Alimentator PWM analogic

PrinzEugen

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yeah with real one resistor 0r68 it works, (so little resistance that even no need for use)


ok...now test

....tracks needs little polish....i have few jump starts..its not so smooth but with little make up it will be ok. I have whatsoever no buzzing on couple locos and no heating elements on regulator

prefer to use some higher voltage for freq. stability?
can i add some capacitor do smooth regulation?
i heard that pwm control can damage in some period of use magnetic coil of motor?
 

oilen

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Ok . That-s very good. You finally made it. For a proper work use a 17 V DC power supply as mpursu described and use a large capacitor in that supply. This will ensure that your 9V regulator will work correctly and the oscillator will stabilize also.
As for PWM control dammage... i heard those rumors too. but only if the motor is overheating. Using higher frequencies like you have will ensure smooth operation and long life of motor, provided that you are using correct DC motors. Since ALL DCC decoders found in nowadays locomotives are using PWM to drive them....
Personally on my new project for DCC/analog booster station i let the device run at a very slow speed for about 24 hours to somehow burnin test the ehtire electronics. The motor wasn't even heating enough to be felt at hand and the radiator of the driver was at 28 degrees Celsius;
 

PrinzEugen

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thank you guys once again......

ive no brain in few occasions in building this project and of course i have no luck as result.....happy ending after all :D


and final....just few minor modifications...


i will use electrolit 4700 microfarad / 30V large capacitor parallel with capacitor + with IN and capacitor negative with GND 7809...so what happens when i mistakenly swap input rails ..short circuit protection or capacitor just blown up?

i have few metal 50kohm pots from couple speakers, i think they are quality over Piher plastic 100k pot....with which resistor i have to change schematic resistor R1 2k2 then ??? 4k4??
 

mpursu

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mpursu
It is absolutely obvious that you must NEVER swap the input rails, if by those you mean the wires named "+17VDC" and "GND" :-?
However, it is even recommended to use a DPDT reversing switch at the output of this device, in order to connect the wires named "OUT+" and "OUT-" to the rails of the miniature railway either directly (OUT+ to rail1 and OUT- to rail2) or swapped (OUT+ to rail2 and OUT- to rail1), because this is precisely how the travel direction of the miniature train can be reversed.
As for the potentiometer, I would kindly advice you to leave it as it is, of 100kohms. Of course, if you don't like plastic, you may exchange it with another one made of metal, but with the same resistance of 100kohms. If you are really keen to exchange it with another one of 50kohms (DO check carefully!), then you must also change C1 with another one of 2nF in order to maintain the same PWM frequency.
 

PrinzEugen

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:D ole....ive packed pwm controller into old metal box of mehano rivarossi transformer...added led, reverse switch....

i do little research about pwm controllers.....


can we use modification of circuit and add some overload indication??


eventually trimmer for momentum

MOMENTUM SIMULATION has been developed since the early days of model railroading. The effect is to ramp power up and down gradually in response to throttle changes. Sudden throttle changes are mitigated with gradual changes in the actual power settings. This simulates a larger momentum than is actually present in the scaled down train. This simulated momentum can be checked with a "brake application" which increases the rate of deceleration. No actual brakes are applied, the power is simply reduced more quickly.


check out this

http://www.hobbymasters.com/mrc-tech-4-220-w-16va-and-momentum-model-train-controller.aspx
 

mpursu

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These are all good ideas, but, as I was saying, this is a very simple PWM device, which I did not develop any further because I moved on to the digital system. If you do have some good ideas to improve it, then go ahead, you are free to try them and show us the results.
 

PrinzEugen

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one question....


ive read that if you leave DC loco stationary for too long his motor will burn out (this happpens very quickly) with DCC control.

