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Author Topic: Control Kato points  (Read 423 times)

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Offline RMurphy195

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Control Kato points
« on: November 27, 2018, 08:11:42 AM »
I'm looking at setting up a layout with Kato points. These have just 2 wires, so I'm guessing that the different points directions are decided by the polarity of the current supplied.

I'm further guessing that when you use the Kato switches the switch will pass across x current for y no of microseconds - something which I could replicate via a programmable microcontroller or electronically.

But does anyone know what current I need to supply for how long, or where I can find this info? I'm guessing its going to be 12 volt DC.

I haven't found the equivalent of data shets anywhere so far, either on the Kato web site or elsewhere - all I can find is instructions on how to wire up the switch.

Thanks in advance for your help - Richard

Offline PostModN66

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Re: Control Kato points
« Reply #1 on: November 27, 2018, 08:42:54 AM »
Yes, 12v dc.

I use centre off DPDT switches on Lofthole. The points throw instantly when you switch the switch, so I would suggest you start with a pulse of, say, 100ms and see if that works.

I don’t know what current they draw but it seems low, as they go easily; a small fraction of an amp.

Hope this is some use,

Cheers Jon 😀
“We must conduct research and then accept the results. If they don't stand up to experimentation, Buddha's own words must be rejected.” ― Dalai Lama XIV

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Offline ntpntpntp

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Re: Control Kato points
« Reply #2 on: November 27, 2018, 08:46:23 AM »
Interesting question, I've never measured one. They certainly don't need the "thump" of a typical twin coil solenoid point motor.   I would guess probably around 200mA as a starting point, but that's a pure guess.
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline RMurphy195

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Re: Control Kato points
« Reply #3 on: November 27, 2018, 09:52:01 AM »
Thanks for your replies.

Clearly if using a microcontroller the output pins certainly won't take the strain, as for the pulse width I can experiment once I get hold of some points starting with the suggested 100ms.

Jon - I was interested in the use of centre-off switches - I get the impression then that there is a constant supply of current to the points (which is what I was trying to avoid), or does the switch simply return to the centre position after you flick it either way rather than stay in position to indicate which way the points are set?

Offline Nigel Cliffe

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Re: Control Kato points
« Reply #4 on: November 27, 2018, 09:54:59 AM »
As others have said, 12v DC for a short burst.  Reverse the polarity for the opposite direction.   I doubt the time is specified, but 0.1seconds sounds reasonable.  Don't leave them on for a long time, or the coil overheats and burns out.  Jon will be using centre-biased switches - ie. they return to off after use.

An off-the-shelf motor drive H-bridge could deliver the required output, they are cheap.  Fairly trivial to set one of those up onto an Ardunio/PIC/whatever microcontroller you require.   

Offline PostModN66

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Re: Control Kato points
« Reply #5 on: November 27, 2018, 09:58:55 AM »
Thanks for your replies.

Clearly if using a microcontroller the output pins certainly won't take the strain, as for the pulse width I can experiment once I get hold of some points starting with the suggested 100ms.

Jon - I was interested in the use of centre-off switches - I get the impression then that there is a constant supply of current to the points (which is what I was trying to avoid), or does the switch simply return to the centre position after you flick it either way rather than stay in position to indicate which way the points are set?

I use centre sprung switches, so normal procedure is to just flick and release.   However, if a guest is operating the points sometimes they misunderstand and hold them in position.....and nothing bad seems to happen, no buzzing or vibration, smoke or bad smells.......  I have speculated that the points might have some sort of built in isolation so that having switched them they cut off current in that direction, but I haven't got round to investigating this.   If it were true it would be great as, as you say, the switch could be left in position like a real lever frame.

ADDITION: Nigel's post above indicates that this isolation feature doesn't actually exist....shame!

Cheers Jon  :)
« Last Edit: November 27, 2018, 10:00:09 AM by PostModN66 »
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Offline daffy

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Re: Control Kato points
« Reply #6 on: November 27, 2018, 10:22:21 AM »
I came across this interesting discussion on another forum dating back to 2013/14. Post #8 describes the results where one guy did some electrical testing on Kato switches:

Quote
I actually hooked one up to an oscilloscope the other day.... with an old DC power pack, using the AC accessory terminals (16VAC) and the Kato DC adaptor hooked to a Kato controller, I measured 800mA peak (~ 500mA RMS)* in a square wave. It looked like the minimum pulse duration was about 50mS. Not sure if the switch would trip on anything shorter or not, that was the smallest pulse I could generate with the Kato lever.

* The Kato DC adaptor is just a bridge rectifier with no filtering, so the waveform is a full-wave rectified 60Hz sine wave. Hence the "peak" and "RMS" on a "DC" signal...


