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The circuit is an automatic speed control. Allowing start and soft stop Electric miniature trains. 11 connects either the 12V DC output of the original rectifier transformer or on the secondary 12V a conventional transformer. This arrangement allows the reversal of the direction of travel and the general shutdown.

The diagram indicates the different components of this diet. If the input voltage is 12V ~, it is rectified by a bridge of four diodes 1N 4004. If the voltage is 12V =, it is applied after the bridge rectifier.
The capacitor 1000 MF provides filtering in both cases. The potentiometer of 10 K, connected in series with the resistance of 1 K controls the base voltage of transistor 2N1711. This in turn controls the power transistor 2N 3055. The continuous output is on the transmitter. The trimming resistor 1K sets the maximum speed of the power supply when a short circuit. The timing circuit is provided by resistor 4.7K and 22R, and the capacitor 470 MF. When the switch 13 is closed, the base of transistor 11 2N 17 is returned to ground, and the output voltage is zero. When you open the switch, the 470 MF capacitor is charged through the resistor 22R and 4.7 K. The voltage output to the motor increases exponentially and you start up gradually to value selected by potentiometer 10 K.
If one closes the switch, the capacitor is discharged to ground through these resistors. The output voltage decreases to zero and the motor stops gradually. Forward and reverse are obtained by flipping the switch I4 which reverses the polarity of the output terminals S. The switch I2, when opened, automatically cancels the variation. It must in that case be adjusted manually by the potentiometer 10 K. The latter adjusts the speed of the train.
For assembly, no precautions are necessary if this is the proper respect for the orientation of diodes, transistors and capacitors chemicals.
The 2N 3055 transistor is fixed to the printed circuit by two screws. After having checked the last time the board layout, connect the DC input assembly to the original transformer-rectifier, 12V output, commonly used for train systems. If it has a dimmer, simply put maximum.
If one does not have the rectifier transformer, use a conventional 12V transformer that will be connected to the input 12V ~ assembly. Then position the potentiometer 10K to get the maximum output voltage. Put it shorted through a continuous ammeter on the highest caliber. Set the adjustable resistance of 1 K to obtain a current of 1 A. This operation must be carried out quickly because during that time. is the 2N 3055 transistor which supports the short-circuit. Food is well adjusted and can not charge more during an accidental short circuit; for example when a train derails and made contact on the view. It now suffices to connect the outputs S on track.
The assembly is then completed. It will operate the trains gently and precisely, to give the effect of reality.

I1 general shutdown
I2 manual / automatic
I3 start / stop
I4 front / rear


1-    1- circuit imprimé
2-    2-vis TP M3X10MM
3-    2- écrous diam 3mm
4-    2- rondelles diam 3mm
5-    3- inverseurs à glissière simple I1-I2-I3
6-    1- inverseur à glissière double I4
7-    1-transistor 2N1711 T1
8-    1- transistor 2N 3055 T2
9-    4- diodes 1N4004 D1-D2-D3-D4
10-  1-potentiomètre 10K/A
11-  1- résistance ajustable 1K RA1
12-  1- résistance 22R (rouge-rouge-marron) R3
13-  1-résistance 1K (marron-noir-rouge) R2
14-  1- résistance 4.7K (jaune-violet-rouge) R2
15-  1- cond. chim 470MF/25V/RAD C2
16-  1-cond. chim 1000MF/25V/RAD C1
17-  1- soudure
18-  1-fil

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