[PSUBS-MAILIST] Dive report: Snoopy at Seneca
via Personal_Submersibles
personal_submersibles at psubs.org
Sun Jun 7 17:16:24 EDT 2015
The speed contoler is modulating the current and voltage from the battery by chopping it into pulses, very fast pulses in the 20 khz range. Basically it is a transmitter, so we need to filter the output (a bandpass filter design) to snub the transient voltages and harmonics generated by the oscillating curcit.
There are several different ways to achieve this, most power suppplies do this by using a bridge rectifier and a filtering capacitor ( in the 100,000 mfd + range). Using an o'scope and spectrum analyzer would reveal the waveform (most likely a squre wave) and the varrious harmonics produced by the curcit. Based on these frequencies and voltages one can calulate the capacitance and inductance needed to filter the unwanted output (thus tuned inductors).
Hope this helps..
Keith T
Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Thanks Ken,Keith T mentioned the tuned inductor.http://en.wikipedia.org/wiki/LC_circuit
>I am not familiar with it.In the article I posted it mentioned these sine current controllers.http://www.sinusleistungssteller.de/en_SinusStromRegelung.html
>These have been tested to 70 meters without capacitors, but very expensive.Alan
> From: Ken Martindale via Personal_Submersibles <personal_submersibles at psubs.org>
> To: 'Personal Submersibles General Discussion' <personal_submersibles at psubs.org>
> Sent: Monday, June 8, 2015 3:14 AM
> Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>
>What's a tuned inductor?
>
>Ken Martindale
>
>-----Original Message-----
>From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of via Personal_Submersibles
>Sent: Saturday, June 06, 2015 9:33 PM
>To: Personal Submersibles General Discussion
>Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>
>Also tuned inductors will help disipate the spikes caused by the controlers.
>
>Keith T
>
>Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>>Thanks Ken,I was nearly going to ask you to comment in my post.Is there
>>an alternative to capacitors or to the electrolitic capacitors usually
>>used?I was looking at this
>>option.http://www.dialelectrolux.ru/files/file/electronicon/e61-data-ch
>>arts-engl-deut.pdf
>>Alan
>> From: Ken Martindale via Personal_Submersibles
>><personal_submersibles at psubs.org>
>> To: 'Personal Submersibles General Discussion'
>><personal_submersibles at psubs.org>
>> Sent: Sunday, June 7, 2015 12:19 PM
>> Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>>
>>#yiv9053454032 #yiv9053454032 -- _filtered #yiv9053454032
>>{font-family:Helvetica;panose-1:2 11 6 4 2 2 2 2 2 4;} _filtered #yiv9053454032 {panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv9053454032 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} _filtered #yiv9053454032 {font-family:Georgia;panose-1:2 4 5 2 5 4 5 2 3 3;}#yiv9053454032 #yiv9053454032 p.yiv9053454032MsoNormal, #yiv9053454032 li.yiv9053454032MsoNormal, #yiv9053454032 div.yiv9053454032MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;}#yiv9053454032 a:link, #yiv9053454032 span.yiv9053454032MsoHyperlink {color:blue;text-decoration:underline;}#yiv9053454032 a:visited, #yiv9053454032 span.yiv9053454032MsoHyperlinkFollowed {color:purple;text-decoration:underline;}#yiv9053454032 span.yiv9053454032link-enhancr-element {}#yiv9053454032 span.yiv9053454032link-enhancr-view-on-domain {}#yiv9053454032 span.yiv9053454032EmailStyle19 {color:#1F497D;}#yiv9053454032 .yiv9053454032MsoChpDefault {font-size:10.0pt;} _filtered #yiv9053454032 {margin:1.0in 1.0in 1.0in 1.0in;!
> }#yiv9053454032 div.yiv9053454032WordSection1 {}#yiv9053454032 Adding extra capacitors helps reduce the magnitude of the inductive voltage spikes. Ken Martindale.
