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cuemaker
01-17-2013, 10:26 AM
I have need of a simple machine that I will be making. The part I need help with is they type of motor/electrical setup I need to reverse the spin of a motor.

Basic concept is part go in, goes so far, hits a switch (preferably physical), then the motor reverses. I then need the motor to reverse again for the next input.

What ever the motor/switch is, I can build the rest. I am just unsure of the proper equipment for the electrical side.

A complete cycle is, motor spins clockwise, part goes in, hits switch, motor reverses, part goes out, motor needs to switch again to clockwise.

What also may work and be simpler, is a switch that can be done by hand.

Complete cycle time is 10 seconds or less.

Rosco-P
01-17-2013, 11:01 AM
I have need of a simple machine that I will be making. The part I need help with is they type of motor/electrical setup I need to reverse the spin of a motor.

Basic concept is part go in, goes so far, hits a switch (preferably physical), then the motor reverses. I then need the motor to reverse again for the next input.

What ever the motor/switch is, I can build the rest. I am just unsure of the proper equipment for the electrical side.

A complete cycle is, motor spins clockwise, part goes in, hits switch, motor reverses, part goes out, motor needs to switch again to clockwise.

What also may work and be simpler, is a switch that can be done by hand.

Complete cycle time is 10 seconds or less.

How large (Hp.) a motor? AC or DC? Single phase AC or three phase?

Part goes in, hits a ?? attached to a microswitch which signals a reversing motor contactor, part goes back out.

cuemaker
01-17-2013, 11:09 AM
Sorry, had this info in the first draft...

Prefer single phase... Dont care about AC or DC, whichever works and is best. I will be using a gear reducer. As for HP, .5hp or less I would think..


The part can go in an hit a switch.. or the switch can be done by hand...

I dont even know terms, and that maybe half the battle for me. Microswitch to a reversing motor contactor gives me something to google...

MaxHeadRoom
01-17-2013, 11:29 AM
Most motors, unless fitted with some kind of intelligent drive or VFD etc, do not take kindly to immediate reversal (plugging), so if using say, a couple of MicroSwitches, and a reversing contactor, they can be picked up reasonable on ebay.
And if using a plain direct on motor, then some kind of delay is desirable rather than performing an immediate reverse.
With DC drives and VFD's, the timer is not required as they have an automatic wind down and back up again.
The advantage to using reversing contactors is they have built in electrical and mechanical interlock to prevent both being picked up simultaneously.
Max.

Jaakko Fagerlund
01-17-2013, 11:48 AM
Microswitch triggers the reversal and a one shot timer. Once the timer has done its job, the motor reverses again and spins until the microswitch is pushed again. With a VFD it would be easy, as it has inputs for logic level controlling such as reverse.

cuemaker
01-17-2013, 11:52 AM
I never thought a of a drum switch...

http://www.mcmaster.com/#7065K22

That would make it simpler..Not as efficient, but simpler to build

lwalker
01-17-2013, 12:03 PM
I drew this schematic a few years ago so someone could open/close a chicken coop door automatically with two electromechanical timers.

http://www.cedarlakeinstruments.com/SharedFiles/coopdoor.png

The "move door RIGHT/LEFT" inputs are power (in this case 12V) supplied by the timers. The LEFT and RIGHT switches are limit switches triggered when the moving door touches them. Supplying 12VDC to either input drives the door in that direction until it hits the opposite limit switch and then stops.

This was for a DC gear motor. I haven't built the circuit myself, but the person I designed it for did and he said it works very well. Hope it helps.

Lyndon

lakeside53
01-17-2013, 12:22 PM
Most single phase capacitor start motors will not reverse if they are already spinning in the opposite direction - they need to stop (or very close) first. However, electric gates with safety feature need them - gate opens, hits "something" and immediately reverses. These do not have centrifugal switch and are capacitor start/run. I use 1/2hp 120v motors on our community gates. If you want the part numbers I can look them up.

Paul Alciatore
01-17-2013, 12:38 PM
What others above are trying to say is, AC motors usually need a short period of time to stop BEFORE they can be powered in reverse. So, just hitting a microswitch, even one rated for the inductive load may not produce the desired results. Some AC motors may actually continue to run in the same direction, but with less power. The problem is due to the flywheel effect and it is generally best to allow the mechanism to stop before reversing.

