Can you explain why one setup it harder on the contacts than the other?

 

Without motor connected, Does that show switch is reversing polarity thru those 2 terminals which are the 2 terminal which I attach to the motor ?

Yes, the switch is reversing the polarity and it can carry enough current to power a 1 million ohm meter input. Apparently it can not carry enough current to run the motor.

 

I remember I had an old DC motor that used stator windings instead of permanent magnets. If it was stopped, it would spin in one direction or the other based on the polarity of the power applied. But if it was turning in one direction faster than a few RPM, reversing the polarity didn't cause it to reverse, it just accelerated in whatever direction it was still rotating.
I wonder if your motor is the same thing. When you switch, are you allowing it to come to a stop? Try that & see if it works. If it does, your motor cannot be reversed while still spinning...

It is an old gear motor, bought from a fella who was cleaning out his airplane hanger near Tampa. Said it had been sitting on a shelf for years and couldn't remember when or why he got it but had never been used.
My toggle DPDT switch is 3 position with all positions maintained. When I toggle from left to off position motor comes to a complete stop before I'm able to toggle to the right.

 

For high current/voltage conditions with an inductive load, the arcing when the contacts open can cause an arc flashover (with lots of sparks) to the opposite terminal, which is at the opposite voltage, causing a short across the power.
Thus for any high power application, the bottom circuit is preferred.

Can you explain why one setup it harder on the contacts than the other?

Still learning that the second quotation shows up on the top, but there's your answer, Denesius.

 

.... but there's your answer, Denesius.

So if I understand correctly: the physical presence of the moving contact between the 2 stationary ones (carrying opposite polarity) causes arcing? The induced voltage in the armature upon break (in the second example) is not a consideration?

 

For high current/voltage conditions with an inductive load,

The induced voltage in the armature upon break (in the second example) is not a consideration?

There's your answer, Denesius.

 

Yes, the switch is reversing the polarity and it can carry enough current to power a 1 million ohm meter input. Apparently it can not carry enough current to run the motor.

Motor is 24V 5A with DPDT 12V 30A. Motor will turn in one direction when hooked up to switch but hesitates or won't turn at all when toggled in the other direction. Can not find a 24V DPDT switch anywhere with maintained positions. Gotten conflicting replies concerning using 24V relays and not even sure how that would work. Any suggestions ? Thanks for your help.

 

1) get a switch that isn't damaged
2) search for a better rated switch or relay.

Frantic busy right now. See you in 30 minutes.

 

If you connect the motor directly to the battery with the polarity forward and reverse it work fine in either arrangement?

 

Have a 24V 5A 2 wire DC motor which, when hooked up to 24v 20A Sola power supply runs great forward and when I reverse wires to power supply terminals runs in reverse just as well.

If you connect the motor directly to the battery with the polarity forward and reverse it work fine in either arrangement?

Your answer is in post #1, Flare_Guy

 

http://www.mouser.com/Electromechanical/Switches/Toggle-Switches/_/N-5g2j?P=1z0z2xkZ1z0z2ukZ1z0x8h0

 

Sorry for the noise

 

I remember I had an old DC motor that used stator windings instead of permanent magnets. If it was stopped, it would spin in one direction or the other based on the polarity of the power applied. ..

There must have been something else going on there, you cannot reverse a wound field DC motor by reversing the supply polarity, it will run in the same direction!.
The polarity is normally kept the same and the field is reversed WRT the armature.
Max.

 

So if I understand correctly: the physical presence of the moving contact between the 2 stationary ones (carrying opposite polarity) causes arcing? The induced voltage in the armature upon break (in the second example) is not a consideration?

It's the breaking of an inductive load when the contacts open that causes an arc in either case.

But it's only when the opposite stationary contact also carries the opposite line voltage that the possibility of flashover arcing through the moving contact between both stationary contacts can occur.
The ionized air from the initial arc between the closed stationary contact and the moving contact allows the arc to be established between the moving contact and the other stationary contact.
Once an arc is established in air it only takes 50V or so to maintain it.

