13-03-2019, 11:10 AM
I'm not sure why you want a switch between the 1N4148 and the IC, unless it is for shunting movements where precise stopping is essential so I'm assuming that it is permanently closed and that R2 is set to zero at the start of the sequence.
Turn up R2 to the value required for full speed running.
The 1N4148 conducts, connecting C1 across R2. C1 commences to charge, dragging down the voltage across R2 because of the initial high charging current.
As C2 continues to charge, the voltage across it rises, allowing the train to start and accelerate until it reaches its maximum, 0.7V below that across R2, and no longer has any effect, so that train now runs at full speed.
When R4 is brought into play, it starts to discharge C2, which drags down the adjust voltage via the diode, causing the train to slow down to the point at which R4 in series with the diode are in parallel with R2 and the speed stabilises until either R4 is disconnected, allowing C1 to start recharging again and increasing the speed or R5 is brought into circuit. This has the same effect as R4 but, due to its much lower value, has a much faster and more severe effect on speed.
I assume the value of R5 has been chosen so that the train doesn't quite stop, allowing R2 to be used to stop it at exactly the right point.
Turn up R2 to the value required for full speed running.
The 1N4148 conducts, connecting C1 across R2. C1 commences to charge, dragging down the voltage across R2 because of the initial high charging current.
As C2 continues to charge, the voltage across it rises, allowing the train to start and accelerate until it reaches its maximum, 0.7V below that across R2, and no longer has any effect, so that train now runs at full speed.
When R4 is brought into play, it starts to discharge C2, which drags down the adjust voltage via the diode, causing the train to slow down to the point at which R4 in series with the diode are in parallel with R2 and the speed stabilises until either R4 is disconnected, allowing C1 to start recharging again and increasing the speed or R5 is brought into circuit. This has the same effect as R4 but, due to its much lower value, has a much faster and more severe effect on speed.
I assume the value of R5 has been chosen so that the train doesn't quite stop, allowing R2 to be used to stop it at exactly the right point.
