Physics Rollercoaster- Simple electric circuit

[mike_302]

Physics Rollercoaster-- Simple electric circuit

Hi all,
I'm working on my physics rollercoaster project for grade 11 and I need a simple electric circuit to incorporate into it for more marks. At first I was thinking a circuit to bring the ball back up a hill when it reached the bottom but then, to do it, it got more and more complicated to make it work for a certain amunt of time, stop... etc..

then I am thinking: what about some sort of LED circuit? My idea now is to somehow have the steel bearing ball (at hte very end of hte rollercoaster, when i don't mind slowing the ball down) run through some sort of.. pathway of aluminum foil that creates a bunch of circuits to LED's that line the last... 3 feet? maybe? of track? along hte side. I have a bunch that I happened to buy on Ebay and they'd do fine. I'd only use maybe... 12 in total along those 3 feet, and id want them to light up closely in relation to where the bearing is. My question in this is obvious: will it work? or will i have to have the ball slow down a LOT in order for it to create a circuit long enough for hte lights to shine?


Unless anyone else has some other SIMPLE circuit sugestion?

 

[Danger]

Just mounting some micro lever or push-button switches under the track so that the ball runs over them should work fine. The lights will flash, but you might have to slow the ball for the flashes to be long enough for visual registration. (that's unlikely; the ball would have to be really hauling to escape notice.) Alternatively, you could have a latching switch for each one so that it stays lit after the ball has left.

 

[mike_302]

OK, and... Are these switches easy to find at say... The Source or something, and are htey FAIRLY inexpensive.. obviously I don't want to pay $10/piece for them since I'm using maybe... 8-12 of them. And, consider the ball: steel bearing, 16mm in diameter, its not super heavy, and the switch that it hits will haev to allow it to just basically FLICK buy it because... It WILL be going fairly fast, as you can see if you search youtube for: physis rollercoaster ISU

 

[berkeman]

Make your own switches cheaply with just some simple spring material or something. Use the fact that the ball is conductive to close the switch.

 

[mike_302]

If I had little tinfoil flaps do you think that would work? I mean, in the end, I'm just not sure, and would prefer to find out BEFORE I use the LED's and (it would have to be all setup in the end in order to work properly, and for me to find out the hard way) , how much contact and time for contact, will be needed to make the lights light up.

 

[berkeman]

Tinfoil is not a good choice -- too deformable, and lousy conductivity. Paperclips would work (bend them to the shape you want), shim brass is very good (and you can solder wires to it). Check out the spring selection at your local hardware store for ideas.

 

[Danger]

The homemade switches are a great idea. Copper or even steel brushes could also be used for that. Just fraying the end of a regular multi-strand wire would work.

 

[mike_302]

yep, for sure. The only real question to it all is how much contact is going to be needed in order to make the LED light up for a length of time that is recognizable since the steel bearing is likely to be going FAST

 

[berkeman]

yep, for sure. The only real question to it all is how much contact is going to be needed in order to make the LED light up for a length of time that is recognizable since the steel bearing is likely to be going FAST

Just stretch the pulse with an R-C circuit. Have the contact switch charge up a capacitor on the base of the low-side NPN LED drive transistor, and connect the cap to the base of the transistor through a resistor. The charge up of the cap will be quick because of the direct ball bearing connection to a power supply, and the discharge time constant will be on the order of R*C.

 

[dlgoff]

You might be able to make your switches "latch" in the "on" position so that the ball is only used to switch the thing with it's weight (as opposed to using it's conductivity). This way you can get a string of LEDs to stay on from top to bottom of rollercoaster.

 

[berkeman]

You might be able to make your switches "latch" in the "on" position so that the ball is only used to switch the thing with it's weight (as opposed to using it's conductivity). This way you can get a string of LEDs to stay on from top to bottom of rollercoaster.

Good idea. Or if the OP wants to learn a little more electronics as part of the project, they could put a flip-flop at each LED location, to clock in and hold the passing of the ball. A single master clear that went to each flip-flop would clear the LEDs back to off for the next run.

 

[mike_302]

The capacitor Idea might just work. In the end, I'll have to see how the whole thing goes together because from waht I can tell, the ball doesn't go AS fast as I had hoped so... And I only JUST got the hose, and the hose is not exactly what I had hoped, being lined with wire so it will be thick and hard to cut.

 

[dlgoff]

There's another thing you can learn from this project. The engineering aspect of bringing minds together as you are doing here. On a small scale you are doing project managment. Breaking the project down into task and using your resources to gain information to perform these task.

Good luck with the construction.

 

[Danger]

Another thing that I will kick in is that if a hose hadn't been specified, I would have gone with acrylic or other hard plastic tubing or else steel wire rails as are used in pinball games. You get a lot better travel for your buck.

