I have finally finished this project of refurbishing this model train controller.
There has been a lot of fiddling around making a mounting for the 3 push buttons that I wanted to fit.
I have completely redesigned and rebuilt the circuit board, changed the component values and added extra smoothing.
I also changed the small 1 amp bridge rectifiers, which failed before, with 6 amp types. As they were the same price I got 1000v types so I have a couple of useful spares now.
With the higher input to output voltage difference, as a result of smoothing the supply, the regulators were getting excessively hot relatively quickly. So I have made a heat sink out of an old aluminium echo sounder mounting bracket, and drilled a few holes to allow a little ventilation.
The whole affair works well, just getting warm after a half hour at about 1 amp total load. (300mA each channel)
There is also now better regulation of the voltage under differing loads.
I have discovered the lower value resistors for R1 give better regulation.
The output voltage from the new smoothed 21v supply was rather high on full speed, over 16v, so I have added a 4.7k resistor in parallel with the resistance track on all the 5k potentiometers. That has bought the max voltage down to 12.9v with R1 at 270 ohms.
Two of the channels work in the same principle as before, variable voltage of 1.25v to 12.9v, and with a switch to set the channel to have a max voltage of around 6.7v for half speed.
The third channel has the same normal voltage control but this time the high/low switch connects in the push button controlled "inertia" circuit .
When the inertia circuit is switched in, the train accelerates from stationary to full speed (12.5v) in 40 seconds. With the first button pressed the train slows to just over half speed (8v) over 25 seconds, the second button takes the train to a crawl (5v) over 15 seconds, and the final button allows the train to come to a stop (2.8v) over 5 seconds.
So I am happy with that at the moment, I may tweak the resistor values at a later date when it has had a bit more use.
Here are some photos of the controller.
This one is of the inside before my alterations, the red tape on the transformer is there just in case I accidentally leave the mains switched on whilst working on the insides.
This one shows the new final circuit layout.
and here are a couple showing the finished controller.
This was the plan for the component layout, viewed from component side, the copper tracks are below (the scan of the RS stripboard was inverted)
Mike
There has been a lot of fiddling around making a mounting for the 3 push buttons that I wanted to fit.
I have completely redesigned and rebuilt the circuit board, changed the component values and added extra smoothing.
I also changed the small 1 amp bridge rectifiers, which failed before, with 6 amp types. As they were the same price I got 1000v types so I have a couple of useful spares now.
With the higher input to output voltage difference, as a result of smoothing the supply, the regulators were getting excessively hot relatively quickly. So I have made a heat sink out of an old aluminium echo sounder mounting bracket, and drilled a few holes to allow a little ventilation.
The whole affair works well, just getting warm after a half hour at about 1 amp total load. (300mA each channel)
There is also now better regulation of the voltage under differing loads.
I have discovered the lower value resistors for R1 give better regulation.
The output voltage from the new smoothed 21v supply was rather high on full speed, over 16v, so I have added a 4.7k resistor in parallel with the resistance track on all the 5k potentiometers. That has bought the max voltage down to 12.9v with R1 at 270 ohms.
Two of the channels work in the same principle as before, variable voltage of 1.25v to 12.9v, and with a switch to set the channel to have a max voltage of around 6.7v for half speed.
The third channel has the same normal voltage control but this time the high/low switch connects in the push button controlled "inertia" circuit .
When the inertia circuit is switched in, the train accelerates from stationary to full speed (12.5v) in 40 seconds. With the first button pressed the train slows to just over half speed (8v) over 25 seconds, the second button takes the train to a crawl (5v) over 15 seconds, and the final button allows the train to come to a stop (2.8v) over 5 seconds.
So I am happy with that at the moment, I may tweak the resistor values at a later date when it has had a bit more use.
Here are some photos of the controller.
This one is of the inside before my alterations, the red tape on the transformer is there just in case I accidentally leave the mains switched on whilst working on the insides.
This one shows the new final circuit layout.
and here are a couple showing the finished controller.
This was the plan for the component layout, viewed from component side, the copper tracks are below (the scan of the RS stripboard was inverted)
Mike
