Model Boat Mayhem
Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: rem2007 on August 23, 2008, 10:35:28 am
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There are 2 reasons why I am having difficulty sleeping. The first pictures shows the main culprit to our dilemma. The second is preventing me from doing final ballasting and sea trials. The problem is that when I screw the motor into the motor mount I get just alot of noise and no revolutions forward or reverse, yet when I loosen the screws a half a turn ther motor moves freely, but is out of alignment. Do I require washers on the motor mount screws?
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your motor screws are to long maybee and think about changing the wire on the last few inches of the motor wire.up to it you will be able to push a few amps if you get a stall they will heat up like a electric fire as you have no fuse.
Proteus
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Try the washers Robert. O0
Proteus is right, you need a fuse.
My wife says can she have your dog when you get fed up with it. ;)
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I think they still have a couple left if the litter, probably take £100 now. Do you want there number?
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Shhh, keep your voice down, the one I've got is enough thanks Robert. ;)
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I thought the wiring on the motor was rather thin, bought them from Model Motors Direct, wired and suppressed. I'll try the washers, and failing that change wiring from motor. As far as fusing from motor, a mate in my club was showing me his Neptune last week and I noticed he never had an in-line fuse, he says hes never used them, just disconnects his batteries each week when he goes home, never had a problem. Thanks for the help Proteus and Dicky O0
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Shhh, keep your voice down, the one I've got is enough thanks Robert. ;)
O0OK
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As far as fusing from motor, a mate in my club was showing me his Neptune last week and I noticed he never had an in-line fuse, he says hes never used them, just disconnects his batteries each week when he goes home, never had a problem. Thanks for the help Proteus and Dicky O0
Do yourself a favour Robert, use an in line fuse, its cheaper than a new speed controller should anything go wrong. O0
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mate in my club was showing me his Neptune last week and I noticed he never had an in-line fuse, he says hes never used them
he's very lucky
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I'm going out on a limb here but I rarely use fuses in my boats! :D
Don't get me wrong but there are a couple of sound reasons:
1. I only use tested setups and know I won't overload the system even in the event of a motor stall.
2. I only use electronic speed controllers with overload protection or thermal shutdown.
When experimenting, I do use a slow blow at the rated speed controller limit, ie. 10Amp or a 10 controller.
Question. Most people put fuses between the battery and the speed controller, does anyone put a fuse between the motor and the speed controller?
Martin.
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I think I will do the fuse, in the correct position of course. The washers worked great though, purrs like a kitten now, with 1 kilo of ballast to bring her down to the waterline. Stopped by the auto wreckers yesterday after work and he had loads, sea trials went very good in the pool, but as our pond is very open at Goodrington, may wait for open water trials, thanks again for all your input, using a 10A Micro ESC Mtroniks and set up was dead easy.
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Question. Most people put fuses between the battery and the speed controller, does anyone put a fuse between the motor and the speed controller?
I do both. The fuse on the positive side of the battery is to protect the boat's electrical installation. The fuses on the motors stop the controllers being overloaded if a prop picks up weed or gets jammed etc. As somebody else pointed out, fuses cost pennies but can save you hundreds of pounds. :)
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I'm going out on a limb here but I rarely use fuses in my boats! :D
Don't get me wrong but there are a couple of sound reasons:
1. I only use tested setups and know I won't overload the system even in the event of a motor stall.
2. I only use electronic speed controllers with overload protection or thermal shutdown.
When experimenting, I do use a slow blow at the rated speed controller limit, ie. 10Amp or a 10 controller.
Question. Most people put fuses between the battery and the speed controller, does anyone put a fuse between the motor and the speed controller?
Martin.
Yes.
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I'm going out on a limb here but I rarely use fuses in my boats! :D
Don't get me wrong but there are a couple of sound reasons:
1. I only use tested setups and know I won't overload the system even in the event of a motor stall.
2. I only use electronic speed controllers with overload protection or thermal shutdown.
When experimenting, I do use a slow blow at the rated speed controller limit, ie. 10Amp or a 10 controller.
Question. Most people put fuses between the battery and the speed controller, does anyone put a fuse between the motor and the speed controller?
Martin.
Like Colin, both between motor and ESC and in positive lead from battery to main switch.
