Today's Message Index:
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1. 09:15 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury)
2. 10:37 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (user9253)
3. 10:53 AM - Product Review - Voltmeter (Robert L. Nuckolls, III)
4. 01:29 PM - Re: Product Review - Voltmeter (C&K)
5. 01:44 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury)
6. 02:42 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury)
7. 04:57 PM - Re: Z-31 questions (Robert L. Nuckolls, III)
8. 04:57 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (user9253)
9. 08:39 PM - Re: Re: Non-aero app: 120/240 AC through 24vdc switch? (Robert McCallum)
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Joe and Charlie,
The switch controls an electronic lamp ballast driving two 75W UVC producing. I
don't know if that is inductive or resistive load. Steady state amperage is
800ma
And found this white paper(excerpt) on electronic ballasts. :
"Design Considerations for Electronic Ballasts
Inrush currents at turn-on, produced from some electronic
ballasts can cause premature relay contact failures.
These inrush currents can be much higher than those
experienced with traditional tungsten or magnetic ballast
loads because many electronic ballasts employ large
energy storage capacitors. Such capacitors can charge up
to 400V for a 277V line voltage, and will briefly draw high
current from the line to achieve this voltage.
As mentioned above, these typically short inrush currents
can climb as high as 100 times the nominal operating
levels.
.
Type of Load
Inrush Current vs. Steady State Current
Incandescent Lamp
10 - 15x
Fluorescent or HID Lamp with Magnetic Ballast
Up to 15x
Electronic Ballast (Capacitive Load)
Up to 100x
The inrush current magnitude and duration depends upon
the value of the capacitance (measured in F), along with
circuit and power distribution network impedances. This
current may weld relay contacts and other switching
devices or possibly fuse semiconductors. "
Below is an excellent, graphic explanation of how fluorescent lamps work. It describes
a building magnetic field during start up that is collapsed to produce
an inductive kick. Is that the smoking gun?
http://www.edisontechcenter.org/Fluorescent.html
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472092#472092
Message 2
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Switches can bounce when closing. If the inrush current is 80 amps (100 times
normal) then that explains why the 5 amp switch is prematurely failing. A switch
rated at 15 or 20 amps would last longer. A double pole switch might help
also. Connect the two halves of the switch in parallel. That will divide the
current between the two sets of contacts. While the switch is bouncing, maybe
one half will be closed while the other half is closed. Or maybe not. Anyway,
a bigger double pole switch should last longer.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472097#472097
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Subject: | Product Review - Voltmeter |
A few weeks back we had some discussion about
digital voltmeters. I opined that the 'net
sources for such devices were legion but
expressed some warm fuzzies about easy to
mount, easy to wire, good performance
and, of course, cheap!
Found this guy on eBay
http://tinyurl.com/ycrez6hh
Ordered in a couple to play with. They
seem meet all the qualifications for
warm fuzzy status.
Both articles were within 0.1 volt of
true at 14.2 volts. They mount in ROUND
holes and wire in with 1/4" fast-ons.
At $8 each, they're not expensive. The only
potential down side is sun-light viewability.
Bob . . .
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Subject: | Re: Product Review - Voltmeter |
Yes I have to shield those with my hand to read them on outdoor
equipment but they seem durable and are available even cheaper and with
free delivery if you don't mind the wait from overseas.
Ken
On 23/08/2017 1:52 PM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> A few weeks back we had some discussion about
> digital voltmeters. I opined that the 'net
> sources for such devices were legion but
> expressed some warm fuzzies about easy to
> mount, easy to wire, good performance
> and, of course, cheap!
>
>
> Found this guy on eBay
>
> http://tinyurl.com/ycrez6hh
>
> Ordered in a couple to play with. They
> seem meet all the qualifications for
> warm fuzzy status.
>
> Both articles were within 0.1 volt of
> true at 14.2 volts. They mount in ROUND
> holes and wire in with 1/4" fast-ons.
>
> At $8 each, they're not expensive. The only
> potential down side is sun-light viewability.
>
>
> Bob . . .
>
>
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Joe,
Would installing a flyback diode across the Line (diode banded end) and Load terminals
on the switch snub the inductive spike?
Aesthetically, I'm partial to the switch I'm using. It may have a DPDT cousin,
but not sure.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472110#472110
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Joe,
Your idea re splitting the load on a DBDT is the right direction for a po' boy
solution. I looked at Crydom Zero-Cross relays for my app but they're pretty expensive.
Going to look at hi amp latching relays too.
This from Crydom, mfgr of Solid State Relays re Zero-Cross relays:
Electronic Ballasts typcially do not present an inductive characteristic, so an
inductive spike at turn-off is not the issue n your application. Rather they
are more like "switching" power supplies and present more of a capacitive characteristic,
particularly on power up. The inrush current at turn-on can be
many times the normal load current for a few milliseconds, especially if the
power happens to be applied at the peak of the AC sine wave. That is what is
likely causing your switch to stick on when you try to turn it off.
You're thought of using a zero-cross SSR is actually the way to go, but not for
the turn-off. Rather it ensures that the AC line power is connected at the
zero-cross point of the AC wave, minimizing the inrush current to the (essentially)
"discharged" capacitive circuitry of the electronic ballast.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472112#472112
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Subject: | Re: Z-31 questions |
At 09:12 PM 8/20/2017, you wrote:
>Whoa, Bob, that's one heckuva story! Thanks for explaining. I had
>thought that the ground power jacks in my old Cherokees had been
>hardwired to the bus but, not having the wiring diagrams handy, I
>did not know for sure.
Everybody has their own ideas. I looked through some early
Cessna 100 series drawings and found for the
most part, ground service was the 3-terminal,
AN2552 receptacle with only the two fat terminals
utilized to hook ground power right to the battery.
C177 1968-75 moved ground service power to the bus
with diode in pilot terminal to guard against
reversed polarity on ground cart.
In the C310 circa 1974, the ground power was AN2552
with a ground power relay energized from the pilot
terminal and tied right to the bus.
1998 A36 uses AN2552 with diode in pilot terminal
for reverse polarity protection. External power
goes right to the battery.
It would be interesting to know the narrative for
design decisions in each case.
It was kind a deja-vu reading through the electrical
system narratives on the single engine Cessnas.
Can't be absolutely sure after all these years
but I wrote a lot of that stuff back then and
the writing style seems very familar.
Bob . . .
Message 8
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Since the problem is inrush current to charge a capacitor, not inductive generated
current, a diode is not going to help. I see two possible solutions: limit
the inrush current or use a switching device that can handle the current. The
switching device can be a bigger switch or a mechanical relay or a solid state
relay.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472113#472113
Message 9
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Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
The only function of a diode would be to explode when connected in either
direction across the 240VAC
Bob McC
>
> ---------- Original Message ----------
> From: user9253 <fransew@gmail.com>
> Date: August 23, 2017 at 7:56 PM
>
>
>
> Since the problem is inrush current to charge a capacitor, not inductive
> generated current, a diode is not going to help. I see two possible solutions:
> limit the inrush current or use a switching device that can handle the
> current. The switching device can be a bigger switch or a mechanical relay or
> a solid state relay.
>
> --------
> Joe Gores
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=472113#472113
>
>
>
>
>
>
>
>
>
>
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