# How To Wire A Universal Motor For Reversing (switches)



## bvd1940 (Dec 4, 2015)

I have a 1/15 hp 110 volt ac/dc universal motor I am trying to figure out how to fix the switches on my surface grinder to reverse the table and what type of switch as the table travel,s back and forth.
I know how to swap the black and blue to reverse the direction BUT my 75 year old brain aint working as it did back in the 60,s and cant wrap my brain around the switch needed.

red & blue wires hooked together
black & yellow are line & neutral
You swap black and blue wires for reversal of motor.
I can not get it through my old gray cells what type of switch that will work like a micro switch till the end of each stroke. Is that clear enough????
Any help would be appreciated, my left arm is getting deformed from cranking it back and forth.


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## Tony Wells (Dec 4, 2015)

I wouldn't recommend reversing the table feed in such an abrupt manner. It will draw considerable current and be pretty tough on any relays or solid state switching you do. Not too easy on the mechanics either for that matter, jerking the mass of the table, chuck, vise, part, or combination thereof. Ideally, you should put a delay at the end of each end of the stroke and deal with the mechanical shock as well as the back EMF and the high current surge.

oh, try the right arm for a while, things will even out


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## RJSakowski (Dec 4, 2015)

For a brush type motor, the two wires would be connected to the two center terminals of a DPDT switch.  The remaining four terminals are connected in a criss-cross fashion and two wires from the same end or side  outside terminals are connected to the motor.


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## RJSakowski (Dec 4, 2015)

If there is a concern about high current draw due to reversal, select a DPDT  center off switch.  Hold in the center position for a second to allow the movement to stop.  I use a similar scheme for controlling a pulse width modulated trolling motor that draws 35 amps.  A lower speeds, I can safely switch between forward and reverse.  I never do so at full power for the reason stated by Tony.


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## Tony Wells (Dec 4, 2015)

I've been mulling over the same project. There are just too many ways to get there! I don't use my grinder much, and have my eye on another one.....so I might never tackle it. But I'll be interested in watching your progress.


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## bvd1940 (Dec 4, 2015)

Tony Wells said:


> I wouldn't recommend reversing the table feed in such an abrupt manner. It will draw considerable current and be pretty tough on any relays or solid state switching you do. Not too easy on the mechanics either for that matter, jerking the mass of the table, chuck, vise, part, or combination thereof. Ideally, you should put a delay at the end of each end of the stroke and deal with the mechanical shock as well as the back EMF and the high current surge.
> 
> oh, try the right arm for a while, things will even out


I have thought about that abrupt stop and am not to worried about the amps as it is a 1/15 hp motor that is geared down + a speed control for keeping the thing moving slower which would be slow enough not to hurt anything but what do I know.
I have one of the HF router speed control witch works real good on that low amp motor. (1.3 amp) with lots of torque.
But you are right, still thinking.


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## bvd1940 (Dec 4, 2015)

RJSakowski said:


> For a brush type motor, the two wires would be connected to the two center terminals of a DPDT switch.  The remaining four terminals are connected in a criss-cross fashion and two wires from the same end or side  outside terminals are connected to the motor.
> View attachment 115908


At low speed you do not have a problem with instant reverse?? If that is the case it should be OK to run this at the reduced speed I have set up for it.
This is run off of 115V AC and regulates the speed of the motor great.


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## bvd1940 (Dec 4, 2015)

RJSakowski said:


> If there is a concern about high current draw due to reversal, select a DPDT  center off switch.  Hold in the center position for a second to allow the movement to stop.  I use a similar scheme for controlling a pulse width modulated trolling motor that draws 35 amps.  A lower speeds, I can safely switch between forward and reverse.  I never do so at full power for the reason stated by Tony.


I want to turn this on and let it run back & forth continually so it will have to be a trip switch on each end.
I think I might go onto Flebay and see what else the chicom,s have to offer again, I was being a tightwad as I had this real nice small gear reduced ac/dc Dayton motor in my spare parts that fit the location so nice and the HF variable speed worked soooooo nice. I have even tried to figure a system like my shaper has but it requires to large of a wheel to get the stroke I want.
Bill


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## Tony Wells (Dec 4, 2015)

I'm leaning towards a hydraulic or pneumatic cylinder I have one with about a 3/4" bore, but it's only a foot or so stroke. Not sure about the effect, if any, on the reciprocating action of the table. Mine has plain vee ways, so I'm wondering about where to do the mount, and if it will try to twist or lift the table. If I can get it all worked out, I can have variable length and speed. I'll get a longer cylinder if I get that far. I've thought about using a sprocket on the handwheel shaft tied to the cylinder by a #35 chain or so.....and an extension spring on the "free end" of the chain to anchor it.

