Electric Vehicle C

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Re: Electric Vehicle C

Post by Bazinga+ » February 9th, 2016, 6:39 pm

Private Wang Fire wrote:How much of an advantage is it using an ESC over something like a simple transistor circuit? Seems like a pain with all the calibration and stuff, what's the benefit?
Not sure how you would control a brushless motor with a transistor circuit. ESC is definitely necissary, and it works by sending pulses to the brushless motor at the correct frequency.
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Re: Electric Vehicle C

Post by Private Wang Fire » February 9th, 2016, 6:45 pm

Bazinga+ wrote:
Private Wang Fire wrote:How much of an advantage is it using an ESC over something like a simple transistor circuit? Seems like a pain with all the calibration and stuff, what's the benefit?
Not sure how you would control a brushless motor with a transistor circuit. ESC is definitely necissary, and it works by sending pulses to the brushless motor at the correct frequency.
With the transistor you can do the same with PWM on the arduino, just wondering what the specific advantage of an ESC was.
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Re: Electric Vehicle C

Post by iwonder » February 9th, 2016, 6:50 pm

Brushless motors require three different 'PWM' signals all 120 degrees out of phase from the other. To get a reliable speed control you need to worry about correctly commutating the motor and some sort of speed detection (via sensor or back-emf measurement). I'm not even sure if the arduino uno has the power to do this properly, it's not just a matter of sending PWM.

Now, brushed motors are a different story. The major benefit of an ESC with a brushed motor is probably just having all the hard part done up in a nice box, no concerns about heat dissipation or switching issues. For smaller motors, designing your own h-bridge circuit is probably cheaper and quite simple. Great learning experience to boot.
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Re: Electric Vehicle C

Post by Bazinga+ » February 9th, 2016, 6:58 pm

Private Wang Fire wrote:
Bazinga+ wrote:
Private Wang Fire wrote:How much of an advantage is it using an ESC over something like a simple transistor circuit? Seems like a pain with all the calibration and stuff, what's the benefit?
Not sure how you would control a brushless motor with a transistor circuit. ESC is definitely necissary, and it works by sending pulses to the brushless motor at the correct frequency.
With the transistor you can do the same with PWM on the arduino, just wondering what the specific advantage of an ESC was.
For many ESCs you can adjust settings like punch and obreak strength which is pretty useful. I'm still not sure how you can control a brushless motor right from an arduino. I think you are thinking of brushed motors which can be controlled in that fashion, but brushless motors have 3 wires(3 phases) and each sends pseudo-AC current, which can't come directly from the arduino. So the advantage of an esc is that you can control brushless motors which are much stronger and faster than brushed or regular DC motors.
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Re: Electric Vehicle C

Post by Private Wang Fire » February 9th, 2016, 7:07 pm

Bazinga+ wrote:
Private Wang Fire wrote:
Bazinga+ wrote: Not sure how you would control a brushless motor with a transistor circuit. ESC is definitely necissary, and it works by sending pulses to the brushless motor at the correct frequency.
With the transistor you can do the same with PWM on the arduino, just wondering what the specific advantage of an ESC was.
For many ESCs you can adjust settings like punch and obreak strength which is pretty useful. I'm still not sure how you can control a brushless motor right from an arduino. I think you are thinking of brushed motors which can be controlled in that fashion, but brushless motors have 3 wires(3 phases) and each sends pseudo-AC current, which can't come directly from the arduino. So the advantage of an esc is that you can control brushless motors which are much stronger and faster than brushed or regular DC motors.
Hmm, my brushed motor must be pretty op then... probably not going to switch this far into the season. Thanks for the info!
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Re: Electric Vehicle C

Post by HandsFreeCookieDunk » February 28th, 2016, 7:15 am

Sorry to whine on here, but I'm a little confused.

Why is the voltage limit for battery packs 7.2V when the two cell LiPo battery packs that are recommended for pretty much every motor are labeled 7.4V? I mean, I guess it's not that big of an issue since I can switch to regular 9V batteries, but I was wondering if anyone knew if the intent of this rule was to ban the two cell LiPos.

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Re: Electric Vehicle C

Post by finagle29 » February 28th, 2016, 7:23 am

Banning two cell LiPos was probably a safety thing
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Re: Electric Vehicle C

Post by Ed63 » February 28th, 2016, 7:44 am

Brushless motors are great, but a brushed motor is just fine for this event. We're using a brushed motor and battery directly connected and getting times in the 1.75 to 1.80 sec range. We have been the fasted car at both invitationals so far this year. Sometimes simpler is better.

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Re: Electric Vehicle C

Post by windu34 » February 28th, 2016, 7:51 am

Ed63 wrote:Brushless motors are great, but a brushed motor is just fine for this event. We're using a brushed motor and battery directly connected and getting times in the 1.75 to 1.80 sec range. We have been the fasted car at both invitationals so far this year. Sometimes simpler is better.
What how?? I am barely getting those times with my brushless setup
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Re: Electric Vehicle C

Post by Ed63 » February 28th, 2016, 8:48 am

3000mah 7.2V NiMH battery, DC brushed motor, belt driven gear set. We originally had a faster motor but didn't have enough traction to use it. Kept spinning out.

You can definitely get enough speed with a brushed motor setup.

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