Reversible Motor Problem

Discussion in 'The Projects Forum' started by oilcan67, Jun 14, 2008.

  1. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Greetings...my first post here.

    I have a reversible motor and I would like to have one switch run the motor one direction (when pressed) then another switch run the motor the other direction (when pressed). Then have the motor not run at all when the switches aren't pressed.

    The motor has four wires (blue, black, yellow and red) and runs with a permanent split capacitor. It's a 110v ac motor.

    The directions say:
    -Twist the blue and black wires together with one line from the AC.
    -The red line goes to one side of the capacitor and the yellow goes to
    the other side.
    -The other line from the AC goes to the yellow side of the capacitor.
    -Then, to reverse the motor - simply switch the red and black wires.

    Seems simple enough but after days puzzling over this I can't figure it out. I'm an inventor but not much experience with electricals.

    I have a bunch of SPDT switches and four 8-pin relays. (octal configuration)

    Any help would be greatly appreciated.

    oc
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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    Seems pretty straightforward...
    motorreverse.jpg

    Just don't press both switches at the same time...
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Thingmaker, I'm sorry to inform you that your schematic won't work as you've drawn it.

    For this kind of application, you really should consider using a drum switch. They have three positions; forward, off, reverse. Unfortunately, good ones are no longer inexpensive. Square D units start off at around $100.
    http://www.grainger.com/Grainger/items/2BW44?BaseItem=2BW46
    You might find one at a place where they sell industrial salvage.
    Here is a Square D datasheet for installation of a drum switch:
    http://ecatalog.squared.com/pubs/Mo...ches/Reversing Drum Switches/65013-019-89.pdf

    However, see the attached.
    S1 controls power on/off.
    S2 controls direction.

    Not precisely what you asked for, but it sounds like the relays you have available are most likely DPDT. To get what you want would require 3PDT. I don't recommend using two separate relays.
     
    Last edited: Jun 14, 2008
  4. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Thanks to you both very, very much. I did try wiring it as described in the first post and it didn't work. I think I can get it to work with the diagram with the 3pdt relay. Maybe if I use two switches for the directional control.

    Quick question...what is that rectangle thing with the wire wrapped around it? (after the S2 switch?

    Thanks again. I was struggling.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
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    I see it now. Either the red or black connects to hot and blue. The other connects to neutral. I apologize for my error, and thanks to Sarge for setting me straight.

    It can be done with a pair of DPST switches:
    motorreverse2.jpg
    Pushing both buttons at the same time would be a Very Bad Idea. Fabricating some type of lever arm to actuate the switches, one at a time only, might work.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Thingmaker3, you're getting closer - except that you have left the blue wire unswitched. This would leave the motor partially powered; an un-good thing. Additionally, leaving the possibility of a dead short if both switches are pressed simultaneously is a very un-good thing. Yes, I know - Microsoft does it all the time. :rolleyes: ;)

    As I've already mentioned, for this motor to be reversible a three pole switch is a minimum requirement.

    You have a 3PDT relay? You mentioned octal relays - which I assumed you meant they have a total of 8 pins configured as the old octal tube sockets, that were DPDT (that uses six of the pins) and the other two are for the relay's coil.

    If you do in fact have a 3PDT relay, you can then do what you really want.
    You will also need a SPST NO pushbutton and a DPST NO pushbutton.

    The circuit that I originally posted will work safely, and it is not possible to select a combination of switches that will result in an unsafe condition. If the motor is capacitive start (you hear a click right after the motor starts) then toggling the direction switch while the motor is running will do no harm. If it is a split-phase motor, it will be very hard on it.

    That represents the coil of the relay. When power is applied across the coil, the relay's contacts toggle states.
     
    Last edited: Jun 15, 2008
  7. SgtWookie

    Expert

    Jul 17, 2007
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    OK, here's a variation on the circuits provided thus far.

