|
|
Re: static electricity shock
Static
is definitely a problem to be avoided! Maybe not for the mount, but other
stuff, absolutely..
I
have smoked a couple cameras from static..
?
Derek
?
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From: [email protected] [mailto:[email protected]] On Behalf Of Rappnron via Groups.Io
Sent: Monday, December 30, 2019
7:29 PM
To: [email protected]
Subject: [Losmandy_users_io]
static electricity shock
?
bottom line ...? do I need to and/or how do I ground the mount ?
Out here in the wild west we get offshore "Santa Ana " winds and the humidity drops
real low. Then when I touch the mount or my metal bodied ZWO camera I might get
a shock of static electricity.
So am I to worry?, not enough power to cause harm right?
Im using a 110v power ( guess this ground doesnt matter as Im getting shocked)
and? imaging on a wooden rooftop deck under a ROR so presumably the mount
is a floating insulated ground?
I have clamped a copper wire to one of the leg mount screws and connected to a
nearby metal vent pipe
But perhaps I should ground myself to the vent pipe?
How best to ground the mount?
Will this help ?
Ron
|
bottom line ...? do I need to and/or how do I ground the mount ?
Out here in the wild west we get offshore "Santa Ana " winds and the humidity drops real low. Then when I touch the mount or my metal bodied ZWO camera I might get a shock of static electricity.
So am I to worry?, not enough power to cause harm right?
Im using a 110v power ( guess this ground doesnt matter as Im getting shocked) and? imaging on a wooden rooftop deck under a ROR so presumably the mount is a floating insulated ground?
I have clamped a copper wire to one of the leg mount screws and connected to a nearby metal vent pipe
But perhaps I should ground myself to the vent pipe?
How best to ground the mount?
Will this help ?
Ron
|
Hi Michael,
?
I did not think that you went off the deep end. Rather, I thought your post was very informative.
?
Greg
?
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From: [email protected] <[email protected]>
On Behalf Of Michael Herman
Sent: Tuesday, 31 December 2019 6:07 AM
To: [email protected]
Subject: Re: [Losmandy_users_io] Mount power supply
?
Hi John,
I really apologize for going off the deep end on that lightning topic.? I feel like the nutty character in one of the old Abbott and Costello movies..."slowly I turned...step by step...".?
I have a long history in high voltage electronics, and did my PhD on Field Emission, also called cold cathode emission (of electrons from surfaces). I was examining metal and silicon needle surfaces with 10,000 volts near the tip.? ?So
when you mentioned lightning, I really went off.? I apologize!
Anyway, you got the reasoning correct.??
Does Richard Berry discuss any of this in his articles or books?? I recall reading one where he recommended a rolloff roof observatory.
Is there a company in the world that makes metal domes who could discuss this with you?? It would be great to have some experience talking!
All the best and happy New Year,
?
Michael,
Thanks for the detailed analysis. The choices seem pretty clear. Keep the roof ungrounded (will need to check if it really is) and the equipment totally unplugged. There is a wooden support structure/trelise which the roof rolls onto when open, and I suppose
I could put a rod or pole off the far end. Or maybe something even further away from the whole shed itself. I got rid of all my old and tall trees sometime ago, but can't say the same for the surrounding yards.? But hopefully with a rod close enough and high
enough, any lightning bolt would hit there instead of the shed. I dread to think of the time and money it would take to replace everything if it really did get hit.
Thanks again,
John?
|
Very nice, John. I was not familiar with the existence of such plans... sounds like a great idea.??
Send a link to your Astro images if you?can.? ?Love to see the amazing work everyone is doing.
Clear skies and happy holidays,
Michael
[Edited Message Follows]
Hi Michael,
My shed is a 6 x 8 foot wooden structure and built from plans from Skyshed, if you are familiar. I think paid about $60 for the schematics and instructions download which was well worth it for the planning and materials involved. The roof rolls out using garage door type wheels and tracks, which has pretty smooth operation. This past fall I also added a Genie worm drive garage door opener which now allows me to close up without making a trip outside in the cold morning air (nice!).
The roll off is preferable to me over domes, since you can see the whole sky and clouds coming; but domes are better winds breaks from what I have read. I used some standard white colored sheet metal roofing, with insulation board underneath to stop sweating. My Celestron 925 Edge with guide scope on top just fits its range of motion within the walls; for a 10 inch or larger SCT, an 8 x 10 foot design would probably be required.?
But planning ahead for electrical supply and storm events are definitely in one's own better interests.
Cheers,
John
|
Hi Michael,
My shed is a 6 x 8 foot wooden structure and built from plans from Skyshed, if you are familiar. I think paid about $60 for the schematics and instructions download which was well worth it for the planning and materials involved. The roof rolls out using garage door type wheels and tracks, which has pretty smooth operation. This past fall I also added a Genie worm drive garage door opener which now allows me to close up without making a trip outside in the cold morning air (nice!).
