I do not know of another way to describe this electronically so I will try this

Imagine all the cars in a rollercoaster all connected but removable so you could have a string of 3 or 5 or x modules that can be connected electrically via a plate on the front and back of each module.

In addition each has a taillight on it

What I was wondering is if you put a charge through these module I would like the taillight to light up only on the very first module. Current would begin at the last module going along all of them and when it hit the last module the tailight would turn on. No other lights would turn on.

If the first module is removed from the circuit then the tail light of the next car would turn on, it being the new first module.

In other words as the first module with its taillight lit is removed from the chain of modules the "new" first module of the remaining chain would then light up

No physical switches only electrical something in the module itself that would either let the current go through to the next or stop if it is the last in the chain and light the taillight

Please bear with my description I could not come up with an easier way to describe it

Thanks

 

Forget about switches for the moment. The logic of what you are proposing is relatively simple, and can be constructed as a truth table. Let F be true if there is a car in front, false otherwise. Let B be true if there is a car behind, false otherwise:

+---+---+---+
| F | B | L |
+---+---+---+
| 0 | 0 | 0 |
+---+---+---+
| 0 | 1 | 1 |
+---+---+---+
| 1 | 0 | 0 |
+---+---+---+
| 1 | 1 | 0 |
+---+---+---+

The resulting boolean equation is simply L = !F * B where L=1 if the lamp is to be on. Easy.

Next, I assume each car is identical and interchangeable with all the others. That implies that each car must operate independently and provide its own power for lighting the lamp. Or, each car must independently gather power externally, perhaps from the tracks. No car can rely on the presence of another for such power.

In this case, I think it is impossible that the control signals can be generated by a conduction or interruption of current by another car. As far as I can tell, no "current loop" could be established amongst the many cars. I could probably prove this mathematically if I had the time to work it out.

Therefore, each car must have a way of independently determining the presence or absence of a car ahead and behind. If you don't want to use switches, then you could use a proximity sensor, magnetics, optical techniques, pattern recognition, etc. to create the inputs.

Outside of that, I think the answer is no.

 

Pure electronic sensing the presence / ausence of an inserted pin. The pin is supplied by the "new" one.

Tailight of the first. Looks weird but OK, is your project.

 

Pure electronic sensing the presence / ausence of an inserted pin. The pin is supplied by the "new" one.

For this to work according to his rules, both the car with the pin, and the car being engaged with the pin, must sense the presence of the engagement.

 

I think the way to put this is, What would I have to do to make it work. In this scenario, any car that finds its rear plate grounded by the car behind it can not light up. If these conditions do not fit your requirements, do not use this circuit.

 

I think the way to put this is, What would I have to do to make it work. In this scenario, any car that finds its rear plate grounded by the car behind it can not light up. If these conditions do not fit your requirements, do not use this circuit.

This doesn't satisfy the first condition: one car, no light.

 

Tailight of the first. Looks weird but OK, is your project.

This makes perfect sense to me:

If I'm on the freeway travelling 80 mph, and there are a train of cars tailgating me, I tap the brake lightly to illuminate my brake lights. It's fun to watch them all freak out in my rear view mirror!

 

Normally closed reed switch at the front of the car opened by appropriately placed magnet on the rear of the car in front. Normally open reed switch at the rear closed by appropriately positioned magnet on the nose of the car behind. Therefore each car would require a reed relay and magnet front and rear. Battery, lamp and the two reed switches all in series. Hall effect devices and some simple control circuitry could be used instead.

 

I thank you for your help maybe I can clarify I guess the main thing is the light does not have to stay on. I was thinking of something like a fusible link. the modules would be almost like parallel circuits paths and once current is applied the last link 'lights' and then blows the fusible link making the one behind it the last in the overall circuit it lights and blows and so on until there are no more modules left and thus no full circuit path. The key is I is I want the last circuit to blow first and then sequentially go until all are blown. Maybe my rollercoaster was not a good idea.

 

No switches allowed.
This is coming back to joeyd. Too many restrictions for this to work.

