Circuit anomaly

[acesareking]

This concerns a model electric car circuit in an oblong shape 8 feet by 13.5 feet. The entire circuit is 43 feet long with 4 equally rounded corners. The drawing is not to scale but is approximately right.

The power is connected to the circuit at the position shown and the cars run smoothly clockwise at a fixed steady speed till they get to the slow/dead zone when they suddenly slow down between there and just before the power supply and then they resume their normal speed till they hit the slow/dead zone again.

I've substituted lengths of track from the fast section into the slow section and it makes no difference to the slowdown in speed in the slow/dead zone.

I can vary the voltage going to the circuit and when I lower it to a certain point the cars will actually stop at the start of the slow/dead zone until I manually pick them off the track and place them anywhere outside the slow/dead zone and then they resume running till they hit the slow/dead zone again.

Can anyone explain why the loss of speed of the cars occurs where it does instead of the opposite point from the power supply?

 

[3DDave]

I expect that there is a failed connection in the counterclockwise direction so the resistance increases continuously in the clockwise direction. Move where the section of track where the power comes in to the opposite side.

Imagine if the power is at one end of a straight track - as the car moves away the resistance goes up and the voltage left for the car is reduced by trying to supply current to the motor.

 

[acesareking]

Thanks 3DDave,
I've been thinking about adding another power supply to the circuit and placing it diagonally opposite as in the pic here.
What do you think?

 

[davidbeach]

Just find and fix the high resistance connection(s).

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[IRstuff]

My understanding was that the electrical connection is a continuous loop on the track, so if you have a dead zone, you actually have multiple bad connections, one between the power connection to the track and the dead zone, which is likely a complete open circuit, and another on the other side of the dead zone, which is highly resistive.

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[waross]

I concur
Find and fix the bab connoctoon.
If uou replaced some track. Then the last section that was not changed may have dirtu connection pins.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

Take a close look at the pins and sockets. Try cleaning the pins first.

These connectors have a tendency over time and use to loose clamping force, this shows up an a poor or intermittent connection. Sometimes this can be fixed by slightly squeezing the socket to make it a bit tighter on the pin.

 

[acesareking]

Thank you I checked the track for resistance and over 12 feet including the slow section I am getting 0.2 ohms resistance.
It doesn't seem like much but is that enough to slow the cars down?

 

[IRstuff]

This is a slot car setup? If so, then 0.2 ohm sounds OK.

Can you confirm the following?
> The power source disconnected from the track
> Resistance check should be from where the power source enters the track to different parts of the slow section, including where cars stop altogether. Measurements should be to spots between power source and points just left of point B, various points between A and B, points just right of A


Another possibility is that your contacts on the car are not making good contact with the track in section A-B, although that should be unlikely. Might try running some steel wool along the track connections in A-B

TTFN (ta ta for now)
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[analogkid2digitalman]

IR: "Might try running some steel wool along the track connections in A-B"

With the track energized

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"It's the questions that drive us"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[IRstuff]

With the track energized

Only if you're interested in a different activity ;-)

TTFN (ta ta for now)
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[3DDave]

A Scotchbright pad might be a safer solution. Less likely to let the pixies get loose.

I'd see if there is a place to measure the voltage at each segment while the car is running as well as seeing that the metal conductors are the correct height above the track so the brushes are making contact.

 

[waross]

I am starting to suspect that we are being given inaccurate or incomplete information.
The information, as it stands does not pass my smell test.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[3DDave]

It would pass the smell test if they used steel wool with the power on.

 

[acesareking]

It takes me a while to set the whole thing up in its running condition which I haven't been able to do again since my first posting but I've rechecked the sections of track where the car is slowing down and the values are almost exactly the same as previously stated except the max resistance reading I got this time was 0.1 ohm.

The track and cars are almost brand new and have less than 2 hours total running so I'm pretty sure the track is not to blame but one thing I haven't tested is whether or not another car on the same track behaves the same way so next opportunity I get to have some run time I will check that out and report the result.

I've also bought a second power supply so I will try adding that in to the circuit to see if that solves the issue.

Thank you all for all your input.

 

[IRstuff]

The track and cars are almost brand new and have less than 2 hours total running so I'm pretty sure the track is not to blame

There are 3 possibilities in this engineering problem
> the track has a fault
> the car knows where it is at all times and knows to slow down in one particular section
> the power supply knows where the car is and knows to slow down the car in one particular section

A couple of other things you could try to eliminate some possibilities
> reverse the power supply connections and run the car(s) in the opposite direction on the track
> run multiple cars in both directions and see if they all slow down or stop in the same section

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[cranky108]

I would suspect the connections between the sections of track. My recollections of cars like this, it only takes one of the connection pins of the track(there should be two per car), just bend the pin a little so it makes good connection with the next section of track.

I have similar issues with model trains, if the track is dirty, then cleaning it helps. But bad joiners between section of track can cause this.