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Forum: µC & Digital Electronics Wikinger decoder for Marklin digital


Author: Vasilis Vas (billys)
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Hi! This is my first post.

I am trying to built the wikinger decoder from here 
http://www.frederiksson.dk/indexeng.html. I have built the hardware many 
times, using Pic 16F628 or 16F84. I programming them well. When i put 
the pic on the socket of the decoder, it works fine but pwm on RB2 RB3 
always unstable.
 I attach you the hex of the Pic16F628, and a schematic.


Any information will be helpful.

Thank you!
Vasilis

Author: Hanspeter (Guest)
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Hallo,

Unstable in the sense that the locomotive changes speed?
The PWM on RB2 RB3 is realised in software which makes it probably a bit 
irregular.

Regards

Hanspeter

Author: Vasilis Vas (billys)
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Why this way makes it irregular?

Author: Hanspeter (Guest)
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While the code executes scanning and evaluating the input to receive a 
valid instruction he also executes any valid instruction received and 
all the while he calls from different places the subroutine to switch 
on/off the outputs to simulate a PWM.

I don't know if they have counted/timed the milliseconds inbetween 
calls, but I guess not, so this results in different on/ cycles.

There is no feedbackloop to regulate/compensate different 
feeding-voltage scenarios of the tracks

The PWM in the chip is not used, also there are no Interrupt subroutines 
used.

Does the speed of your locomotive vary? Do you use original Märklin 
Motorsets?

Author: Vasilis Vas (billys)
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I use original equipment of Marklin.

I try it, not on the tracks but on a breadboard so there is no problem 
of distortion from the sliding of the loco on the tracks.

The decoder obey to the control unit (mobile station). The problem is 
obvious when i keep the speed steady. The motor works fine, for a few 
seconds, and for a millisecond the speed decrease, and then it works 
fine, and for a millisecond the speed decrease, and again and again...

If the PWR in the chip is not used, how the motor works?

Author: Daniel Ramirez (daru)
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Hi

I built the decoder with 16f628 and is ok.But with changes
can't find some ci only the pic.
I have ac motor,you used el dec 3-1 is for dc motors
How you programm the decoder whith mobile station?,i can't

Regards

D.Ramirez

Author: Vasilis Vas (billys)
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Did you made changes to the code?
I could n't programming with the mobile station.

Author: Hanspeter (Guest)
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It stops after about 4 sec, its the overcurrent protection of the 
terminal.
A problem around the H-Bridge?

Author: Daniel Ramirez (daru)
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Hello Vasilis

Yes, the speed is stable,not very much but similar another decoder with 
ac
motor ( this is problem the ac motor)
Today Marklin not use ac motors only dc and dc brushlees.
When i  built the deco i can´t find the ic for drive the motor, i try 
with
different mosfet, only the 2sk2499 running well
another posibility is transisitor bipolar darlington BD681 with 4k6 
resistor
I have another problem with the transistor for lamps ,used 2n7000 and 
bs170,
very inestables
Used bc547 and resistor 4k7 o bc337 for smokegenerator

I not made change to the code

When i programing pic said  "error adress29" but function well , i can
program on track , i built the encoder from "Frederiksson page"

I send you file.hex and two bmp the hardware.

Where are you from?

Regards, Daniel

Author: Hanspeter (Guest)
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On the schematic dec-3-1-b the MCLR is connected to VCC. Om the print 
its hanging in the air. Connecting MCLR to VCC stops the flashing of the 
outputs and also the motor becomes stable.

The resistors R8 and R9 are fine with 980ohms.

On the schematic the ZHB6790 is drawn with the pins not following the 
actual order

What is funny when you install it in a loco and run it on a actual 
layout with boosters is that on pressing start it runs about 30cm at 
high speed no matter at what speed its supposed to be. During 
initialisation the FETs hanging in the high impedance outputs. They need 
some pull-down resistor.

Also generally its not possible to run at slow speeds, maybe a 
reprogramming of the speed curve would help.

Author: Hanspeter (Guest)
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After review I saw that I forgot R8 with 3.3k, after changing it to 1k 
it does not run at high speed anymore after pressing start.

All elements required you could order at Digikey.com

Author: Vasilis Vas (billys)
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Sorry for the delay.
I have made many of these circuits for DC and for AC motor with the 
pic16F628. All these had the same result. They never been stable enough.
Also the programming of the decoder with the pic16F628 always had an 
error on the memory address 0029.

If you try to construct the circuit with the pic16F84 you will find that 
it is more stable by far from the others circuits.
Here there is a link for the same decoder with some improvements
http://home.arcor.de/dr.koenig/digital/ewiking.htm

I continue to believe that the circuit with the pic16f628 could be 
better if someone has the pleasure to improve the code.

For the components, i made some changes. I use a ULN2004 for powering 
the four extra functions and the lights.

For the motor, you can use a h-bridge like that i attach you. A better 
circuit is, using the IRF9103 and it is attached on the second 
schematic.

All the components i found them very easy on ebay.

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