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Batteries Or Super-Capacitors ?
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 Posted: Tue Mar 9th, 2021 07:45 am
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Steve Soar
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I agree with much of the above.

I have been looking for a value of maximum current on the pickups.
 
I had decided that 1A is a good starting point,
and as my loco has 3 pairs of pickups,
then 3A is a good starting point.  


I now have approx 30hrs run time,
and have stripped down the loco and pickups are fine.
However time will tell.

I have no evidence of arcing, but again time will tell,  
the voltage is low and there is no inductance in the circuit.


Beginning to think that the battery option has big advantages.

Cheaper than supercaps.
Much longer run time.
Smaller.


Regards, Steve

 

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 Posted: Tue Mar 9th, 2021 12:18 pm
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Helmut
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I have arrived at powering my RC (Deltang) radio controlled TT-scale locos from the rails.

The occasional dead spots that hamper operation (much more than with DCC)
are overcome by using flat 0.47F@5V supercaps that were once made by Murata,
nowadays they are hard to come by as only cylindrical ones are offered.

The only firm offering them is CAP-XX  at prices that'll make you cry.
I was lucky enough to secure my batch when prices were affordable some years ago.




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 Posted: Wed Mar 10th, 2021 06:08 am
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Steve Soar
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Several suppliers on ebay.  

Search for : " supercaps 0.47F 5V " 
    

Regards Steve


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 Posted: Wed Mar 10th, 2021 08:33 am
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Steve Soar
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Also listed at 'Farnell' UK   

Part number 2696625 - £2.09 + handing + VAT   

Quantity pricing is not too bad.

:thumb:

Steve


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 Posted: Wed Mar 10th, 2021 10:05 am
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Helmut
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As I told you, cylindrical ones abound,

only prismatic ones are hard to come by at decent prices.


And I do not mean the standard 6.3x14mm² twin-packs,

but 2mm or less  thickness.




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 Posted: Wed Mar 10th, 2021 11:40 am
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davecttr
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Idiots question.
Will supercaps recharge while the loco is moving and powered via the rails,
or only if the loco is stationary?


I think I will try the supercap idea.
Set up a test rig first, with a loco on unpowered rolling road,
with motor fed from a Rx60-rectifier and fixed voltage power supply.


Which is best, DC or DCC ?

How do I construct a rectifier, which components needed?




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 Posted: Wed Mar 10th, 2021 09:08 pm
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Helmut
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The supercap will charge when there is voltage across the rails.

A rectifier is best bought as a ready-made item.
You need filtered DC.

Only when you operate your loco on DCC,
all that has been said about DCC applies.




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 Posted: Thu Mar 11th, 2021 09:07 am
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Steve Soar
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Hi,   

I agree prismatic is best, but, the cost is a bit prohibitive.
 
I have been using 'Farnell' order-code 2696625
Less than £2.50 each, with an ESR of only 0.3 Ohms, they are a good buy.


I have used these in a stack of three connected in series (see photo),
this loco has been running for three years with no problem. 

It's preferable to take precautions when connecting in series, to balance the charge.
I suggest a 4V7 Zener-diode in series with a 220R resistor, across each capacitor.


With 2.3 Amp-seconds it will run on unpowered rail for almost 1 meter, 
this is more than sufficient to carry the loco over a reverse loop gap.

No voltage-regulator or boost circuit required, 
it's just bridge-rectifier, capacitor assembly, receiver.  
 

I can post a diagram if requested.

Regards Steve





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 Posted: Thu Mar 11th, 2021 10:07 am
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Helmut
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@Steve

I'd prefer to use a 5V1 Zener-diode,
as you can use the capacitor to its fullest then.


When operating on DCC, as I assume you do,
one must be sure the DCC voltage doesn't exceed 15V
(which is NMRA S 9.1. for H0/00).

However I found that almost all manufacturers,
deliver DCC output voltage ranges of more than that,
up to 22V, and still intend it for H0/00 operation.


The decoders will not fry, they withstand that voltage anyway.
But your capacitors will suffer.

The current surge when switching on after long standstill,
has to be accounted for, too.


The smaller scales don't have the space for such a capacitor bank,
and must turn to step-up converters, or internal low-voltage operation.

Of course life is much easier when you operate rail-powered R.C.
Even the surge is not much of a concern then.




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 Posted: Thu Mar 11th, 2021 11:01 am
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Steve Soar
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Hi

Point taken, 5V1 Zener-diode in future.   

I no longer use DCC, generally 12V or 15V DC. 
Much prefer R.C.


You obviously have a good understanding of electronics, 
I am retired now, but much of my working life was electronics based. 

I do not have a model railway layout, just a test track, 
I like to look at control systems more than modelling. 


I have made my own PIC based decoder/motor driver,
and use a very cheap 433MHz 4 channel receiver. 

Push-button control on a handheld transmitter,
controls acceleration, deceleration, forwards and reverse. 
 
Not perfect, but it is cheap!!


Thanks for your input.

Regards Steve


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