The roll off is preferable to me over domes, since you can see the whole sky and clouds coming; but domes are better winds breaks from what I have read. I used some standard white colored sheet metal roofing, with insulation board underneath to stop sweating. My Celestron 925 Edge with guide scope on top just fits its range of motion within the walls; for a 10 inch or larger SCT, an 8 x 10 foot design would probably be required.?
But planning ahead for electrical supply and storm events are definitely in one's own better interests.
Cheers,
John
|
Ok I assembled the? G11 "no problems their"? put the power to it and the RA motor is much louder then the DEC motor. Am I needing to ajust something or is this normal?
|
Fortunately, our activity of observing or imaging forbids doing this in lightning storms!
Now as to golf.... fore!!!
The thing about lightning rods is you must present the lowest impedance path to an effective ground. A truly lightning rod system would use similar gauge rods on insulated standoffs down the side of the structure and a deeply driven section of larger rod to earth. I visited a historic inn which was a few hundred years old and for some reason has a very high frequency of lightning strikes. The entire collection of inn structures is topped with multiple pointed spikes with multiple smaller stalks with more spikes. The spikes are all on a huge bus bar that is held off the roof with glass insulators and this practice is carried down the side of the all of the inn's structures and into a collection of iron rods all mechanically clamped to the main rod from the structure roofs. These grounding rods are hammered into the earth several feet and inspected annually. They seem to take it very seriously, it works as far as I can tell because we were there in a summer lightning storm and they called us all in from the grounds as the lightning storm hit. You can feel it in the air on your skin!?
But as Michael suggested it is far safer to have an effective lightning rod some distance from the structures being protected to minimize the impact on the structure wiring and electronics. It must be significantly taller than surrounding structures to be effective.?
--
Chip Louie - Chief Daydreamer Imagination Hardware
|
The thing about lightning rods is you must present the lowest impedance path to an effective ground. A truly lightning rod system would use similar gauge rods on insulated standoffs down the side of the structure and a deeply driven section of larger rod to earth. I visited a historic inn which was a few hundred years old and for some reason has a very high frequency of lightning strikes. The entire collection of inn structures is topped with multiple pointed spikes with multiple smaller stalks with more spikes. The spikes are all on a huge bus bar that is held off the roof with glass insulators and this practice is carried down the side of the all of the inn's structures and into a collection of iron rods all mechanically clamped to the main rod from the structure roofs. These grounding rods are hammered into the earth several feet and inspected annually. They seem to take it very seriously, it works as far as I can tell because we were there in a summer lightning storm and they called us all in from the grounds as the lightning storm hit. You can feel it in the air on your skin!?
But as Michael suggested it is far safer to have an effective lightning rod some distance from the structures being protected to minimize the impact on the structure wiring and electronics. It must be significantly taller than surrounding structures to be effective.?
--
Chip Louie - Chief Daydreamer Imagination Hardware
|
Re: Mount power supply...
If you don't have a dc ampmeter. You can also put a light bulb between the power source and the motor. The light will dim down if the motor is drawing more current.
We do this in the oilfields to adjust the counter weights on pump iacks
On Sat, Dec 28, 2019 at 11:41 PM -0600, "Michael Herman" <mherman346@...> wrote:
Thanks, Derek, for the nice testimonial! (True you were not paid for that, but also true that I have your 12 inch Meade SCT in my living room, awaiting optical alignment tests...? my hostage!)
Actually, Derek is nicely mentioning that using a DC ammeter on the Gemini input power to sense motor current can help you with worm to ring gear adjustments.? If the worm and ring gear are too tight, you'll see the motor current increase when you slew.? The ammeter also helps you see if your system is badly unbalanced for the same reason.??
I forgot this added benefit to having an ammeter on the power supply, as once the gear mesh is well set up and bolted down, which I did years ago on my systems, I have not needed to ever muss with it.??
Happy new year, all, and thanks again, Derek!
Michael
Yes, I made several custom voltage booster units for people, who seem
happy with them
***
AWESOME!..
I use the ammeter to set my worm to ring gap.. It’s a perfect little device..
?
And
no, I have no financial incentive to say so.. I say so because I love mine and
could never live without..
?
Derek
?
?
Thanks for asking about my power booster units, Brian.
Yes, I made several custom voltage booster units for people, who seem
happy with them.? They are not a mass production product....just for
either Gemini1 or Gemini2.??
If anyone is interested, let let me know with a private email, and I'll
sell you the fee I have now, or make up a new batch if there is sufficient
interest.? ?I do have two G1 and two G2 units still at home ready to
go.? I use mine all the time on my CG11, G11, and GM8 / GM811 mounts, and
the design has been robust over many years of use.??
Here is a picture of one in use. The voltage is the top display, the
amps on the bottom.? You can see the Gemini1 it is running draws very
little current while tracking a balanced load.? If not tracking, either
parked or at terrestrial setting, the Gemini logic circuits take even less
power.??
The boost from variable input voltage about 12V, up to 17V amplifies
the motor torque by 17/12, about 45%.? This does reduce the issue of motor
stalling.?