Barrie
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When something goes wrong, the excess current comes from the power supply (battery), so surely the place for the fuse is in the positive power supply line before it gets to the electronics. I have worked on this principle for about 60 years and it hasn`t failed me yet. Pete M
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I tend to agree with PeterM, one fuse is sufficient in positive line from battery, or if a multiple circuit then a separate fuse for each circuit in its power line.
The second fuse in the motor line will only introduce extra resistance and reduce efficiency.
Regards
Nick
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I'm with Martin here!
I rarely use fuses in my models. I've yet to have any model or RC equipment damaged or lost when a fuse might have saved the day. Indeed, in my early days I've had models left powerless due to the fuse "blowing" when subjected to momentary overloading which would not have damaged the driveline in any way.
This is not "Luck" as I plan, install, test and (most importantly) try to be aware of what the model is telling me when I sail. I do not advocate never using a fuse, some modellers I know would be foolish to sail without a fuse, but fuses are not essential for everyone in everycase.
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The second fuse in the motor line will only introduce extra resistance and reduce efficiency.
Sorry, I don't understand that. A correctly rated fuse should carry the required current and not introduce resistance - otherwise it would get hot and blow!
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Colin,
You have described how fuses work, i.e. the current passing through the resistance of the wire element causes heating (P=I2R). If the fuse element cannot conduct this heat away quickly enough then its temperature rises until the element melts.
Such a mechanism is not going to "blow" as soon as the current exceeds its rated value. The greater the excess current is, the quicker it will "blow" but, notheless, a 10 Amp fuse will let a current larger than 10 Amp flow for a short while.
As my son-in-law keeps on reminding me, fuses are there primarily to protect the wiring not the device they are in series with.
GlynnG
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2. I only use electronic speed controllers with overload protection or thermal shutdown.
.... and the advantage of a built in device is it fast enough to protect itself and usually they automatically reset.
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Hi there
Certain manufacturers of model boat equipment supply a ready fitted fuse in the positive line; this is to protect from human error and also protect against mishaps whilst out boating. Along with this fuse there is a built in overload.
Now, when we get our wires mixed up and we connect the positive wire to the negative on the battery; the first thing to blow is the fuse.
If we replace the fuse with a higher rating one and do the same trick again, the second thing that blows is internal - it normally is the printed circuit that gets it.
If we are really unlucky, the diode gets it as well.....
If we are really persistent & short the whole lot out again, the main power transistor gets it; so you know when we send our electrical appliances back to certain manufacturers and they say - did you get the wires mixed up and we say no.......when they open them up they know we were telling porky pies.......
aye so fuses whether we like them or not; are a good thing to have.
aye
john e
bluebird
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Fuses look Funky... ;)
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Just reading back on my posts here, maybe I should make myself clear... FIT FUSES!
Any additional form of protection for your expensive electronics is highly recommended.
Has anyone used those electronic type fuses / circuit breakers? I hear they react very fast!
... do as i say not as I do! ::)
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QUOTE FROM THE BOSS
... do as i say not as I do! ::)
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You know John you have more than a passing resemblance to Martin, pose is very similar to. Did your Dad have a bike. :angel:
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actually, his boss told him to count the number of ceiling tiles so he could suss out the paint required for re-decorating...psst martin, wake up... :D
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Just reading back on my posts here, maybe I should make myself clear... FIT FUSES!
Any additional form of protection for your expensive electronics is highly recommended.
Has anyone used those electronic type fuses / circuit breakers? I hear they react very fast!
... do as i say not as I do! ::)
If medals were awarded for speed
GOLD http://www.datasheetcatalog.org/datasheet/siemens/BTS555.pdf
SILVER http://catalog.tycoelectronics.com/catalog/feat/en/s/23161?BML=10576,17593
BRONZE Fuses
They all have pros and cons.
If tyco parts are what you mean by electronic I'm drowning in them and use them.
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Quote
2. I only use electronic speed controllers with overload protection or thermal shutdown.
.... and the advantage of a built in device is it fast enough to protect itself and usually they automatically reset.
It has been recorded in a thread on this site that a self-protecting ESC, having an internal fault, is perfectly capable of incinerating both itself and its surroundings if its supply is unfused.
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It has been recorded in a thread on this site that a self-protecting ESC, having an internal fault, is perfectly capable of incinerating both itself and its surroundings if its supply is unfused.
