emancipate this clock.
April 21, 2010 6:51 PM   Subscribe

Clock Repair Question: I have a slave clock that I would like to run as an independent. How do I do it most easily?

I picked up an old Edwards brand school clock photo, photo for a few dollars at a stoop sale. As far as I can tell, it is a slave clock, and will not run when wired into a standard (USA) wall outlet. If possible, I would like to make it work in my apartment without spending more than two hours or $30. I know very little about electricity and the mysteries of time.

I am looking for a cheap kit that I can buy off of the internet that will allow me to splice some wires and plug the existing mechanism into the wall. If that doesn't exist, or if the motor is fried, I wouldn't mind putting the old hands on a new motor and reassembling the clock. If I do buy a new motor, can I get one from any old electric clock, or should I look for something specific?

My wife and I live in a tiny studio apartment, so it is also important that the clock have a sweeping mechanism or tick very quietly and not keep us up at night. I would rather plug it into the wall than power it with batteries, but am up for whatever is easiest.

Here are the technical details written on the back of the clock:
Edwards NO. 1962
Series NO. M
12 Flush Clock
Motor Type B2
115 Volts, 60 Cycles, 4 Watts
It has two grey wires coming out of the back, and one black one.

Thanks for the help.
posted by abirae to Technology (6 answers total)
make sure that the slave clock gets a copy of the Emancipation Proclamation, then it will run independently. :-)

Many slave clocks cannot be converted from my understanding.
posted by chinabound at 8:40 PM on April 21, 2010

The Slave Driver seems to do what you're looking for.
posted by contraption at 9:16 PM on April 21, 2010

Depends on the type. That wikipedia article is a bit confusing in some respects, as there's 3 basic types I've encountered:
  1. Complete slaves - the clock requires a pulse every 30 secs or 1 minute; without that it won't advance. These clocks don't have a second hand.
  2. Hourly - the clock has its own synchronous (i.e. locked to the mains freq) motor, the clock runs by itself, and the time is sync'd every hour (as the article says, at xx:57:54).
  3. 12 Hourly - same as hourly, except that it only happens twice a day (at 11:57:54 am/pm)
I've also seen ones that sync once a day, at 2pm.

Usually, all bar the first type will run happily without a sync pulse, although they're not terribly accurate - why bother building an accurate mechanism when they're pulled into line at least once a day?

It's possible to build a circuit to recreate the sync pulse pulse. I once did it for an amateur horologist friend who had some old telephone exchange slave clocks, before he managed to scrounge a master. Back then (circa 20 years ago!) I used a clock chip, some clever decoding circuitry, and a pulse stretcher to drive a relay to provide the sync pulse. If I were to do it today, I'd use a RTC chip and a PIC or Atmel micro.

That's the basic theory, anyway. I'm not familiar with the Edwards (now Edwards Signaling, part of G.E. Security) clocks, so I can't give any info as to what sort of sync pulse it's looking for. The ones I'm familiar with have been old BPO (possibly Siemens or Plessey?) or APO (probably locally-licensed knockoffs) clocks, running from 50V DC.

On preview: I see contraption has posted a link to a master driver - although I'd be digging to find out exactly what sort of voltage and such your particular slave needs to run & sync.
posted by Pinback at 9:38 PM on April 21, 2010

Yeah, I'm not 100% certain that the driver I linked is compatible with your particular clock, but they do say:
There are many varieties of slave dials, and the SlaveDriver can be customized to work with most them. At the right end of the circuit board are several metal pins where you can apply jumpers to select the parameters of operation. It can be configured to provide an impulse every second, every 30 seconds, every 60 seconds, or once per hour. The duration of the impulse can also be set, from as short as 100 milliseconds to as long as 1 second.
so it sounds like it supports a fairly wide range. If you send your description to the manufacturers of the kit they might be able to tell you if they support it, or if they can modify their circuit a bit to make it work (small custom electronics shops are often willing to do that sort of thing.)
posted by contraption at 10:56 PM on April 21, 2010

Update: I ended up buying an electric movement off of the internet to replace the original slave mechanism. I am hoping the original hands fit on the new movement. I will post again when it arrives.
posted by abirae at 1:50 PM on April 26, 2010

Update: the movement that I ordered was not powerful enough to move the metal hands. I tried a battery operated movement, but the ticking amplified by the metal clock face was too loud for my apartment.

Two days ago I found an old electric office clock at a stoop sale for $7. I used its motor in the Edwards clock. It worked perfectly. To attach the hands, I needed to superglue them on top of the hands on of the stoop sale motor.
posted by abirae at 1:34 PM on May 18, 2010

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