But what happens with PWM control of DC loco in this project, motor is equipped with full voltage from PWM all time (preety much same as DCC) whether loco motor is running or not, is that harmful ?
 

oilen

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@PrinzEugen, I have let one DC 12V motor stationary for 24 hours controlled by PWM and 50 KHZ. and one night at about 2 rotations per minute. The DC motor still works flawlessly. The problem arise when the DC motor is either fed with a too hight voltage ( motor is for 9 Volt and PWM is at 12 or 16 volt. And let's be fair... do you think that any company would push DCC control if they new that it will harm your loco in such a short time? usually there is a warranty period for the loco's equipped with DCC devices.
PWM control is used widely to control many other kinds of machines and motors. Think just for a second that the servo motors used in CNC machines are PWM controlled. These machines usually run for hundreds of hours and their motors are much more expensive than the one you have in your loco. Even your electrical screwdriver uses a PWM module to regulate the rotation speed. On the other hand usually tha vast majority of PWM or DCC controllers have PID and feedback circuits to reduce the EMF and wear on the motors. Your PWM controller is cheap but it can be improoved with aditional feedback and PID. But you are safe for now.

Regards.
 

PrinzEugen

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ok...i dont know if you understand me very well, but when you running analog loco DC on DCC control it will burn out when engine is stopped. Am i right?

so if im planning to switch to dcc to buy lets say roco multimaus i need to convert all my dc locos with decoders and to remove theirs inductors and capacitors from engines?

so pwm control from 20-24khz in this project has nothing wahtsoever with DCC control in some point. im confused about pwm freq thats all...
 

oilen

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ok let-s crack this frequency problem.

You basically can run loco's on DCC enabled boosters and infrastructure because of the feature called "Zero Stretching". The frequency of DCC signal is lower than the PWM signal so in theory you can run DC locomotives on a DCC enabled track. I did not tested this option yet to run both DC and DCC locos on a layout but when i will finish my Analog/DCC combined booster i will shurely try this option also.

On the DCC side as far as i read it is recommended to convert all your locos to DCC if you plan to migrate to digital.

to enlighten a little more, the digital signal used by DCC is a set of very fast and short pulses sent onto the tracks by switching the DC power given by a power supply unit. from the standing point of a dc motor coupled to this kind of signal the motor will see this signal as a PWM signal since the period of '1' logic is about 57 microseconds and a period of a logic '0' is longer. by "stretching " the period of '0' logic the booster can control with a simulated PWM a DC motor. But this is limited and from my point of view sometimes very hard to implement. Basically this is why i started designing a combined Analog/DCC power booster.

regards.
 

PrinzEugen

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yeah...on every forum they dont advise dc on dcc...as result analog dc motor gets confused from impulses and final outcome is overheating and burning motor coil... especially when engine is stopped...


as i understand ...this cheap pwm send clean pulses to analog dc motor....in desirable period of time...nothing confusing to motor.


i have Mehano alco s1 one axle motor builded....

http://desmond.imageshack.us/Himg204/scaled.php?server=204&filename=alco1000frontright.jpg&res=medium

interesting when using pwm...i wait for couple sec to start loco when pot is near min....to slow start

of course at some point towards max i have jump start....issue?


with other mehano and piko motors i have no buzzing and no waiting
 

oilen

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The problem is in generally generated by the number of poles the motor has. if the number is low ( 3) then the motor will behave a little awkward. with the new kind of motors with 5 or 6 poles you do not have such problems. Also you will have a problem using PWM with low frequuency on brushless motors. But this can be corrected.
Amother issue is how the motor is built. I have several general use motors i am testing PWM with and some of them behave exactly as you describe indifferent of the PWM frequency i use. Cheaper motors are built with "cheap" in mind so the collectors and the gaps on the collector are larger and this impacts on the capacity of motor to rotate at lower speeds. Another issue is the magnetic field generated by the stator magnets. THese magnets on "El-Cheapo" versions can loose their magnetic properties in time. As a consequence the performance of the motor decreases..

regards.
 

PrinzEugen

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ok....now im switching to spur1....ASTER FULGUREX..... :D

i hope there will be no problem....just some fuel... :roll: