I've been messing about with capacitors. Here's a short video. (It's OO rather than HO but close enough I hope.)
https://youtu.be/I13EPnmBuz8
Can you elaborate what it is you are doing ? I'm not seeing anything obvious in the video.
Also, how are you wiring a reversable DC supply to capacitors that are polarity sensitive ?
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
As a Forum newbie your first few posts are delayed by moderators. If he’s using non polarized caps they would be as large as a flywheel if not larger and their life expectancy is not very long. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
So by using capacitors, he's not turning a throttle knob, he pushing switches.
Not sure just how practical it would be.
Mike.
My You Tube
Hi Mark,
There are four capacitors in the locomotive. When I open the switches I am cutting all power to the track and the cpacitors act as an electronic flywheel to keep the train moving. The switch on the left supplies power for right to left travel and the switch on the right reverses the connections.
The meter shows the voltage on the track which is actually the motor voltage when I cut the power.
For emergency stops it is only necessary to discharge the capacitors by connecting a low value resistor across the track. A dead short works too but that's being a bit unkind to the capacitors.
Cheers,
Andy
RR_MelIf he’s using non polarized caps they would be as large as a flywheel if not larger and their life expectancy is not very long.
They last a very long time if you know how to hook them up correctly
This is how they are connected. Four one farad 3 volt caps connected in series for a total of 250,000 microfarads and good for 12 volts.
Where is the circuit diagram?
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
richg1998 Where is the circuit diagram? Rich
Hi Rich,
I posted it before you asked but my posts are delayed because I'm new here and I'm still on probation.
My Stewart Baldwin switchers, before converting to DCC, would run a long way on the flywheels. Not very big locos, so the flywheels weren't big, but a smooth mechanism got the most out of them. They ran long enough to experiment with different resistors for different braking speed - and the LED headligh tremained lit the entire time it was coasting.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
richg1998Where is the circuit diagram?
The forum is set up not to embed images. You have to provide a valid URL for them (which usually in practice means hosting them on one of the commercial photo sites and then, if necessary, using their tools to put the URL or link into a post appropriately.
Could you post a link for the caps, I can’t find any 3 volt 1F non polarized caps that would even come close to fitting in a HO locomotive. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
The instructions for posting photos are at the beginning of the General Discussions Model Railroader forum.
Sorry for the "radio silence". Big storm rolled through and falling trees took out a lot of power lines and pretty much blacked-out the entire county. Fortunately our utility co-op is great they restored our power tonight.
I now understand about posting pix here. Thanks!
The caps are polarised. I used caps from AVR, p/n SCCR12E105PRB. Available from several sources. I happen to get mine from Mouser. Around $1.50 a pop.
I'll try to paint a word picture. The trick, if there is a trick, is by connectiing two equal polarized (electrolytic) capacitors in series back-to-back (pos to pos or neg to neg) you have created a non-polarised capacitor with half the capacitance of each, but the voltage is twice the voltage of each.
This is not a new idea. It's been around for many, many years but it is usually applied in AC systems that require a large capacity non-polarized caps.
For 12 volts you need two of these pairs in series and if you are not sure about your power supply voltage you might want to go with three to provide some margin. I'm using a controllable DC regulator that supplies smooth DC up to 12 volts so I know I'm safe.
If you add more of these things you will reduce the total capacitance because caps in series works the same way as resistors in parallel but even with the four I used to produce 0.25 Farads there was plenty of energy to spare, as you can see.
I also included a 1 ohm resistor between the track pickups and the caps to limit the current inrush to the caps. A choke might be a better choice.
The big unknown is "does this really work with DC?" It definitely works with AC and, so far, I have not found a lot of explanations that describe exactly why it works with AC. There is a lot of wavy arm stuff out there and I have found nothing that descibes anything like what I'm doing here with DC.
I have a sort of sketchy idea to explain why it should work with DC - something to do with limited charge transfer - but that's about it. On the other hand the limited empirical evidence I have so far suggests that it definitely does work (to be honest I was slightly surprsed).
BTW, if you are worried about "overrun" just apply a low ohm resistor across the track and it will discharge the caps PDQ. You might also build a controller with a push-pull output that giveth and also taketh away.