If I were designing such a system I would do one of three things:

1. Use a stepper motor with suitable drive circuit. Steppers can be reversed much faster but a small delay may be needed if there is significant rotating mass.

2. Use a permanent magnet DC motor. DC motors are also better for fast reversals.

3. If an AC motor is necessary, you will need a good control circuit instead of just a reversing switch. The exact details will depend on the characteristics of your machine, especially the amount of time needed for the motor/mechanism to coast to a stop. You should not apply reverse power until it has stopped or at least is going very slow. This can be done with time delay relays or with some kind of electronic controller. Note that larger motors with more mass will need longer stop times so proper motor size is important.

Another possibility would be a brake to stop the rotation before reversing the motor.

A micro-controller (for number 3 above) would probably be less expensive than time delay relays but takes more expertise of the computer variety to implement. And you would still need motor control relays.

Here is another thought. How about a clutch mechanism that would allow choosing between forward and reverse gearing? The motor runs at one speed, in one direction and the reversing is done mechanically. The reversing could be automatic at one end via a toggle mechanism that positively trips when the set point is reached. At the other end (start end) you would probably want auto stop with a manual reverse to allow the next part to be inserted. Here you only need a simple on/off switch for the motor and all the rest is mechanical. There are many ways to implement this with gears, pulleys, etc.

I assume you are making a machine to make a particular part. Part of your choice of methods should/would depend on how many of these parts you expect to make. The micro-controller would be the most reliable for a lot of parts while a mechanical clutch may need more maintenance over thousands or hundreds of thousands of cycles. Micro switches that carry heavy currents (motor current) will wear out a lot faster than such switches that only carry small control currents. This can be a major factor in long term operation.

cuemaker
01-17-2013, 12:53 PM
If a DC motor give me what i need..then that is the way i would go.

Can someone do some shopping for me? An example of a DC motor..limit switch and whatever else i need to switch the motor. I am thinking roughly 30 cycles a minute

Tim in D
01-17-2013, 02:02 PM
Funny, I'm trying to spec the exact same requirement. I need a "plug reversing" motor to drive a simple drive screw set up. I'm looking at a small stepper motor but haven't found a source for a SIMPLE DRIVE module. Something that has an onboard variable speed pot. I don't need no stink'n program!!!! Anyone have a source? (not Gecko)

Tim in D

lwalker
01-17-2013, 02:25 PM
A motor like this perhaps? (http://www.automationdirect.com/adc/Shopping/Catalog/Motors/DC_Motors_-_General_Purpose_IronHorse_%280.33_-_2HP%29/Permanent_Magnet_DC_Motors_-z-_90_VDC_Armature_%280.33_-_1.5HP%29/MTPM-P33-1L18).

I missed the part where you said it had to auto-reverse at the limit, so the circuit I linked to won't do that. 30 cycles per minute for how long? Switching with electromechanical relays is cheap and easy, but if this thing has to run 24/7 then the relays won't last long.

I have circuit boards for a product I make, so I can build you a controller that won't be expensive. Send me a PM if interested.

Lyndon

MaxHeadRoom
01-17-2013, 02:43 PM
I don't know what rpm you need, but if you need a motor that is instant reverse, instant stop/start and does not need a controller, you may be able to use an AC synchronous stepper, these are basically the same as a DC stepper but are designed for 120vac use.
The used to come up on ebay cheap, because they were no use for CNC positioning etc.
One of the principle Manuf. was Superior Electric.
The limitation is they are 72rpm on 60Hz,.
Max.

becksmachine
01-17-2013, 03:23 PM
You can get single phase AC motors that will instantly reverse.

Graingers probably still sells them.

Dave

Paul Alciatore
01-17-2013, 04:38 PM
I have to go out. I can do a DC motor schematic later tonight.

oldtiffie
01-17-2013, 04:59 PM
I have a very high torque brushless DC motor on my Sieg SX3 mill which has a "tapping" control/switch - tapping capacity = 1/2".

I have not had a problem with it reversing frequently under load.