 

[mike_302]

ya. Taht steel track IS a good idea but from the picture he showed me of the ONLY design to ever include that (that he has had in his class) it looked like a project for a team of professional engineers to take on... He had spent over 20 hours in shop class and at home welding ,soldering, cuttign, and resoldering his track. But, anyways, I am stuck with the tubing. And, not to completely throw away other ideas for the electrical circuit but I'm also contemplating the idea of creating a V section at hte bottom of the track where I angle some sort of arm that "kicks" the ball forward almost like a pinball machine's arm. I don't expect to get enough force to brign it back to the top but at least I could waste ALL the energy going through the vertical loops (because they get me the most points) right to the bottom, then have this pinball style arm give me the force I need to finish 2 horizontal, compulsory 360 degree turns. Simple enough. I think hte only idea/input I need here would be if anyone could suggest an electrical part that I could use that DOES that. I actually HAVe a little arm that runs on 12 V: It's a car door unlocker. The only problem I had with IT was that, when I hooked it up to 12V of a simple C cell battery series, it didn't have much kick at all. If there is some way I could force it to kick more, I'd appreciate the knowledge. Thanks in advance!

 

[Danger]

It's a car door unlocker. The only problem I had with IT was that, when I hooked it up to 12V of a simple C cell battery series, it didn't have much kick at all. If there is some way I could force it to kick more, I'd appreciate the knowledge. Thanks in advance!

The odds are that the unlocker solenoid demands a few amps, whereas your 'C' batteries supply a few milliamps at best. Try using a motorcycle or gel-cel battery instead, and it should kick the thing half-way out of the universe. Alternatively, you could use a constantly rotating set of arms, or a rubber wheel.

 

[mike_302]

Is there a smaller type of battery that I can get (something that won't make my project weigh 15 lbs extra , aha) or a way I can wire up a bunch of AA or C batteries in order to give it more amperage? Basically, because this electical component can do so much for my project (it will have two roels: prolong it, annnd add the electical mark I need) I think htat I will do this IF I can get more kick out of it in any way.

 

[Danger]

My 'Alien' Hallowe'en costume was activated by the 6-way power seat motor pack from a Mustang. Initially, I used a 12V motorcycle lead-acid battery, but that proved troublesome. I replaced it with a 12V/6Ah gel cell that is intended to be the back-up power for an alarm system. It weighs less than a Kg, and measures about 6.5 x 8 x 9 cm. It drove that motor hard enough that it wore out the brass drive gear after a couple of dozen uses. (On the other hand, it cost $70 wholesale 20 years ago; I have no idea what one would be retail today.)

edit: If you respond to this, don't expect anything too soon. My shift just ended, so I have to cash out and go home. I'll log back in briefly from there.

 

[mike_302]

hmm. Now that's an idea. I have an OLD alarm system in my house (it was replaced with a newer version, but the old panel was never removed) and there IS a 7Ah battery in it. Few questions with that: Obviously it's not rechargeable... Would 7Ah be overkill just for me to shove the ball upwards about.. at most, a 20 cm incline? Or, if that battery is "unavailable" to me, could I buy one similar with say... 1 or 2 Ah and get all I need out of that?

edit: Found one that MIGHT interest me for example: an alarm system battery from the Source (radioshack, Circuit City-- Canada's version) that is 4.5 A/h ... What kind of power would be too much for this small part, and how far might 4.5A/h push this ball, assuming the part can handle 4.5 A/h ?

 

[Danger]

To start with, they most assuredly are rechargeable. They recharge constantly from line current during their normal life, and only discharge during mains failure. I used the same charger for the gel cell that I bought with the motorcycle battery. You just have to keep an eye on it to make sure that it doesn't overheat during charging. Also, the amp-hour rating is the capacity, not some intrinsic necessity to discharge that much. The higher that number is, the longer you can sustain a given load. Since I have limited electrical knowledge, I'll leave the rest of this to Berkeman or other professionals.

 

[mike_302]

Sure, OK, thanks. So then, my question would be, if the A/h is the capacity, then I'm assuming there is another value that belongs to the battery that is the amperage, which IS related to how powerful the arm will "pop" ?

 

[deakie]

if you are using a tube an the ball is traveling inside, then i would simply drill some very small holes...say 1mm diameter...very tiny drill bit, careful you don't break it on the first go...;)
then stick some loose telephone wires in on opposite sides of each other where you want your switching to occur...after experimenting, you can glue them in place or tape them...
join all the wires on the bottom section of the hose and this will be your ground wired section back to your circuit.
the top wires will individually go to your leds.
use old telephone wires.

now for the electronic bit...

if you download a 555 timer sheet...
http://en.wikipedia.org/wiki/555_timer_IC <-----choose any at the bottom of the list...they are basically the same...

see what values you want for how long you need your led lighted for...

then buy the four in one variety...they are very cheap...should be less than a couple of bucks each...
get your resistor and capacitor values at the same time...
and if you don't want to go soldering, ask them at the shop for a wire wrap board...you use wires to wrap the terminals for connection...otherwise its a solder job...

when the ball passes through and connects both wires by rubbing against them, it will close the circuit and your led's should light one after the other as the ball travels...and without slowing the balls to much...
the same shop should have battery holders...you shouldn't need more than a nine volt battery for this...

hope this helps...have fun!