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Author Topic: motor power  (Read 9408 times)

dogbone

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Re: motor power
« Reply #25 on: January 21, 2009, 09:05:03 am »


stallspeed- its still a bit cool here up north for a trip on the water so i will finish off the deck and cabin in warmth first.

max power- what would you say  for the fuses? go straight in with a 15a, os start lower, do'nt want to go for a paddle you know
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Max Power

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Re: motor power
« Reply #26 on: January 21, 2009, 10:27:52 am »


stallspeed- its still a bit cool here up north for a trip on the water so i will finish off the deck and cabin in warmth first.

max power- what would you say  for the fuses? go straight in with a 15a, os start lower, do'nt want to go for a paddle you know
I would go for the 15A fuse, assuming that the speed controller can take short bursts in excess of 15A. Best of all would be to borrow an ammeter, if you do not have one, and check the current with the boat in the water before releasing it. I did  it in the warmth of my own home by placing the boat in a bath full of water  O0
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stallspeed

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Re: motor power
« Reply #27 on: January 21, 2009, 02:48:02 pm »

Dogbone,if you had a scrap telly or computer you'd have a ferrite to make a 15+ amp ,100uH choke which might just have prevented the shutdown feature in the first esc.Remember the amp rating it quoted?
If it was a high frequency esc a choke would almost certainly have done the trick.

You are now using a 15 amp esc and a motor that will draw twice the current.
I think it would be a wise investment to purchase a multimeter and do some skiddling about with a basin of water.
Pull the curtains and watch the room light up with a glass encapsulated ten amp fuse.I would do that with the prop immersed in water and the motor connected to a battery.
A £6 meter would not be damaged by 30 amps but it can't give a reading beyond ten amp.To measure your current so you need to use a low resistance and measure volts generated by the current passing through it.

By the way,I'm staring out at snow capped peaks closer to Max power than Arrow5.That probably makes you down south. ;D
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MartinI

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Re: motor power
« Reply #28 on: January 21, 2009, 05:28:19 pm »

The first speed control was probably shutting down as the BEC would struggle to handle 12V and a servo. A better BEC would be about 3A or you could go to a switching BEC for higher voltages. (I am coming to this from aircraft and cars.)

Receivers and servo run on perhaps 5V. The BEC has to take the 12V of your battery and step it down to a voltage that won't fry the radio equipment. That 7V differential is disposed of in heat. If you add multiple servos, high drain servos, (and the small ones are often higher drain than we might expect), or a binding linkage, you are adding more current, creating more heat which has to be dissipated by the BEC. Usually, speed controllers can deal with up to 4 servos on 6 NiCds, (7.2V), 3 servos on 7 or 8 cells, (8.4-9.6V),  2 servos on 9 cells, and 1 servo on 10 cells. Better controllers are more tolerant of stretching these guidelines, and cheap controllers often don't.

Martin
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stallspeed

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Re: motor power
« Reply #29 on: January 21, 2009, 05:33:16 pm »

The rudder was working.  :-))
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Shipmate60

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Re: motor power
« Reply #30 on: January 21, 2009, 07:15:36 pm »

Martin.
Standard BECs are rated at 1 amp.
Sub BECs are rated 1 1/2 -2 amps.
For 3 amps you would need a stand alone BEC.
I amp is plenty to run 1-3 servos and receiver.

Bob
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MartinI

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Re: motor power
« Reply #31 on: January 22, 2009, 01:22:07 am »

"The rudder was working. :-))"   Missed that!

Bob, Castle Creations ESCs have 3A BECs, but that is more a plane controller.

That's why I'm here - to learn boat stuff! :embarrassed:

Martin
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malcolmfrary

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Re: motor power
« Reply #32 on: January 22, 2009, 01:14:36 pm »

The rudder servo worked, so the RX must have been working, so both had power.  If I understood the problem properly, the motor battery supplied all of the power via the BEC in the ESC, so the ESC should have worked.  Therein lies the mystery.  I suspect that at 12 volts the ESC BEC was warming up, and warming the ESC protection circuit as well, beyond the point where the ESC would shut down.  At 6 volts, it didn't do as much work, ran cooler, and everything worked.
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stallspeed

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Re: motor power
« Reply #33 on: January 22, 2009, 04:58:00 pm »

The rudder servo worked, so the RX must have been working, so both had power.  If I understood the problem properly, the motor battery supplied all of the power via the BEC in the ESC, so the ESC should have worked.  Therein lies the mystery.  I suspect that at 12 volts the ESC BEC was warming up, and warming the ESC protection circuit as well, beyond the point where the ESC would shut down.  At 6 volts, it didn't do as much work, ran cooler, and everything worked.
EL Model ESC - 110A  (Rds =0.0076 ohm omitted from this Ebay listing)

Yes,agreed: the esc couldn't maintain 110 amp continuous unless it had a Pentium heatsink+fan but it has two smartfets which trigger it seems from a Torpedo 800 stall current.

Well almost déjà vu as last time it was a Torpedo 850 and possibly on 10 or 12 cells.

Quote
This is a new ESC only taken out of the package for picture. The El Model 110 ESC when connected with motor, it is capable of supplying up to 110 Amps (forward) and 40 Amps (reverse) of continuous motor current. Its integrated Battery Eliminator Circuit (BEC) powers the receiverfrom the motor battery, with automatic cutoff of the motor power to preserve receiver power as the battery becomes depleted. It is small, powerful and waterproof..........

This ESC is for Brushed Motors ONLY.

Due to the nature of this Hobby item is sold AS-IS

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