Spindle Speed (steps / rpm) - Variable (100-1750rpm)

One of those motors and controllers should work fine.

http://www.machineryhouse.com.au/M155

HAP
01-17-2013, 06:27 PM
Garage door motor...

sch
01-17-2013, 07:15 PM
Surplus center had stripped garage door opener motors on the GDO base plate for $15-20 but they are not easy to find on their website. They do have maxheadrooms "Slosyn" 72 RPM plug
reversible motors for $10: http://www.surpluscenter.com/item.asp?item=10-1032&catname=electric They require an auxiliary 500 ohm 50W resistor and 0.75 mf cap in series with one lead
to operate but they do plug reverse and have a fixed 72rpm so no gear down needed, or controller if the rpm is fast enough.

Any gear drive motor obviates the plug reversal problem, since the gear drive gives you an instant brake, at least for under a few hundred rpm. Even VFD have a cycle time of a second or so to 'plug reverse'.

J Tiers
01-17-2013, 07:52 PM
You CAN do this with an AC induction motor..... It has to be a "PSC" type, which is a capacitor start/run motor with no centrifugal switch.

It works the best with the type of motor in which both windings are identical, in which case the capacitor is connected between the ends of the two windings, the AC is switched between those ends to reverse, and the other end is commoned up with the other AC wire.

In no case is the motor "stopped on a dime", basically the torque is fixed, and the accel torque is about the same as the decel torque, so accel and decel times will be similar. A combination of this reversal with a DC braking will speed it up a lot.

A VFD will do that with a 3 phase motor, and garage door motors are often 3 phase (larger doors/industrial doors). I have a garage door motor (3 phase) from "Doerr" running the lathe right now.

Doing it with an AC single phase motor may not be the optimal way to get your job done.... how open to other ideas are you?

MaxHeadRoom
01-17-2013, 08:25 PM
They do have maxheadrooms "Slosyn" 72 RPM plug reversible motors for $10: They require an auxiliary 500 ohm 50W resistor and 0.75 mf cap in series with one lead
to operate but they do plug reverse and have a fixed 72rpm so no gear down needed, or controller if the rpm is fast enough..

They will also take a stall condition, current will remain the same as when running, instant stop and reverse.
Max.

The Artful Bodger
01-17-2013, 08:55 PM
Stopping and immediately reversing may be stressful for a motor especially if it is done repeatedly. One option is to couple two motors and wire them run in opposite directions then switch one or the other as required.

Each motor only runs 50% of the time but being coupled together their cooling fans are running almost all the time.

Deja Vu
01-17-2013, 09:15 PM
an option might be to put an electric brake on the motor shaft to stop and release. Or somewhere in the drive train.

J. R. Williams
01-17-2013, 09:31 PM
Why not do the same thing with a simple mechanical pulley system? I have an old Jet tapping machine that changes the direction of the output shaft by raising and lowering a handle. Two friction clutches in the unit.
Starting and stopping a motor with lead to failure of the motor with heat.

cuemaker
01-17-2013, 10:15 PM
Doing it with an AC single phase motor may not be the optimal way to get your job done.... how open to other ideas are you?

I am open to what ever is most efficient and simple. I had a talk with Lwalker.. and he suggested a 12vdc or 24vdc gear motor...I need to firgure out how much "force" I need... But I dont think its going to be very much at all...

darryl
01-17-2013, 10:53 PM
There are several styles of 12v dc gear motors out there- I just bought a couple from Princess Auto for less than $10 each. Most of these are worm gear types, which means you would use it to turn a threaded shaft which runs your mechanism back and forth. The ones I just got look like they might be seat adjustment motors. A slightly larger version is a window crank motor.

They start and stop fairly quickly, so you might get by with a simple double pole, double throw toggle switch. If you put a low value resistor in series with the motor, it will limit the pulse current from instantaneous reversal. Depending on the motor, the resistance could be in a range from .3 ohms to about 3 ohms. You might find that the length and gauge of wire you use to wire up the motor, switches, and power supply would give you enough resistance to keep peak currents within switch ratings.

You do need to figure out what force and speeds you need, and what distance the part must be moved each way. If a small dc motor can do this job, then the task is easy.

If the stroke is going to be fixed, then you could go with a reciprocating mechanism. It could be a crank, but it doesn't have to be. I saw one mechanism which had a metal strip with a slot in it, and teeth all around the inside of the slot. A drive gear rotating continuously in one direction alternately drives the strip one way, then the other. The strip is basically a connecting rod, but it gives a long stroke relative to the short side movement it makes as the gear drives around the end zones.