Hi Malcolm,
You are correct spot on there ! Haven't seen that post but boats are in water (water and electrics don't mix.)
That reminds me ,P.T.C. breakers I have just mentioned ,by Tyco and Bourns and the like ,can shatter if badly installed so beware.
I don't yet know if that's what Martin meant in his post about "electronic fuses"
If you use said breakers the quickest acting type are the lowest voltage (RGEF @16volt) and also have the largest rupture capacity @ 100 amps.
They stay hot until the fault is removed.(DO NOT EXCEED VOLTAGE OR THEY'LL EXCEED 125 Celcius)
They do not provide isolation and trigger times are longer for the physically big sizes.
I put a breaker between motor and ESC & blade fuse in + ve line (Manufacturer Tekin included a solder blob {-) in case the external battery was reversed) and added polarity protection.(I'll post a diagram if I find how to do that!)
Overkill some may say.... well no......each protection method has a function.When a weed problems occurs,it only triggers the breaker so I only need to lift the stern to de-fowl the prop and not take the beast out the pond.
As with fuses,every electrician knows your wiring must not permit a fault current to exceed rupture capacity.Breakers warm up due to their P.T.C. ,their resistance rises and effectively causes a near open circuit but a surge in excess of their rating may cause them to shatter.
The ideal place for such devices is between ESC and motor as the current is limited to the motor stall figure. My 550 would stall at only 40 amp so the breaker is safe (and has been proved to work).
These metal-oxide P.T.C. breakers are faster than fuses in the region of faults 2 to 5 times the nominal value ,as Martin asked. However,the voltage and low-ish rupture capacity shouldn't be exceeded.
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hi there Rem2007
Will you do the rest of this forum & me a big favour my friend, fit an inline fuse to your motor setup in your picture you have shown. Let's be done with it. Before we get a 6-page essay from barry park :) :)
Only several people could understand and would be interested in a 6-page essay.
The other people on here want to have a good discussion/build models and sometimes sail them.....
aye
john e
bluebird
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You know John you have more than a passing resemblance to Martin, pose is very similar to. Did your Dad have a bike. :angel:
Dicky me dad had a pushbike but I don't think he rode it doon to Peterborough :D :D :o :o ::) :-\ me dad never told me owt about it anyway.
ps Dicky when I first read your comment last night - I was too tired and mis-read it....instead of reading 'resemblance' I thought you had typed get a passing ambulance hahahah - wonder where that came from.
Aye
john e
bluebird
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Hi John
Had a word with Robert this morning and he is fitting a fuse.
He could not quite see how his simple question could get certain people writing volumes of techno babble for so long.
Could he be on about the thoughts of chairman barry park do you think. ? :-\
What would you be wanting an ambulance for then ? :angel:
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Lightning fast fuses for semiconductor protection http://en.wikipedia.org/wiki/Semiconductor_fuse
Six pages {-) http://en.wikipedia.org/wiki/Fuse_(electrical)
Barry Park
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Well Dicky you were so right what a load of twaddle that guy posts I think it is a sad case of you will listen to what i say and do as I am right all the time,funny thing is we have not seen one of his installations or even a boat!!!!!!!!!!!!!!!!!!!!!!!
Stavros
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well I would install it, only its a bank holiday and I'm really not doing much aside from picking up after you know who. besides that anyone i'd purchase gear off was at ellesmere and seeing as I live in a foreign country, I have to wait til these nice folks get back to work.
curious how one simple question can cause such good hearted debate amongst the model boat community :o, never mind, consider the culprit dilemma rectified O0
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OK, my take on fuses and so forth.....
1/. Always fuse at least the main line from the battery. Select the fuse so that there is no nuisance tripping under normal maximum operating conditions. This protects the whole installation from wiring failures or from failures in the electronics. I have started, on the larger installations, to fuse the feeds to the motors to prevent meltdown of the ESC in the event of the motors becoming jammed. Use normal automotive grade fuses - they are good enough for most cases.
2/. I see no benefit in using semiconductor rated fuses - the fast fusing does not really give any additional protection - the drive transistors in the ESC should be designed to have sufficient overload capacity for inrush - if they cannot cope with a significant short term overload then buy a different ESC. Bitter experience tells me that semiconductor fuses do not fuse fast enough to protect FETs.
