Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: Angus64 on December 23, 2011, 06:07:05 am
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Hi. Today I fitted my rudder sevo everything is going well, Still waiting for my ESC to arrive from Hong Kong. I am using a 12 volt 10 amp hour gel battery and I am wondering if someone can tell me where the current gets broken down to operate the servo & receiver I understand they are lower voltage around the 7 Volt. I don't want to blow things up so I thought it best to find out what happens. Thank to anyone who might be able to shed a little light on this subject for me.
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The voltage required by the servo and receiver is 4.8-6 volts, this is usually supplied by a 4 cell AA pack. If your ESC has BEC (Battery Elimination Circuit) then the ESC will supply the receiver and servo through the ESC's receiver connection wire. In this case don't use the extra 4 cell battery.
In the case of BEC all you need to do is plug in the servo and ESC receiver connection to the receiver (duh) then connect your motor to the ESC motor output and connect the 12 volt battery to the ESC power input, the ESC then supplies the correct voltage to the rest of the system.
Cheers
Nick
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Exactly what Nick said. I would just add that if your receiver says "BEC", that is best ignored. It was mainly aimed at the car boys to reassure them that using a 6 cell pack was OK. I think.
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Thanks Nick.
I said I knew nothing about electronics in my first post, I guess I just made that even clearer. But you have helped me out again, I can see what happens now, So I will keep on working with my bunch of wires & hope everything works for me. If I get stuck it will be back to the forum with more Questions. Normal Wiring around autos or boats I don't have a problem with, Electronics is a different thing altogether I still have to get my head around that one.
Angus.
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Hi Boys. I received my ESC today, But not certain about the specifications so I thought I should get back to the forum & ask a few questions. The input says 6V-8.4DC (1/10 ESC) is this the amount put out by the ESC or the amount of power (volts) that can be put into the ESC, I can understand the BEC:5V 1A. I have put the Specifications below.Hope there is someone out there that is willing have a go at explaining those to me.
Specifications.
INPUT:6V-8.4 DC (1/10 ESC)
BEC:5V 1A
Current Drain: 20A(Forward).MAX(spark):300A:150(ba
ck,spark)
size 35mm(L)X33mm(W)X30mm(Heightof cooling plate) Weight:48.2g
Applicable:540/20T motor and above
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INPUT:6-8.2 V DC that means can have an input voltage of 6-8.2 volts which basically means a 5 to 7 cell Ni-XX pack ( so its really designed for 6 cell RC buggy packs) The 12 volt Gel cell mentioned in your first post has too high voltage. DC is Direct Current i.e. from a battery
5v 1A, BEC is the output through the servo connector to the receiver its 5 volts and 1 amp, 1 amp is enough to run the receiver and 1 or 2 servos)
20A forward is the maximum current the motor is allowed to draw, you can ignore the 300A (spark) rating, for info its the theoretical maximum/ peak the ESC can handle momentarily. in reality don't exceed 20 amps.
Applicable:540/20T motor and above, ts designed for buggies and they classify motors by the number of Turns (20T) on the armature the more turns the slower the motor (and the more appropriate for most scale boats)
I don't know how well you understand electrical theory but an analogy can be water in a pipe, voltage is the pressure, Amps is the volume, too high a voltage(pressure and the pipe bursts) to small a pipe and the volume(amps) are restricted.
Cheers
Nick
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Hey angus 64 roughly whereabouts in tassie are you?
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Thanks Nick. I had better look for another ESC in that case I have the 12 volt battery fitted, But you have explained that very well, I will get there eventually if I keep trying. I might give the cheap Chinese electronics a miss, They don't explain things very well.
Angus.
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MERMOD. Not far away from you, Penguin.
Angus.
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M TRONIKS RANGE OF SPEED CONTROLLERS ARE HAPPY WITH 12 VOLT INPUT, THE MARINE RANGE OF VIPERS SEEM TO BE POPULAR....
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Not all of the mtroniks range are good with 12 volts- make sure you check the spec carefully before purchase.
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M TRONIKS RANGE OF SPEED CONTROLLERS ARE HAPPY WITH 12 VOLT INPUT, THE MARINE RANGE OF VIPERS SEEM TO BE POPULAR....
Best to read the spec given in post #4. This is one of the 8.4volt max types, and will rapidly die if connected to a 12 volt supply.
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Thanks to all who have given advice on ESC, Can anyone advise me on a ESC that will handle a 12 Volt 12 amp hour battery, I have a 12V 12AH sealed lead acid gel battery installed in my boat, But there so many ESC's out there & so many conflicting ideas that it makes it difficult to know which one will best do the job,I don't want to spend a fortune on on ESC's , This is my first boat so I am working in the dark a bit, Any advise would very much appreciated.
Angus.
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Hi
What type motor ? what type and size of boat ?
all good info to help find the right BITS
Timo2
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For brushed motors I use microgyros ESC's. Excellent quality and best specification.
http://www.microgyros.com
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Hey Respected modeler..you can simply make an ESC with BEC, within an hour, by using the ic 555 and two or three IRFZ 48 MOSFETs.. will haul up to 50 amps..and can boost the BEC up to 5 amps, with 4.6 or 5 or 6 volts..adjustable..will work from 6 volts to 18 volts..will within about 4 dollars..make it..fix it..run it..
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The important things to consider are
1. the battery voltage. The capacity of the battery is relatively unimportant, it determines run time.
2. the power required. This is affected by the motor used, but also by the load imposed on the motor by the choice of prop.
A large (10 or 12AH SLA) makes me think of a fairly large displacement hull, and this in turn points to a relatively large prop with a fairly large motor with a lot of poles. Not high speed, but lots of torque.
