need suggestions on uni project. (mechatronics project)

[konzen]

guys, i'm a 2nd year engineering student majoring in mechatronics and i found this forum while looking for ideas for my design project.

basically we're supposed to build a machine that at a push of button will start launching 'seeds' to the left and right into designated patches on the track while travelling on an L-shaped track which has an overall length of about 5 meters. the machine has to stop at the end of the track. points will be deducted if our machine rolls off the track.

all the different systems of the machine have been planned. push button > machine moves and launches seeds > cut power to motor and brakes are applied. my team members and i have opted to electronically switch from one stage to the other but i am now having problems as to how this can really be done. i am not very good at applying my electrical and electronic knowledge in real life yet so any suggestions are most welcome. thanks for your time.

 

[akg]

my team members and i have opted to electronically switch from one stage to the other but i am now having problems as to how this can really be done.

whats do u mean by the electronicaly switched stage ?

 

[konzen]

okay my machine's operation is basically divided into a few stages,

1. push a button (START)
2. the vehicle travels along an L-shape track while launching 'seeds' left and right into pre-determined patches on the track.
3. because the machine can't roll off the track after its operation(pts deducted), power must be cut from the main motor
4. brakes are applied to completely bring the vehicle to a stand still(END)

some extra info, my machine must weigh less than 15 kgs and not be more than 40 cm cube in volume. so basically i have to design a circuit to switch from one stage to the other. we do not want to do this mechanically since its pretty unreliable at our current level of skill. once again thx for your time. hope my explanation is clear enough

 

[akg]

okay my machine's operation is basically divided into a few stages,

1. push a button (START)
2. the vehicle travels along an L-shape track while launching 'seeds' left and right into pre-determined patches on the track.
3. because the machine can't roll off the track after its operation(pts deducted), power must be cut from the main motor
4. brakes are applied to completely bring the vehicle to a stand still(END)

some extra info, my machine must weigh less than 15 kgs and not be more than 40 cm cube in volume. so basically i have to design a circuit to switch from one stage to the other. we do not want to do this mechanically since its pretty unreliable at our current level of skill. once again thx for your time. hope my explanation is clear enough

it's a finite state machine model , which can be easily implemented using a microcontroller . try it using a 16f628a micro, or 89S52 micro.

 

[konzen]

thx lots. not really familiar with micro controllers but will read it up in the micro controller section.

another question, any ideas on how i should implement the brakes? i definitely need a braking mechanism. i was thinking of improvising from a car's disc brake.

1. fix a rigid disc to the axle of my vehicle
2. place a small dc motor on each side of the disc
3. connect each motor to a rack (horizontal gear) and attach rubber pads to the ends of the racks.
4. when power is supplied, the rubber pads on the racks should press against the disc, creating friction on the disc and slowing the vehicle down.

can you guys picture it? any other ideas?

 

[suicidalmonkey]

You could use solenoids to apply pressure to the discs.

What uni are you studying at?

I'm currently a first year mechatronics student at the Uni of Wollongong, in New South Wales, Australia (an hour or so drive south of Sydney).

 

[konzen]

solenoids? as in using an electromagnet?

i'm studying at monash malaysia. mechatronics student 2nd year.

 

[bloody-orc]

asfor brakes you could just short the motors two wires (conenct both wiret to ground OR V+). the motor then is its own brake and you save a lot of money and time (use both to partey )

 

[konzen]

short the motor? what will happen?

 

[Nigel Goodwin]

short the motor? what will happen?

It provides quite a high degree of braking, get an electriv motor and try it! - spin the unconnected motor with your fingers, then try it again with a short across the motor - it's MUCH harder to turn then.

 

[bloody-orc]

motor is creating its own electricity and then sends it straight back to himself and then "bubu" it wont run that well anymore creating nice braking. (even better than "external2 brakes cause this "brake" can't get dirty or wet and slippery .

 

[konzen]

okay ill try it. but can the motor be reused again? i mean like shorting it won't damage the motors original function will it? i am going to need to test the system numerous times.

 

[akg]

It provides quite a high degree of braking, get an electriv motor and try it! - spin the unconnected motor with your fingers, then try it again with a short across the motor - it's MUCH harder to turn then.

but would it work at low speeds , as in this context.?, (he may be using steppers for his drive) .or else he will have to a good gear system, so that motor runs at higher speed than wheels.

 

[akg]

okay ill try it. but can the motor be reused again? i mean like shorting it won't damage the motors original function will it? i am going to need to test the system numerous times.

yes. short it using a power relay , because u can expect arching .

 

[bloody-orc]

yes you can use the motor again cause it does nothing to the motor. (nothing signifficant). you can test it and use this brake for many-many years. (at least i have done so.

 

[Nigel Goodwin]

Assuming the motor is driven by an H-bridge?, they are usually designed so you can apply braking in this fashion - a relay across the motor would really be rather crude?.

 

[konzen]

thanks alot for your help guys. i'll update you guys on the status of my project.