Another key element of the voltage booster unit is that it protects the
output polarity going to the Gemini, no matter what you connect as the input
polarity.? It was intended for field use in the dark, so that in case you
plugged in a 12V battery backwards, or somehow mixed up the polarity, it would
always output the correct Gemini polarity.? I think that polarity errors
kill more mounts, Gemini or Synta, etc, easily shorting out the internal
circuits, than any other reason.??
Both types of unit also can take as input any cable having a 5.5/2.5 mm
male input connector.? Any DC polarity will work as the input, from 11V to
15V.? I provide a 5 amp 115V AC/12V DC "brick" for household
power.? ?The Gemini1 units have a dedicated G1 DIN output plug, and
the G2 units have a separate male to male cord that fits the
Gemini2.??
Very best, and happy holidays,
?
On Fri, Dec 27, 2019, 9:04 PM Brian Valente
<bvalente@...>
wrote:
>> ?I
use a power supply that I make for Gemini units.?
Michael just to clarify you offer your Gemini power
supplies for sale as well, right?
?
On Fri, Dec 27, 2019 at 8:45 PM Michael
Herman <mherman346@...> wrote:
Hi Deric,
I agree with you that we should protect our expensive Gemini
units.??
However, each system is driving a different load, do knowing how much
current your gear needs means you should try to measure that.? My data
follows...
If perfectly balanced, the only thing the motors are driving with
current are the torque coming from accelerating the load (scope, cameras, and
counterweights).??
The fuse protects using only a current sense (melting a resistive wire
from the current).? But the current used by a Gemini on the DC motors will
depend also on DC voltage (same power = current x voltage, so if V goes up, I
goes down).
My G11 units typically use under 1.5 amps and usually under 1.2
amps.? That peak current is only observed during a Park, where both motors
are slewing as fast as possible.? Normal Sidereal rate tracking uses under
0.4 amps.??
I drive my Gemini units at 17VDC.? If you are driving
at 12VDC, expect the current to be about 1.5 X as high as what I'm
reporting.? I think that if you use (try) a 3 amp fuse in line with the DC
power input,? it should be fine.? (I did have an old motor start to
go bad and it was drawing 1 amp DC over the other motor during fast slews.)
Definitely use a "surge protector" type of AC
power strip.? That is a must especially if you live near any possible
lightning.? Also unplug your Gemini DC input power when not using the
unit.? ?
The Gemini units are designed intelligently to prevent
damage to themselves or to the motors. If the Gemini senses a motor is drawing
too much DC power, it will show a "Stall" or maybe "Lags"
warning.??
Finally, I use a power supply that I make for Gemini
units.? That has a DC voltage and current monitor, as well as a voltage
pump that changes 12 VDC in to 17 VDC out that then goes to the Gemini.?
The current meter allows me to see anything abnormal: if my system is
unbalanced, or a motor is going awry, or my gears are getting jammed (worm to
ring gear used to be a problem if their spacing was mis-set).?
?
What type of fuse or breaker should I use for short and over current
protection? I have already been party to this before. My AVX mount went up in
smoke after it shorted out and the Lithium battery did a rapid discharge
through the mount. Celestron is replacing it, I dont want this to happen to the
G11. Is their pre built devices or a good schematic for a device? I guess That
I can build one but it has been awhile " a Heathkit Ham radio" Thank
you and Clear skies.
--
|
No apologies necessary, it was interesting.?
Sent from my Galaxy Tab A
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-------- Original message --------
From: Michael Herman <mherman346@...>
Date: 12/30/19 1:07 PM (GMT-06:00)
Subject: Re: [Losmandy_users_io] Mount power supply
Hi John,
I really apologize for going off the deep end on that lightning topic.? I feel like the nutty character in one of the old Abbott and Costello movies..."slowly I turned...step by step...".?
I have a long history in high voltage electronics, and did my PhD on Field Emission, also called cold cathode emission (of electrons from surfaces). I was examining metal and silicon needle surfaces with 10,000 volts near the tip.? ?So when
you mentioned lightning, I really went off.? I apologize!
Anyway, you got the reasoning correct.??
Other thoughts:
Does Richard Berry discuss any of this in his articles or books?? I recall reading one where he recommended a rolloff roof observatory.
Is there a company in the world that makes metal domes who could discuss this with you?? It would be great to have some experience talking!
All the best and happy New Year,
Michael
??
Michael,
Thanks for the detailed analysis. The choices seem pretty clear. Keep the roof ungrounded (will need to check if it really is) and the equipment totally unplugged. There is a wooden support structure/trelise which the roof rolls onto when open, and I suppose
I could put a rod or pole off the far end. Or maybe something even further away from the whole shed itself. I got rid of all my old and tall trees sometime ago, but can't say the same for the surrounding yards.? But hopefully with a rod close enough and high
enough, any lightning bolt would hit there instead of the shed. I dread to think of the time and money it would take to replace everything if it really did get hit.
Thanks again,
John?
|
Hi John,
I really apologize for going off the deep end on that lightning topic.? I feel like the nutty character in one of the old Abbott and Costello movies..."slowly I turned...step by step...".?