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Thanks boys for replying to my post. I should of included more information in my last post, My boat is a big one at 1.5 mts, A model of my own design built from the dimensions of a 85 foot fishing boat I maintained for 30 years I was a marine Diesel fitter now retired, but there was no electronics in what I worked on I have a 12 volt 300 watt motor turning an 80mm 4 blade Raboesch propeller, Malcolmfrary you are on the right track when you say fairly large displacement hull, Hope this can help with solving my ESC problem I am having.
Angus
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The controller I linked to will be perfect then.
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If you are operating the motor at its rated power of 300 watts then the motor will draw 25 amps (300 /12), do you happen to know the no load RPM or if not do you have a multimeter and a drill press with a known RPM to do a test ?
Nick
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Thanks Boys for the advice it is much appreciated. I will check the ESCs out & see what I can sort out there is a lot of them out there to choose from but I don't want to buy the wrong one again. I noticed there are a lot of Buggy & car ESCs to that might be Ok if they were kept dry, Has anyone tried them in boats I thought the Novak Super Rooster sounded as if it would do the job, Any thoughts on that one I have listed below.
Angus.
SPECIFICATION
Input Voltage (1.2VDC/cell) 6-7 cells 6-10 cells
Case Width 1.63 inches 1.63 inches
Case Depth 2.02 inches 2.02 inches
Case Height (w/h.sinks) 1.22 inches 1.22 inches
Weight (w/heat sinks) 3.00 ounces 4.00 ounces
On-Resist.–Fwd. (@Trans) 0.018 Ω 0.002 Ω
On-Resist.–Rev. (@Trans) 0.018 Ω 0.004 Ω
Rated Current–Fwd. 100 amps 320 amps
Rated Current–Rev. 100 amps 160 amps
Braking Current 100 amps 160 amps
Rev. Delay (after Smart Braking) Zero Sec. Zero Sec.
BEC Voltage 5.7 volts DC 6.0 volts DC
BEC Current 0.5 amps 3.0 amps
Power Wire 16G / 6” 14G / 14”
Signal Harness 26G / 6” 26G / 15”
Transistor Type MEGAFET HYPERFET III
PWM Frequency 1250 Hertz 1250 Hertz
Motor Limit Mild Modified No Limit
Part Number 1850 1860
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Novak kit has a good reputation amongst it's users, although I have never tried any of it- certainly isn't cheap.
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To be honest Angus, it's not only the speed controller spec you should be interested in, it's the quality of the product and the backup service / warranty issues need to be checked.
Me, I'm a cheapskate, so my decision making process usually goes...
1. What spec. do I need?
(Max volts, max Current Amps?)
2. Buy ESC with at least minimum voltage and 2 x max estimated current.
( Votage needs to be closely related to selected battery voltage for best control, eg, 6, 7.2. 12, 14.4v etc.)
( For 'reputable' ESC manufacturers, Amps are pretty much a conservative estimate, ie 20A ESC will usually happily handle 25A.)
( For "Chinese" ESC ( ie. non labelled, no website, cheap imports), estimated Amps x 2, x 4 or even x 10! .... "Chinese" Amps seem to conform to a different interpretation of Ohms law... )
3. What 'sort' of ESC do I want?
( For scale ie good low end control, linear speed range. Speed race, ie. handle a lots of power ... and abuse!)
4. What feature are required?
( 'Normal' or Brushless - obviously. But things like BEC, reversing, brake, "self setting", programmable, etc.)
5. What physical size?
( Will it fit? )
6. Will water cooling be required?
( Usually applied to power boats. )
7. What connectors does it come with?
( Am I happy changing, soldering different connectors as required? )
8. What manufacture has "best" reputation? What do others recommend on here?
( Buy one of these! )
9. What am I willing to spend?
10. Buy the cheapest ESC I can possible find on Fleabay. Burn it out. Rant at poor Chinaman that sold it to me. Get another one sent from China. Burn that out too. Swear and curse all Chinese take-aways as I wait for the the smoking boat will drift back in and hopeit reaches shore before it sinks. Throw boat to back of shed. Resurrect said boat from back of shed a year later, having conveniently forgotten where I got the unlabelled ESC from. Buy another one from Fleabay, get lucky and sail way past sunset on a warm Sunday evening wishing I had better low end control. Go back to step 10 and do that!
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Hi Angus
You look at the rest OK now have a look at the BEST = http://www.action-electronics.co.uk/home.html :-))
Check out the INFO page as well O0
Timo2
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Hi boys. I had a goods look at Action electronic , Sent him all the specification of the motor & prop size ect. He is easy to deal with & answered any questions I had & prices are good. So I took Timo2's advice and went with Action electronic,He sent them air freight so they should be here soon. Thanks to all who took the time to reply & give there advice it is much appreciated.
Angus.
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You wont go far wrong with Daves gear. Its also repairable should you make a mistake. John.
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Hi John S. He is very well respected around the model boat builders, I noticed his repair policy on the home page of his web site although I will be trying hard not to make a mistake with the fit up :-)).
Angus.
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Hi Angus, you will be impressed with the quality of Dave's kit , & he is super fast at replying to any questions you may have, Dave is a credit to the hobby & he is the reason I did not quit just after I started, he sorted out my problems in a day or two.( I didn't have a clue what I was doing). Mick B.
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Hi Mick B. You are right about his being super fast replying to questions. This is my first model boat & the electronics were way out of my field, I learned a lot on this one & there will be a lot less of a head ache building the next one. I named my model after my youngest grand daughter, only problem is I have two more granddaughters who want one named after them, I have plenty of time now i am retired so that won't be a big to difficult.
Angus.