Hi sghioto, The way the motor is connected to the relay contact requires both relays to be energised for one direction

Yeah I totally missed that using the relays as a DPDT switch.

 

Please can you support it with a diagram. I mean the modification of post #17 which it is referred to post #15

If your circuit is working fine I wouldn't change it.
Post 15 requires limit switches to change direction and the positioning of the switches to determine the timing.

 

Here is a version using three single pole double throw relays.

I have shown separate power supplies for the motor and relays but you can use a single supply if the relay coils are the same voltage as the motor. To the right of the dotted line the circuit is the same as yours in post #17. To the left of the dotted line is the latching circuit from post #15. This latches ON when the NO limit contact is actuated by the moving platform. When the NC limit switch is actuated by the platform the latch goes to the OFF state.

EDIT. Do you want the platform to reverse direction at no particular positions or do you want it to reverse at fixed positions ?

Les.

 

Given that the statedpurpose of the project is to wipe circuit boards it seems that the only sesible scheme will be to use the limit switches. If the control runs for a fixed amount of time then it will not be consistent as the load varies the motor speed. And certainly the wiping friction will slow the motor a fair amount.
This seems like a very large amount of effort just to wipe a PCB dry after washing it. Plus, it will not do a very good wiping job.

 

Here is a version using three single pole double throw relays.
View attachment 272292
I have shown separate power supplies for the motor and relays, but you can use a single supply if the relay coils are the same voltage as the motor. To the right of the dotted line the circuit is the same as yours in post #17. To the left of the dotted line is the latching circuit from post #15. This latches ON when the NO limit contact is actuated by the moving platform. When the NC limit switch is actuated by the platform the latch goes to the OFF state.

EDIT. Do you want the platform to reverse direction at no particular positions or do you want it to reverse at fixed positions ?

Les.

Before I answer this question I want to show how post #17 circuit work. In post #17 the circuit has two 12 relays the first relay NO (that's positive supply ) is connected to the second relay NC (that's negative supply ) and the second relay NO (negative supply ) Is connected to the first relay NC (positive supply ). The first relay has a positive supply through the COM and the second relay has a negative supply through the COM. When the coils of both relays energized the motor moves reverse and if the relay is de-energized then it move forward. The diagram below shows how the circuit work. I have read all your replies and I learn something great from it which I have to work them out later. But what I was asking is that since my circuit is working fine can I continue to use it or do I have to modify it? The below diagram shows how the relays forward and reverse the motor.

 

If post #17 circuit is doing what you want then there is no reason not to use it. My origin understanding was that the platform moved backwards and forward between the ends of a track and at each end it reversed. With post #17 it will move in each direction for a fixes time. If the forward and reverse distance moved is not EXACTLY the same then is will slowly move it's position along the track. At some point it will reach the end of the track and stall the motor. This could damage the motor unless you build in a current limiting circuit to protect the motor when it is stalled. If you show us a picture of the mechanical part of your setup we will understand your requirements. Your description in post #1 give very little information. It could be moving a sample a few mm backward and forwards under a microscope or it could be moving several tons backwards and forwards on a railway track. It is always better to give FULL details of your requirements when asking for help.

Les.

 

The concern expressed in post#26 is valid! and if the project is used as originally described by the TS, certainly the load on the motors will vary, and so certainly the speed will be slower and certainly the platform will not be moving the same distance each move. THAT is the reason that the limit switches are needed instead of a timer.
And I suggest that using a single DPDT relay is a much better choice for the reason that with the circuit as shown, if only one relay operates there will be a problem. I leave it to the TS to look at the circuit and understand what that problem will be.
There is a simple solution available.