I have a long history in high voltage electronics, and did my PhD on Field Emission, also called cold cathode emission (of electrons from surfaces). I was examining metal and silicon needle surfaces with 10,000 volts near the tip.? ?So when you mentioned lightning, I really went off.? I apologize!
Anyway, you got the reasoning correct.??
Other thoughts:
Does Richard Berry discuss any of this in his articles or books?? I recall reading one where he recommended a rolloff roof observatory.
Is there a company in the world that makes metal domes who could discuss this with you?? It would be great to have some experience talking!
All the best and happy New Year,
Michael
??
Michael,
Thanks for the detailed analysis. The choices seem pretty clear. Keep the roof ungrounded (will need to check if it really is) and the equipment totally unplugged. There is a wooden support structure/trelise which the roof rolls onto when open, and I suppose I could put a rod or pole off the far end. Or maybe something even further away from the whole shed itself. I got rid of all my old and tall trees sometime ago, but can't say the same for the surrounding yards.? But hopefully with a rod close enough and high enough, any lightning bolt would hit there instead of the shed. I dread to think of the time and money it would take to replace everything if it really did get hit.
Thanks again,
John?
|
Michael,
Thanks for the detailed analysis. The choices seem pretty clear. Keep the roof ungrounded (will need to check if it really is) and the equipment totally unplugged. There is a wooden support structure/trelise which the roof rolls onto when open, and I suppose I could put a rod or pole off the far end. Or maybe something even further away from the whole shed itself. I got rid of all my old and tall trees sometime ago, but can't say the same for the surrounding yards.? But hopefully with a rod close enough and high enough, any lightning bolt would hit there instead of the shed. I dread to think of the time and money it would take to replace everything if it really did get hit.
Thanks again,
John?
|
Michael Herman said, "Have fun, and don't play golf in a lightning storm!"
"Anyway, the good Lord would never disrupt the best game of my life!"
|
Interesting thread Michael, I enjoy the way you get me thinking.
Sent from my Galaxy Tab A
toggle quoted message
Show quoted text
-------- Original message --------
From: Michael Herman <mherman346@...>
Date: 12/29/19 4:06 AM (GMT-06:00)
Subject: Re: [Losmandy_users_io] Mount power supply
Nice topic: high electric fields...! ?
The key thing that "attracts" lightning is the local electric field outdoors. ? For this purpose, lightning rods are grounded metal, and sharp at the vertical point. ?(The electric field F at the tip of a metal rod, having a spherical radius
R at the end, and V is the voltage difference to the other electrode, is about F = V / {5 X R} ). ? The tree, if it got wet (anyway would have wet phloem wood inside the bark) and had sharp tip, and it certainly was grounded, it would intensify the electric
field at the tip top of the tree to the sky cloud above it.? So tall isolated trees get struck. ?
When old wooden sailing ships at sea encountered a lightning storm, sometimes the air around the top of the mast tip would ionize and glow.? This was called "St Elmo's Fire" by the fishermen ( see this mentioned in the Melville book Moby Dick).
?[I think there was another Herman Melville book about a scam artist who offered to sharpen lightning rods... maybe called "The Lightning Rod Man" ?]
When the electric field is large enough, the air around the metal sharp tip lightning rod ionizes, and this provides a somewhat conductive path for current flow (like having salt in water, or acid in a battery).? The remaining insulating conductive
path up to the clouds shrinks in size, and this shorter path above the lightning rod becomes the shortest distance for the cloud to discharge its stored charges...so the lightning occurs at that tip of the lightning rod more frequently than areas with low
field. ?(Also why spark plugs in gas engines have a sharp metal tip)
So houses will have a grounded metal lightning rod with a sharp tip, sticking up above the brick or stone chimney.? The rod will be on the outer part of the chimney so if it gets hit and heats up, it won't trigger a fire on any wood it encounters.
?
The current has to flow from the cloud (holding the charges) to the earth. ?
If your roof is not grounded, it will not be effective as a lightning rod.?
If your roof is totally flat and horizontal, it will not be effective.
If it were grounded, the sharpest point could get hit, at the corners of the rectangular roof. ?
I'd suggest you put up a metal pole with a sharp tip, like a flag pole with a sharp tip, a close distance from your observatory.? I wouldn't put that on the observatory itself, because you would like to keep the current flow from the lightning
away from the observatory as much as possible.? The high current flow (maybe a million amps?) generates a voltage, and the resulting transient voltage on the ground node can cause damage to the (capacitively) other wires that are still at the former ground
=0 volts condition.?
That said, Bob Runyan in the Midwest lives in a rural area (great skies) near railroad tracks that are infrequently hit.? His observatory electronics got damaged when lightning struck, and some of his house appliances got killed.? I think his
TV (maybe from the metal antenna) got damaged? ? So did his Gemini-1 in his nearby observatory.? His Gemini-1 serial port chip and surrounding capacitors got blown up, as the serial cable was left plugged into his PC in the observatory.? It was a lot of work
to wire up a replacement chip to replace the damaged circuit board at that location, but that board is still working (or Bob would let me know!).? So... my advice is to leave the connections off the Gemini if you are not going to use the system (certainly
if a lightning storm is coming!).
