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How to drive train models


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#41 Paul Newton

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Posted 20 April 2012 - 07:54 PM

Wise man once say "Wise man only as good as Google search".

2x2x2AWG24 comes up a lot in searches.
From looking at lots of pages I found this page which unfortunately for me is in French.

Through the wonder of Google translate:

SYT PLUS NUM 1 AI n x 2 x AWG24 + batch number + metric marking
With n: number of pairs
So I think the second "2 x" means the wires are in pairs, and the first number is the number of pairs.

If you strip off more of the outer sheath of the cable you may find that the wires are actually twisted.

I guess that the "A10-41/04" is something to do with the batch number and metric cable size.

Sorry not much help - Paul

#42 Kermit

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Posted 20 April 2012 - 09:10 PM

Yes, I had already googled to find the same results (am I entitled to be called 'a wise man', too? :-)). What I was pointing out was that even if this is not the best cable I can use (it's another order of mine, still waiting for 100 meters of CAT5E FTP), I could easily obtain perfect results on a 5 meters cable (and at 1Mhz!), that, for what I was told here, wasn't expected... Andrea

#43 Kermit

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Posted 21 April 2012 - 08:48 AM

Did you spot the problem? - The Netduino only has 4 PWM outputs, so you might need to use a PWM shield to get enough PWM outputs for your 5 sets of rails.


Hi, Paul, since my first tests are ok, I'm now thinking again to the problem of loco controlling.
You told me about a pwm shield, I saw it, and I think it can be a good (and cheap!) solution. What I cannot understand is that to me it seems that I'm using in the shield the same PWM pins that I have on the Netduino, so I cannot reach the five PWM that I need.
Moreover, if I understand it well, I need TWO PWM pins to control a single loco? Forward/reverse? Please, can you give me some hint?
Andrea

#44 Kermit

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Posted 21 April 2012 - 05:40 PM

PWMs
Ok, since I had started (and quickly closed!) a related thread, I consider the problem of the many PWMs closed (with just another order for new components!!! :-)))
Andrea

#45 Paul Newton

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Posted 21 April 2012 - 07:11 PM

OK, I only just read you posts, I spent today drilling holes for electric sockets. Per rail: you need one PWM for speed, and an on/off digtal signal for direction. Motor driver circuits (shields) will have an "H" bridge of 4 transistors to do this. My legs are going to hurt tomorrow - Paul

#46 Kermit

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Posted 21 April 2012 - 07:57 PM

...you drilling with your LEGS??? :-) Andrea

#47 Paul Newton

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Posted 21 April 2012 - 09:06 PM

...you drilling with your LEGS??? :-)
Andrea


LOL.

No, I have to kneel down to hold the drill and then the hammer and chisel.

Tomorrow I have to lift all the floor boards to run the cables under the floor. I will have hands full of splinters after that.
And if the cat goes under the floor it will come up covered in spider webs.

:rolleyes:

#48 Kermit

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Posted 28 April 2012 - 10:25 PM

Update (even if my spare time is never enough...): As Mario Vernari suggested, applying 12VDC to the rail exchange (instead of the requested 16VAC) makes the rail exchange function without any problem (but it comes to my mind to ask if with time this can damage someway, somewhere...). More important, I'm testing how to modulate voltage to the rails, and it all looks ok, apart from a little problem... ehm...: how I can give NEGATIVE voltage to the rails, if I have in input a positive DC, and transorming (linearly or with PWm) in the voltage I want, but always positive? Do I have to make two different circuits? Even in this case, how can I apply one or the other, excluding totally the other one? Thanks, as always... Andrea

#49 Paul Newton

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Posted 29 April 2012 - 08:37 AM

Hi Andrea, DC vs AC: There are two things I can think of that might make DC a problem. 1/If the DC is turned on and left on by mistake, I think more current will flow than with AC. (A coil has a higher impedance to AC than it does to DC.) This higher current might cause damage (heat) if left on for a long time. 2/ Something I just thought of... If you use AC, any parts in the device that can be magnetised with be rapidly de-magnatised again because the AC is always changing. With DC there is a chance that parts of the device /could/ become permanently magnetised - and this /might/ then cause problem. Forward & Reverse: Most motor shields or motor driver chips have two sets of transistors - 4 in total. They are arranged in the shape of the letter "H". The motor is accross the middle. On either side there are transistors above (from the supply) and below (to the ground). There is then a logic input (on/off) that controls which pair of transistors is used - this controls which way the current flows accross the H and so controls the direction of the motor. What are you currently using to drive the motors? Paul

#50 CW2

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Posted 29 April 2012 - 09:11 AM

how I can give NEGATIVE voltage to the rails, if I have in input a positive DC, and transorming (linearly or with PWm)

You don't need negative voltage, you just need one to be "more negative" than the other. If you connect rail 1 to PWM and rail 2 to ground, the motor turns in one direction, if you connect rail 1 to ground and rail 2 to PWM, the motor turns in the opposite direction. Thus, you can connect two PWM channels to rails (one-to-one), set one PWM channel duty cycle to zero and control the speed with duty cycle of the other PWM channel, switch to go in opposite direction. This is basically how the motor controller works - you'd probably want to use specialized shield or IC, as suggested by Paul, they have some additional features worth having (power stage, various protections etc.).