    S1 is shown as a SPDT, but it can be a SPST NO instead.
    S2 is shown as a DPDT, but it can be a DPST NO instead.
    RLY1 is a DPDT; that is not negotiable. ;) The rectangle with the diagonal line through it is the coil of the relay.
    S1 and S2 individually provide the 3rd pole that is necessary for the circuit to work properly.

    When S1 is ON, the motor will run in the forward direction.
    When S2 is ON, the 2nd set of contacts causes the relay to energize, reversing the connections between the red and black wire, so the motor runs in reverse.

    Nothing terrible will happen if both are turned on at the same time, if the motor is capacitive start.

    See the attached.
     
    Last edited: Jun 15, 2008
  8. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Excellent. I'll try it this week and report back.

    A million thanks. I don't have a 3pdt but I am near a McMaster-Carr and I have a little money to throw at this project.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    You don't need a 3pdt relay if you have a DPDT relay.
    What are the part numbers on the four 8-pin "octal relays" that you have?
    What is the HP rating of the motor, and the current draw?
    Do you have a DPST NO or DPDT switch that you could use for the reverse configuration?
     
  10. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    If you are not absolutely set on push buttons, Grainger has a nice switch (Dayton brand) for about $35.00. I am assuming you are in the USA.
    John
     
  11. thingmaker3

    Retired Moderator

    May 16, 2005
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    So the blue wire has to switch from hot to neutral when the red and black are reversed?

    Indeed, three poles would be needed.

    I much prefer working with my DC motors.:rolleyes:
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    No, the blue wire simply has to be disconnected. It is connected to hot only when the red/black are connected to hot/neutral or neutral/hot; otherwise current would be applied to one of the field windings constantly.

    Yes, AC motors can be a pain.

    When I was a teenager, my Dad gave me the job of connecting up the motor to his metal turning lathe; whomever he bought it from (used) had removed it for use on something else. Fortunately for me, he'd brought home a Square D drum switch similar to the one I posted earlier. It took a good bit of head-scratching, reading the directions a dozen times and comparing them with the instructions on the motor, and several trial-and-error hand-drawn schematics, but I managed to get it hooked up and working the first time around.

    It's still working, 30+ years later. It does pay to get quality equipment.
     
  13. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Sorry for being such a gump but where would the capacitor go in this configuration? The capacitor has two posts with 4 lead-ins on each post.

    I took this info right from the the motor: Input HP: 1/60@60Hz Ratio108.6 Torque 67 in. Lbs.@50/60 Hz F/L RPM @ 60 Hz: 14 F/L RPM @50 Hz: 11 Volts: 115 Hz: 50/60 SF: 1.0 F/L Amp @ 60 Hz: .36 F/L Amp. @50 Hz: .38 Ph: 1 Ins. Class: A 40degrees C. Amb. Mtr. Ref. No.: EM5H-15-1

    Requires 5 MFD-370 VAC oil-filled capacitor for 50/60Hz operation.

    The relays that I have are NTE R02-11A10-120 The switches are are all microswitches SPDT but I live in Los Angeles so I can get just about anything in about an hour or less.

    Thanks for that. Yeah, my shop is near a Grainger but I do need push buttons that activate with about 3lbs of pressure. The micro switches I've been using work perfectly (besides not being wired properly)

    The application is something like this. I have a rail that pivots in the center. The rail has a ball on it and when the ball rolls to one side of the rail the weight swings a pendulum (mounted directly down from the center of the rail) The pendulum hits a switch and the gear motor forces the pendulum the opposite direction. This would tilt the rail in the opposite direction and the ball would roll the other way until the weight of the ball forces down the other side etc... Ultimately, it would just be a ball that rolls back and forth on a rail.

    Seems like a lot of work for something so esoteric but that's the nature of my biz..

    Thanks again everyone...

    oc
     
    Last edited: Jun 16, 2008
  14. SgtWookie

    Expert

    Jul 17, 2007
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    You are NOT being Gump-ish! That's a very good question, and I'm going to have to look at it more. It makes it a lot harder when you don't actually have the pieces in front of you to look at. It seems that I have erred by not specifically including the capacitor in the schematic. Please do not try to connect your motor by the last schematic I posted. I'll have to take some time to think this through again. The last time I connected one of these things up was over 30 years ago, and it took a good bit of thought to get it right the first time - and I had everything right in front of me. Now I'm trying to do it remotely!

