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Track Buffer-Stop Used For Battery Charging
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 Posted: Mon Apr 12th, 2021 02:01 pm
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Steve Soar
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Hi Juergen,

Thanks for your interest.


The DPDT centre-off switch, between charger and track buffers,
can reverse the polarity at loco buffers A and B.


When A is positive and B is negative, the battery charges up via diode D5,  
capacitor C5 is discharged, and taken negative by the diode-drop,  
FET Q3 is 'off', so no supply to the loco control circuit.  

So whenever the battery is on charge, then the loco is 'off'.

When A is negative and B is positive,
then capacitor C5 charges to battery voltage + charger voltage, 
and FET Q3 is 'on'. 

The loco can be driven off the buffers,
and is kept alive by the charge on capacitor C5.  

The FET Q3 gate-to-source is only 100nA,
so a 1uF capacitor keeps it on for days   

When the loco returns for a recharge and buffers are set to charge,
the loco will switch off as soon as capacitor C5 discharges, 
FET Q3 turns 'off' and isolates the supply to the control circuit.


I have also used this circuit on track charging,
same principal but uses loco pickups instead of buffers. 
(no need for buffers)


Hope this is clear enough,
if you want more info then let me Know.


Regards
Steve


Components.

RL3  1K
C3   1uF ceramic
Q3   IRFD14
D5   1N4001
D8   1N4001





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 Posted: Thu Apr 15th, 2021 05:25 pm
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Toeffelholm
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Hi Steve,

Many thanks for your information.
Very smart solution.

Juergen




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modelling in 1:22.5 on 32mm and 16.5mm track
Actual project: 7/8" scale on 45 mm track
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 Posted: Sun Apr 18th, 2021 03:29 pm
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Steve Soar
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Hi Juergen

Thanks.


I have made some improvements,
now using a 2mm dia. x 3mm long magnet.

Also made a plastic buffer stop frame,
and hidden the wiring.  

The weaker magnets still give good contact,
but allow the loco to pull away without assistance,
so quite pleased with the results.


I am well aware that not all locos have buffers !!  

I have a prototype system,
which has the magnets on an insulated plate which sits between the rails,
and can be raised to contact with two metal wires under the loco.

Operation is the same as the buffer version,
but the magnets have to be pulled off the loco after charging. 

This is done from under the table,  
easy to do, but not as satisfying as the buffer version.


More info available if wanted.

Regards
Steve





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 Posted: Tue Apr 20th, 2021 02:48 pm
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Steve Soar
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Hi,  

The "bufferless loco" charger works ok,
and is still a prototype.

A couple of photos to look at.      


The underside of the loco has 2 wire pickups for the feed,
these are made from Soft-Tie garden wire,
with the soft covering removed.

The wire is 1mm diameter,
and hopefully being for garden use, will not rust!   
It is magnetic.


The magnet board sits between the rails,
and the 2 magnets (3mm dia. x 3mm) line up with the loco wires.  

This board has locating bars, which pass through to the underside of the board,
and are free to be raised and lowered, to supply power to the onboard charger.


Works in the same way as the buffer charger.  
However it needs to be pulled off the loco wires when charged.

For now this is done by reaching under the table and pulling it down.    
So I need a nice simple mechanical way of doing this.

Any ideas ?  ???





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 Posted: Tue Apr 20th, 2021 02:49 pm
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Steve Soar
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Best regards to all.

Steve





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 Posted: Wed Apr 21st, 2021 03:23 pm
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Helmut
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Attach the contacts by soft coil springs,
that are compressed when the magnets pull the contacts down.

Thereby it's an all automatic operation.




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 Posted: Wed Apr 21st, 2021 04:03 pm
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Steve Soar
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Thanks for the suggestion.


As I have it at the moment, the magnets board,
is free to jump up to the fixed contacts on the loco.

Not very good.  


I will try with fixed magnets and movable contacts,
as you suggest.

Should solve the problem. 


Drive on - charge - drive off.  


Regards
Steve

:thumb:


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 Posted: Sun Apr 25th, 2021 12:52 pm
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Steve Soar
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I have converted a tender loco to buffer-charging,
with all the Battery Powered Radio Control stuff, inside the tender. 

I have used 2 cells out of a PP3 battery (with protection circuit).
Size is 54mm x 27mm x 22mm, and just fits into the tender space. 

I have glued steel discs to the tender buffers,
and taken wires from these to the control circuit.

Dismantling the PP3 is fairly easy, but needs a bit of care,  
the terminal end can be removed and disconnected,
the 2 cells pulled out.... carefully.

Photo shows side view.

Regards to all
Steve





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