3/. Don't rely on active protection schemes - they are not fail-safe. In the event of a failure of the component your protection scheme is out of the window. Remember, standard failure mode of a FET is short-circuit. An intelligent high-side switch (for example) relies on being able to turn itself off to protect itself - if it has failed then the protection is shot.
4/. Circuit breakers - by all means use them, better yet - use a fuse and send me the money you have saved on the breaker. If you are getting enough nuisance trips that you need to keep popping the breaker back in, then there is something wrong elsewhere - fix the cause rather than the symptom. If you do use breakers, use magnetic breakers rather than thermal ones - thermal breaker operating current is too dependent on ambient temperature, especially with the self resetting ones (been there, done that).
5/. Polyswitches - never used them (at least on a model boat), but again, like a circuit breaker - if you are getting nuisance tripping, address the cause rather than the symptom. Remember that a polyswitch does not open in the same way as a fuse - it keeps a flow of current going. Also it does not give an indication of tripping - as soon as the power is off it self-resets.
OK so I am a conservative at heart - but I fail to see any significant benefits of using anything more complex than a simple automotive type fuse. Also do not worry too much about the rupture capacity fuses - if the fault current is high enough that you risk rupturing the fuse then perhaps you shouldn't be running the model off the mains.
Absolute minimum fusing - a single fuse in the positive line, use smallest value that prevents nuisance tripping.
Normal practice - Fuse in the positive line plus one in each motor positive line.
Belt/Braces and piece of string - as above but also a fuse feeding each ESC.
Wom
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Oer thats a long post for you
Stavros
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Long? yes, but at least I could understand it all, unlike some of the other "helpful" advice :'(
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Oer thats a long post for you
Stavros
Nah, wait till Wombat's authoritative tome on model boat electrics comes out - this topic will get a whole chapter not just a couple of short paragraphs. I didn't even mention the correct grading of fuses or the relative merits of time delay and fast blow fuses. Or automotive versus HRC, or indicating fuses
Put it this way - got four pages in on wire and still got to actually talk about specific wire
Wom
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Hey Wombat, more info please!
For those old codgers who use braces ,but no belt, here's my definition of your "string"
A big shunt diode will protect an ESC , in conjunction with a fuse ,where the person is COLOURBLIND i.e. prone to connect the battery the wrong way round.
A reverse-polarity induced fault current is likely to destroy fully electronic (non-2-pole relay ESC's ) on 12 volts even when a fuse is present.
An alternative is a low resistance FET transistor to block reverse voltage altogether.
My semi fuse ref was only because Martin said he heard polymer PTCC's were faster than fuses (I think thats what he meant)
Like you, I know (i squared t) and have used up a few sheets of log graph paper too! :)
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Please Wombat dont encourage him he dont need it, he's a self winding, how do you spell geek, is that right ?. :-\
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DickyD O0
stavros
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It doesn't really matter how much protection is built in, someone, somewhere, will find a way round it. I know this having either seen the results or done it myself. The suicide diode, provided it can outlive the fuse, works well, but there will always be somebody who puts a bigger, better fuse in. There will always be somebody who, when presented with a blue and yellow pair of wires with instructions to connect them to the motor, and a red and black pair with instructions that these go to the battery, will shuffle them, because he did it with his trusty Bobs Board.
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It doesn't really matter how much protection is built in, someone, somewhere, will find a way round it. I know this having either seen the results or done it myself. The suicide diode, provided it can outlive the fuse, works well, but there will always be somebody who puts a bigger, better fuse in. There will always be somebody who, when presented with a blue and yellow pair of wires with instructions to connect them to the motor, and a red and black pair with instructions that these go to the battery, will shuffle them, because he did it with his trusty Bobs Board.
That is so true! {-) It must be all the solvents they huff !
I just wish someone would publish a solution to putting yellow & blue to batteries.
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Its really a Darwin sort of thing. Although its rarely fatal, once, where you have to pay for it, is usually enough.
The protection in modern units is already pretty good, the big problem is defining the limits of electrical devices for people who are very very good at shaping wood. If they can refrain from laughing at my floating logs, I will accept that electric will remain a mystery to them.