Paul Alciatore
01-17-2013, 11:54 PM
OK, here is a drawing for controlling a DC motor, hopefully in the way you want.

http://img.photobucket.com/albums/v55/EPAIII/DCMotorReverseNStop1.jpg

I am assuming that economy is important. The only control elements you need are three switches that can handle the Voltage and current. S1 is a standard DPDT (Double Pole, Double Throw) toggle: it should have two sustained, on positions. S2 is a momentary, SPST (Single Pole, Single Throw) toggle that is Normally ON. S3 is a momentary, SPST (Single Pole, Single Throw) toggle or push button that is Normally Off. It serves as the cycle Start button. These three switches can be purchased new for under $15, probably under $10 so it should be economical. This is probably as simple and inexpensive as it gets.

The overall carriage movement can be almost any distance as long as it is greater than the distance needed to activate the switches. The sliding rod which trips S1, the reversing switch, only moves far enough to activate that switch.

The circuit operates as follows:

1. The mechanical sketch and schematic are both shown in the left hand or off or start position. S1 (Reverse) is set for right hand motion but since both S2 and S3 (Start) are open, the motor does not run. S2 is a Normally Closed switch, but the moving carriage is resting against it so it is open.
2. When S3 (Start) is pressed, the motor runs and the carriage moves to the right.
3. Shortly after the carriage starts moving, S2 is released and comes to it's Normally Closed position. This allows the motor to continue running through it. It remains in that position for the rest of the cycle until the carriage returns to the left in step 6 below.
4. S3 (Start) can be released by the operator shortly after S2 closed.
5. When the carriage reaches the right end of travel, it hits the arm on the right hand end of the sliding rod which trips S1 (Reverse) to the opposite position. This reverses the direction of travel and the carriage now moves left.
6. When the carriage reaches the left end, two things happen at the same time:
a. It hits the arm on the left end of the moving rod and that trips S1 back to the forward position.
b. It hits S2, turning the motor off.

In building this I would suggest two things:
1. The pins that activate the switches (S1 and S2) should have some spring action. Perhaps a rubber tube over them would work or perhaps an actual spring would be needed. This slight spring action is needed to allow the motor time to reverse or stop as these actions are not instantaneous. I show pins as a concept, not a design detail.
2. The timing of switches S1 and S2 at the left end of travel is critical. It is probably best if S2 turns off first and then S1 reverses as the motor coasts to a stop. This may require tight mechanical tolerances and a careful set-up. It would be good to incorporate features that make adjusting these switches easy.

The circuit may be adaptable for reversible AC motors.

Paul Alciatore
01-18-2013, 12:30 AM
I did a fast bit of research on AC reversible motors and from what I can see, they are controlled by a Three Pole, Double Throw (3PDT) switch. Such switches can be purchased in the toggle form and easily substituted for the S1 in my other post. You may have to move the S2, S3 combination to line side of S1, but otherwise they would work as described above. So my concept and circuit would be adaptable to AC reversible motors. And timing would be a lot less critical.

If you decide to go with an AC motor and need more help with the circuit, I can do a drawing for that.


Another thought here would be to use a crank style mechanism. That way the motor can run in one direction only. And it would provide extra force at the end of the stroke where you may need it the most. An offset would provide for a faster reverse stroke. Your controls would be one switch to stop it at the end of a stroke (like my S2 above) and another in parallel with it to start it for the next cycle (like my S3 above). A cam/paw on the crank arm would serve to activate the Stop switch.

AlanHaisley
01-18-2013, 01:18 AM
More information would be useful. You specify a <=10 second cycle but you also specify 30 cycles per minute - which is a 2 second cycle time.
How many total "parts" is this machine going to process? If it's a few hundred or less, you could build simpler, figuring that you would be done before switches or motors have burned out.
Might something like a spring return work for the part removal part of the cycle? In that case there might be a way to have the motor only turn in one direction.

HarryG
01-24-2013, 02:42 PM
Just tried to send you a PM and got an error message: "your mailbox is full..."

cuemaker
01-24-2013, 02:59 PM
Just tried to send you a PM and got an error message: "your mailbox is full..."

All fixed...