 

Normally closed reed switch at the front of the car opened by appropriately placed magnet on the rear of the car in front. Normally open reed switch at the rear closed by appropriately positioned magnet on the nose of the car behind. Therefore each car would require a reed relay and magnet front and rear. Battery, lamp and the two reed switches all in series. Hall effect devices and some simple control circuitry could be used instead.

You're spoiling the fun. He explicitly said no switches! Your reed-switch solution was my first thought.

 

It may be a good idea but to honest I'm still not sure what you are after doing?

 

I thank you for your help maybe I can clarify I guess the main thing is the light does not have to stay on. I was thinking of something like a fusible link. the modules would be almost like parallel circuits paths and once current is applied the last link 'lights' and then blows the fusible link making the one behind it the last in the overall circuit it lights and blows and so on until there are no more modules left and thus no full circuit path. The key is I is I want the last circuit to blow first and then sequentially go until all are blown. Maybe my rollercoaster was not a good idea.

Well, that's different! But too much to think about right now.

This reminds me of a tour I took, when I was a child, of a nautical museum. I was amazed by an old lighted buoy that had a string of lamps that rotated on a belt. Only the lamp on top would light. When it burnt out, the belt would automatically rotate to the next lamp, and that one would light. This process would continue till all lamps where exhausted, at which time the harbor master would send someone out to replace all the lamps.

I was about 5 or 6 at the time...but it made a HUGE impression on me!

 

You're spoiling the fun. He explicitly said no switches! Your reed-switch solution was my first thought.

Hall effect devices then!

 

Wow I have to say I am very impressed with the level of knowledge of the responders and to do it so quickly for someone who does not know anything really about this is amazing. I do thank you all greatly for your responses.

It is basically a chain reaction from the last point to the first.

 

Wow I have to say I am very impressed with the level of knowledge of the responders and to do it so quickly.

There is enough brain power on this site to light up a lamp, but the quality of answers depends very much on the quality of the question.

 

There is enough brain power on this site to light up a lamp...

Yes, but can it light up said lamp under the imposed constraints?

 

What I am trying to figure out and I do not want you to think that I am a gun nut or anything but was dimply trying to figure out how this worked. I saw this on the military channel. This one company that had an gun with an incredible rate of fire and no moving except a trigger which was basically a power switch parts thus no other switches.

In this method they filled the barrel of the gun with bullets say 5 or 6 and when they put a charge through the barrel it would ignite the firing charge of the frontmost bullet it would fire and then the next would get ignited and so on and so on until all bullets had been fired.

It happened so fast that three shots could be fired out of the barrel before the gun would even see any recoil so it was also extremely accurate, but each round fired independently and in front of barrel to stock order. The gun they showed had 3 barrels and the front round would fire from each and so on and so on at 7 shots per barrel they could shoot all 21 shells extremely fast basically the iginition time of the powder which could be 1/100 of a second.

It was truly amazing

 

What I am trying to figure out and I do not want you to think that I am a gun nut or anything but was dimply trying to figure out how this worked. I saw this on the military channel. This one company that had an gun with an incredible rate of fire and no moving except a trigger which was basically a power switch parts thus no other switches.

In this method they filled the barrel of the gun with bullets say 5 or 6 and when they put a charge through the barrel it would ignite the firing charge of the frontmost bullet it would fire and then the next would get ignited and so on and so on until all bullets had been fired.

It happened so fast that three shots could be fired out of the barrel before the gun would even see any recoil so it was also extremely accurate, but each round fired independently and in front of barrel to stock order. The gun they showed had 3 barrels and the front round would fire from each and so on and so on at 7 shots per barrel they could shoot all 21 shells extremely fast basically the iginition time of the powder which could be 1/100 of a second.

It was truly amazing

First...no problem with you being a gun nut...I've been known to go off to the gun range quite often and fire a couple of hundred rounds through my Glock...

Second, what you describe I do every Fourth of July -- we have great fun shooting Roman candles at each other!

 

That rules out reed switches then!