Too many ways to approach it.


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## RJSakowski (Dec 4, 2015)

bvd1940 said:


> At low speed you do not have a problem with instant reverse?? If that is the case it should be OK to run this at the reduced speed I have set up for it.
> This is run off of 115V AC and regulates the speed of the motor great.


I would think that you are fine at typical milling speeds.  If you are doing a rapid traverse, just pop the switch to the center off position until the table stops and then reverse.  I used a transistor switched control and early in its life, I did flip the switch under full power and blew the transistors.  Since then, I make it a practice to only switch at low power and have not blown a transistor in twenty five years.  Here are some possible candidates for your switch.  
http://www.digikey.com/product-sear...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

Bob


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## JimDawson (Dec 4, 2015)

When I get out to the shop today I'll dig out a schematic of the switching for a universal motor, it's different (and a little more complex) than a brushed DC motor.  I did this for the power draw bar on Alloy's Shizouka.  The problem I see is that an instant reverse at the end of stroke.  The table needs to accel, run at speed, then decel to a stop before reversing.  This could be accomplished, sort of, by setting a delay before reversing, at least allowing the motor to coast to a stop before switching direction.  It's going to take a little electrical hardware the get it right.

An air cylinder would work pretty well since it is ''squishy'' on the start and stop, and could be well controlled by another dampening cylinder that is filled with light oil.

I am going to do the same thing and have been scrounging parts for some time.  I have the parts on the shelf now, but I haven't had time for that project yet.  Hydraulics work but I hate hydraulics.  My DoAll is all hydraulic and that hardware is going to be removed and servo control installed.


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## bvd1940 (Dec 4, 2015)

Tony Wells said:


> I'm leaning towards a hydraulic or pneumatic cylinder I have one with about a 3/4" bore, but it's only a foot or so stroke. Not sure about the effect, if any, on the reciprocating action of the table. Mine has plain vee ways, so I'm wondering about where to do the mount, and if it will try to twist or lift the table. If I can get it all worked out, I can have variable length and speed. I'll get a longer cylinder if I get that far. I've thought about using a sprocket on the handwheel shaft tied to the cylinder by a #35 chain or so.....and an extension spring on the "free end" of the chain to anchor it.
> 
> Too many ways to approach it.


Now that chain and cylinder is food for thought, with a flow control and a soft stop/reverse that should work good but you still need hyd/air to run it.


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## bvd1940 (Dec 4, 2015)

RJSakowski said:


> I would think that you are fine at typical milling speeds.  If you are doing a rapid traverse, just pop the switch to the center off position until the table stops and then reverse.  I used a transistor switched control and early in its life, I did flip the switch under full power and blew the transistors.  Since then, I make it a practice to only switch at low power and have not blown a transistor in twenty five years.  Here are some possible candidates for your switch.
> http://www.digikey.com/product-search/en?pv783=247&pv783=263&pv783=382&pv783=239&pv783=238&pv783=400&pv783=262&pv783=219&FV=fff40011,fff80064,2080004,3ac0003&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
> 
> Bob


This is not a mill it is a surface grinder and I just need about 13 inches of travel at a very low speed, the switch will need to be tripped by the table ,s back and forth movement unattended. I may have to go to steppers but did not want all the extra electronics +$$ and programming.


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## bvd1940 (Dec 4, 2015)

JimDawson said:


> When I get out to the shop today I'll dig out a schematic of the switching for a universal motor, it's different (and a little more complex) than a brushed DC motor.  I did this for the power draw bar on Alloy's Shizouka.  The problem I see is that an instant reverse at the end of stroke.  The table needs to accel, run at speed, then decel to a stop before reversing.  This could be accomplished, sort of, by setting a delay before reversing, at least allowing the motor to coast to a stop before switching direction.  It's going to take a little electrical hardware the get it right.
> 
> An air cylinder would work pretty well since it is ''squishy'' on the start and stop, and could be well controlled by another dampening cylinder that is filled with light oil.
> 
> I am going to do the same thing and have been scrounging parts for some time.  I have the parts on the shelf now, but I haven't had time for that project yet.  Hydraulics work but I hate hydraulics.  My DoAll is all hydraulic and that hardware is going to be removed and servo control installed.


I appreciate any help with this as I am feed up running the table by hand, I can put a fine tooth pawl on cross feed  then very little arm movement will be involved. Also do like they do on my shaper for down feed. (dream on old fool)
Thanks to all for imput as you are making my gray cells wake up 
I will take a pic of the motor mounted on the grinder & you will see why I would like to use this setup.


