe with a
> phototransistor on the other end. That would isolate you from
anything short
> of a lightening strike. I would concur with the rest of the group
that you
> don't want a direct electrical connection between a 700 volt supply
and any
> low voltage circuitry. Too many things to go wrong with potential
> life-threatening results.
>
> BTW: I was very stupid in my youth while working on a tube guitar
amp with a
> 600-volt DC supply 30 years ago. My left hand was on the chassis
and my
> right hand on the screwdriver which slipped and touched the power
supply
> cap. Last thing I remember was my arm flying past my head and me
flying into
> the corner as the blackness descended. I woke up what could have
been a few
> seconds or few minutes later feeling like I had been kicked in the
chest.
> Two important lessons from this... Always keep one hand in your
pocket while
> working with any lethal voltages (yes, 120 Volts AC is lethal). This
> minimizes the chance of a hand-to-hand shock which can stop your
heart. And
> secondly, never ever work by yourself on any high voltages. Always
make sure
> someone else is close by that can dial 911, at least. A few lessons
in CPR
> would be a good thing as well. I was EXTREMELY lucky, and could
have been in
> fibrillation on the floor and then died. My unlucky parents would
have found
> me dead the next day. I think about this every time I dive into a
> high-voltage circuit, which is probably what keep me from
> electrocuting myself
over the
> following 30 years.
>
> Mike Sokol
> www.modernrecording.com
> mikes@m...
Interesting, anyone know what it takes to make a Jacobs ladder ?
Not THAT would be a really COOOL ! circuit monitor.
heck, you could monitor that with an AM radio from a long distance.
Or a Tesla coil ?
why be stuck with a boring meter display when you can have huge arcs ?
and as a note, on high voltage stuff, a friend who worked for the
power company told me he firmly plants his hand on the box and passes
his thumb over the contacts before doing any work.
if said that if the meter was faulty, he would rather suffer damage
to one hand than have power pass thru his body.
Guess, it was his final go/no-go test.
And I think his idea was that BEFORE he risked his own hand, he darn
well made sure everything was safe. I know I would !
Dave
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