Using Capacitors to Simulate Momentum at Signal Stops

[fairflixt]

As a small update, I've been collecting electrical components to build the capacitor "circuit". Not a big project for the experts here, but I figured I'd share how I'm going to build it and hopefully not embarrass myself too much. I'll be traveling for work in the coming days so no time to test anything on track yet. The plan would be to connect the below to a track section that would become unpowered when a DPDT relay (LGB 12030) is switched by a reed switch (LGB 17100 Track Contact) as per the schematic in my first post. I'll start with 10k uF capacitance and work my way up to whatever works (per my research probably more like 30-40k).



I added the current limiting resistor R1 as suggested here and I included the 10k Ohm R2 to slowly drain the capacitor(s) when the system is turned off.

One thing I couldn't figure out is if there was a way to protect the capacitors from a voltage reversal in case I wanted to move a train backwards. Given that it is easy to do with my knob-turn throttle, I'm really worried it might happen. I'd be happy for any advice! Correct me if I'm wrong, but I think if I put a diode on the negative side of the capacitor, then I wouldn't get the capacitor to discharge into the unpowered track. I'm just having this thought - what if I put a diode in the power connection to this part of the track (via the DPDT), in other words, so that a train could only ever go forward in this section and if track power is reversed, this portion of track would become unpowered?

Also - the plus side of the capacitor (long leg) is to be connected to the plus side of the power supply/rails, right?

On the voltage dropping piece, I think I'll try it with two full wave diode bridges (per Greg's site) with 4 diodes in the path for 2.8V drop per segment. I've just set these up on a breadboard and will test and can easily add more depending on need. But it will take 3 isolated track sections which, as I've been warned, will take up a lot of space and the reality is I'll probably need more. All but one of my locos are LGB analog single motor models so I at least have the advantage that they don't need high voltage to run at a reasonable rate (at least that's what I'm telling myself until I find out otherwise) and so maybe I can get away with two steps.

 

[fairflixt]

OK, I managed to test the capacitors out! 30k uF and you don't get much rolling distance running a Stainz at what I would have called a reasonable speed but only 11V on the throttle and hence only 11V charged on the caps. I did install the diode for protection of the track piece containing the capacitors to prevent sending the wrong polarity at the capacitor. Then I tried it with a recent acquisition which is a mystery unto itself as it's tagged as a 2071, has steam installed (but not labeled as 2071D) and is in gray color and a different chimney than any pics of 2071 I could find online. I presume a mod by the previous owner.

As everyone already predicted, a sort of lukewarm result. Nevertheless, it was fun. More to come on the diode drop sections and maybe I'll combine the two circuits for some alternating loco operation and throw in a few more capacitors for kicks.

As a warning, these are unrehearsed single takes on my phone. Watch at your own risk of dying of boredom!

Stainz;

2071:

If there's anything you're intersted in having me test, now's the time to ask while things are set up. Thanks again to all for suggestions and advice!

 

[Paul M]

Unfortunately the videos are showing as unavailable.
Still you've had some fun and learnt something you can share, so all's good. Good luck with your further endeavours

 

[fairflixt]

Unfortunately the videos are showing as unavailable.
Still you've had some fun and learnt something you can share, so all's good. Good luck with your further endeavours

I tried to fix the links, hopefully they work now.

 

[Paul M]

Looks a lot better than a jerk to a halt

 

[fairflixt]

Looks a lot better than a jerk to a halt

This is a very good point, I was more focused on what I could achieve and not the outcome that it does look better than the alternative. Perspective is everything!

I thought I'd use this update as a quick shout-out to The Shed who sent some great resources as well as some previous discussions from users in this forum, in particular Melbournesparks .

Give Your Engines the Capacity to Ignore Ditry Track

Thermistors, the Magic Behind Smooth Acceleration

Right now, we have family visiting so I've been building various layouts with my young nephews in the basement. They are rather untrustworthy if left to their own devices so not really a great set up for more experiments, but it's been fun to run some trains with them!

 

[dunnyrail]

That is certainly a good result.