 

Can not find a 24V DPDT switch anywhere with maintained positions. Gotten conflicting replies concerning using 24V relays and not even sure how that would work. .

KB & Baldor DC drives makes a reversing switch especially for this application, it has on-off-on capability with braking resistor terminals, the switch does not allow moving the toggle from one side to the other without a stop in the centre for the motor to brake.
Max.

 

Either one of these two switch configurations should work:
View attachment 80325View attachment 80303

Since the motor manually runs fine in either direction the power supply is fine. While the switch is 12 volt rated @30Amp I don't see the 24 volts as a problem. The drawings are old and one reflects a 5V motor but matters not. It looks like you have a pause and are not changing motor direction without a pause as some SMPS power supplies really hate that. You do have a pause correct? Since you can manually run the motor fine in either direction less the switch and when the switch is added you have problems things seem to point to the switch and the stall maybe something the power supply dislikes. Can you measure the motor voltage when this happens as well as the supply, upstream from the switch? Measure on ether side of the switch in other words?

Ron

Am I missing something here? The way the first diagram is drawn, the switch will always either put a positive or negative potential on both sides of the motor. And unless I am missing something no difference of potential means no current flowing = no spin of the motor. Just saying.

 

Am I missing something here? The way the first diagram is drawn, the switch will always either put a positive or negative potential on both sides of the motor. And unless I am missing something no difference of potential means no current flowing = no spin of the motor. Just saying.

Welcome to the forums and yes, that would be correct. The switch as drawn does not have for example a center off position so yes, the motor is always running.

Ron

 

Welcome to the forums and yes, that would be correct. The switch as drawn does not have for example a center off position so yes, the motor is always running.

Ron

The question/comment I really had is not that the motor will run all the time but how can the motor ever run if both sides of the motor are connected to either the positive side of the battery or both side of the motor is connected to the negative side of the battery at the same time. I know I must be missing something here, so please bear with me, but the last time I hooked up a motor one side had to be connected to positive side of the battery and the other lead of the motor had to be connected to the negative side of the battery. If both sides are connected to either side of the battery no current can flow. So help me understand my misunderstanding of the first diagram. The second diagram will always connect one side of the motor to either the positive or the negative while connecting the other side of the motor the the opposite side of the battery.

 

The question/comment I really had is not that the motor will run all the time but how can the motor ever run if both sides of the motor are connected to either the positive side of the battery or both side of the motor is connected to the negative side of the battery at the same time. I know I must be missing something here, so please bear with me, but the last time I hooked up a motor one side had to be connected to positive side of the battery and the other lead of the motor had to be connected to the negative side of the battery. If both sides are connected to either side of the battery no current can flow. So help me understand my misunderstanding of the first diagram. The second diagram will always connect one side of the motor to either the positive or the negative while connecting the other side of the motor the the opposite side of the battery.

Oh crap, would you believe I never caught that. Post #2 shows a few circuits. The image on the left is the one that now looking at it is wired incorrectly as drawn, unless of course we use a magic motor. There is also a time limit to edit post which I believe has likely passed so I can't fix the thing. I have looked at that incorrect drawing a hundred times, yeah, yeah, DPDT switch to reverse a DC motor, yeah and yeah. Never caught that. Call me slow on the uptake.

<EDIT> Fixed It! </EDIT>

Thanks Again
Ron

 

Oh crap, would you believe I never caught that. Post #2 shows a few circuits. The image on the left is the one that now looking at it is wired incorrectly as drawn, unless of course we use a magic motor. There is also a time limit to edit post which I believe has likely passed so I can't fix the thing. I have looked at that incorrect drawing a hundred times, yeah, yeah, DPDT switch to reverse a DC motor, yeah and yeah. Never caught that. Call me slow on the uptake.

<EDIT> Fixed It! </EDIT>

Thanks Again
Ron

OMG,I thought after to many years in this world I had finally lost it and thought there were magic motors or something.
Have a nice one.
R