>>
>>From: Personal_Submersibles
>>[mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan
>>James via Personal_Submersibles
>>Sent: Saturday, June 06, 2015 6:48 PM
>>To: Personal Submersibles General Discussion
>>Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca Thanks for
>>the report Alec, great stuff.re the motor controllers; I've been
>>reading a bit about inductance in long wire runs from battery tomotor
>>controllers, that harms the capacitors on the controllers.This could be
>>a problem that is unique to our submarines & not an issue with things
>>like golf carts& wheel chairs.My reading has been mainly about BLDC
>>motor controllers but asume PWM controllers for brushedmotors would be
>>similar. Because of the rapid switching on & off of the power to the
>>motor, there is acurrent surge hitting the capacitors & the longer the
>>wire run, the more the power in the surge.A water analogy would be
>>turning a valve off suddenly as washing machines do, sometimes witha
>>"thunk" sound & a rattle of the pipes.Hugh mentioned he had problems
>>with his Curtis BLDC motor controllers.Attached is the problem &
>>solution, which is to put capacitors in parrallel along the battery
>>wire; however there must be a better way.Regards Alantoo long battery
>>wires will kill ESC over time: precautions, solutions & workarounds -
>>RC Groups
>>| |
>>| | | | | | | |
>>| too long battery wires will kill ESC over time: precauti...Careful!
>>| too long battery wires will kill ESC over time: precautions,
>>| solutions & workarounds Electric Plane Talk | | View on
>>| www.rcgroups.com | Preview by Yahoo | |
>>| |
>>| | | | | | | | |
>>
>> From: hank pronk via Personal_Submersibles
>><personal_submersibles at psubs.org>
>>To: Personal Submersibles General Discussion
>><personal_submersibles at psubs.org>
>>Sent: Sunday, June 7, 2015 12:20 AM
>>Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca Alec, I
>>don't know what type of speed controller you are using, but I like and use Curtis golf cart controllers. They are rated for huge amperage and seem bullet proof. I have an extra 36V controller I can send you to try out. They use a 10 OHM potentiometer for the throttle. They also have a battery protection mode, a sort of get home conservation mode.
>>I labeled the motor in Gamma for a jumper cable, so that I can get home without the controller. As you said it is electronic and it will fail.
>>If you want the controller send your address of list.
>>Hank
>>--------------------------------------------
>>On Fri, 6/5/15, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>Subject: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
>>To: "Personal Submersibles General Discussion"
>><personal_submersibles at psubs.org>
>>Received: Friday, June 5, 2015, 6:16 PM
>>
>>Hello friends,
>>I just got back from a dive trip to Seneca with Dan Lance and thought
>>I'd share how it went. This was supposed to be a two sub trip with
>>Scott Waters, but unfortunately a business emergency intervened and it
>>ended up being just Snoopy.
>>On the way up the weather was terrible, with driving rain so heavy I
>>could barely see the lines on the road. It had been raining heavily for
>>several days previously. Three times there were emergency announcements
>>about floods, large hail, and damaging winds, and the closer I got the
>>harder it rained. The problem with all that rain is that in your
>>typical lake, the runoff ruins visibility for weeks. That is what
>>happened last year when Trustworthy and Snoopy rendezvoused at
>>Summersville Lake, and it looked very much like this would be a repeat.
>>I'm happy to say Seneca must be rain-proof, because the deluge only
>>reduced the visibility in the top fifty feet or so, and even those were
>>clearer than most lakes.
>>Here's a few things we learned:
>>1) Of props and shroudsThe stern
>>thruster speed control was dead on arrival, although I had tested it
>>successfully before leaving. I opened up the enclosure, pressed down
>>all the spade connectors, and found it now worked - so attributed the
>>issue to road bumps.
>>However, it died within a minute on the first dive. I had a spare speed
>>controller, so switched it out.