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## bvd1940 (Dec 4, 2015)

Well here ar the pics of the Mtr and mount, see if that helps.


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## JimDawson (Dec 4, 2015)

I found the schematic I was looking for, I'm trying to simplify it now.  If I posted it as it is, it would just confuse the issue.  I did find this name plate diagram on line so a good starting point.  I needed to confirm that it is wired the way I thought is was.


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## bvd1940 (Dec 4, 2015)

JimDawson said:


> I found the schematic I was looking for, I'm trying to simplify it now.  If I posted it as it is, it would just confuse the issue.  I did find this name plate diagram on line so a good starting point.  I needed to confirm that it is wired the way I thought is was.
> 
> View attachment 115957


that is the setup I have just need to know what type switch to use to have the table trip it both ways for reversing the mtr.


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## British Steel (Dec 4, 2015)

Dual-pole, Dual-throw, rated well above the motor current, no "centre-off" position - that should do it.
If you were very keen you could use a contactor or two so the switch wasn't handling the motor current (just the contactor coil current), but with such a small motor? not a lot of point IMHO. If you're using a DC feed to the motor, it's a lot harder for the contacts and I'd go with a contactor.

Remember you need to maintain the field current AT ALL TIMES, reversing-switch the armature (brush) current! And a Main Switch that feeds both the field and the reversing switch when the work's done...

Dave H. (the other one)


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## John Hasler (Dec 4, 2015)

British Steel said:


> Remember you need to maintain the field current AT ALL TIMES, reversing-switch the armature (brush) current!


It's a series motor.

I'd use a couple of microswitches and a latching relay.  The relay would need DPDT contacts plus an NO contact for latching.


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## bvd1940 (Dec 4, 2015)

British Steel said:


> Dual-pole, Dual-throw, rated well above the motor current, no "centre-off" position - that should do it.
> If you were very keen you could use a contactor or two so the switch wasn't handling the motor current (just the contactor coil current), but with such a small motor? not a lot of point IMHO. If you're using a DC feed to the motor, it's a lot harder for the contacts and I'd go with a contactor.
> 
> Remember you need to maintain the field current AT ALL TIMES, reversing-switch the armature (brush) current! And a Main Switch that feeds both the field and the reversing switch when the work's done...
> ...


hope to use 115 volt AC trough a speed controller.


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## JimDawson (Dec 4, 2015)

OK, I think this will work.   one 3PDT relay and 2 micro switches.


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## bvd1940 (Dec 5, 2015)

JimDawson said:


> OK, I think this will work.   one 3PDT relay and 2 micro switches.
> 
> View attachment 115963


That looks like it might just do the trick Jim, thanks a bunch.
I will start rounding up the parts and when I get it working I will report back


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## Wobbles (Dec 8, 2015)

bvd1940 said:


> I have thought about that abrupt stop and am not to worried about the amps as it is a 1/15 hp motor that is geared down + a speed control for keeping the thing moving slower which would be slow enough not to hurt anything but what do I know.



In my experience, the electrical issues take a back seat to the mechanical issues when gear reduction is present. In machines I've worked on, the system inertia during instant reverse will overload various components of the gearbox. Keys will shear and gall shafts, or gear teeth will break. If you think finding and wiring a similar electrical switch is hard, wait until you start hunting for exact gearbox replacement parts !!

I'm all for a time delay function. This could be as simple as extending the control switch handle. The physical act of  "throwing" an electrical switch with a 12" long handle takes much longer than a 3" handle. 

Harder to implement after the fact, but more forgiving in its action, would be a flat or V-belt that would slip well before mechanical damage occurred. Examples of this design are found on inexpensive garden tillers.


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## bvd1940 (Dec 8, 2015)

Wobbles said:


> In my experience, the electrical issues take a back seat to the mechanical issues when gear reduction is present. In machines I've worked on, the system inertia during instant reverse will overload various components of the gearbox. Keys will shear and gall shafts, or gear teeth will break. If you think finding and wiring a similar electrical switch is hard, wait until you start hunting for exact gearbox replacement parts !!
> 
> I'm all for a time delay function. This could be as simple as extending the control switch handle. The physical act of  "throwing" an electrical switch with a 12" long handle takes much longer than a 3" handle.
> 
> Harder to implement after the fact, but more forgiving in its action, would be a flat or V-belt that would slip well before mechanical damage occurred. Examples of this design are found on inexpensive garden tillers.


The motor is so low HP 1/15th and slow speed with very low amp draw I can not foresee any problems with a timing belt reduction on top of all that.
I can put a spring loaded pulley to take up the shock if needed.
If I have to much problem with it I will pop for a stepper + Arduino + power supply


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