Guys,
After many years I have decided to resurect an idea iv'e had with respect to a model train controller and would apreciate your help and guidance. This entails modifying the circuit below which is a bit of a classic in the model train world. This circuit uses full wave rectified but NOT smoothed ac as helps the slow performance of the dc motors. We have R2 our speed controller pot and also (switchable) R7 which is a pot which acts as a initia/braking feature.
What I would like to do is modify the circuit such that when the speed pot (R2) is at its minimum, approx 4 v is present on the output to the track.My simplistic view is that a suitable resistor in series with the bottom of R2 is all that is required though I do not believe it to be that simple.
So why do it I expect you are wondering. By doing so I can configure the model loco's to only run when a voltage of greater than 4 volts is applied. Again why? This 4v rms can be smoothed to give me a 5v (approx) supply for onboard engine auxileries such as lights and sound. The very simple arrangement of an inverse parrellel diode array is connected between track supply and dc motor to inhibit this 4 volts thus rendering the loco stationary.
But of course there is more! Traditional dc controllers work on a 0 -12v range. Now by reducing this range, my limited knowledge tells me that the resolution and hence controlability via R2 would be improved. So looking at a initial 4v ( no movement) + 10v for engine so nominally 14v.
This circuit is I believe about 40 yrs old and I think it could be further modified by replacing the darlington pair with a ' single' darlington component, the individual transistors probably not available anymore here in uk.
I hope you will find this project of interest and I would truly welcome your comments and advice.
Yours
Willy
After many years I have decided to resurect an idea iv'e had with respect to a model train controller and would apreciate your help and guidance. This entails modifying the circuit below which is a bit of a classic in the model train world. This circuit uses full wave rectified but NOT smoothed ac as helps the slow performance of the dc motors. We have R2 our speed controller pot and also (switchable) R7 which is a pot which acts as a initia/braking feature.
What I would like to do is modify the circuit such that when the speed pot (R2) is at its minimum, approx 4 v is present on the output to the track.My simplistic view is that a suitable resistor in series with the bottom of R2 is all that is required though I do not believe it to be that simple.
So why do it I expect you are wondering. By doing so I can configure the model loco's to only run when a voltage of greater than 4 volts is applied. Again why? This 4v rms can be smoothed to give me a 5v (approx) supply for onboard engine auxileries such as lights and sound. The very simple arrangement of an inverse parrellel diode array is connected between track supply and dc motor to inhibit this 4 volts thus rendering the loco stationary.
But of course there is more! Traditional dc controllers work on a 0 -12v range. Now by reducing this range, my limited knowledge tells me that the resolution and hence controlability via R2 would be improved. So looking at a initial 4v ( no movement) + 10v for engine so nominally 14v.
This circuit is I believe about 40 yrs old and I think it could be further modified by replacing the darlington pair with a ' single' darlington component, the individual transistors probably not available anymore here in uk.
I hope you will find this project of interest and I would truly welcome your comments and advice.
Yours
Willy