If its a simple system, a fuse at the battery positive is enough. A more complex system, with multiple motors and/or accessories would be better with a disribution panel. Putting too many protective devices into a system eventually becomes a fault liability.
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Its really a Darwin sort of thing.
I tell you! It's solvent abuse!
Although its rarely fatal, once, where you have to pay for it, is usually enough.
The protection in modern units is already pretty good, the big problem is defining the limits of electrical devices for people who are very very good at shaping wood.
And what do they stick bits of wood with? If they can refrain from laughing at my floating logs,
Aha ! I will accept that electric will remain a mystery to them.
If its a simple system, a fuse at the battery positive is enough. A more complex system, with multiple motors and/or accessories would be better with a disribution panel. Putting too many protective devices into a system eventually becomes a fault liability.[/size]
Malcolm, I only put the thing in the diagram into a sealed compartment after accidentally reversing the battery on week one. (I can't fit a normal comnnector.)You can put it in a potting box with a glossy label on it,add two LED's and charge £16. I'll post it on an open forum for the vero enthusiasts.
Barry Park
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Guys, guys -
Many moon ago, when a certain sinful lady used to frequent these pages, I seem to recall a helluva lot of members who took a whole load of delight in kicking the crap outta her. And all because she had the balls to speak her mind.... even though what she said was always the truth. Remember?
That was a long time ago. But since then I thought that we had grown up a little - started acting a tad more civil towards fellow members.
Then I tuned in tonight and was genuinely surprised to see that the very same mentality still rides loud and proud on Mayhem.
Guys, listen to yourselves. I mean, if you MUST bad-mouth Barry Park, then at least to do it in private... or at least with a hint of style. Real men would have sent him a PM. Instead, everything I've read here tonight merely tantamounts to nothing other than plain rudeness.
I'd bet my aunt Fanny's panties that all those making all the noise would be the FIRST to go running to Martin if it were happening to THEM (right?).
Give the man a chance, for Gawd's sakes. You don't HAVE to like or even agree with what he says. But to be so RUDE about it??
Barry Park,
Dude, I'll take the curtesy of using upper-case initials on your name - even if you won't. You come across as the sort of bloke with skin as tough as a buffallo's butt. But there is no doubting your that you do indeed have a head for electronics. For may part, I come into 'my-boats-look-like-logs' catagory. I think the buzzword for people like I is 'nerd' / 'geek', blah. Personally, I much prefere the term 'love god', but I daren't say that for fear of causing a whole shipload of jealousy.
Instead, what are the chance of seeing that Veroboard layout you talked of?
Dances With Fuses.
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Forever the pacifier PMK, O0 at least there will always be some semblance of sanity and tolerance while you're posting :)
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Pacifier? Isn't that one of those things that our Yanky cousins shove in their kiddies mouths to stop 'em squawking?
What do we call the same thing over here?... A dummy?
Thanks, Circlip (I think!).
At the risk of sounding like a dummyfier, am I the only one who happens to like the simplicity - not to mention functionality - of BP's circuit?
Talking of fuses... Whatever happened to the so-called 'crowbar' circuit? Wasn't a silicon-controlled rectifier supposed to work MUCH fast than a fuse?
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Done and dusted.... sorry I started this little tete-a-tete.....always thought a pacifier had something to do with the people who lived near the pacific ocean :D
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No need to apologise. It's been an interesting excursion but having read all the pros and cons I'll just stick with the standard fuses on the main battrey and motors as I've always done.
Colin
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Well Dicky you were so right what a load of twaddle that guy posts I think it is a sad case of you will listen to what i say and do as I am right all the time,funny thing is we have not seen one of his installations or even a boat!!!!!!!!!!!!!!!!!!!!!!!
Stavros
Stavros,
you asked to see one of my installations.
I'm heavily influenced by three leading British installation artists. I've incorporated elements of all three.
decomposing fruit by Sam Taylor-Wood
the upstairs room by chris ofili ( 3 1/2 lbs of elephant dung)
my bed by tracy emin (the kid's and not mine)
I found some real twaddle too. "rewinding dc motors" in http://www.modelboatmayhem.co.uk/forum/index.php?topic=10984.0
Regards
Barry Park
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wow is that a DEMON speed controler in the middle, I still have a couple and even one with the extra TURBO..
