Auto control of winch to lower a table down and then back up again in one continuous winch movement. Change of direction occurs when the cable is full

Thread Starter

mc281

Joined Jan 17, 2023
3
I would like help with a circuit layout which works without any semiconductors please.... I would like to start a DC motor with a lift cable drum attached.... The motor would run continuously, lowering a table which would stop on a fixed stop but the motor continue in the same direction and pull the table back up without changing direction, just by the winch cable being wound up as the cable runs out and continues back up 'the other side' of the drum.... The table needs to go back to the top and then stop until the motor is restarted by a push button or microswitch.... HOWEVER the motor needs to restart in the opposite direction so the table drops down again, repeating this every time the button is pressed. Note that the table will not want to be stopped until it returns to the top again. Think of the motor as a YoYo up side down.... Help, I've got brain fade!
 

Thread Starter

mc281

Joined Jan 17, 2023
3
No but whatever it does I would like to reverse it... Sequence is closed trigger.. motor runs until back up again.. stop until trigger but reversed this time.. flip flop really.
 

LesJones

Joined Jan 8, 2017
4,227
Have two pulleys close together some distance below the drum and in line with the centre of the drum so the cable will remain in the same position just below that point. Have something clamped to the cable so it will operate a micro switch when the table is in the uppermost position. Call this microswitch 1.
Just below the drum have a spring loaded bar (Or roller.) that would be deflected by the cable when it was winding on that side of the drum. Have a micro switch positioned so it operated when that bar was deflected. This would indicate which direction the motor needed to rotate to unwind the cable. The microswitch that was triggered would decide weather the forward or reverse contactor was triggered when the start button was pressed. Once microswitch 1 was deactivated the selected contactor would remain latched until the table again reached the uppermost position.

Les.
 

LowQCab

Joined Nov 6, 2012
4,296
The mechanical aspects of what You want to do are far more important
than figuring-out the electrical aspects,
and must be determined first.

What happens when some object gets stuck in the way of the Table when raising it ?
What happens when something is in the way of the Table when it is being lowered ?
How much does the Table weigh ?
Will the Table have heavy objects placed on it ?
Is the Table mounted on a hinge ?, or is it completely supported by the Cable(s) ?
Is the Table large enough for people to walk under it ?
How much distance will the Table move ?
How much time is it expected to take for the
Table to to completely lower, and then completely raise ?

After all of the above mechanical aspects are
designed and drawn-out on paper, and/or, created in a Digital-File-Form,
then the safety aspects can then be either solved,
or determined to be too hazardous, or impractical.
.
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.
 

Thread Starter

mc281

Joined Jan 17, 2023
3
The mechanical aspects of what You want to do are far more important
than figuring-out the electrical aspects,
and must be determined first.

What happens when some object gets stuck in the way of the Table when raising it ?
What happens when something is in the way of the Table when it is being lowered ?
How much does the Table weigh ?
Will the Table have heavy objects placed on it ?
Is the Table mounted on a hinge ?, or is it completely supported by the Cable(s) ?
Is the Table large enough for people to walk under it ?
How much distance will the Table move ?
How much time is it expected to take for the
Table to to completely lower, and then completely raise ?

After all of the above mechanical aspects are
designed and drawn-out on paper, and/or, created in a Digital-File-Form,
then the safety aspects can then be either solved,
or determined to be too hazardous, or impractical.
.
.
.
Parcel on table under 3kg
Table (box) is in a square tube.
Open at the bottom and table is actually an open front and open rear box.. Box is caught by a gutter at the front when towards the bottom... The box continues to drop but the gutter forces it to tip backwards, ejecting the parcel.. The box continues on its journey until back to the top ready for next parcel... Stops for parcel then restarts when switch is closed.
No-one can walk under and the whole thing is only 45mm square.
Box cannot jam up as it never leaves it's tube.
I like the idea of the cable pulley side switching. That was my log jam!
Thank you!
 

LowQCab

Joined Nov 6, 2012
4,296
Here's a Circuit that can be adapted to what You want ........
Do You have any pictures of the Motor You will be using ?
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Chicken Door .png
 

sghioto

Joined Dec 31, 2017
5,430
My version with help from the WWW for the K1 circuit.
1673992367824.png

Circuit shown with the table at the top in standby.
Component values dependent on supply voltage and relays chosen.
 
Last edited:

LesJones

Joined Jan 8, 2017
4,227
A possible alternative way to detect which side of the drum the cable is would be to mount the whole motor, gearbox, drum assembly on a pivot on the same axis as the drum. Have a lever from the assembly which was retained in position with two springs. There would also be two mechanical stops to limit how far the lever could move and two microswitches to detect when the lever was against either stop. The torque that was required to hold the table in it's upper position would be enough to cause the lever to be on one of the stops and actuate one of the microswitches. Which micro switch was operated would depend on which side of the drum the cable was hanging from.
I think the mechanical part of the system would be simpler if the motor was reversed at the bottom of it's travel.
Les.
 

LowQCab

Joined Nov 6, 2012
4,296
LowQCab
I have a question on this post.
Please explain circuits and maximum duty?
Slot Car Control FLAT .png
You really should start your own Thread, or PM Me.
Please don't Hi-Jack somebody else's Thread.

Also, your question does not make sense.
This is a Schematic of a sophisticated Slot-Car Controller.
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crutschow

Joined Mar 14, 2008
34,842
Here's my take on a circuit using two SPDT relays:

It is triggered to either go up or down by a V+ pulse at the run input (as from a SPST NO push-button switch).

The circuit is shown in the UP position with the UP limit-switch open (the limit-switches are normally-closed types).

The relay coils should have the same voltage rating as the motor.

The two top relay contacts act as interlocks to remove the Run signal from the opposite relay coil when the Run signal is still there after the relay operates, the motor starts, and both limit-switches become closed.

D7 and D8 latch its respective relay until its limit-switch opens.

It does use some semiconductors (diodes), but you need those anyway to protect the relay and limit switch contacts from inductive transients. :)
1674014573726.png
 
Last edited:

sghioto

Joined Dec 31, 2017
5,430
Looks good for a single push button control but that will reverse the motor when going Up. I thought the TS required the motor to continue to rotate in the same direction when going Up then reverse direction for the next Up-Down run.
Is that no longer the case?
 

crutschow

Joined Mar 14, 2008
34,842
Looks good for a single push button control but that will reverse the motor when going Up. I thought the TS required the motor to continue to rotate in the same direction when going Up then reverse direction for the next Up-Down run.
Is that no longer the case?
You are right. :oops:
That will require some different logic.
Oh well, back to the drawing board. :rolleyes:

To mc281:
Would it not work to reverse the motor at the bottom?
I think the logic (and circuitry) to do that is likely easier.
 

LowQCab

Joined Nov 6, 2012
4,296
Reversing the Motor allows a single loop of Cable, with no "Winding-up" on a drum.
One Pulley at the top, and one Pulley at the bottom,
the Motor can drive either Pulley
No slack, No tangles, just precision motion.
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This sounds very similar to the concept of the "useless machine" - although I'm sure your application has a purpose! The schematic looks like:
1674051639291.png
The schematic as shown is with the motor at rest, not connected to the battery, and the microswitch in the N.O. position. When the toggle switch is thrown the motor starts to run in one direction and the movement of the arm (or any other mechanism, it could be a rope) changes the microswitch from N.O. to N.C. which has no immediate effect. The mechanism moves and eventually throws the toggle switch back to its original position but the microswitch is still in the N.C. position so the polarity of the motor is reversed. The mechanism therefore goes in the opposite direction until it hits the microswitch moving it back to the N.O position and the motor stops.
 
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