Electric Vehicle C

[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?

[iwonder]

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.

Finally someone does it... Did you have any issues hitting resonance points as you accelerate?

[finagle29]

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.

My interpretation of the rules is that if any electricity used to power the motor is controlled in any way by the Vex microcontroller (even if the Vex is just a fancy on/off switch), then the Vex microcontroller's power supply also counts towards the limit specified in the rules.

[windu34]

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.

My interpretation of the rules is that if any electricity used to power the motor is controlled in any way by the Vex microcontroller (even if the Vex is just a fancy on/off switch), then the Vex microcontroller's power supply also counts towards the limit specified in the rules.

Agreed

[InfiniCuber]

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.

My interpretation of the rules is that if any electricity used to power the motor is controlled in any way by the Vex microcontroller (even if the Vex is just a fancy on/off switch), then the Vex microcontroller's power supply also counts towards the limit specified in the rules.

Agreed

I believe there was a rules clarification or FAQ about this...

EDIT: FAQ. Here it is.

[InfiniCuber]

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.

Finally someone does it... Did you have any issues hitting resonance points as you accelerate?

Actually, no I didn't! The acceleration is pretty smooth really. Acceleration is very necessary to get to the higher speeds, so I was a bit concerned about resonance but encountered none of it!