Good evening
I’m a hobby engineer and have a built a small tower clock. I am now building an automatic winder because I have not got an appropriate drop for the weight and would need to wind it too frequently to be manageable

I essentially have a 15w 25rpm AC 220v geared motor and I need to turn this on and off when a rotating cam presses an “on” limit switch and a separate cam presses the “off” limit switch.
The cam will depress the “on” limit switch (or other suitable switch!) and the motor must remain on until the off if depressed.

I presume this would be done with a relay and I was hoping someone may offer some support with the required components and possibly direct me towards a suitable circuit?

For those interested, this is the clock. Any help would really be appreciated!

Chris

 

a simple start stop would be more than sufficient
like this one
https://www.google.com/url?sa=i&url=https://www.wellpcb.com/blog/pcb-projects/start-stop-circuits/&psig=AOvVaw2kxQfCbYdRTuBzSgMmaf62&ust=1733709204015000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCNjQ2Z2Il4oDFQAAAAAdAAAAABAE
(see figure 2)
start is weight down limit switch and stop is your weight up limit switch. Motor start stop is driven by the relay.

 

certainly the classic "start/stop" circuit, with the start limit switch being the normally open and the stop being the normally closed, can achieve the desired function.
One caution is that the relay needs to have two sets of contacts, otherwise the "start" limit switch will also carry the motor start current. How frequent are the rewinds anticipated to be? Just a curious question, not a technical concern.

 

certainly the classic "start/stop" circuit, with the start limit switch being the normally open and the stop being the normally closed, can achieve the desired function.
One caution is that the relay needs to have two sets of contacts, otherwise the "start" limit switch will also carry the motor start current. How frequent are the rewinds anticipated to be? Just a curious question, not a technical concern.

Thanks for the interest. It’ll be easier to tell when I actually have a model of the mechanical aspect of it working. I simplified a little bit when I said the clock turns the cams as I wouldn’t won’t any extra load on the actual clock mechanism. So there will be a line coming up from the weight and wrapped around a pully. The pully will hold the cams. The weight going down will turn the pully in one direction and initiate one limit switch. The motor will kick in, lift the pully and turn it the other way which will then trigger the off cam. This would work really well in if I had a ve try big pully and have a good “lift” or rewind but it’ll look ugly. So in theory it wouldn’t need rewinding until 30 hours or more but this setup might end up rewinding it little and often. I’ll keep thinking as there might be a better way of doing it but either way, I’ll need to setup this start stop relay.
Do you have any full schematics to a start stop circuit and any thoughts on a suitable motor?
Chris

 

a simple start stop would be more than sufficient
like this one
https://www.google.com/url?sa=i&url=https://www.wellpcb.com/blog/pcb-projects/start-stop-circuits/&psig=AOvVaw2kxQfCbYdRTuBzSgMmaf62&ust=1733709204015000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCNjQ2Z2Il4oDFQAAAAAdAAAAABAE
(see figure 2)
start is weight down limit switch and stop is your weight up limit switch. Motor start stop is driven by the relay.

I do appreciate that and I understand most of the principle. I’ll get googling as well as whilst this shows a schematic, I could do with an actual schematic with an actual suitable relay and its connections.
I’ll keep googling but if you have any links to a suitable relay, I’d appreciate it!

 

One caution is that the relay needs to have two sets of contacts, otherwise the "start" limit switch will also carry the motor start current.

That would be a problem! Any ideas on what would be a suitable relay?

 

replace start with a down limit switch, replace stop with the up limit switch, and replace light with your motor connections.
here is a typical ice cube relay that would work. these are jelly bean so a search for 8 pin ice cube relay will come up with thousands of options. All are very similar.
amazon ice cube relay
and connections are pretty straight forward.


pins 2 and 7 are your coil (MCR in the drawing). pin 1 and 3 are one of the mcr contacts (say the maintaining one) and pins 8 and 6 are your other mcr contact. The only thing I would add is a fuse on one leg of the 220v for circuit protection. 15w motor its very little load so a quarter amp fuse is more than sufficient.

 

OK, "J" has provided you with a circuit schematic diagram that is correct. Note that while it is a totally correct circuit schematic, it is not a wiring diagram that shows all of those details of how to connect the wires. So it might leave the TS a bit confused.

 

ts is an engineer, I have faith