Have fun, and don't play golf in a lightning storm!,
Michael
On Sat, Dec 28, 2019 at 10:15 PM John Kmetz < jjkmetz54@...> wrote:
This thread is interesting to me especially since lightning split my neighbor's tree this past summer, which was less than 100 feet from my observatory shed (not in use, of course). Fortunately none of my equipment was affected in any way. The neighborhood
was in the dark for a hour or so and I did need to reset my clocks inside, etc. My AC line comes underground from the garage to a GFCI outlet in the shed, into which I have plugged a wifi controlled outlet:
I always power this outlet down when I'm done for the night, and power it up whenever I'm starting an AP session. I also have two dinky 15A power strips from Home Depot coming out of that for running the Losmandy AC converter and all the other DC supplies for
cameras, filter wheel, focuser and such.?
So I can't say I did the absolute right thing with my power arrangements, or I just got lucky. But perhaps just having the AC line interrupted by the remote controlled outlet was enough to save me. But just to reiterate what already has been said, lightning
is a real threat and it can come close if not strike your property directly.
Sometimes I wonder if the steel roofing on my roll-off is not a magnet for lightning strikes and shouldn't be grounded to earth for protection. So if anyone is using any type of lightning rod arrangement in their observatory I would love to hear about it. Not
sure where to place it exactly but am assuming I would need to run it a ground rod, like those by your meter base, as the end connection. Just shopping for some ideas here.
Thanks,
John
--
|
Nice topic: high electric fields...! ?
The key thing that "attracts" lightning is the local electric field outdoors. ? For this purpose, lightning rods are grounded metal, and sharp at the vertical point. ?(The electric field F at the tip of a metal rod, having a spherical radius R at the end, and V is the voltage difference to the other electrode, is about F = V / {5 X R} ). ? The tree, if it got wet (anyway would have wet phloem wood inside the bark) and had sharp tip, and it certainly was grounded, it would intensify the electric field at the tip top of the tree to the sky cloud above it.? So tall isolated trees get struck. ?
When old wooden sailing ships at sea encountered a lightning storm, sometimes the air around the top of the mast tip would ionize and glow.? This was called "St Elmo's Fire" by the fishermen ( see this mentioned in the Melville book Moby Dick). ?[I think there was another Herman Melville book about a scam artist who offered to sharpen lightning rods... maybe called "The Lightning Rod Man" ?]
When the electric field is large enough, the air around the metal sharp tip lightning rod ionizes, and this provides a somewhat conductive path for current flow (like having salt in water, or acid in a battery).? The remaining insulating conductive path up to the clouds shrinks in size, and this shorter path above the lightning rod becomes the shortest distance for the cloud to discharge its stored charges...so the lightning occurs at that tip of the lightning rod more frequently than areas with low field. ?(Also why spark plugs in gas engines have a sharp metal tip)
So houses will have a grounded metal lightning rod with a sharp tip, sticking up above the brick or stone chimney.? The rod will be on the outer part of the chimney so if it gets hit and heats up, it won't trigger a fire on any wood it encounters. ?
The current has to flow from the cloud (holding the charges) to the earth. ?
If your roof is not grounded, it will not be effective as a lightning rod.? If your roof is totally flat and horizontal, it will not be effective. If it were grounded, the sharpest point could get hit, at the corners of the rectangular roof. ?
I'd suggest you put up a metal pole with a sharp tip, like a flag pole with a sharp tip, a close distance from your observatory.? I wouldn't put that on the observatory itself, because you would like to keep the current flow from the lightning away from the observatory as much as possible.? The high current flow (maybe a million amps?) generates a voltage, and the resulting transient voltage on the ground node can cause damage to the (capacitively) other wires that are still at the former ground =0 volts condition.?
That said, Bob Runyan in the Midwest lives in a rural area (great skies) near railroad tracks that are infrequently hit.? His observatory electronics got damaged when lightning struck, and some of his house appliances got killed.? I think his TV (maybe from the metal antenna) got damaged? ? So did his Gemini-1 in his nearby observatory.? His Gemini-1 serial port chip and surrounding capacitors got blown up, as the serial cable was left plugged into his PC in the observatory.? It was a lot of work to wire up a replacement chip to replace the damaged circuit board at that location, but that board is still working (or Bob would let me know!).? So... my advice is to leave the connections off the Gemini if you are not going to use the system (certainly if a lightning storm is coming!).
