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Thanks Andy for that solenoid relay link. But after
talking to Paul, I have come to realize that perhaps I do not even need a relay
but instead need
a pulse width modulator. I can read some things on
a wiring schematic, but some symbols I do not understand. I am very lightly
educated when it comes
to designing and hooking up things electrical. I
can do some, but I am pretty much a complete novice in that regard. I just
barely grasp the difference between
amps and volts! I feel so ignorant when trying to
design, build and hook up THIS part of my sub project. I realize I need more
knowledge in this regard, but I did
not want to have to become an electrician just to
finish my sub. When I read articles about how ROV builders design and build
their own electrical system I find
my brain switches off and what I am reading becomes
mush and martian in my mind. My ignorance on this is soooo frustrating! I
am very good at the mechanical end though.
So even though it sounds like what I need is a pulse width modulator, I am wondering if I need a
solenoid relay of some kind to turn that on? Does the PWM not
need
a relay solenoid? I have no idea what a pulse
width modulator looks like. Is it a circuit
board? Or is it something in a sealed housing that looks like a
solenoid?
Are there some types more suited to a sub than
other types?
I know what I want to do. I want the motor to run
at a variable speed and for my speed control to be waterproof. I just don't know
exactly what parts to use. If I knew
what parts to use I might be able to figure out how
to waterproof the switch part that controls the variable speed actuator once I
knew what it looked like. I guess I could
not be lucky enough to find a water pressure
sealed pulse width modulator with a waterproof trigger, knob or whatever
type of actuator it uses to work it. But the more
questions you and the other fellows help me
understand, the closer I am coming to understanding what I need. It is a long
educational process. Thanks for your help.
Bill.
----- Original Message -----
Sent: Monday, October 24, 2005 4:04
PM
Subject: Re: Re: [PSUBS-MAILIST] RimTec
Magnetic Clutches
How about
http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/partDetail.jsp;jsessionid=5ZI5JED0CCQFOCXFEOFCFFYK2URYWIV1?SKU=02F1135&N=0
100Amp
400A peek
18 volts dc
Cost $50 + shipping
They also have other
ratings and electronic relays ?no mechanical
contacts?
Andy
From: Paul Kreemer <paulkreemer@gmail.com>
Date:
2005/10/24 Mon PM 12:12:48 CDT
To: personal_submersibles@psubs.org
Subject:
Re: [PSUBS-MAILIST] RimTec Magnetic Clutches
Bill,
I'd say a
couple of reasons for using relays are to minimize the size of
your control
switches and shorten the length of your high current electrical
lines. A
bonus reason would be to keep that high current away from the
operator!
Here's a Minnkota FAQ page that helps you estimate wire size or
gauge for
their motors.
http://www.minnkotamotors.com/support/faq.asp
They
work through a short example of 20ft of wire and a 37amp draw and
recommend
a 6awg wire which is about a sixth of an inch in diameter. So as
your
amperage and wire sizes increase I think you start to look more and
more at
controlling it remotely with a relay.
But like you say, you have a
different situation where you don't want just
an on-off control for your
motors. A relay, as I understand it, is just an
on-off remote switch. It
sounds like you want a pulse width modulation motor
controller to get good
smooth control and more efficiency out of your
battery/motor combo.
Minnkota calls it their Maximizer and here's another
link that discusses a
custom built PWM control for a robot:
http://www.robotwars.ecs.soton.ac.uk/file/pwm_motor_control.html
But
after all these notes, I have no comments on immersing the whole thing
in a
wet sub. :-)
Paul
On 10/24/05, Akins
<lakins1@tampabay.rr.com>
wrote:
>
> Hi Byron.
> I have a completely wet, dual
cockpits, wetsub Byron, it isn't ambient. I
> already have my minnkota
mounted to the hull using
> a motor mount I made from an old stop
sign I cut and bent. If you would
> like to see my sub's set up you have
to belong to yahoo because the
> pictures are at my yahoo group
site at this link....
> http://groups.yahoo.com/group/The_Warbird_Recovery_Team/
once you get
> there and sign in to yahoo,
> just click on
the "photos" section on the left of the page in the yellow
> column and
the album is the first one called "my two person wetsub".
> Thanks
for the info on the hydraulic thrusters but I've already got my
>
minnkota motor mounted. I just need to decide whether to oil or air
equalize
> it.
> Right now I am on the hunt for magnetic
variable speed reed switches to
> activate the relay to the motor. One
thing I am wondering
> about is WHY do I even need a relay
solenoid? Why couldn't I just wire it
> direct from the battery to the
switch and then to the motor? Does it have
> something to do with
too high a voltage or amps going thru the switch and
> that is not good
or something like that? I'm not real good at the
> electrical
stuff. Also I am wondering how a magnetic switch could
> possibly be
variable if it just clicked in a solenoid relay?
> As you
suggested I have talked to some of the ROV guys. I am a member of
> the
yahoo group called "Robotrov" at this link......
> http://groups.yahoo.com/group/robotrov/?yguid=204005530
which is a group for
> robotics and ROV's. Unfortunately even though one
of them
> responded to my post at the group, his link and info did
not lead me to
> switches I need. His link sent me to a site with
electronic circuit boards
> that would be used inside a sealed
unit in a ROV for instance. I need
> something small and compact that I
can use either in the cockpit or attached
> to the joystick in my
wetsub. I thought about using a mercury switch and
> rigging it so that
I could just turn it to make contact. If the attitude
> of
my
> sub was always horizontal that wouldn't be a problem but if
things got a
> bit murky underwater and the sub was not horizontal and I
got disoriented
> the mercury
> switch might make contact
when I did not want it to. So I decided to not
> use it and to continue
to try and locate the magnetic reed switches.
> Ideally I would
like to find a magnetic reed switch that was already
> waterproof and
sealed, but if I can't find one waterproofed, I could rig it
> up
in
> a real small piece of pvc pipe I guess.
>
Bill.
>
> ----- Original Message -----
> *From:* Byron
Selman <byron@flyingfishfoto.com>
>
*To:* personal_submersibles@psubs.org
>
*Sent:* Monday, October 24, 2005 5:57 AM
> *Subject:* Re:
[PSUBS-MAILIST] RimTec Magnetic Clutches
>
> Have you thought of
talking to some of the thruster guys? All of the ROV's
> out there (
except el-cheapo cheapo toys) have some external thrusters. They
> are
almost always electric. I worked for Deep Sea Systems, Inc. as a
>
consultant for about six months, and have been friends with Chris
Nicholson
> (owner/pres) for twenty years. If you can catch Chris's
imagination, he can
> be a world of help. He builds and sells electric
thrusters.
> Innovatum is another group.
> Slightly
different subject, but I gotta ask:
> Have you considered
hydraulic thruster motors? You keep the pump inside
> the sub and use
through-hull fittings to run hydraulic motors outside.
> Putting a piece
of pipe fitting through a sub wall for hydraulic hoses is
> lots easier
than either electric feed-throughs or a shaftdrive with a
> stuffing
gland.
> Or bite the bullet, use the stuffing gland or o-rings on
the spinning
> motor shaft, design for drips and put a small bilge pump
under it venting
> overboard. Need a good check valve and a stout pump
for ambient, but its
>
doable.
>
>
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