|
|
Kelly... first things.. I'm no 'EE'... just have used these
before. Bottom line is they are only good for switching AC current. To
turn on or off they need a zero crossing voltage [when the AC sinoidal wave goes
from + to - or VS ] since DC doesn't have that same waveform [or
at least not a zero crossing wave] they don't work with DC. You are pretty much
stuck w/ a smaller 'ice cube' type mechanical relay for anything
DC. The other issue with these SSR's [if you should have
a used for them in the AC side of things] is they can and often do, fail
'closed' such that you cannot turn off what ever it is that your
switching. I've had this happen a couple times [I used these on my cnc
mill] and it can be.... a bit
scary.
Fwiw
Jarrett
ps- I think my summer
flying schedule is starting to wind down to the place where I could actually get
some laser scanning done... I've been home a grand total of less than 1/2 the
weekends since the start of spring due to flying. I'm not complaining but it
doesn't make my other projects run too smoothly! Currently have my mill
all torn appart while I upgrade some electronic's and servo drives/motors on
it. If I was ever to look like the mad scientist, now would be the
time. Complete w/ hair sticking out every which way, wires sparking and
the odd release of the 'magic' smoke.. :D [ok.. sparking and smoke hasn't
happened yet but... ya just never know when it might!!]
On Tue,
23 Aug 2011 08:12:00 -0700 (PDT), Kelly Troyer wrote:
Ed & Group,
I brought up the question of possible use of Solid State Relays (SSR) to replace the
electro-mechanical contactors
most of us use in our flying electrical systems but I need
to depend on the
smarter "EE" (Electronic Engineer) types of our
group to tell me if this
would be a good
idea...........To the electrically challenged (Me) they look
good.......Light
weight, small, low operating
voltage (down to 3 volts), low current draw, low voltage drop,
high surge amp survival, etc..............They do
require a heat sink to utilize their maximum
amp capibility............They do cost considerably more than
the contactors but do not wear
or degrade and if used within
their limits will probably last longer than me...........
I have included a link to the company that made the SSR that I have purchased on
blind faith that it would
serve as my master relay........It is a "Power-IO" model HDD-06V75
which has been upgraded since
my purchase by the HDD-06V75E which will operate
at
a lower voltage,lower drop and lower current
draw............Both versions will stay operated
at down to 1
volt..........Looking forward for a critique of this idea pro or
con...............<:)
Kelly Troyer
"DYKE DELTA JD2" (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo
From: Ed Anderson
<eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Monday, August 22, 2011 8:37
PM
Subject: [FlyRotary] Re: One Battery - Two Battery was
[FlyRotary] Re: Batteries
Yes, Kelly, back a few years ago, I did look into them. The models
I looked at had some strange characteristics that I didn't fully understand (and
didn't take the time to), so I passed. Besides in my case 3 volts would
taken me a bit closer to the airport before the relay let loose, but would have
done nothing to provide a solution for my problem - head up and locked
{:>).
I'm still waiting for the 16X before I start anything major new on
my aircraft - hope won't have to wait too much longer.
Ed
Sent: Monday, August 22, 2011 8:48 PM
Subject: [FlyRotary] One Battery - Two Battery was [FlyRotary] Re:
Batteries
Ed,
Have you ever considered "Solid State Relays" for contactors..........The DC versions will operate
at down to 3 volts and draw a lot less amperage than the electro mechanical versions...........
Kelly Troyer
"DYKE DELTA
JD2" (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo
From: Ed Anderson
<eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Monday, August 22, 2011 4:12
PM
Subject: [FlyRotary] Re: One Battery - Two Battery was
[FlyRotary] Re: Batteries
Yes, I have also found my GPS can get
confused - especially in the inner city (where you need it the most). So
can my brain when tired and/or under pressure - the old brain can do some
not so funny things.
I left out one important fact about why the switch in the wrong
position caused the engine out landing.
When I had designed that switch in to disengage the battery from
the alternator (in case of an over voltage condition), the switch not only
removed the battery from the alternator line - but also all my critical systems
(fuel, ignition) which were "smartly" tied to my battery bus. So even
though the alternator was putting out plenty of power - even if the battery had
been stone, cold dead, it could have powered all of those power hungry
devices. But having all of that on the battery bus and the battery bus
disconnected from alternator - that pulled that battery down even
quicker.
So the fact that it last 45 minutes including cranking drain for
engine start says a lot about the Odyssey PC 680.
Sent: Monday, August 22, 2011 2:44 PM
Subject: [FlyRotary] Re: One Battery - Two Battery was [FlyRotary]
Re: Batteries
Ed,
Thanks. I remembered you discussing it, but now it makes
sense why you didn't see the low voltage warning from the
battery.
I know that 'fixation' issue, all to well. On business
I'm always running between meetings in new cities, and got to the point where I
really loved (& blindly trusted) my Garmin GPS. Well in Phoenix there was an "W.Shangri-La Rd" vs "E. Shangri-La Rd". Van full
of hungry people wanting dinner, and I kept following the GPS... despite a passenger in the back telling me I was
taking the wrong route. I just figured the GPS
was smarter as it rcd traffic information, and would
get us there faster! Had I thought to look at a map, or listened the my
passenger, but with a load of people, 5pm traffic, and overload after a day in
the sun.... my brain wasn't working. Live and learn!
Tom
From: Ed Anderson
<eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Monday, August 22, 2011 12:27
PM
Subject: [FlyRotary] One Battery - Two Battery was [FlyRotary]
Re: Batteries
Actually, Tom, in that particular incident - a second battery
would have only enabled me to fly too far away from the only safe airport
to make a return and dead stick into. IF I had realized the root
cause (a switch accidently put in the wrong
position) then one battery would have worked just as well as two {:>).
