Model Boat Mayhem

Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: Peter57 on September 26, 2019, 05:15:46 pm

Title: Help please - "runaway" motors
Post by: Peter57 on September 26, 2019, 05:15:46 pm
I own a beautifully built paddle steamer which I recently acquired second hand. When I first got the boat everything was working as expected.

Having not used the boat for 3 to 4 weeks I found two problems when I tried to connect the power supply:
1) The transmitter (Futaba F14 "Navy") and receiver appeared to be not communicating.
2) As soon as I switched on the power supply the motors ran at (probably) about 80% of full speed.

With the help of a member of my local club we traced the first problem to a failed BEC, which is taken from a power distribution board. Once this was bypassed we were able to get the transmitter and receiver working, e.g. rudder control was restored.

Unfortunately, the motor problem persisted. Moving the throttles to full did result in a slight increase in motor speed and reversing them abruptly reversed the motors. So some communication appeared to be present, but there was no neutral position or proportional throttle at lower power. Unfortunately, the ESCs are  amongst the least accessible electronic components, but I believe from the information I have they are Action Electronics P80s.

Does anyone have any thoughts or suggestions as to how I could further investigate and hopefully fix this problem?

Many thanks in advance.
Peter
Title: Re: Help please - "runaway" motors
Post by: john44 on September 26, 2019, 09:24:01 pm
Hi Pete, sounds like a question for Mr DM.


John
Title: Re: Help please - "runaway" motors
Post by: DaveM on September 26, 2019, 11:24:44 pm
My expert technical appraisal is that they need repairing..... If they are indeed P80s then it sounds like the MOSFEts have a dose of backwards electricity and walked off the plot. Are you able to remove the speed controllers and send them to me for checking over?
DM
Title: Re: Help please - "runaway" motors
Post by: Peter57 on September 27, 2019, 07:36:51 am
John and DM - many thanks for your comments and suggestions.

I will have a go at removing the ESCs. As I mentioned they are amongst the least accessible components, as they are buried under a power distribution board. It will be an interesting test of my (lack of) dexterity!

Regards
Peter
Title: Re: Help please - "runaway" motors
Post by: malcolmfrary on September 27, 2019, 10:23:52 am
It should be normal practice for the distribution board to have been installed so that it would be removable.  If that was the deliberate mistake that the original builder put in, now is the best time to rectify it. 
Title: Re: Help please - "runaway" motors
Post by: Akira on February 07, 2020, 02:35:04 pm
"It should be normal practice for the distribution board to have been installed so that it would be removable.  If that was the deliberate mistake that the original builder put in, now is the best time to rectify it."  Absolutely!!Just to rule out other potential issues, try unpluging one or more of the ESC's from the receiver and plug a servo, does not matter which one, into the receiver and see if the servo acts appropriately to the transmitter commands. 
Jonathan