Hope this makes a little sense.
Even at a ⅝” cube the caps are too large for my steam without removing weight and weight wins out over a cap flywheel for me.I can see it working in a locomotive with the room. I fill all the available area with #8 bird shot for added weight to boost traction.The AVX Super Caps do have a better lifetime spec than other non polarized caps at 10 years, most are listed at 2000 hours.Thanks for your input Andy and again to the Forum.Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Well, I watched the video, and it is interesting.
But I already had that level of DC performance 20 years ago when I switched to the Aristo Train Engineer radio wireless throttles which use full voltage pulse width modulation speed control.
It does not require me to install anything in my locos.
The wireless throttles are also "push button" which I like.
The control is very precise.
Not the best picture, but hopefully you can see the throttle:
Five buttons:
FASTER - SLOWER - <DIRECTION - DIRECTION> - EMERGENCY
150' range
Great slow speed control, adjustable momentum, full voltage pulses make headlights work great.
My biggest thing these days, I could never go back to a fixed location throttle.
Sheldon
I guess if you stuff the tender full of supercaps...
Putting in a larger physical flywheel also adds weight, which is a double benefit (unless it's not located properly - all the weight in the world won;t help a steam loco that's not properly balanced). So if I can both increase the rotating mass for energy storage AND add weight to the loco for more pulling power - win/win.
Both mechnical and electronics means have the same issue - namely the slower the speed, the less the stored energy. If running along at half throttle, 6 volts, the caps can only charge to 6 volts. And the motor will only turn so fast, so a flywheel can only accumulate so much energy. The advantage of using capacitors with DCC is they can charge up to the full track voltage regardless of the loco speed.
Quite true Randy. The caps do have the avantage that they don't put a large load on the motor while accelerating. They also don't load up the motor bearings.
I have tried mechanical flywheels but there usually is not enough room in my models to add flywheels that are big enough to be much use. None of them were anywhere near as effective as the caps. I've also tried the "free flywheel" method and it was pretty much useless. Yes, caps can work well with DCC but I don't want to use DCC.
Each cap is 0.33" in diameter and 0.48" long so four of them don't take up a lot of space and they can be distributed around the locomotive.
AndyID Quite true Randy. The caps do have the avantage that they don't put a large load on the motor while accelerating. They also don't load up the motor bearings. I have tried mechanical flywheels but there usually is not enough room in my models to add flywheels that are big enough to be much use. None of them were anywhere near as effective as the caps. I've also tried the "free flywheel" method and it was pretty much useless. Yes, caps can work well with DCC but I don't want to use DCC. Each cap is 0.33" in diameter and 0.48" long so four of them don't take up a lot of space and they can be distributed around the locomotive. Cheers, Andy
Andy,
Have you ever experimented with any Full Voltage Pulse Width Modulated throttles?
They are very well suited to using buttons or rotary knobs, and they work very well.
ATLANTIC CENTRAL Andy, Have you ever experimented with any Full Voltage Pulse Width Modulated throttles? They are very well suited to using buttons or rotary knobs, and they work very well. Sheldon
Hi Sheldon,
Oh yes! I think it's 45 years since I made the first one.
I've also made pure DC feedback controllers that maintain constant speed regardless of gradients and curves.
Cheers!
Two more videos.
First video with capacitors (the blue things) disconnected.
Second video with capacitors connected. No other changes.
As you can see on the meter the track voltage is the same in both cases. It's smooth DC supplied by a LM217 regulator. The switches only connect and disconnect the regulator from the track with the correct polarity for forward or reverse.
The track and wheels are not dirty and current pickup is on all six wheels.
(The loco chassis is ancient Tri-ang 3F with Romford wheels and a Sagami motor.)
Clean track and wheels? My old design Mantua 0-6-0 (with blind center drivers - so how much does it even pick up from those?) runs much better over a couple of sections of Peco flex than that. Doesn't stall. With no caps and there's not even a flywheel on the motor (I think - haven't torn it apart - but the original Tyco version with an open frame motor had no flywheel).