Have fun, and don't play golf in a lightning storm!,
Michael
On Sat, Dec 28, 2019 at 10:15 PM John Kmetz < jjkmetz54@...> wrote: This thread is interesting to me especially since lightning split my neighbor's tree this past summer, which was less than 100 feet from my observatory shed (not in use, of course). Fortunately none of my equipment was affected in any way. The neighborhood was in the dark for a hour or so and I did need to reset my clocks inside, etc. My AC line comes underground from the garage to a GFCI outlet in the shed, into which I have plugged a wifi controlled outlet:
I always power this outlet down when I'm done for the night, and power it up whenever I'm starting an AP session. I also have two dinky 15A power strips from Home Depot coming out of that for running the Losmandy AC converter and all the other DC supplies for cameras, filter wheel, focuser and such.?
So I can't say I did the absolute right thing with my power arrangements, or I just got lucky. But perhaps just having the AC line interrupted by the remote controlled outlet was enough to save me. But just to reiterate what already has been said, lightning is a real threat and it can come close if not strike your property directly.
Sometimes I wonder if the steel roofing on my roll-off is not a magnet for lightning strikes and shouldn't be grounded to earth for protection. So if anyone is using any type of lightning rod arrangement in their observatory I would love to hear about it. Not sure where to place it exactly but am assuming I would need to run it a ground rod, like those by your meter base, as the end connection. Just shopping for some ideas here.
Thanks,
John
|
This thread is interesting to me especially since lightning split my neighbor's tree this past summer, which was less than 100 feet from my observatory shed (not in use, of course). Fortunately none of my equipment was affected in any way. The neighborhood was in the dark for a hour or so and I did need to reset my clocks inside, etc. My AC line comes underground from the garage to a GFCI outlet in the shed, into which I have plugged a wifi controlled outlet:
I always power this outlet down when I'm done for the night, and power it up whenever I'm starting an AP session. I also have two dinky 15A power strips from Home Depot coming out of that for running the Losmandy AC converter and all the other DC supplies for cameras, filter wheel, focuser and such.?
So I can't say I did the absolute right thing with my power arrangements, or I just got lucky. But perhaps just having the AC line interrupted by the remote controlled outlet was enough to save me. But just to reiterate what already has been said, lightning is a real threat and it can come close if not strike your property directly.
Sometimes I wonder if the steel roofing on my roll-off is not a magnet for lightning strikes and shouldn't be grounded to earth for protection. So if anyone is using any type of lightning rod arrangement in their observatory I would love to hear about it. Not sure where to place it exactly but am assuming I would need to run it a ground rod, like those by your meter base, as the end connection. Just shopping for some ideas here.
Thanks,
John
|
Re: Mount power supply...
Thanks, Derek, for the nice testimonial! (True you were not paid for that, but also true that I have your 12 inch Meade SCT in my living room, awaiting optical alignment tests...? my hostage!)
Actually, Derek is nicely mentioning that using a DC ammeter on the Gemini input power to sense motor current can help you with worm to ring gear adjustments.? If the worm and ring gear are too tight, you'll see the motor current increase when you slew.? The ammeter also helps you see if your system is badly unbalanced for the same reason.??
I forgot this added benefit to having an ammeter on the power supply, as once the gear mesh is well set up and bolted down, which I did years ago on my systems, I have not needed to ever muss with it.??
Happy new year, all, and thanks again, Derek!
Michael
Yes, I made several custom voltage booster units for people, who seem
happy with them
***
AWESOME!..
I use the ammeter to set my worm to ring gap.. It’s a perfect little device..
?
And
no, I have no financial incentive to say so.. I say so because I love mine and
could never live without..
?
Derek
?
?
Thanks for asking about my power booster units, Brian.
Yes, I made several custom voltage booster units for people, who seem
happy with them.? They are not a mass production product....just for
either Gemini1 or Gemini2.??
If anyone is interested, let let me know with a private email, and I'll
sell you the fee I have now, or make up a new batch if there is sufficient
interest.? ?I do have two G1 and two G2 units still at home ready to
go.? I use mine all the time on my CG11, G11, and GM8 / GM811 mounts, and
the design has been robust over many years of use.??
Here is a picture of one in use. The voltage is the top display, the
amps on the bottom.? You can see the Gemini1 it is running draws very
little current while tracking a balanced load.? If not tracking, either
parked or at terrestrial setting, the Gemini logic circuits take even less
power.??
The boost from variable input voltage about 12V, up to 17V amplifies
the motor torque by 17/12, about 45%.? This does reduce the issue of motor
stalling.?
Another key element of the voltage booster unit is that it protects the
output polarity going to the Gemini, no matter what you connect as the input
polarity.? It was intended for field use in the dark, so that in case you
plugged in a 12V battery backwards, or somehow mixed up the polarity, it would
always output the correct Gemini polarity.? I think that polarity errors
kill more mounts, Gemini or Synta, etc, easily shorting out the internal
circuits, than any other reason.??
Both types of unit also can take as input any cable having a 5.5/2.5 mm
male input connector.? Any DC polarity will work as the input, from 11V to
15V.? I provide a 5 amp 115V AC/12V DC "brick" for household
power.? ?The Gemini1 units have a dedicated G1 DIN output plug, and
the G2 units have a separate male to male cord that fits the
Gemini2.??
Very best, and happy holidays,
?