>>The replacement died within five minutes on the second dive. This time
>>at least the cause was obvious, the prop was jammed by weeds. The
>>current Minnkota props have a little twist at the end of the blades,
>>and Snoopy's shroud is made with almost no clearance. The little twist
>>to the blade tip causes any object coming between prop and shroud to
>>jam tight, and had already smoked one controller during the convention
>>in the Keys. I'm going to put the prop on the lathe and take off the
>>tips to eliminate the pinching effect and to reduce the amperage draw a
>>little so the motor goes lighter on the speed controller. By the way,
>>the speed controller was protected by a fuse rated a little below the
>>controller spec current draw, so perhaps those specs are optimistic.
>>Anyway, as a result of the double failure all of our dives were done on
>>just the side thrusters because I was out of spare speed controllers.
>>Lesson for next sub: Design the electrical system with a controller
>>bypass, so I can operate thrusters with simple on/off switches if a
>>speed controller fails. They're electronic, they will fail.
>>2) Of air bubbles in compensation oil
>>Snoopy is now routinely diving deep (250 ft) and this has showed up a
>>puzzling issue with the thrusters. They were feeble during dives, one
>>died altogether on one dive, and they kept coming up leaking oil. At
>>first we thought the seals were failing, perhaps due to some chemical
>>incompatibility. We found suitable seals at an Amish farm supply store
>>that sold things like tractor spares (viva trolling motor simplicity!)
>>When I disconnected the bladder hose I got quite well sprayed with oil.
>>The motor turned out to be pressurized.
>>Previously, I thought if one had a small quantity of air left in the
>>system it would not be an issue so long as the compression volume of
>>that air could be handled by the flexibility of the hose (aka
>>compensation bladder.) Wrong. I now think what happens is that if the
>>dive exceeds the pressure rating of the shaft seal and there is a
>>bubble of any size, you will get water added to the oil and the bubble
>>stores the pressure. Upon surfacing, the bubble squeezes oil and water
>>back out until the pressure in the motor falls to the "cracking
>>pressure" of the seal. Thus, you get an oil leak even though the seals
>>are fine. Lesson: Zero tolerance with oil bubbles, even a small bubble
>>is unacceptable if you are diving deep. I'm going to put set screws on
>>the motor caps so I can get rid of the bubbles more easily.
>>3) An easy way to add
>>buoyancySnoopy's buoyancy is adjusted by placing trawl floats in PVC
>>tubes. On one occasion, the oncoming passenger's weight required the
>>addition of just one float (i.e. the new guy weighed seven pounds more
>>than the one getting off). The support diver wasn't suited up and the
>>water was 42 degrees, so I just pushed a float under the lip of the
>>forward MBT. It worked like a charm, and the float even stayed in place
>>throughout the tow back to the ramp. Lesson: You can easily add a few
>>floats for buoyancy on a standard K sub, no special tubes required.
>>Most of our dives were along a very steep incline, not quite a wall but
>>more like a series of ledges and very steep slopes. Between the steep
>>terrain and the good visibility, the K250 dome for once offered a
>>really good view. We typically made our way down the slopes using very
>>slightly negative buoyancy, trailing the back corner of a skid on the
>>slope. Looking aft, you could see a zigzagging trail of silt hanging
>>motionless in the water and tracing our path. The sub compresses with
>>depth, so slightly positive buoyancy at the surface turned into
>>slightly negative at depth, but we're speaking of just a couple of
>>pounds and not anything that caused difficulty. In fact at one point we
>>stopped dead in the water four or five feet above a flat bottom for
>>about five minutes, just waiting for a pre-arranged touch-point call on
>>comms. The sub didn't rise or sink an inch, she just hung there
>>completely immobile for five minutes. At about 140 feet the visibility
>>would improve significantly, and the water changed from green to blue.
>>It looked like ocean instead of lake water.
>>I'll post a video, but that'll take a few days to put together. The
>>only "incidents" we had were a cold bath we took when we closed the
>>hatch over a corner of the crew's shirt, and when we got hooked on a
>>log at 220 feet - fortunately reversing got us right off it.
>>
>>Best,
>>Alec
>>
>>
>>
>>
>>
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