Electric Vehicle C

[windu34]

I'm confounded already... What is this mysterious design...

Stepper motors, anyone?

I dont know of any step motors which can give you a good run time (2-3 sec), but they definitely give you good accuracy. Unfortunately, speed is multiplied by 10, so being 2 or 3 seconds slower than someone else is the same as automatically being off by 20-30 cm.

Agreed. I highly recommend staying away from steppers due to speed problems.

[InfiniCuber]

Stepper motors, anyone?

I dont know of any step motors which can give you a good run time (2-3 sec), but they definitely give you good accuracy. Unfortunately, speed is multiplied by 10, so being 2 or 3 seconds slower than someone else is the same as automatically being off by 20-30 cm.

Agreed. I highly recommend staying away from steppers due to speed problems.

My run time is 2.6 and i found a way to get it faster, although I have to admit it has been a long journey and a PAIN to do.

[antoine123]

I really am not to experienced in motors so is a brushless motor going to give you a significant advantage over a brushed dc motor with decent torque and rpm's. Can you get a powerful brushless motor at the allowed voltage?

[JonB]

I really am not to experienced in motors so is a brushless motor going to give you a significant advantage over a brushed dc motor with decent torque and rpm's. Can you get a powerful brushless motor at the allowed voltage?

Well, you can get very fast brushless motors- which is really what you need.

[Bazinga+]

I dont know of any step motors which can give you a good run time (2-3 sec), but they definitely give you good accuracy. Unfortunately, speed is multiplied by 10, so being 2 or 3 seconds slower than someone else is the same as automatically being off by 20-30 cm.

Agreed. I highly recommend staying away from steppers due to speed problems.

My run time is 2.6 and i found a way to get it faster, although I have to admit it has been a long journey and a PAIN to do.

I'm guessing you geared it a lot or some other solution, but the problem with gearing is that you sacrifice your accuracy. If you gear your steppers 1:2 then that means they are about half as accurate. This is usually not a problem since steppers are really accurate, but once you gear it more, the problem becomes very apparent.

[Bazinga+]

I really am not to experienced in motors so is a brushless motor going to give you a significant advantage over a brushed dc motor with decent torque and rpm's. Can you get a powerful brushless motor at the allowed voltage?

Well, you can get very fast brushless motors- which is really what you need.

Brushless can definitely go way faster than you need. My brushless motor is labeled to be able to go 70 mph (31.3 m/s so a theoretical potential run time of like .3 seconds) when on a 3 kg car and my car is like 1 kg. I've experimented with a lot of brushed motors and it doesn't seem like any 9 volt powered motors can provide enough torque and rpm to get a decent time, but i could be wrong. The best dc motor i found, with the optimal gear ratio and wheel size, I was just barely able to get a 5 second time. With brushless i'm able to break 1.5 (of course i have to use the correct algorithm for accelerating to avoid slipping and inconsistency).

[InfiniCuber]

Agreed. I highly recommend staying away from steppers due to speed problems.

My run time is 2.6 and i found a way to get it faster, although I have to admit it has been a long journey and a PAIN to do.

I'm guessing you geared it a lot or some other solution, but the problem with gearing is that you sacrifice your accuracy. If you gear your steppers 1:2 then that means they are about half as accurate. This is usually not a problem since steppers are really accurate, but once you gear it more, the problem becomes very apparent.

Actually, It isn't geared by much at all, it is nearly 1:1, perhaps 1:1.5 or so, not 100% sure. But I had used it at 7:1 and i was able to get within 10 cm and sometimes 5. Now i can do 5 consistently for the most part and once testing is done I SHOULD be able to get even closer, just need to do more testing because I'm changing my code at the moment.

[windu34]

If you are really getting the speeds you speak of using the stepper motors, then thats pretty good.

[retired1]

One of out teams wants to use a Vex microcontroller to act as a conduit for electricity to the motor and to use a coupled encoder to shut off the power. Even tho it is only acting as an on/off switch, some of the group thinks that it might not be allowed by the state ES under the interpretation of "anything" that controls the motor can not have a self contained additional power supply. The motor would be powered by the allowable battery pack thru a voltage step up device.. The microcontroller is acting as nothing but an "off" switch.

Comments please.

[samlan16]

One of out teams wants to use a Vex microcontroller to act as a conduit for electricity to the motor and to use a coupled encoder to shut off the power. Even tho it is only acting as an on/off switch, some of the group thinks that it might not be allowed by the state ES under the interpretation of "anything" that controls the motor can not have a self contained additional power supply. The motor would be powered by the allowable battery pack thru a voltage step up device.. The microcontroller is acting as nothing but an "off" switch.

Comments please.

I'm not sure I understand: is the microcontroller in series with a battery pack, or does it have an additional battery that powers it?