Hi all. I have a project for school where we have to design a fire escape system for a sky scraper. I think my group is convinced that lowering a car with eggs on it to the ground and having it drive to the offical safe zone is the best idea. I am having trouble figuring out the best way to do the car controls. I was thinking stepper motors because I have a few and then I wouldn't need an encoder to measure distance, but I am having trouble finding stepper controlers. I am also trying to firuge the best microcontroller to use as brains. I can get MSP430's from TI as samples, but I have never used them and don't know how well they will work for this. I also don't know if they need a special programmer. Maybe AVR's would be better. Any advice is appricated.

 

I would use DC Gearmotors as the drive motors, use the motors with a couple of LMD18200T H-Bridge, homemade shaft encoders, and pic microcontroller, and you should be on your way pretty easily.... I would also build some type of IR beacon in the "safe" zone so instead of remote controlling the bot, it could autonomously look for the beacon and head towards it.....


Or you can substitute the DC gearmotors for a couple of Hobby Servo motors that have been modified for full rotation, this will make the bot lighter and less circuitry to build, all you would need for the drive system is a battery pack (4 AA's), 2 servo's (modified for full rotation) and a pic microcontroller....


B. Morse

 

Servos sound good. I would love to use a stop beacon if possible. We are not allowed to start with anything on the ground. Everything must start on the building, so I don't think that will work. I don't really want to use a PIC just because I am not very good at assembly programing and have yet to come across a good open-source C compiler for the pics. I hear good things about AVR's and ARM's and how easy they are to program.

 

Servos sound good. I would love to use a stop beacon if possible. We are not allowed to start with anything on the ground. Everything must start on the building, so I don't think that will work. I don't really want to use a PIC just because I am not very good at assembly programing and have yet to come across a good open-source C compiler for the pics. I hear good things about AVR's and ARM's and how easy they are to program.

To each his own.... ( I have not seen too many AVR or ARM's based projects around here that got much help.... but then again I could have just been missing them....)

B. Morse

 

Aluminum rail and a cart using magnets. The magnets slow the vehicle on the rail. to a steady rate. Gravity does all the work. If you need to slow further, use friction brakes, but if you space the magnets correctly, you can adjust the fall speed.

And yes I know aluminum isn't magnetic.

 

And yes I know aluminum isn't magnetic.

But if you slide a Neodymium magnet on an aluminum plate, you will notice the magnet will slow down as it slides down the aluminum, this is because the magnet will produce eddy currents in the aluminum to counter act the magnetism from the magnet.... pretty cool...... I have placed small rare earth magnet on top of a spinning hard drive platen and got it to levitate about 1/8" above the spinning aluminum platen... because of the eddy currents induced into the plate by the magnet.....

An eddy current (also known as Foucault current) is an electrical phenomenon discovered by French physicist François Arago in 1824. It is caused when a conductor is exposed to a changing magnetic field due to relative motion of the field source and conductor; or due to variations of the field with time. This can cause a circulating flow of electrons, or a current, within the body of the conductor. These circulating eddies of current create induced magnetic fields that oppose the change of the original magnetic field due to Lenz's law, causing repulsive or drag forces between the conductor and the magnet. The stronger the applied magnetic field, or the greater the electrical conductivity of the conductor, or the faster the field that the conductor is exposed to changes, then the greater the currents that are developed and the greater the opposing field.

B. Morse

 

But if you slide a Neodymium magnet on an aluminum plate, you will notice the magnet will slow down as it slides down the aluminum, this is because the magnet will produce eddy currents in the aluminum to counter act the magnetism from the magnet.... pretty cool...... I have placed small rare earth magnet on top of a spinning hard drive platen and got it to levitate about 1/8" above the spinning aluminum platen... because of the eddy currents induced into the plate by the magnet.....

B. Morse

Polish Railgun?