Old OO Gauge model railway points not passing track power - an easy solution using a bistable relay
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OLD POINTS NOT PASSING TRACK POWER #modeltrains #modelrailways
Often insulated frog type points start to fail to pass the track power reliably.
Repair can be difficult and replacement is costly and inconvenient.
One solution is to use a bistable relay to sort a point that has started to fail to connect the track routing power.
Assuming you always switch your points using the points motor and not manually (i.e. by hand) and also that you are using DC (i.e. not AC) to power the points motor then this might be of interest. It works fine with a CDU (capacitor discharge unit).
So what is a bistable relay?
It is a relay with two coils and so the relay can exist in two states without needing power to be applied continuously.
Power only gets applied to change state.
The versions I use are double pole, double terminal relays.
They are ideal for points track power routing as each of the two blades operate on different rails when using insulated frog type points.
The relay coils are powered by the same power that operates the points motor so the relay changes state when the points are thrown; it is therefore quite straight forward to wire the relay contacts such that they join the appropriate tracks together that the point itself is failing to reliably do.
There follows an example with an old Hornby SYSTEM 6 point that has faulty power routing contacts. By connecting the coils of the bistable relay to the power supply of the points motor, the contacts of the relay can be used to ensure proper track power routing.
Note that the relay coils are polarity sensitive and you must take that into account when wiring to the points power. The wiring diagram assumes that the points common line is negative.
Wiring is quite straight forward as all connections needed are local to the point and the relay can either be placed beneath the board or on the surface and concealed with scenery of some sort or just painted over to look like line-side equipment.
Triang used to do a bistable relay under part number RT406. It was a lot bigger than the modern version! It was intended for a form of automatic train control and worked in conjunction with a pair of trip switches. A search on YouTube for R406 Automatic Train Control will show details of that.
Where the points are working properly (i.e. the power feeds via the points blades or already sorted using a bistable relay), a bistable relay can be used to control the power feed direction to a return loop. Just control the relay off one of the feed points and ensure that only one point is open at any time. This allows the train to be taken into the return loop, stopped, the points changed from one side to the other and the train to be taken out the other side.
These relays can also help when using single or double slips by recognising the slip settings from the point motor operation and connecting the slip rails to the appropriate track feed power. Depending on the application, you may need to use two relays.
16 pin DIL bistable relays are widely available on line. A search for “bistable latching relay” will show what’s available. Prices vary but usually available for between £3 and £4. The coil voltage should be selected to match the points motor supply you are using. Details of the relays are in the video.
OLD POINTS NOT PASSING TRACK POWER #modeltrains #modelrailways
Often insulated frog type points start to fail to pass the track power reliably.
Repair can be difficult and replacement is costly and inconvenient.
One solution is to use a bistable relay to sort a point that has started to fail to connect the track routing power.
Assuming you always switch your points using the points motor and not manually (i.e. by hand) and also that you are using DC (i.e. not AC) to power the points motor then this might be of interest. It works fine with a CDU (capacitor discharge unit).
So what is a bistable relay?
It is a relay with two coils and so the relay can exist in two states without needing power to be applied continuously.
Power only gets applied to change state.
The versions I use are double pole, double terminal relays.
They are ideal for points track power routing as each of the two blades operate on different rails when using insulated frog type points.
The relay coils are powered by the same power that operates the points motor so the relay changes state when the points are thrown; it is therefore quite straight forward to wire the relay contacts such that they join the appropriate tracks together that the point itself is failing to reliably do.
There follows an example with an old Hornby SYSTEM 6 point that has faulty power routing contacts. By connecting the coils of the bistable relay to the power supply of the points motor, the contacts of the relay can be used to ensure proper track power routing.
Note that the relay coils are polarity sensitive and you must take that into account when wiring to the points power. The wiring diagram assumes that the points common line is negative.
Wiring is quite straight forward as all connections needed are local to the point and the relay can either be placed beneath the board or on the surface and concealed with scenery of some sort or just painted over to look like line-side equipment.
Triang used to do a bistable relay under part number RT406. It was a lot bigger than the modern version! It was intended for a form of automatic train control and worked in conjunction with a pair of trip switches. A search on YouTube for R406 Automatic Train Control will show details of that.
Where the points are working properly (i.e. the power feeds via the points blades or already sorted using a bistable relay), a bistable relay can be used to control the power feed direction to a return loop. Just control the relay off one of the feed points and ensure that only one point is open at any time. This allows the train to be taken into the return loop, stopped, the points changed from one side to the other and the train to be taken out the other side.
These relays can also help when using single or double slips by recognising the slip settings from the point motor operation and connecting the slip rails to the appropriate track feed power. Depending on the application, you may need to use two relays.
16 pin DIL bistable relays are widely available on line. A search for “bistable latching relay” will show what’s available. Prices vary but usually available for between £3 and £4. The coil voltage should be selected to match the points motor supply you are using. Details of the relays are in the video.
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