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TREVOR GIBBS MODEL RAILROAD PAGE 8


MAIN

MODEL PAGE 2

MODEL CHASSIS

LATHE TURNING 1

LATHE TURNING 2

LATHE TURNING 3

OPERATING THE LAYOUT

Ersatz Ground Signals

TRANSISTOR THROTTLES I USE

SCALE SPEED

FURTHER PICTURES

OTHER PROJECTS

EXHIBITIONS


PASSES


The Transistor Throttles...

Despite teaching Systems and Technology, I do not feel that I could hold a candle to many of my peers in the electronics field. The basis of this design came from an Australian Model Railway Magazine about 20 odd years ago. Although it was portrayed as an N scale throttle, I have had little problem using it for many of the locomotives I have had over the years although it does not like the higher current drawing motors such as Mantua's open frame types. It is based on a 2N3055 type transistor and  have built it as a stand alone and as a walkaround.

You might like to change some of the values such as the capacitor and brake resistor for the inertia to suit as I like to have a fairly long braking sequence but in essence it should work well.

VR1   MAIN THROTTLE CONTROL

50 KILO OHM POTENTIOMETER

VR2   BRAKING CONTROL

200 KILO OHM POTENTIOMETER

VR3 & VR4  UPPER/LOWER  SPEED CONTROLS

5 KILO OHM POTENTIOMETER

S1& S2

SINGLE POLE SINGLE THROW ON/OFF SW

S3 REVERSE SWITCH

DOUBLE POLE DOUBLE THROW SWITCH

C1 INERTIA CAPACITOR

1000 UF 30WV CAPACITOR

C2 FILTER CAPACITOR

470 UF 30WV CAPACITOR

C3 FILTER CAPACITOR

220 UF 40WV CAPACITOR

R1

560 OHM RESISTOR

R2

15K OHM RESISTOR

D1 AND D2

1N4004 DIODES

TR1

BFY50 NPN Transistor

TR2

2N3055 NPN TRANSISTOR

POWER SUPPLY

24-30 VOLTS DC 2 A preferable

HOW IT WORKS

The Main throttle VR1 is fed by two variable resistors VR3 and VR4. VR4 sets the Minimum speed of your throttle control while VR3 allows you to set your maximum speed.

C2 filters the control of your circuit but your supply to the track is unfiltered and maximises your motor performance. The Minimum speed provides a "bleed" of power to the inertia capacitor so your starting is fairly instantaneous. You should get a very good pulsing effect but ensure that you have capacitor C3 in place or you may be disappointed in the output

When your throttle is turned off, your inertia capacitor will take over and start discharging through the base of TR1 and the brake VR2.

The "Braking effort"/ coasting distance can be increased/decreased by turning VR2 and bringing the train to a stop earlier.

Some people I know substitute a Resistor for VR2 and a push button  which could lead to an infinite slowdown time for the train... that is your choice!

Adjusting your throttle speeds

When first setting your throttle, turn your inertia switch (S1) OFF. Move your main throttle from its minimum speed setting about 60 degrees (I prefer to refer to it as 2 o'clock as I start with it in the 12 o'clock position) then adjust VR4 so that your light engine will just begin to move.

Then set your throttle to its maximum speed and use VR3 to set your throttles maximum speed or the desired maximum speed for your layout. This will enable you to use most of your throttle to control your train speed and provide a bit of insurance against those who want to run a train like a slot car! This is especially handy if you have a switching layout and want refined control

Aside from that enjoy... I will get a PC board design for the circuit as soon as I can on this page... watch this space...

 

 

Hope you enjoyed all this and please feel free to write if you need clarification

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