On Fri, Dec 27, 2019, 9:04 PM Brian Valente
<bvalente@...>
wrote:
>> ?I
use a power supply that I make for Gemini units.?
Michael just to clarify you offer your Gemini power
supplies for sale as well, right?
?
On Fri, Dec 27, 2019 at 8:45 PM Michael
Herman <mherman346@...> wrote:
Hi Deric,
I agree with you that we should protect our expensive Gemini
units.??
However, each system is driving a different load, do knowing how much
current your gear needs means you should try to measure that.? My data
follows...
If perfectly balanced, the only thing the motors are driving with
current are the torque coming from accelerating the load (scope, cameras, and
counterweights).??
The fuse protects using only a current sense (melting a resistive wire
from the current).? But the current used by a Gemini on the DC motors will
depend also on DC voltage (same power = current x voltage, so if V goes up, I
goes down).
My G11 units typically use under 1.5 amps and usually under 1.2
amps.? That peak current is only observed during a Park, where both motors
are slewing as fast as possible.? Normal Sidereal rate tracking uses under
0.4 amps.??
I drive my Gemini units at 17VDC.? If you are driving
at 12VDC, expect the current to be about 1.5 X as high as what I'm
reporting.? I think that if you use (try) a 3 amp fuse in line with the DC
power input,? it should be fine.? (I did have an old motor start to
go bad and it was drawing 1 amp DC over the other motor during fast slews.)
Definitely use a "surge protector" type of AC
power strip.? That is a must especially if you live near any possible
lightning.? Also unplug your Gemini DC input power when not using the
unit.? ?
The Gemini units are designed intelligently to prevent
damage to themselves or to the motors. If the Gemini senses a motor is drawing
too much DC power, it will show a "Stall" or maybe "Lags"
warning.??
Finally, I use a power supply that I make for Gemini
units.? That has a DC voltage and current monitor, as well as a voltage
pump that changes 12 VDC in to 17 VDC out that then goes to the Gemini.?
The current meter allows me to see anything abnormal: if my system is
unbalanced, or a motor is going awry, or my gears are getting jammed (worm to
ring gear used to be a problem if their spacing was mis-set).?
?
What type of fuse or breaker should I use for short and over current
protection? I have already been party to this before. My AVX mount went up in
smoke after it shorted out and the Lithium battery did a rapid discharge
through the mount. Celestron is replacing it, I dont want this to happen to the
G11. Is their pre built devices or a good schematic for a device? I guess That
I can build one but it has been awhile " a Heathkit Ham radio" Thank
you and Clear skies.
--
|
Re: Mount power supply...
Yes, I made several custom voltage booster units for people, who seem
happy with them
***
AWESOME!..
I use the ammeter to set my worm to ring gap.. It’s a perfect little device..
?
And
no, I have no financial incentive to say so.. I say so because I love mine and
could never live without..
?
Derek
?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Saturday, December 28, 2019
1:27 PM
To: [email protected]
Subject: Re: [Losmandy_users_io]
Mount power supply...
?
Thanks for asking about my power booster units, Brian.
Yes, I made several custom voltage booster units for people, who seem
happy with them.? They are not a mass production product....just for
either Gemini1 or Gemini2.??
If anyone is interested, let let me know with a private email, and I'll
sell you the fee I have now, or make up a new batch if there is sufficient
interest.? ?I do have two G1 and two G2 units still at home ready to
go.? I use mine all the time on my CG11, G11, and GM8 / GM811 mounts, and
the design has been robust over many years of use.??
Here is a picture of one in use. The voltage is the top display, the
amps on the bottom.? You can see the Gemini1 it is running draws very
little current while tracking a balanced load.? If not tracking, either
parked or at terrestrial setting, the Gemini logic circuits take even less
power.??
The boost from variable input voltage about 12V, up to 17V amplifies
the motor torque by 17/12, about 45%.? This does reduce the issue of motor
stalling.?
Another key element of the voltage booster unit is that it protects the
output polarity going to the Gemini, no matter what you connect as the input
polarity.? It was intended for field use in the dark, so that in case you
plugged in a 12V battery backwards, or somehow mixed up the polarity, it would
always output the correct Gemini polarity.? I think that polarity errors
kill more mounts, Gemini or Synta, etc, easily shorting out the internal
circuits, than any other reason.??
Both types of unit also can take as input any cable having a 5.5/2.5 mm
male input connector.? Any DC polarity will work as the input, from 11V to
15V.? I provide a 5 amp 115V AC/12V DC "brick" for household
power.? ?The Gemini1 units have a dedicated G1 DIN output plug, and
the G2 units have a separate male to male cord that fits the
Gemini2.??
Very best, and happy holidays,
?
On Fri, Dec 27, 2019, 9:04 PM Brian Valente
<bvalente@...>
wrote:
>> ?I
use a power supply that I make for Gemini units.?
Michael just to clarify you offer your Gemini power
supplies for sale as well, right?
?
On Fri, Dec 27, 2019 at 8:45 PM Michael
Herman <mherman346@...> wrote:
Hi Deric,
I agree with you that we should protect our expensive Gemini
units.??
