Synchronous motor for a clock

Projects
1

I want to make a bike chain clock with some students - something like this

http://wornandwound.com/chain-clocks-a-wall-mounted-mechanism-for-time-telling/

As far as I can see I need an AC synchronous motor which should plug into the mains to get it’s timekeeping

Just wondering if I would be safer with a transformer first to drop the voltage they are playing with so I can use a 12v AC synchronous motor - something like this

http://www.ebay.co.uk/itm/49x20mm-AC12V-50-60Hz-Synchronous-Motor-5-6RPM-CW-CCW-4W-For-Microwave-Turntable-/201607534320

Now - is there actually a transformer inside this white box? The fact that is is dimmable and refers to ‘primary’ and ‘secondary’ leads me to think it might be, rather than a bunch of electronics.

http://www.ebay.co.uk/itm/LED-And-Halogen-Driver-Transformer-10-60-W-12-V-AC-Dimmable-White-Set-/272279615528?hash=item3f65213828:g:s1QAAOSwYmZXLgEZ

Any thoughts?

2

This one looks more like a transformer

3

There’s a bunch of 12v transformers in the snug that I dropped off last year. Have a look at them, def some ones with a toroidal feel to them there.

1 Like
4

I’d be very surprised if you can keep time with that. I’d go for a stepper and µC with a real-time clock, though I can see that ups the price / complexity (assuming there’s not an all-in-one controller/driver somewhere).

As far as that white box goes, yes there’s a transformer in there. I think the specific point of a dimmable LED driver is to output constant voltage, variable current while coping with the mains AC oscillating waveform being truncated by a dimmer switch.

5

Oh – I’ll be dumping a load of 240v-12v transformers for halogen lights into Makerspace’s electronics recycling when I arrive for open evening next Wednesday. Holler if you do want them. Replaced 20 halogen MR16s + transformers with GU10 mains LED units.

6

No it is a switching psu in the white box , totally useless in this for this motor.
You need a proper iron one .
Some in the back the space

7

That’ll do it :slight_smile:

8

The mains is spot on over a 24hour period. It’s the way all electronic clocks used to work

9

I was thinking the 50hz could lock it in, but how would you get the precise RPM? Genuinely curious.

10

The clue is in the thread title :smiley:

11

Well I’ve ordered the bits, now let’s see if the students can make it work.

Sammy’s computer science club is doing a Makerthon to create resources for an East London primary school STEM room.

12

It’s something in between a stepper motor and an induction motor.

13

Well, I leant something today. The gearbox is going to have to be exactly right though (but that’s also how you get round starting the motor, which was another thing that had occurred to me while wondering about 50hz lock).

14

I’ve also bought a high torque clock mechanism in case the motor thing doesn’t work out

15

Some times there a second winding for starting and sometimes you have to accept this the direction is random so switch on and off until the clock runs in the right direction

16

This explains why the turntable in my microwave sometimes goes one direction, sometimes the other.

2 Likes
17

I think I’ve seen clocks with a start button - some kind of mechanical means of kicking the motor off in the right direction

18

That would work , but it might require quite a lot of talk with that gearbox.

19

Slightly late in posting, but it will work. You may also like to know that you can use a stepper motor as an AC synchronous motor.