Obviously, capacitors can provide an electronic flywheel action. Not disputed. I wonder, though, if it would be so simple with a more typical power supply that uses pulse power and isn't nice smooth DC - you tend to get a charge pump action charging the cap to the peak voltage rather than the average voltage, unless the load is sufficient to keep it drained.
Case in point - many moons ago at the club I belonged to (all DC< before DCC was even available), one of our members outfitted one of his models with a fairly sophisticated constant voltage device to run the headlights and warning beacon. I forget who made it, it was a commercial product, not homemade. We had two power supplies, both beefy with with walkaraound memory throttles. Two different brands, so one was the eat main and one was for the west main. One provided only smooth DC, the other used pulse power. On the pulse power track, even with the throttle on 0, the lights came on, and the only way to shut them off was to cut power to the block the loco was sitting in. On the other power supply, with smooth DC, the lights only came on if the throttle was advanced, and then not until the loco was already moving, basically the same as it worked without the constant lighting board.
So I wonder how this would all work with a more typical model railroad power pack. For some, the loco with capacitors might not even run at all - like a PWM system such as the Aristo (and there are others). Or an SCR throttle, with it's very choopy waveform (which really aren't suited for modern motors anyway), or a common unit like MRC that has an automatic pulse injection that becomes closer to smooth DC as the speed increases.
You would generally get better slow speed and smoother starts with some sort of pulse though. How much pulse, at what frequency, depends on the motor, which is why the really high end throttles had readily available adjustments for these things. Or like the PAT-V in MR in the 70's, had pluggable 'personality modules' you built for each loco. Basically, the throttle had various adjustments with potentiometers, you could measure the settings and then build a module (DIP header with resistors) using the closest standard value resistors, and then instead of trying to remember all the settings for each loco, you just plugged the module in and flipped a switch to use the presets instead of the manual controls.
DCC makes that all obsolete though, you program the running characteristics in each loco's decoder, and it's set for life. And always follows the loco. Some decoders even set the motor control characteristics automatically. Which is a very good thing, because trying to figure all that out manually is pretty much impossible for someone without the engineering background to understand BEMF and PWM drive as it applies to individual motor characteristics. There have been rules of thumb and guidelines for doign it manually, but it generally boils down to trial and error, and with 3 or more parameters that are adjustable, that can take forever to find the perfect sweet spot for every motor.
Hi Randy,
Works fine with a conventional controller, even pulsed. The huge capacitance will integrate any DC component into smooth DC. I'm running it off a regulated supply to show that you don't need any sort of pulse power.
The caps do exactly what a flywheel will do. They store energy with the advantage that they take up a lot less volume than a flywheel with equivalent storage and they don't put a gigantic load on the motor when it is starting. Also, they don't overload the motor's bearings. You can also discharge them quite quickly if necessary. So what's not to like?
They are also a lot less expensive than DCC and they could be compatible with much simpler layout automation although that does remain to be seen.
Lastly I spent forty years building and programming bloody computers and the last thing I want to do is progam my locomotives
When connecting large capacitors in series to increase their combined DC voltage limit, you need a series resistor divider network in parallel with the capacitors to even out the voltage on the individual capacitors. It can be a fairly high impedance network, depending on the (dis)charge current, so as not to excessively diminish the filtering ability of the network.
Otherwise, the capacitors do not always (dis)charge evenly (particularly as they age), and result in more than 1/4th the voltage across an individual capacitor. In extreme cases, almost the entire voltage can be seen across a single capacitor, with predictably poor results.
-- Andy - Arlington TX
Hi Andy.
Someone else suggested that was the correct configuration. I better do it!
Many thanks,
Andy (North Idaho and it is snowing a little.)
I've done a fair bit of testing and I'm glad to say I have not run into any problems. In fact, it gets better. These are double-layer supercaps and it turns out the electrodes are symmetrical. It doesn't make any difference whether you charge them positive or negative relative to the terminals. The designation seems to be arbitrary. That means you can connect them in series any old way you like
To provide a bit more voltage margin to be able to run up to 12 volts it's best to use five of these caps in series.
If you are concerned about too much flywheel effect it's not difficult to build a DC controller with a "push-pull" output that can both charge and discharge the storage caps.