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IBM Slave Clock Wiring

EscapeWheel

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Hi! I was hoping somebody might have an idea of how to wire this setup... I'm trying to hook up an interval timer to my IBM slave clock. I want to give it a half-second pulse (which will advance the minute hand), wait 60 seconds and pulse again.
I'm using a Velleman MK111 interval timer hooked up to a 19v power supply. I just can't figure out how to wire the clock from the timer. I have plus, minus, normally open, common and normally closed to work with. I've labelled the clock wires A B and C.
Any idea?
Thanks! Phil Slave2.JPG Slave3.JPG Slave5.jpg Slave.JPG Slave1.JPG
 

Tim Orr

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Good evening, EW!

I suppose you've tested the clock? You will want to know what voltage the clock uses, and which pair of wires advances the clock. One wire, I am going to guess, is for hourly correction. That I figure is why you have that snail-like wheel on the clock. A lot of times, one wire just releases the minute hand, and a weight on the end of the minute hand causes the hand to jump straight up. You won't be using that feature, I'd guess.

If the clock is 12v, you might be able to get away with using your 19v supply to advance the hand. lf that's so, I might suggest wiring the "+" terminal of the supply (same as the "+" on the timer terminal strip) to the common on the clock, and then the other wire on the clock to the NO on the timer terminal strip. Then, you'd jumper the common of the timer terminal strip to the "-" or "ground" of the timer terminal strip.

You'd need to set pot B so that the interval is 60 seconds, and pot A until you get the right pulse duration. I would be very surprised if you would need a half-second pulse. That seems really long. I'm betting something more like 0.2 sec. It would be simple enough to set the timer to a relatively short interval, then keep backing down pot A until the pulse is no longer long enough to reliably advance the clock, then goose it back up again until it's reliable.

If your clock is relatively low voltage, like 6v, you might be overpowering it and need to reduce the voltage. If it's a 24v clock, as many are, the 19v might or might not be enough. Either way, you might need to set up the power for the clock separately to get the voltage right.

I don't know how accurate the interval is on your timer, but if it's not very precise, you may have to tweak that over time. Someone else probably knows how long-term accurate a 555 timer is likely to be. Seems to me I've heard they're not exactly quartz accuracy.

Ken Reindel of kensclockclinic.com makes all kinds of devices to drive clocks of this sort. They even self-adjust their voltages to optimize for the clock you're using.

Best regards!

Tim Orr
 
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Toughtool

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I thought about using a 555 timer but thinking about the quality of the RC components, drift and temperature, I looked for a different approach. This circuit may be more accurate than the 555 timer. All you need is do to adjust the time is to fine adjust the programmed numbers. I think it is simpler that the 555 timer, no relays and its all solid state. You can use either 12 volts or 24, depending on the coil voltage of your secondary. For your setup you will need to connect the black and white wires together and to your one minute output, loosing the self correction feature. The green wire is the 12 or 24 volts wire and the magnet is energized by taking either (or both) A or B, depending on the secondary's time, to ground.

I have also developed some micro MPU masters that use the NTP time servers for accuracy if you are interested. These will run the secondary with the self correction.
Joe


As of 7/2020
Introducing Trinket Trinket 5V, 8Mhz $6.95 ea
https://www.amazon.com/MP1584EN-DC-DC-Converter-Adjustable-Module/dp/B01MQGMOKI/ref=sr_1_16 6/$9.99 Amazon ($1.66 ea.)
https://www.amazon.com/WeiMeet-RFP30N06LE-N-Channel-Mosfet-Arduino/dp/B07CTF1JVD/ref=pd_sbs_60_1/135-8599131- 5 Volt logic version 10/$8.00 ($0.80 ea)
These parts total $9.41 plus misc parts like a small prototyping board and terminals will bring it up to about $15.00.

Here is the software:
It is the Blink example from the free Arduino IDE program. I only changed the ON time to 600 mS (milliseconds) and the OFF time to 60000 mS . Simple!
Please note: I have highlighted the comments and “programming comment syntax”, in Red. The Black is the actual syntax and code that is compiled and loaded.(Well the colors didn't work, sorry.)

/*
Blink
Turns ON an LED for 0.6 second, then OFF for 60 seconds, repeatedly.

This example code is in the public domain.

