# Using capacitors to gradually start stop loco's



## eugbro (May 5, 2009)

Hello all

I have analogue lgb control system, looking for a circuit I can use on board my loco's using capacitors etc so when I turn the throttle up full the loco will gradually accelerate and brake. Like what

happens on digital systems. I know there are delays on some controllers but im actually looking for a circuit to be on the loco between the track and motor block. Has any one done this or know
of any circuits.


your help would be great

Eugene

Australia


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## Dan Pierce (Jan 2, 2008)

Good thought, but it would be easier with multiple engines to do this with a controller. 

Some of the Radio controlled transmitter/receivers have this feature built in. 

For sure the Aristo train engineer (27mhz version) has this built in and has 5 presets. 

You are in Austrailia and perhaps Tony Walsham has a solution for you as he is based in Austrailia and is on this forum.


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## lownote (Jan 3, 2008)

I'm pretty sure Dave Bodnar has written an article on this--try here

http://www.trainelectronics.com/articles.htm


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## pdk (Jan 2, 2008)

I did just that years ago, so it does work. It was fun swapping in and out different capacitors to finally get the right stopping distance. You have to remember to plan ahead, just like a real train. Good luck

Posted By eugbro on 05/05/2009 12:13 AM
Hello all

I have analogue lgb control system, looking for a circuit I can use on board my loco's using capacitors etc so when I turn the throttle up full the loco will gradually accelerate and brake.Has any one done this or know
of any circuits.





Eugene

Australia


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## Torby (Jan 2, 2008)

I'd think that would take a monster capacitor. But then, there are 4 farad caps available from audio shops.


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## dbodnar (Jan 2, 2008)

Posted By eugbro on 05/05/2009 12:13 AM
Hello all

I have analogue lgb control system, looking for a circuit I can use on board my loco's using capacitors etc so when I turn the throttle up full the loco will gradually accelerate and brake. Like what

happens on digital systems. I know there are delays on some controllers but im actually looking for a circuit to be on the loco between the track and motor block. Has any one done this or know
of any circuits.


your help would be great

Eugene

Australia 




Eugene - I wrote two articles about just what you are describing - one uses large capacitors to slow trains gradually and the other uses NTC (negative temperature coefficient) thermistors to start them out gradually.

You want the articles listed under:

http://www.trainelectronics.com/articles.htm 



*Your Trains can Accelerate and Decelerate Smoothly* 

 Give Your Engines the Capacity to Ignore Ditry Track

 Thermistors, the Magic Behind Smooth Acceleration 
dave


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## SE18 (Feb 21, 2008)

thanks for the info. Cool stuff. This undoubtedly would work with R/C besides track power, if you are using your own makeshift R/C setup like I am


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## stanman (Jan 4, 2008)

Four farad caps? Hard for me to comprehend! Back when I was in EE school (over 50 years ago...) I can clearly remember that one of the profs was trying to impress us with how huge a capacitance _one_ farad would be. He said that a one farad capacitor would be as large as a box car!

Just one more "fact" relegated to oblivion. But it is strange that he used "box car" for his comparison.


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## SE18 (Feb 21, 2008)

When growing up we were warned against touching the back of a TV as the capacitor still has a lot of juice in it even when TV turned off.


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## Semper Vaporo (Jan 2, 2008)

Posted By SE18 on 05/05/2009 9:57 AM
When growing up we were warned against touching the back of a TV as the capacitor still has a lot of juice in it even when TV turned off.


Yep! That picture tube was the biggest culprit in that realm... and the cause of the most serious injury I ever had in working on TV's... Neighbor gave me a Sentinel TV that had been in his attic for over a year, unplugged. I got it home, took the back off and reached in to disconnect the HV lead from the picture tube. The injury? Deep gouges along the tender side of my arm from elbow to wrist as I jerked my arm from deep inside the sharp edged metal chassis when I got "bit"







on the charge still on the tube! OUCH!


