#51 Kermit

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Posted 29 April 2012 - 09:53 AM

...long way for me, to get the grip on these things... Obviously I already knew of H-bridge, L293D and similar, but when trying REALLY to do things, you have to reelaborate what you know, and if you don't have experience, it's really a tough work... I hope to get more brilliant in the next times: I'm tired of my red faces!!! :-) What always puzzles me is how much you are approachable, and kind, to always answer my silly questions... Andrea

#52 Kermit

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Posted 01 May 2012 - 01:09 PM

Hi to everyone! :-) Here is the silly man again! :-))) Today's question is: since I asked my friends to find for me old car radios, printers, and whatever has a little motor in it, and now I have more than 30 small motors in my hands, all perfectly functioning (for my Christmas animated nativity), how can I find out what are their characteristics, first of all Voltage, since noone has anything written on it? Is it silly enough, for a question here? :-) Andrea

#53 MrSmoofy

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Posted 01 May 2012 - 01:54 PM

Have you considered DCC/Digitrax or any of the other dozens of products that use Model Railroad DCC communications? If you used this in all your devices and loco's it would probably be better/easier for you write computer software that communicated with the DCC communications.

#54 Paul Newton

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Posted 01 May 2012 - 04:39 PM

Hi to everyone! :-) Here is the silly man again! :-)))
Today's question is: since I asked my friends to find for me old car radios, printers, and whatever has a little motor in it, and now I have more than 30 small motors in my hands, all perfectly functioning (for my Christmas animated nativity), how can I find out what are their characteristics, first of all Voltage, since noone has anything written on it?
Is it silly enough, for a question here? :-)
Andrea


If you have not removed the motors, you might be able to turn on the equipment and measure the volts when the motor is running.

If they can't be run any more in the equipment, and there are no markings, you may get a clue from the supply voltage of the equipment you removed it from.
E.g.
Something from a car will run on 12V or less.
From a lorry 24V or less.
Something that has a DC wall adapter will run on the output of the adapter or less.
...

If you have another motor whose voltage you do know, you could try turning the unknown motor into a DC generator. (This will only work if the motor has permanent magnets.)
Do this by coupling the two motors and use one to drive (turn) the other. When they are both turning, use a multi-meter to measure the voltage generated by the unknown motor. This will be approximately the right voltage for driving it.

If you can't drive one motor from another, try spinning the shaft with your fingers and measure the voltage. This will be best done with an analogue voltmeter (not a digital one) because the voltage will not last long.


Finally, test your theory using a number of AA batteries in series. Connect them up one at a time and see how many you need to make each motor turn.
Once turning, see how much work the motor can do by touching the shaft with your fingers - if it stops straight away, you probably need more volts.

Paul

#55 Kermit

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Posted 01 May 2012 - 04:52 PM

@MrSmoofy: No, digital solutions are not an option, we already talked about this previously in this thread. Thanks anyway. @PaulNewton: Paul, you are always the man! :-) Every message of yours gives me enough sparks to think about, and learning (or remembering) something interesting. But: since I already tested with PWM to change speed, and I saw that Voltage and Amperes are different at each speed, if I turn the wheel with my fingers, or with another motor, I can only get the voltage (and Amperes) for that speed. I will never know if the wheel is at its maximum speed, or to the maximum 'normal' speed that I have to run it to! The question came to my mind just because I tried many motors, at different input voltages, and different PWMs, but I cannot know if I'm going to burn them soon! It's not a great problem, I think that in another two weeks I'll have more than 100 of them, but just to know and learn... :-) Andrea

#56 MrSmoofy

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Posted 01 May 2012 - 04:56 PM

@Kermit Sorry I missed that and I even read through most of the thread.

#57 Kermit

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Posted 01 May 2012 - 09:33 PM

No problem at all! Rather, thank you for your interest! Andrea

#58 dwfunk4475

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Posted 02 May 2012 - 02:19 AM

Oh, no... the beauty of the system is that some of the trains are *really* old, so are most of the railways: so the project is to add control, but leaving all the (physical) model as is... Digital trains are not an option!
Thanks anyway for the idea!
Andrea



C/MRI . . . That's what you need to keep the older analog trains running.

The inventors website: http://www.jlcenterprises.net/

A help forum: http://groups.yahoo....oup/CMRI_Users/

I'm retrofitting my PC driven C/MRI system with Netduino Plus based controllers so I can network them to further eliminate huge bundles of wiring.


-david

#59 dwfunk4475

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Posted 02 May 2012 - 02:23 AM

Update (even if my spare time is never enough...):
As Mario Vernari suggested, applying 12VDC to the rail exchange (instead of the requested 16VAC) makes the rail exchange function without any problem (but it comes to my mind to ask if with time this can damage someway, somewhere...).
More important, I'm testing how to modulate voltage to the rails, and it all looks ok, apart from a little problem... ehm...: how I can give NEGATIVE voltage to the rails, if I have in input a positive DC, and transorming (linearly or with PWm) in the voltage I want, but always positive? Do I have to make two different circuits? Even in this case, how can I apply one or the other, excluding totally the other one?
Thanks, as always...
Andrea



You need to leave the AC alone on the "rail exchange function" You will burn out the coils in the switch motors with DC usage.

C/MRI system handles all of the analog functions.



-david

#60 Kermit

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Posted 02 May 2012 - 09:53 AM

Yes, I already find out that I can find ready-made solutions, but this is not a forum about trains, but on the Netduino: I'm pretty sure that my solution will cost more, in the end, and will be less stable, but it will be MY solution, and I will learn (as I'm already doing) a lot of things. So, I thank you for your help, I find the sites very interesting, I'm looking on them, but I want to try to make all by myself! You know, there are things in life called challenges... :-) Andrea




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