Whole webpage is here: http://www.trainboard.com/highball/index.php?threads/kato-turnout-throw-current.74277/

Any help?
Mike

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Offline RMurphy195

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Re: Control Kato points
« Reply #7 on: November 27, 2018, 11:39:03 AM »
I came across this interesting discussion on another forum dating back to 2013/14. Post #8 describes the results where one guy did some electrical testing on Kato switches:

Quote
I actually hooked one up to an oscilloscope the other day.... with an old DC power pack, using the AC accessory terminals (16VAC) and the Kato DC adaptor hooked to a Kato controller, I measured 800mA peak (~ 500mA RMS)* in a square wave. It looked like the minimum pulse duration was about 50mS. Not sure if the switch would trip on anything shorter or not, that was the smallest pulse I could generate with the Kato lever.

* The Kato DC adaptor is just a bridge rectifier with no filtering, so the waveform is a full-wave rectified 60Hz sine wave. Hence the "peak" and "RMS" on a "DC" signal...


Whole webpage is here: http://www.trainboard.com/highball/index.php?threads/kato-turnout-throw-current.74277/

Any help?


Certainly is, thanks. Makes me think that to switch several points "simultaneously" (e.g. a complete route) it might be best to do them one after another to minimise peak current draw - at say 100ms each with a tiny delay between each one that should suffice for my needs.

One of these things that gets more interesting the more you think about it!

Offline Malc

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Re: Control Kato points
« Reply #8 on: November 27, 2018, 05:43:12 PM »
The Kato lever switches are a passing contact, so there is no standing power to the switch.
I'm not sure if life is passing me by, or trying to run me over.

Offline dannyboy

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Re: Control Kato points
« Reply #9 on: November 27, 2018, 07:35:01 PM »
to switch several points "simultaneously" (e.g. a complete route) it might be best to do them one after another

I don't know if this affects your calculations, but the Kato 'crossover' is, in effect, four points that all change at the same time. This is by using one switch, I use DPDT centre off switches on a 12v DC supply.
« Last Edit: November 27, 2018, 07:36:47 PM by dannyboy, Reason: added a bit! »
David.
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Offline Malc

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Re: Control Kato points
« Reply #10 on: November 28, 2018, 11:23:03 AM »
to switch several points "simultaneously" (e.g. a complete route) it might be best to do them one after another

I don't know if this affects your calculations, but the Kato 'crossover' is, in effect, four points that all change at the same time. This is by using one switch, I use DPDT centre off switches on a 12v DC supply.
I usually have to do a treble throw on the crossovers to make sure all 4 points have gone over.
I'm not sure if life is passing me by, or trying to run me over.

Offline dannyboy

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Re: Control Kato points
« Reply #11 on: November 28, 2018, 12:09:06 PM »
Just occasionally, I might have to operate the crossover switch 2 or 3 times if the crossover has not been changed for a week or two, but normally they operate first time for me.  @Malc
David.
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Offline Malc

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Re: Control Kato points
« Reply #12 on: November 28, 2018, 02:04:03 PM »
I agree, usually the first time if I haven’t used the layout for a while, but I always do a visual check as well.  @dannyboy
I'm not sure if life is passing me by, or trying to run me over.

Offline Miek

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Re: Control Kato points
« Reply #13 on: November 28, 2018, 07:16:49 PM »
I have used an arduino and a separate 12V supply to make a Kato point motor control. The Arduino and is connected to the point via a L293D Push Pull Four Channel Driver With Diodes to power the solenoides. The chip costs around £3. It has four outputs - so you can use it to change two kato solenoids. I found that I needed a 12V supply and 300mA. The pulse was set to 25ms. I can post the sketch if it is of any use.

Offline RMurphy195

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Re: Control Kato points
« Reply #14 on: November 29, 2018, 10:30:51 AM »
I have used an arduino and a separate 12V supply to make a Kato point motor control. The Arduino and is connected to the point via a L293D Push Pull Four Channel Driver With Diodes to power the solenoides. The chip costs around £3. It has four outputs - so you can use it to change two kato solenoids. I found that I needed a 12V supply and 300mA. The pulse was set to 25ms. I can post the sketch if it is of any use.


Thankyou Miek.

To develop my techniques/sketches I have used a DRV8833 h-bridge and am happy with my sketches thanks (to be honest as an ex-IT bod the software development is a good part of the fun!).

The timing and power consumption info is very useful. The H-bridge I have been using will not support 12v so will be looking at alternatives to give me the voltage I need, current thinking is to use something like this  https://www.sparkfun.com/products/13845 Though it could be done slightly cheaper, I've found these breakouts to be much more compact than I can make for myself!

Depending on the complexity of my final layout, the Arduino may be replaced by a tiny85 or 84 - these can be quite fun to use :D

UPDATE 7/2/2018: Unlikely to use the ATTiny processors since I've found that I need to "supercharge" the PWM frequency for driving the loco, and the code library wouldn't work on the Tiny chips. For the H-Bridge I've ordered a couple of these to play with http://www.hobbytronics.co.uk/tb6612fng-driver-board
« Last Edit: December 07, 2018, 09:33:56 AM by RMurphy195, Reason: Updated info »

 

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