I remember seeing a 1000 quantity of 1000 uf capacitors used to display a 1 Farad capacitor and it took most of the "end cap" display at the electronics store, and that was a shock because I, too, had been told that nobody would ever be able to make a capacitor of 1 Farad. I told the instructor at school what I had seen and he would not believe me (nor would he go see it for himself!).


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## Guest (May 5, 2009)

dave, 

i just sniffed around your website a bit. 
just what i need! 
simple explanations, enough pics and diagrams to show the guys in the electronic parts shop what i want. 
(and not garnished with the council to leave analogue for something else...) 
thanks!


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## dbodnar (Jan 2, 2008)

Posted By kormsen on 05/05/2009 11:03 AM
dave, 

i just sniffed around your website a bit. 
just what i need! 
simple explanations, enough pics and diagrams to show the guys in the electronic parts shop what i want. 
(and not garnished with the council to leave analogue for something else...) 
thanks! 



I am pleased to hear that you found some things that might be of value - please let me know if you have any questions.

thanks!

dave


PS the diagrams and simple explanations are an occupational hazard - I spent my career teaching students (and then teachers) how to use technology.... great fun!


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## Torby (Jan 2, 2008)

That picture tube is a big leyden jar. Also, there were some pretty big capacitors in the TV's power supply, but nothing near a farad. 

10 farad 24v capacitor 









100 farad capacitor 








Dimensions: 2.72"W X 2.88"D X 4.23"H 
Said to be able to crank a car. 

(I think these are really VERY high current rechargeable batteries.)


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## astrayelmgod (Jan 2, 2008)

Those capacitors are called super capacitors or ultra capacitors. Conceptually, it's pretty straightforward: The surface area of the plates are increased by several orders of magnitude. So you really do have the capacitor the size of a boxcar (my electronics teacher said trash can, but I'm younger than you), it's just crammed into a can the size of a flashlight battery. You can't do that with aluminum foil, so they use activated charcoal. Researchers are looking at carbon nanotubes, which should be good for another large increase in capacity. The downside to all this is that they are good for only 2-3V, so to get higher voltages, you have to have series strings.


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## Del Tapparo (Jan 4, 2008)

While in the Navy, I was stationed at a Naval Radio Station (NRST Lualualei) on Oahu. We had a VLF (Very Low Frequency) transmitter that sent data to submarines. I can't remember the exact frequency, but in was somewhere around 100 HZ. The lower the frequency, the bigger the parts get! The transmitter filled an entire building, and the control room was literally inside of the transmitter. The capacitors used in the transmitter filled an area about 20' X 30'. There were 20 (?) caps, and each one was about 3'X3'X3', and filled with oil. I don't think I ever knew the farad value for them, but it was an amazing sight (45 years ago). Then there was the antenna ... 6 towers, if I remember right, hundreds of feet tall. This is probably how TOC got his e-mail in those days.


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## Semper Vaporo (Jan 2, 2008)

I need to add a further WARNING about capacitors and getting "BIT"... My granddaughter dropped her Nikon "Coolpix" camera and the case broke. She tried to glue it back together but couldn't get it to stay together very well. If you held it just right and squeezed a certain way, it would turn on, but that could take several minutes of fiddling... 

I bought her a new camera and she is happy.

I kept the broken camera to take it apart to see what kind of motors and stuff are inside to make the lens extend and focus. It hasn't had batteries installed for about a week, thus it hasn't been turned on for that long either. I decided to take it apart just now... removed what screws I could find and got the case apart. Then started removing tiny screws on the inside and removed a shield and the display module. 

I could not get the main circuit card loose even after removing all the exposed screws. So I began to lift small pieces of tape that might be covering other screws. 

I lifted a piece of tape to look under it and got my thumb across two soldered terminals under the tape and felt a small shock! Hmmm? Must have still had a bit of a charge on the flash capacitor! 

