Calling All Electricians. Help!

[V153]

Years ago my Dad drew me a diagram that showed how to wire a Double Pole Double Throw switch to make an electric motor run in fwd or reverse. Naturally I can't find it ... Does this look correct?

 

[TerryMSU]

Re: Calling All Electricians. Help!

My original answer was wrong. This will not work and can result in a fire if you do not have a fuse or breaker.

... most continuosly variable trolling motors will not work with reverse power. Also, the current draw is on the order of 50 amps. You will need a switch rated for at least a 50 amp MOTOR load. Motor loads are nasty to switch.

TerryMSU

 

[Star]

Re: Calling All Electricians. Help!

DO NOT HOOK THIS UP LIKE THAT YOU WILL HAVE A FIRE!! YOU SHOW A DEAD SHORT ACROSS + AND - of the battery. i don't have time to show you now, the cross wire connection is right feeds are wrong.

 

[sman60]

Re: Calling All Electricians. Help!

Star is correct DON"T use that method, you will have a dead short and if not fused you could start a fire.

The method below will work, BUT the switch must be able to take the current that the motor will draw.
You will have a HUGE current spike if you switch from forward to reverse quickly.
As trolling motors seem to have permanent magnets in them I am not sure if this will even work.

I would not use this method to reverse the motor


View attachment 136662

 

[Don S]

Re: Calling All Electricians. Help!

Assuming this is for a trim motor, you need to use the switch to control relays or solenoids. You can't run heavy enough wire or find a heavy duty enough switch for the trim motor without going broke in the process.

 

[NMShooter]

Re: Calling All Electricians. Help!

I agree.... trying to find a switch to handle this load will be a bear. You might be better off finding a heavy duty relay. Or if you have the ability to do a little breadboarding, use some heavy switching FETs instead.

Here is a schematic of how to wire it up. Make sure to use break befor make switches. :

Anything that switches DC has harder duty than an AC switch, especially for inductive loads like motors. The reason is because of arcing. The great thing about AC, is that the current goes through a zero point twice every cycle. So it shuts itself off. Not so with DC. DC can arc and just keep on burning.

If you have ever done DC stick welding, you know what a trick it can be to stop that arc as compared to an AC welder.

This is why many switches have a DC rating that is substantially less than the AC rating for the same switch.

 

[smokeonthewater]

Re: Calling All Electricians. Help!

you ABSOLUTELY need relays (can be done with two of em) for your trim motor.... switches big enough would be expensive and hard to find.

common terminals (30) on the relays go to the two load wires from he motor.

terminal 87 on both go to negative and 87a on both go both go to positive.... switching one relay will run trim up and switching the other will run trim down. If somehow you switched both, nothing would happen as both leads would change from negative to positive

 

[TerryMSU]

Re: Calling All Electricians. Help!

My error. Thanks so much for catching this. I was under the weather when I answered this and just gave it a very quick glance. The design is flawed, but my general concerns are correct as far as this sort of design.

Sorry,
Terry Hicks

That looks correct, but i cant read the text so i cannot promise it is exactly correct. A couple concerns... most continuosly variable trolling motors will not work with reverse power. Also, the current draw is on the order of 50 amps. You will need a switch rated for at least a 50 amp MOTOR load. Motor loads are nasty to switch.

TerryMSU

 

[Don S]

Re: Calling All Electricians. Help!

Is this on an IO, Outboard or what? Why don't you just fix what you have instead of re-inventing the wheel?

If this isn't for a repair, here is how you can wire two relays to reverse a motor on the 2 wire motor. This procedure will not work on a 3 wire motor.

 

[smokeonthewater]

Re: Calling All Electricians. Help!

that picture don put up is the same circuit I was describing.... works perfectly.