Chief Delphi paper: Simple Motor Calculator
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#16
01-27-2012, 02:28 PM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by bmlarson12 WOW!!! How did you do this? I have been looking for a graph of the information so I could get the general values, but this is far better!
If you assume that the speed vs torque and the current vs torque "curves" are straight lines (which is the standard assumption for almost all the motors used in FRC), then most of the equations are fairly straightforward to solve explicitly.

For example, at the rated voltage and for a given torque tau, you can find the speed as follows:

speed = free_speed*(1-tau/stall_tau)

some of the other calculations, for example solving for efficiency or finding voltage when given rpm and torque, are a bit trickier, but not too bad.

#17
01-27-2012, 03:37 PM
 wireties Principal Engineer AKA: Keith Buchanan FRC #1296 (Full Metal Jackets) Team Role: Mentor Join Date: Jan 2006 Rookie Year: 2004 Location: Rockwall, TX Posts: 588
Re: paper: Simple Motor Calculator

Ether == Awesome - any chance you'll part with the source so I can compile a Linux version?

TIA
#18
01-27-2012, 06:31 PM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by wireties Ether == Awesome - any chance you'll part with the source so I can compile a Linux version?
It would be good to have a Linux version.

I'll pull out the formulas and post them.

Give me a couple of days.

#19
01-27-2012, 06:41 PM
 wireties Principal Engineer AKA: Keith Buchanan FRC #1296 (Full Metal Jackets) Team Role: Mentor Join Date: Jan 2006 Rookie Year: 2004 Location: Rockwall, TX Posts: 588
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether It would be good to have a Linux version. I'll pull out the formulas and post them. Give me a couple of days.
If it was a windows console app, it will probably just compile and run quickly with minor changes. You can send the source if you want.
#20
01-30-2012, 10:08 AM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether It would be good to have a Linux version. I'll pull out the formulas and post them. Give me a couple of days.
Here ya go.

#21
01-30-2012, 01:15 PM
 wireties Principal Engineer AKA: Keith Buchanan FRC #1296 (Full Metal Jackets) Team Role: Mentor Join Date: Jan 2006 Rookie Year: 2004 Location: Rockwall, TX Posts: 588
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether Here ya go.
I'm a busy guy - no time soon to re-write the program, not with work for 3 customers in process and being in the middle of build season. I apologize if I was not clear. I was offering to take your source and re-compile to create a Linux executable. No disrespect intended but I don't need the formulas ;o). I'm an EE and have been designing opto-mechatronic embedded control systems for 30 years - I know the formulas.

Thanks anyways.
#22
01-30-2012, 02:35 PM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by wireties No disrespect intended but I don't need the formulas ;o)
Of course. I thought you were after some of the more arcane calculations, like solving for operating range given operating volts and desired minimum efficiency*. I've never seen that published anywhere.

Anyway, unless you have an old copy of Kylix the source wouldn't serve the purpose intended.

Oh well, the equations are out there for anyone who might be interested.

*it's not as useful as other calculations, I know, but I included it because it's interesting to play around with and may provide some insight

#23
01-30-2012, 02:38 PM
 wireties Principal Engineer AKA: Keith Buchanan FRC #1296 (Full Metal Jackets) Team Role: Mentor Join Date: Jan 2006 Rookie Year: 2004 Location: Rockwall, TX Posts: 588
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether Anyway, unless you have an old copy of Kylix the source wouldn't serve the purpose intended.
Well, it just so happens that I do ... BTW, FIRST Team 1296 very much appreciates all the great advice you regularly disperse on CD!
#24
02-21-2012, 12:28 AM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

There have been a number of occasions recently where I wanted to calculate a motor's applied voltage given rpm and amps. To make this more convenient I added another option to the motor calculator.

I have also changed the display to show waste heat watts instead of input watts, since that seems to be of somewhat more interest. Input watts is easily calculated by adding output watts and waste watts.

#25
01-12-2013, 04:56 PM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether Thread created automatically to discuss a document in CD-Media. Simple Motor Calculator by Ether
New version just uploaded. Includes VEX MiniCIM and BAG motors.

#26
01-26-2013, 12:13 PM
 Ether systems engineer (retired) no team Join Date: Nov 2009 Rookie Year: 1969 Location: US Posts: 4,597
Re: paper: Simple Motor Calculator

Quote:
 Originally Posted by Ether Thread created automatically to discuss a document in CD-Media. Simple Motor Calculator by Ether
Motor Calculator has just been updated to include the now-legal Banebots M5-RS555-12 motor.

The new version (MCALC_2013b) is at the bottom of the list of attachments.

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