Ha ha ha! I got "bit". Right after I had posted the above comment about ripping up my arm on a TV chassis once. At least it was just a minor tingle and my arm was not deep inside a metal chassis with sharp jagged edges.

I decided to make sure the circuit was fully discharged, just in case I got my fingers there again. I peeled the tape farther back, being sure to not touch those two soldered terminals. The tape slipped off my finger and fell back over the spot I was looking at. My fingers are too fat to get it back up, so grabbed my screwdriver to stick it under the edge to lift it again.

The camera is now on the other side of the room behind the table and will take a few minutes of furnature moving to get to it. 

Please, understand, I did NOT throw it over there in any sort of frustration or anger, nor was I throwing it at anything for target practice. 

Really... I did not intentionally or purposely throw it at all, but upon my receiving what I think was several hundreds (felt like millions) of Volts of electrical charge from my left hand holding the screwdriver to my right hand holding the camera, the camera just kinda went over there... in a hurry.

I know that the capacitors we are discussing in this thread do not hold that high of a Voltage charge and do not present a shock hazard if you touch the terminals, but they are capable of holding tremendous amounts of Current such that if you short them out, you do run the risk of melting what you short them with, presenting a burn/fire hazard.


Well, it has been about 20 minutes now and my arms and chest don't hurt so bad now... I think I will go find some rubber gloves and see if I can find the camera.


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## dbodnar (Jan 2, 2008)

A few years ago I did an animation for a layout that included a flash unit from a disposable camera that simulated a gold mine explosion. See: 



Gold Mine Explosion 

Have a look at the reading on the volt meter in a photo from that article! That will surely ruin your day!














dave


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## Torby (Jan 2, 2008)

When fiddling with these things, keep one hand in your pocket just to minimize the aftereffects of convulsively flinging it across the room.


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## SE18 (Feb 21, 2008)

Dave, very nice site you have there with the "how-to" mine disaster.


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## Torby (Jan 2, 2008)

I've had your site linked for a long time. Nice to see you here.


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## Dan Pierce (Jan 2, 2008)

The screens in tv's and cameras, cell phones have a backlight. 
These lights run from a 90 or more volt source!!!!! 

If the screen is lit, there are high voltages present and you can get bit. 

Old tube type color tv's had between 20,000 to 50,000 volts available depending on screen size and when turned on, these were lethal as 150 milliamps was available. 

Labels on many electrical consumer devices states no servicable parts inside which really means Danger, stay out of this device!!!!


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## Semper Vaporo (Jan 2, 2008)

Just to complete my off topic saga...

I retreived the camera from where I had involuntarily chucked it behind the table, being very careful where I put my fingers when I picked it up.

I then put an INSULATED handle screwdriver across the two points I thought were the leads that had given me the jolt. No sparks, no nuttin'.

I thought that maybe it had discharged completely finally, but having been bitten twice by this beast, I decided I should maybe check a few other places.

I touched the tip across two other points and the resulting "BANG!" left my ears ringing and the spark was bright enough to have taken a photo with, as it left that little "floating" spot in my field of vision for a couple of minutes. It also melted the solder enough to stick the screwdriver to both of the spots I had put the tip across. It didn't really make a good solder joint but I had to flex it a couple of times to get it loose.

I waited a few minutes (to let that "floater" in my vision go away) and then VISUALLY inspected (carefully) the points I had shorted across and then I touched them with the screwdriver again. Even though the screwdriver had been "Soldered" across those points earlier, I still got some minor sparks again and a dull snapping sound. I waited a few minutes more and tried it again and got nothing that time. I am confident (well, warily so) it is discharged now.

Sorry for wandering off the topic of this thread a bit... I am an "old electronics" guy and I am used to components that could hold a charge that could hurt you that were physically big enough to "look like" they could hurt you. The capacitor in this camera is about 1/4 inch in diameter and less than 1.5 inches long. My point here is that if you decide to experiment and re-purpose components from other devices, BE CAREFUL with them until you know what they are and what voltages they have on them. Even if they look benign they might not be.


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