I’ve been messing about with capacitors. Here’s a short video. (It’s OO rather than HO [:)] but close enough I hope.)
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.
[#welcome]
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.
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
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
Hi Rich,
I posted it before you asked but my posts are delayed because I’m new here and I’m still on probation. [:)]
Andy
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
I don’t think he knows the ‘secret forum lore’ yet about how to get images to display.
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.
Rich
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 char
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 [#welcome] 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.
–Randy
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.
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!
Andy