Proteus
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Banana
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Ah, this proves this man has a wicked sense of humour; I LIKE IT {-) {-)
I can see a couple of 'ancient' Electronize speed controllers there, and, possibly one or two Maplins' so it proves he has been or is a Member of Time Team and been on an archaeological dig O0 {-) {-)
All we need to do now is extract his information in a clear and easy format - so that those with little knowledge of electronics can gain unwaffled knowledge :D :D ::) ;D {-) {-)
aye
john e
bluebird
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More goodies than you can shake a stick at, but nope - definitely a banana SKIN.
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It's black now!
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Must be 3 days old and on the 27MHZ band that banana {-)
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I'm trying to make a serious point!
You can avoid all that if you use a fuse.
......and also remove the cover of Electronize ESC's.
Heat build up melts the relay plastic & shorts out the relay.
They can be fixed if a fuse blows but not after 100 Amps fries the pcboard.
Barry Park
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Hey Wombat, more info please!
For those old codgers who use braces ,but no belt, here's my definition of your "string"
A big shunt diode will protect an ESC , in conjunction with a fuse ,where the person is COLOURBLIND i.e. prone to connect the battery the wrong way round.
A reverse-polarity induced fault current is likely to destroy fully electronic (non-2-pole relay ESC's ) on 12 volts even when a fuse is present.
An alternative is a low resistance FET transistor to block reverse voltage altogether.
My semi fuse ref was only because Martin said he heard polymer PTCC's were faster than fuses (I think thats what he meant)
Like you, I know (i squared t) and have used up a few sheets of log graph paper too! :)
What more information, Barry, you sure like to get your thrupence worth.
Liked the installation - though the banana was perhaps gilding the lily (unlike my more normal practice which seems to be more akin to polishing a 'xxxxx')
I have a reluctance to put in series diodes to protect the user from connecting the unit up incorrectly as they suck up power. A parallel diode when used as a flywheel protection device is fine. I have had to do this on one case because the the built in flywheel diodes in the FETs weren't up to the job when used with some rather hot motors. The thinking on the three fuse system was this:
1/. Main line fuse - last ditch protection when all else fails to prevent the possibility of fire
2/. Fuses on each motor line to protect the ESC in the event of a motor jam - I would suggest this even if the ESC has protection itself after seeing a few protected ESCs let out the magic smoke given that encapsulated ESCs do not have a smoke reinstallation valve.
3/. Fuses on the input to each ESC - really only needed in a multiple motor application - if one of the ESCs goes PHUT, this fuse should fail leaving the rest of the system operational allowing you to limp back to the shore.
Polyfuses - I suspect the characteristics will be similar to Varistors - I use those for mopping up the energy from lightning strikes along with spark-gaps and transient diodes - on the higher current ones the thermal mass could make the characteristic a bit soggy on marginal overloads . My preference is still for something that gives you a clear indication of a problem. Polyfuses ISTM are for applications where overload is to be expected (for instance finger trap protection on car winders or surge protection on a telecomms line) rather than where it is a sign of an abnormality on the the system.
Wom
The Prat-in-the-hat's trivia
Banana error - one of the classic programming errors - when you fail to terminate a loop correctly. From the little girl who stated "I know how to spell banananana, I just don't know when to stop"
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Sorry Wom, but I skip long posts and I advise anyone to do likewise.
1 Do you recognise the 3 1/2 lb tome? You have the switchgear one I bet! (fuses )
2 You and Malcolm missed the deliberate mistake on the "anti-shuffle" circuits
3 What is all this c..p about increasing motor torque by rewinding? Seriously!
Barry Park
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What more information, Barry, you sure like to get your thrupence worth.
Liked the installation - though the banana was perhaps gilding the lily (unlike my more normal practice which seems to be more akin to polishing a 'xxxxx')
I have a reluctance to put in series diodes to protect the user from connecting the unit up incorrectly as they suck up power. A parallel diode when used as a flywheel protection device is fine. I have had to do this on one case because the the built in flywheel diodes in the FETs weren't up to the job when used with some rather hot motors. The thinking on the three fuse system was this:
1/. Main line fuse - last ditch protection when all else fails to prevent the possibility of fire
2/. Fuses on each motor line to protect the ESC in the event of a motor jam - I would suggest this even if the ESC has protection itself after seeing a few protected ESCs let out the magic smoke given that encapsulated ESCs do not have a smoke reinstallation valve.