    Tell me more about the 4 lead-ins on the cap - is there anything else connected to the capacitor? Can you take some pictures with a digital camera, and post them?

    I really want this to work the first time around, and not fry anything. I know you want that, too.


    OK, good deal. It helps a lot to have complete documentation on things, particularly the original reference material. It is all too easy to miss a tidbit, and then you're sunk!
    OK, great. With the fractional horsepower rating (about 12.4 Watts), you have a broad range of switches you can use. Lever-actuated microswitches would be a likely choice.

    Interesting - sounds like you're making a clock!

    Any chance of posting a pic of it when you're done? :)
     
  15. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Hello SgtWookie...

    Yes! I'll get a picture up tonight of the capacitor and I'll definetly post pics when I'm done with the thing.

    I appreciate how cordial everyone has been...

    oc
     
  16. oilcan67

    Thread Starter New Member

    Jun 12, 2008
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    Freakin eureka! It works!

    Sgtwookie: I looked at your diagram for a long time and figured out where to put the capacitor. (One pole of the capacitor to yellow and the other pole to the split that toggles between red and black.) Not sure why that didn't cross my mind before.

    Do you drink scotch? I have a good bottle for you!

    oc
     
  17. SgtWookie

    Expert

    Jul 17, 2007
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    Outstanding! I just finished updating the schematic, complete with pin numbers for your relay. You're correct.

    See the attached for the relay pinout and your updated schematic, with non-matching pin numbers X'd out and your pin numbers added in.

    Side note: when Square D company started marketing those relays in the 60's, they called them "Ice Cube" relays. They were heavily used in industrial applications, as they were so easy to replace when they failed/wore out. They will fit in a standard radio tube octal socket. I suggest you use a socket rather than attempting to solder to the relay's pins, as you may damage it.

    Do fish drink water? :D

    Offers of Scotch will always be accepted.
    Offers of GOOD Scotch will be most graciously accepted. ;)
     
    Last edited: Jun 16, 2008
  18. tim_howard26

    New Member

    Mar 9, 2009
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    0
    can sum 1make a more simple drawing explaining this. i have the same problem in a duct cleaning machine and for the life of me cant figure out how to reverse the motor. i thought maybe the relay was bad so i changed it, that wasn't it and the switch was worn so i got a new one, but it wasn't hooked up. so i assume because the switch no longer worked it had been unhooked and the machine was sold as is. my problem is i don't know how to wire the switch to make it reverse the motor. i'm not real sure the relay is hooked up right either. please help
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    Hi Tim,
    Although your situation is similar to the original poster's, your situation is quite different.

    Our original poster knew what all of the connections to his motor did; after that, it was just a matter of connecting them up correctly.

    In your situation, you have given us very little information; just that you have some kind of duct cleaning machine that has a relay and a switch, both of which you have new ones for.

    I suggest that you get the manufacturer and model number, and see if you can get a schematic from the manufacturer. Failing that, take it to a small appliance repair place - if you make a mistake connecting it up, you may wind up burning things out.
     
  20. meff00

    New Member

    Nov 7, 2009
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    Hey Sarge,
    I have the same issue as the original poster in this thread. I have a reversible dayton split phase gear motor I am attempting to set up for both directions. It will be used to drive a set of ACME screws on a band saw. What switch would I need to make this work. I currently have 1 DPDT on-off-on and I have a DPDT (ON) OFF (ON) momentary coming in the mail. I would really like to run this with just one switch. Is it possible? THe motor draws 4.6 amps continuous. It has a capacitor. Inside the electronics cover you see 2 screw posts, top has Black and blue connected. bottom has white and yellow. next to each screw terminal are 2 male quick connect flat terminals. I am not great at reading schematics but I may be able to figure it out. THanks for ALL and any help!!!!
    Adam
     
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