Capacitance flywheel.


dgrafix

dgrafix

Well-Known Member
I am sure this is a thing that i did with my gdad long ago..
I seem to remember a "train onboard" DC layout jigger requiring 2 capacitors(a bi directonalsystem), with something like 2 diodes (in set directions) to protect them, that made the train power up and slow down naturally when the power was cut to a section of line (or over unpowered points or dirty sections). It added a kind of realistic spongey feeling to the controller where you set the speed and the train woud respond and when you wrench it to zero you get a sense of "braking slowly". If i run my HSTs over dead track it just goes from like scale speed of 320kmh to 0 almost immediately which of course would likely kill or best case injure everyone onboard.
Can anyone help me with this? I am not the engineer he was but would like to recreate. Not that i will be hacking apart any of my brand new trains to try it, but might be a fun experiment on one of my pocket line trains as a POC. Or is it already a familiar thing for DC? Not had much luck with googling it, it seems many just say capacitors are just used to eliminate EMF on DCC. But i beg to differ.. there was no DCC back then and i know nothing about that.
 
Last edited:
yes, two capacitors back to back [so they work in both directions under DC], with two diodes, and [as a suggestion] two resistors to limit inrush current ....
the same result can be achieved by using the 'momentum' slider on your power supply [if you have that] ..
i had made one for DC but it didn't work very well, at slow speed the track voltage was also low, and the capacitors did not store much energy ..
 
wvg_ca said:
yes, two capacitors back to back [so they work in both directions under DC], with two diodes, and [as a suggestion] two resistors to limit inrush current ....
the same result can be achieved by using the 'momentum' slider on your power supply [if you have that] ..
i had made one for DC but it didn't work very well, at slow speed the track voltage was also low, and the capacitors did not store much energy ..
Click to expand...
awesome. do you have the component specs of the caps? Or a C-diagram of what you mean? I have 2 diodes that can handle 12v at (edit: 500ma 😁) which should work, but microfarads are are a mystery to me :D
What does inrush current mean? Unfonately i am horrible with electronics, but needto learn!
As for controller i have 2x Kato SX controllers that can sullply 12v@1.2A max
 
Last edited:
dgrafix said:
awesome. do you have the component specs of the caps? Or a C-diagram of what you mean? I have 2 diodes that can handle 12v at 5ma which should work, but microfarads are are a mystery to me :D
What does inrush current mean? Unfonately i am horrible with electronics, but needto learn!
As for controller i have 2x Kato SX controllers that can sullply 12v@1.2A max
Click to expand...
no i never did make a wiring diagram, just put it together about six to eight years ago .. i do remember that the diodes were 1N4001 as i do have several hundred of them ..
it's a shame that your SX controller doesn't have momentum as that way would be a lot easier ...
 
dgrafix said:
I have 2 diodes that can handle 12v at 5ma
Click to expand...
Yeah, but, One should really want components with twice the voltage rating of the expected usage level. I buy stuff rated at least 25V for my MR needs.
dgrafix said:
What does inrush current mean?
Click to expand...
Try this. Think of a capacitor as a battery, only it wants to charge and discharge instantly rather than slowly like a battery does. When electricity is first applied to a capacitor it immediately wants to charge to full power. It sucks every bit of current available until it is full. The larger it is the more current it tries to draw in. That "rush" of current to fill capacitor(s) is called the inrush. Once the capacitor is charged it doesn't need any more, and the current drops to the normal consumption for the circuit.

So to answer your question, to get a locomotive to skip over dirty track and other glitches will require some pretty large capacitors. The exact size is dependent on the motor of the loco being "sustained". A super high efficiency motor will not require as large a capacity as, say, an old Athearn blue box.
 
Last edited:
12 volt at 5 ma is nowheres sufficient ...
you should have diodes rated for 50 volts [or more] and 1 amp or better
 
Sorry I meant 500ma... half an amp 😳
Oh and it's N scale so I would assume it would only draw about a half of the HO/OO current?
 
Last edited:
You must log in or register to reply here.



Back
Top