3/. Fuses on the input to each ESC - really only needed in a multiple motor application - if one of the ESCs goes PHUT, this fuse should fail leaving the rest of the system operational allowing you to limp back to the shore.
Polyfuses - I suspect the characteristics will be similar to Varistors - I use those for mopping up the energy from lightning strikes along with spark-gaps and transient diodes - on the higher current ones the thermal mass could make the characteristic a bit soggy on marginal overloads . My preference is still for something that gives you a clear indication of a problem. Polyfuses ISTM are for applications where overload is to be expected (for instance finger trap protection on car winders or surge protection on a telecomms line) rather than where it is a sign of an abnormality on the the system.
Wom
The Prat-in-the-hat's trivia
Banana error - one of the classic programming errors - when you fail to terminate a loop correctly. From the little girl who stated "I know how to spell banananana, I just don't know when to stop"
Right!
Read your post as far as line 4
shunt diode.....What series diode are you on about?
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Wom, I've just finished reading that and I now understand what they were all on about!
I've now rejoined huminity.
You might be out of date on "Polyfuses"
Barry Park
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OK,see what you mean now.
There is no diode forward voltage drop on the "anti-shuffle" The transistor is enhanced and about .01 ohm if the battery is connected right.
The mistake is on the P-fet version,by the way.
Barry Park
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Oh, I geddit now!........
The 3.5lb tome is there to denote your loathing of long posts (not your own long post - just those from other members), and the banana could signify someone either slippery or cowardly, and all those broken gadgets are to show your affinity with rubbish.
The floozy I'm with this weekend, she just said: "I much prefered his old signature... skin as tough as a rhino' ass."
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Does this bloke not know when to stop, or have we got to put up with this twaddle clogging up the postings for ever.
What do you reckon PMK ?
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Hi Barry
OK I will keep this short in deference to your limited attention span :P
Don't recognise the tome...."Power Electronics Handbook" - but whose, couldn't quite make out the publisher. The book of reference for my generation was Lander - came with a pink cover. Surprisingly, don't have a handy tome on switchgear but since part of the company designs the stuff, there is no substitute for a bit of face-time.
Anti-shuffle circuit - didn't really look at it if truth be told.
Hey don't get me started on motor torque and model boats - if it can spin the prop in a bucket of water it has got enough torque AFAIC.
Polyfuses - have to admit my use of them is limited - they still fall into a gap for my (professional) applications - really need a higher voltage rating in most cases and a higher energy rating. A self resetting fuse is no good if you end up picking bits of it out of your teeth each time it is triggered. Also looking at some of the higher voltage ones they are pretty slow responding - time to trip on a 10* overload on the ones I looked at are of the order of 1 second. I note that the smaller ones do not specify a trip time - biggest disincentive for me though is the thermal derating curve - over the expected temperature range the trip current varies by 30% from the nominal.
If it is still too long just drop every other word.
Wom
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Wom, I didn't read that one either.
PMK,
You see the problem in ping-pong emails and message boards ? {-)
Nobody has a clue what anyone is on about!
I've got to go now! But I'm posting a question in Electrics and all things and I'll see how sharp or completely random the answers are.
There were no posts in this section for 24 hours. Did you notice?
Who scared everyone away? :embarrassed:
Come back! I love to read all these crazy but helpful tips like "got a metal to metal joint somewhere?" It's payback for the hours learning a craft repairing tight fisted old pensioners' write-offs.
There must be 100+ commonly occuring R/C faults so diagnosis requires logical deduction and eliminating half known issues at a time.
Barry Park
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2 You and Malcolm missed the deliberate mistake on the "anti-shuffle" circuits
3 What is all this c..p about increasing motor torque by rewinding? Seriously!
I learnt on valves, the instructors were struggling with the new-fangled fad of transistors, so what I did pick up was all about bipolar types, silicon transistors were a thing of wonder, and FETs happened after I had moved on. Humorous FET drawings therefore pass me by. Sorry.
Taking all the wire out of a motor and replacing it with a similar volume of different thickness wire will alter the motor characteristics. Easy for those practised in the art, potential disaster for those who aren't. The curly wire part of C&G co-incided with finding out about booze, bikes and birds. No contest.