However, each system is driving a different load, do knowing how much
current your gear needs means you should try to measure that.? My data
follows...
If perfectly balanced, the only thing the motors are driving with
current are the torque coming from accelerating the load (scope, cameras, and
counterweights).??
The fuse protects using only a current sense (melting a resistive wire
from the current).? But the current used by a Gemini on the DC motors will
depend also on DC voltage (same power = current x voltage, so if V goes up, I
goes down).
My G11 units typically use under 1.5 amps and usually under 1.2
amps.? That peak current is only observed during a Park, where both motors
are slewing as fast as possible.? Normal Sidereal rate tracking uses under
0.4 amps.??
I drive my Gemini units at 17VDC.? If you are driving
at 12VDC, expect the current to be about 1.5 X as high as what I'm
reporting.? I think that if you use (try) a 3 amp fuse in line with the DC
power input,? it should be fine.? (I did have an old motor start to
go bad and it was drawing 1 amp DC over the other motor during fast slews.)
Definitely use a "surge protector" type of AC
power strip.? That is a must especially if you live near any possible
lightning.? Also unplug your Gemini DC input power when not using the
unit.? ?
The Gemini units are designed intelligently to prevent
damage to themselves or to the motors. If the Gemini senses a motor is drawing
too much DC power, it will show a "Stall" or maybe "Lags"
warning.??
Finally, I use a power supply that I make for Gemini
units.? That has a DC voltage and current monitor, as well as a voltage
pump that changes 12 VDC in to 17 VDC out that then goes to the Gemini.?
The current meter allows me to see anything abnormal: if my system is
unbalanced, or a motor is going awry, or my gears are getting jammed (worm to
ring gear used to be a problem if their spacing was mis-set).?
?
What type of fuse or breaker should I use for short and over current
protection? I have already been party to this before. My AVX mount went up in
smoke after it shorted out and the Lithium battery did a rapid discharge
through the mount. Celestron is replacing it, I dont want this to happen to the
G11. Is their pre built devices or a good schematic for a device? I guess That
I can build one but it has been awhile " a Heathkit Ham radio" Thank
you and Clear skies.
--
|
Deric and greg
There is a way to be hooked up to AC power and protect your equipment from power surges,? including lightning strikes.? Aircraft use transorbs or surge protectors that are back to back zeners rated at 10 to 20 kw but only for about 10 microseconds.?? You connect them from your DC plus line to ground and they do not conduct until the zeners voltage is exceeded, say 15v.?? For the inline DC voltage,? there is a device whose name I can't remember that is made of conductive material in a non-conductive matrix.?? These devices are rated for a certain amount of current and should they exceed that current (say 3 amps)? they start to heat up and expand and their resistance increases,? limiting excessive current.? These devices suffer from one limitation that over time they degrade and should be replaced every three or four years.? With these modifications,? you can protect from surges.?? However,? a battery will not surge.?? Just a thought.
Chuck
On Saturday, December 28, 2019 Deric Caselli <[email protected]> wrote:
Thank you Greg, yes Lightning is a funny beast, I have had it strike the airplane and nothing and other times I got to land it fast.
Sent from my Boost Mobile Phone.
-------- Original message --------
From: Greg Crawford <rover53@...>
Date: 12/28/19 10:39 AM (GMT-06:00)
Subject: Re: [Losmandy_users_io] Mount power supply
Deric,
?
Even the fastest of fast blow fuses will not protect your mount in the event of a short. The purpose of the fuse is to protect the power supply and power lines. If current flows through these because of a short, the power
supply and cables heat up very quickly and can start a fire. Before any fuse has blown, damage to electronic components is already done.
?
In regard to a nearby lightning strike, simply unplugging everything from the power is not enough. Electrostatic and electromagnetic forces from a nearby strike can induce significant current in any long lead whether plugged
in or not. In anticipation of a nearby strike, long leads need to be disconnected from your mount as well. To this end, I have a single power cable coming to my mount pier, where the power divides into separately fused short cables to components on the mount.
At the first sound of thunder, *one* power lead needs to be disconnected. I also have a single signalling cable (Ethernet) that comes to a network switch on the mount and is disconnected at the sounder of thunder.
?
To prepare for a direct lightning strike, keep your funeral insurance up to date.
?
?
-Greg
?
?
?
From: [email protected] <[email protected]>
On Behalf Of Deric Caselli
Sent: Saturday, 28 December 2019 3:14 PM
To: [email protected]
Subject: [Losmandy_users_io] Mount power supply
?
What type of fuse or breaker should I use for short and over current protection? I have already been party to this before. My AVX mount went up in smoke after it shorted out and the Lithium battery did a rapid discharge through the mount.
Celestron is replacing it, I dont want this to happen to the G11. Is their pre built devices or a good schematic for a device? I guess That I can build one but it has been awhile " a Heathkit Ham radio" Thank you and Clear skies.
|
Ron
Michael Herman
Chip Louie