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well... heck.. I guess I need to slow down and take time to read all the links
in the future.. thanks Kelly!
Jarrett
On Tue, 23 Aug 2011
09:34:23 -0700 (PDT), Kelly Troyer wrote:
Jarret,
The "Power-IO" SSR's in my links
are all for DC switching...........Many different amp
capabilities to choose from.............
Kelly Troyer
"DYKE
DELTA JD2" (Eventually)
"13B ROTARY"_ Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50 Turbo
From:
Jarrett Johnson <hjjohnson@sasktel.net>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Tuesday, August 23, 2011 11:21
AM
Subject: [FlyRotary] Re: The Case for Solid state Relays
(SSR)
Thanks William.. I learned something new!! Now
I need to find some of these DC ssr's for
my cnc mill... the mechanical relays
are a pain in the long run due to well.. their mechanical nature. Gonna
have to research this some more. Is DC SSR's a new development from recent years? Every EE I've talked to about these in the last
3-4yrs has always spoke of them as AC
relays. Thanks! Jarrett On Tue, 23 Aug 2011 10:10:31 -0600,
William Wilson wrote:
Not all SSR's require AC current. A DC SSR is, effectively, a giant MOSFET transistor. There is, however, a difference
between a DC and AC SSR, so you need to
get the right kind. An AC SSR will
not switch DC current correctly, and a DC SSR will pass half of an AC wave. Ed's description of
the pros and cons is pretty accurate. SSRs also tolerate vibration much better, and as long as you
manage their heat, generally fail less often. The heat situation is
different, as it depends on the current flowing, vs. a conventional relay which
pretty much generates the same heat whenever it's closed based on how much
current you activate it with. Although we tend to think of solid state
electronics as being more delicate, SSRs
can be made as big and tough as you need. They are used in power
substations and industrial motor controllers, among other things. The only
real reason to use a mechanical relay is for cost, or possibly heat
reasons.
On Tue, Aug 23, 2011 at 9:25 AM, Jarrett
Johnson <hjjohnson@sasktel.net>
wrote:
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
www.innovention-tech.com
www.innovention-tech.com
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