Please Check my work (trolling motor circuit)

Thread Starter

avenger64

Joined Aug 20, 2023
3
I’m working out plans to add an electronic speed controller to a 12V trolling motor setup in order to have variable speed control. However I’d like to create a bypass switch in order to cycle between,
[battery>motor]-[off]-[battery>esc>motor]
The system would also run a linear actuator that can be linked to the trolling motor and operated by two momentary foot switches corresponding to extend/retract. And finally the system would include a lanyard style kill switch and voltmeter.
My knowledge of circuits is mainly from guitar pedals so taking current into consideration and the use of relays is new to me.
Please let me know if any of this makes sense or is possible.
IMG_0099.jpeg
 

geekoftheweek

Joined Oct 6, 2013
1,106
That is a lot of relays for a battery operated system, but for the most part it will work. You could combine relays 2,4,5 into a single relay to cut down on the current draw of the relay coils if the motor current is low enough. 3 and 6 could be combined into a single relay also. I would find a way to eliminate relay 1 myself just to lighten the load.

You're missing a few connections on your linear actuator. To get both directions you would need to connect your leads from the actuator to 30 of both relays. Then 87a to ground and 87 to power.
 

Thread Starter

avenger64

Joined Aug 20, 2023
3
That is a lot of relays for a battery operated system, but for the most part it will work. You could combine relays 2,4,5 into a single relay to cut down on the current draw of the relay coils if the motor current is low enough. 3 and 6 could be combined into a single relay also. I would find a way to eliminate relay 1 myself just to lighten the load.

You're missing a few connections on your linear actuator. To get both directions you would need to connect your leads from the actuator to 30 of both relays. Then 87a to ground and 87 to power.
Thanks for the response. You’re correct about the linear actuator, that was an oversight when I transcribed my drawing into something neater.

As for the relays, I also thought it was an excessive amount but I am under the impression that the motor negative needs to be connected to the motor negative terminal at the ESC and that this ground connection needs to be isolated from the battery ground. That’s the purpose of relays 5 & 6.

Maybe I am wrong and this isn’t required? The rest of the relays further “isolate” the ESC from positive power but I also thought this may be redundant.

My goal with the bypass switch is to be able to run the motor close to max without the risk of overheating the ESC, an issue I’ve had with PWMs in the past.

Thanks for the help.
 

Alec_t

Joined Sep 17, 2013
14,014
Welcome to AAC!
The way you show it, the kill switch will be ineffective if the contacts of relay 1 happen to weld closed (a distinct possibility when switching high current DC loads).
 

LowQCab

Joined Nov 6, 2012
3,609
A properly designed ESC will act like a virtual "Switch" at "Full-Speed",
and will produce the most amount of Heat at ~50% Speed.
So bypassing would not be needed.
The Heat shouldn't be very significant, even at ~50% Speed.
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geekoftheweek

Joined Oct 6, 2013
1,106
As for the relays, I also thought it was an excessive amount but I am under the impression that the motor negative needs to be connected to the motor negative terminal at the ESC and that this ground connection needs to be isolated from the battery ground. That’s the purpose of relays 5 & 6.
I was debating whether or not the ESC needs isolated myself, but thought without documentation stating otherwise that it probably would be a good idea.

As far as combining relays I meant DPST and 3PST and the like. I don't know what kind of battery you have or how long exactly you are planning to run your motor so the relay count may not be a problem. I just know personally I would try to find ways to eliminate some coils.

LowQCarb's advice sounds logical. Maybe your issues in the past were from faulty circuits.
 

Thread Starter

avenger64

Joined Aug 20, 2023
3
I was debating whether or not the ESC needs isolated myself, but thought without documentation stating otherwise that it probably would be a good idea.

As far as combining relays I meant DPST and 3PST and the like. I don't know what kind of battery you have or how long exactly you are planning to run your motor so the relay count may not be a problem. I just know personally I would try to find ways to eliminate some coils.

LowQCarb's advice sounds logical. Maybe your issues in the past were from faulty circuits.
A properly designed ESC will act like a virtual "Switch" at "Full-Speed",
and will produce the most amount of Heat at ~50% Speed.
So bypassing would not be needed.
The Heat shouldn't be very significant, even at ~50% Speed.
.
.
.
Thanks guys. I do think my past issues were due to cheap PWM units which is what led me to thinking of a bypass switch. It also had me look into alternative solutions which is how I came to an ESC.
I’ve been looking into it more and I realize I’m trying to solve one problem with two separate solutions and the ESC on its own should suffice.
I plan to wire the unit in a box separate from battery and motor so I can still physically remove it from the circuit if needed making the bypass switch a convenience I’m starting to think I don’t need anyway.
 
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