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Post by Gareth on Jan 18, 2011 16:36:10 GMT
Hi
Is there a clearer photo or board layout of the motor decoder?
I am struggling to determine the component identity for some items. The lines from the component name ie D6, D5 to the items shown on the vero board are not to precise.
Gareth
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Post by kennedylanduk on Jan 19, 2011 8:19:25 GMT
Is the attached any use? It's what I use to build these. Attachments:
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Post by Gareth on Jan 19, 2011 14:59:05 GMT
Hi
Much better thanks. Forgive for being cheeky but where did you get the vero board template?
Gareth
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Post by kennedylanduk on Jan 19, 2011 23:35:10 GMT
I think I just copied a section from the original diagram and replicated it a lot in paint shop pro.
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Post by Gareth on Jan 20, 2011 4:29:51 GMT
I never thought of that.
Gareth
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Post by 0141trainmad on Feb 14, 2011 10:19:22 GMT
hi its 0141trainmad here your image shows to d4 diodes which is the right location for d4?
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Post by kennedylanduk on Feb 17, 2011 8:08:53 GMT
I hadn't spotted that.
The "D4" that is near C2 is the real D4, the other one is D6. They are the same values anyway.
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Post by 12noonscot on Feb 25, 2011 8:51:53 GMT
I am working at the Motor Decoder, and also it confused with differences between VEROboard images: a strip cut in the mounting for amp IC covering the 4 strips. Another, posted in the Forum has no cut for amp. Which is it?
Also, D1 is not shown on the layout board, although I am coming to catch the drift of the relationship between Circuit Diagrams and component layout - a bonus.
Jim.
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Post by Paul Harman on Feb 25, 2011 18:19:59 GMT
Jim
The image shown above with no cuts under the L272 is incorrect. Use the one from dccdiy.org.
D1 has been missed off some of the diagrams but it goes in the same holes as the 78L05 regulator.
D1 is not really required in the motor decoder as it stands, it is just there to protect the regulator if the circuit becomes powered from one of the function outputs, for example when driving a load with a big capacitor across it.
Unfortunately the software I use to make the stripboard layout diagrams is broken (now has a 40-day delay before saving!) so some diagrams are not quite as good as I would like.
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Post by Jon Benn on Feb 29, 2012 14:46:52 GMT
Have built a couple of these motor decoders and they work like a dream..thanks everyone for the handy comments on this forum....I've replaced the 1uF input smoothing capacitor with 47uF to help my old triang engines over mucky track & frogs etc. Has anyone found an upper limit for this capacitor? Or is physical size the only limitation.
My next development is to use the function output to drive electromagetic uncouplers. Does anyone know of any reason why Pin 4 on the 12F629 (GP3) can't be used as a second function output please? I've looked through the source code and it looks like it is configured as an input (but not used), and is physically wired to GP2 (pin5) but I can see no reason for it.
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Post by Paul Harman on Mar 2, 2012 23:52:59 GMT
Jonboy
Nice to hear that your decoders are working well.
To answer your questions:-
1. The 1uF capacitor is just to keep the processor running over dirty track, if you make it too big the processor will not shut down and reboot when required in certain programming modes. If you use direct mode or operations mode all the time (the best modes) the size of the capacitor does not matter. If you want a capacitor to keep the motor running you really need one a lot bigger than 47uF and you need to do something a bit fancy using diodes
2. Pin 4 is an input only pin. It is connected to pin 5 for convenience and also for signalling to some versions of the firmware that the comparator input on pins 6 and 7 is being used instead of legacy input on pin 4 only (6 and 7 then become extra function outputs).
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Post by Jon Benn on Mar 3, 2012 21:56:46 GMT
Thanks Paul....re the function outputs Ive taken the approach of piggybacking a 12f675 acting as function decoder on top
of the 12f629 motor decoder....outputs drive 2n2222 through 4k7 base resistors and the open collector
outputs happily give a small electromagnet enough oomph to repel a small magnet to lift the hornby coupling.
Will have a play with larger input capacitors and diodes for the mucky track solution.
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Post by Paul Harman on Mar 4, 2012 7:20:20 GMT
That is a good idea. Decoder lock will enable to program the function decoder first.
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Post by Jon Benn on Mar 16, 2012 21:01:21 GMT
Thanks - found the 2N2222 was getting quite hot even just used for a second or two, so switched to meatier TIP31.
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Post by Paul Harman on Mar 17, 2012 0:30:31 GMT
It might be worth checking the gain of the 2N2222 to make sure that it is fully saturated with 4K7, you might need to reduce the resistor value for a heavy load. hfe=100 will only give you 100mA which might not be enough, the gain of the TIP31 will probably be in the same order or worse, so you might get more heat with the saturation being even less. You can go down to 220R base resistor if your transistor will take it.
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