Having said that, I certainly would not try to get anyone to change
their mind about using two batteries. . Some folks would not feel
comfortable even with two batteries - but, would add a second alternator,
etc. So, you have to think through your scenarios, the risk involved
and your personal risk tolerance. Yes, Bob now has several good electrical
designs - for just about any kind of power system you could come up with.
Back in 1992, I had never heard of Aeroelectric or
Bob.
But, since my previous engine out almost 5 years previous had been
fuel related and the engine was sputtering in a similar manner - my diagnostic
side of the brain got locked in to searching for a fuel problem
(again) - but even switching tanks did no good - because, this time the "fuel
problem" was a decreasing electrical power. This incident clearly pointed
out the need for an emergency check list that involved checking both fuel AND
electrical systems. Coming up with one in your head with the engine
sputtering is not recommended {:>)
Contributing factors were two early design decisions that on
hindsight revealed shortcomings.
One was an electrical system design that permitted my voltmeter to
keep showing me the 13.8 volts being generated by the alternator while the
battery voltage was steadly decreasing. Yes, I
had a low-voltage light right in front of my eyes - but, it was wired into the
alternator powered circuit - so never showed low voltage because the alternator
voltage was fine - up to the point the relay released.
Now, had it occurred to me I might
have an electrical problem - and switched the volt meter to the battery (instead
of alternator) AND had thought to observe it, I would have seen the battery
voltage decreasing and that MIGHT have got me looking for an electrical problem
rather than a fuel problem. But, when you get your head locked into one
focus - and you truly have mental blinders on, NOT GOOD!
The second design deficiency was that the relay holding the
alternator On-Line was provided current solely by the battery - so guess
what happened when the battery juice got too low to hold the alternator
on-line? Right "CLACK!!!!!" followed immediately by all lights,
radios, LEDS, panel going dark. It gets even
lonelier when the lights go out. Had I two batteries - all of this would
have happened further from my emergency airport in Salem, Al.
No, I have not added the second battery back in after the incident
- because in my particular case, the incident had nothing to do with one
battery vs two battery - it was a case of a mis-positioned switch which the pilot never recognized was
the cause - until later on the ground, cleaning off the seat cushion. The
corrective action was to put a switch guard over that particular switch so it
could NOT be accidently toggled incorrectly AND
rewire my relay so that a dead battery would no longer prevent my system from
using the power of a perfectly good alternator.
But, this is just my perspective - provided for anyone to glean
what they wish from it - if that is two batteries, two alternators or what have
you, then as always in this hobby, that is up to individual
choice.
Just don't make the same dumb mistakes I made, we know how
those turned out - advance the state of the art and make NEW mistakes
{:>)
Oh, yes, the switch I accidently
activated (I think I probably hit it with my foot getting out of the aircraft at
the previous refueling stop) was one that enabled me to detach my battery from
the alternator. The thought at design time was that if my alternator
ran-away with high voltage, I could isolate the battery from the alternator
thereby preventing the battery from overheating/boiling and get to an emergency
landing on battery power alone. Seemed like a good idea at the
time.
Ed
Sent: Monday, August 22, 2011 12:35 PM
Subject: [FlyRotary] Re: Batteries
Joe,
Which Bob Knuckles system? Z19?
I realize Ed is happy with one battery, but I like two
batteries. The THUNK of relays all popping open and the
realization of "I turned off the alternator, and voltage dropped
way too low.... followed with LAND NOW!" would have convinced Ed to
have put the second battery back in! It sure got my attention on why two
batteries is a good thing!(Great Story, but I'll let Ed tell
it!)
So two batteries, and a BIG RED LIGHT with "low voltage" will go on
my panel.
I did the spread sheet with 17AH batteries and
flying time. Add in Night, and no place to easily land.... two
batties seem like a good trade off. My biggest
shock was the FORD style contactor
needed 1Amp draw to remain closed. Shutting down non
essential, but leaving contactors, PDF, ECU and coils.... System draw is around
15 Amps. 17AH implies you'd have an hour, but at 15Amp draw... more
like 30-40 minutes, hence two batteries as 1 hour flying time makes
finding a landing strip a little easier.
Tom
From: Ed Anderson
<eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Monday, August 22, 2011 11:20
AM
Subject: [FlyRotary] Re: Batteries
Joe, I
started out using two Concord 25AH RGB each weighing
22 lbs for a total of over 44 lbs of battery (some joked I could get home by
using the start to crank the prop {:>)) ! I then transition to two
Odyssey PC-680 17AH batteries each weighing 14 lbs for a total of 28 lbs.
Then after 6 years of flying with two batteries and never using the second one -
except to help crank on a cold morning, I removed one of them. Have now
been flying for over 4-5 years with one Odyssey 14lbs. I swap it out every
two
years. Ed -------------------------------------------------- From:
< jskmberki@windstream.net> Sent:
Monday, August 22, 2011 11:59 AM To: "Rotary motors in aircraft" < flyrotary@lancaironline.net> Subject:
[FlyRotary] Batteries > What size an type of batteries are required
for the rotary? I am leaning toward using 2 batteries and use Bob Nuckols system. Thanks for any help. >
> Joe Berki> Limo EZ> > -- > Homepage: http://www.flyrotary.com/>
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
-- Homepage: http://www.flyrotary.com/Archive
and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
www.innovention-tech.com
|
|