To upload to your Gemma or Trinket:
1) Select the proper board from the Tools->Board Menu
2) Select USBtinyISP from the Tools->Programmer
3) Plug in the Gemma/Trinket, make sure you see the green LED lit
4) For windows, install the USBtiny drivers
5) Press the button on the Gemma/Trinket - verify you see
the red LED pulse. This means it is ready to receive data
6) Click the upload button above within 10 seconds
*/

int led = 1; // blink 'digital' pin 1 - AKA the built in red LED

// the setup routine runs once when you press reset:
void setup() {
// initialize the digital pin as an output.
pinMode(led, OUTPUT);

}

// the loop routine runs over and over again forever:
void loop() {
digitalWrite(led, HIGH);
delay(600);
digitalWrite(led, LOW);
delay(60000);
}



.

Wind coil pulser.jpg MasterClocksystemWiring.jpg
 
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EscapeWheel

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The clock does work - first, I put 12 volts to wires A & B and the mechanism jerked a little. With 19 volts it advances the minute hand one minute (when it's in its usual upright position). Like you said, at 12:00 pulses stop working. One of the strip contacts opens - I'll have to figure that out as well. The movement has 24M printed on it.
I'll try your wiring suggestions today and see how it goes. Yes, tweaking the pots will be needed. Thanks for the input!
 

ibm clock

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Sep 5, 2005
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Its simple. When using a clock impulser, you need to tie the A and B wires together. Without clock in front of me to look at, I cant remember which is which. The usual voltage on IBM slaves is 24v DC. Isnt the schematic sticker still in the clock? One of the contacts is supposed to open between 59 to 4 seconds which would be normal if the clock was wired into a three wire correction system. And to label your clock the way IBM would, the terminal at the far left is C or the common. The A and B wires are on the contact. So, just tie the two contact wires togther and it will work. Here are some attachments explaining the IBM Correction System.

IBM Time 1.jpg ibm time 2.jpg
 
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EscapeWheel

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Wow. It's working!
The + and - wires from the power supply are connected to + and - on the timer. I changed my wire letters to the IBM standard (per ibm clock); C is common and A & B are twisted together. C is connected to + on the timer, A & B are connected to NO (normally open) on the timer and there's a short connecting wire between negative and COM (per Tim).
I have a lot of timer tweaking to do - I'll shorten the "pulse" to the minimum needed and lengthen the "pause" to 60 seconds and see how it keeps time. Right now the pause is 15 seconds and it has run through an hour with no problems that I can see.
I can't thank you guys enough! The knowledge here is unsurpassed.
 

praezis

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EW, you don't supply the 19V to your timer board, do you? Your schematic says 12 V and the 555 is rated at max. 18 V.

A 555 timer is not precise enough to control a clock, unless you want to adjust daily...

Frank
 
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EscapeWheel

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Frank, good point! It shows 12 - 15VDC. I wouldn't just hang it on the wall and let it run. It's more just to prove to myself that I could get the clock to do more than just sit there.
 

Tim Orr

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Good afternoon, EW!

Glad you got it working, and special thanks to IBM for clearing up the clock wiring issue!

You said your power supply is 19v. Is that unregulated? Might be marginally OK for the timer.

Best regards!

Tim
 
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EscapeWheel

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Thanks! It ran very well for about 45 minutes, then the hand stopped advancing - but it continued to pulse. I gave it a rest and it started up again. I'm thinking you and praezis may be right - maybe the timer doesn't like that much power and overheats and shuts down? I might look into giving the timer 12 volts and adding this step-up module to give the clock 24 volts. It's an SX1308 - about $5. Input voltage: 2-24V - output voltage 2-28V, adjustable. Wish I knew more about electronics...

slave6.jpg
 

Toughtool

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Here is my schematic for the same thing. (except for the polarity) You are probably going to need the protection diode to keep from damaging the DC to DC " boost" converter.

12V to 24 volt secondaryDrv.jpg
 
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EscapeWheel

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Thank you Toughtool! When I get the converter I'll have my next-door-neighbor-electronics-whiz kid interpret it all for me. I've learned a lot about capacitors and resisters but so far, diodes, ICs and mosfets throw me for a loop.
 

Toughtool

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I built this circuit without the diode and after a couple of weeks it died. (I think after a storm) The problem is; when current is flowing in a coil, a magnetic field is built. When this current is abruptly stopped, the magnetic field collapses, inducing a damaging high voltage into the coil with the opposite polarity. This counter voltage can destroy a low impedance power source. The diode is placed across the coil to short this high induced counter voltage back through the coil.

After thinking about this circuit I think the best way to solve your problem is to get a 24 volt power source (power adapter) and use a DC to Dc Buck voltage converter. This allows you to have the 24 volts for the coil and adjust the DC converter to the lower voltage to power the 555 circuit. Much easier.
 
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