Warm loco standby
Years ago in the old forum there was a discussion about warm loco standby to minimize the waiting time for exhibition visitors between two loco runs. There was no solution at low cost.
Today PWM controllers have become very cheap due to their mass use in LED dimming.
I did a quick check of a small 8 amp dimmer serving a loco standby track, cost is less than 5.- GBP.
- Connect "IN" of the dimmer to the Hornby transformer output, watch polarity !!
- Connect "OUT" of the dimmer to a piece of track. There must be a dead section between this track and the main line !
- For the test I connected a DC-voltmeter to the track. This shows the PWM average voltage, not the PWM peaks (which are close to 17 volt).
- Put loco on track.
- At the "OFF" position of the knob nothing happens.
- Turning the knob a little you can hear the loco relay click, voltmeter shows less than
0.5 volt. As well the loco starts to beep, frequency is lower compared to the Hornby Controller.
- Turning further, the beep becomes a little louder and the cab lamp starts to glow.
- I did not turn higher than 12 volt to avoid stress for heaters and dimmer (rated 96 watt max.)
- I did not evaluate the optimum "keep warm" voltage, just wanted to check the feasibility.
- I did not try a short circuit. There is another LED dimmer rated 30 amp max. for less than 10.- GBP, this should be more robust.
Conclusion:
- You can keep the loco warm with a LED dimmer, the heater power can be fine-tuned to avoid safety valve blow-off.
- The max. position of the knob should be limited mechanically (or maybe by resistors added to the pot).
- Of course there will be no alarming when the boiler is empty.
- If you are interested search in ebay for "dimmer led".
- And finally: I myself will not use it, I have time to wait for steaming up.
Thanks for this detailed information, these are impressive efforts !
The dimmer is in it´s intended home use now, LED lighting application of a show case :-) Anyhow it was fun to do a quick test for the OOLS application.