Go Back   EcoModder Forum > EcoModding > Fossil Fuel Free > Open ReVolt: open source DC motor controller
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-28-2009, 02:38 PM   #691 (permalink)
Deadly Efficient
 
Tango Charlie's Avatar
 
Join Date: Jun 2008
Location: Goshen, Indiana
Posts: 1,234

Olivia - '03 Pontiac Vibe base
90 day: 36.01 mpg (US)

R2-D2 - '00 Honda Insight
90 day: 58.81 mpg (US)
Thanks: 132
Thanked 175 Times in 91 Posts
Quote:
Originally Posted by Intrigued View Post
...I don't know how many times I've worked over the 20-or-whatever-it-is minutes on a post, only to have to use the back arrow, cut the text, sign back in, and paste it in a new reply...
Are you clicking the 'remember' check box when you sign in?

__________________
-Terry
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-28-2009, 02:48 PM   #692 (permalink)
Losing the MISinformation
 
Intrigued's Avatar
 
Join Date: Oct 2008
Location: Southern Missouri
Posts: 393

Quad Cam - '00 Oldsmobile Intrigue GX
Last 3: 25.94 mpg (US)
Thanks: 15
Thanked 3 Times in 3 Posts
Hmmm... no. I thought that was for the difference between private or public computers...

Besides, I can forget anything twice...

I'll try to "remember" for a while, and see how that goes!
__________________


The brake pedal is my enemy. The brake pedal is my enemy. The brake pedal...
  Reply With Quote
Old 03-28-2009, 03:25 PM   #693 (permalink)
Losing the MISinformation
 
Intrigued's Avatar
 
Join Date: Oct 2008
Location: Southern Missouri
Posts: 393

Quad Cam - '00 Oldsmobile Intrigue GX
Last 3: 25.94 mpg (US)
Thanks: 15
Thanked 3 Times in 3 Posts
Okay, quick try for a late reply. Did it work???

[Edit:] It works!!! AARRGGGHH! Now if I can just remember to "remember"...
__________________


The brake pedal is my enemy. The brake pedal is my enemy. The brake pedal...
  Reply With Quote
Old 03-28-2009, 04:10 PM   #694 (permalink)
PaulH
 
MPaulHolmes's Avatar
 
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
Posts: 3,832

Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
Thanks: 1,368
Thanked 1,135 Times in 749 Posts
I was just about to go out there in the pouring rain right now to test it to find the right P and I, because I hooked up everything earlier, and I just checked the program, and I had one line commented out during debugging that is CRITICAL in real life. This is horrible. Here I go again! Dang it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!11 i HAD THE CURRENT LIMITING COMMENTED OUT!! IDIOT!!!! STUPID IDIOT!!!! ANGRY!
__________________
kits and boards
  Reply With Quote
Old 03-28-2009, 04:58 PM   #695 (permalink)
EcoModding Lurker
 
Join Date: Nov 2008
Location: Georgia
Posts: 19
Thanks: 1
Thanked 4 Times in 3 Posts
Paul,

Thanks for the insight on the diodes and MOSFETs. Can you tell us the part numbers, distributors, and price for the cheaper sets that you located?

Also what was your cap choosing strategy? Your original schematic had 200V 470 mF electrolytics. Why did you choose that value?

And a reminder: Don't comment out the current limiting code!

Thanks,

ga2500ev
  Reply With Quote
Old 03-29-2009, 07:19 PM   #696 (permalink)
EV Converter
 
Join Date: Mar 2009
Location: Saugerties, NY
Posts: 51
Thanks: 0
Thanked 1 Time in 1 Post
I like the wheel design, but I would go with copper instead of aluminum. But the basic idea makes sense in that the current paths are equadistant. Ideally, freewheel diodes whould be mounted the same way and the capacitors negative lead tied right in to keep the "holly trinity" path as short as posible. I don't think the gate wiring matters that much. You just don't want too much inductance that may delay the gate turn off.

IMO, the best theng this design has going for it is that it eliminates the need to solder those little terminals to the thick copper. I once read that a compression connection is a lower resistance connection than a solder connection. If that's true then this would be a better way to go. Also, it takes less skill from the DIYer.

Also, Paul, I have been following your thread on EVTech DL about the current sensor. I think the noise is normal for a PWM current. You definitely have to filter the LEM output to smooth it out, otherwise the output will be a scaled distorted version of the PWM current going through the sensor.
  Reply With Quote
Old 03-29-2009, 08:26 PM   #697 (permalink)
PaulH
 
MPaulHolmes's Avatar
 
Join Date: Feb 2008
Location: Maricopa, AZ (sort of. Actually outside of town)
Posts: 3,832

Michael's Electric Beetle - '71 Volkswagen Superbeetle 500000
Thanks: 1,368
Thanked 1,135 Times in 749 Posts
Quote:
Originally Posted by Roger Heuckeroth View Post
Also, Paul, I have been following your thread on EVTech DL about the current sensor. I think the noise is normal for a PWM current. You definitely have to filter the LEM output to smooth it out, otherwise the output will be a scaled distorted version of the PWM current going through the sensor.

Holy Cow!!! You are right Roger! I forgot that the current going through the aperture isn't nice and perfectly smooth. I'm such a whippersnapper sometimes, I forget things! Thank! Now, I need to smooth that LEM output.

Since I couldn't figure out the right P and I, I just changed the code to have throttle be directly proportional to current by incrementing pwm if current is less than throttle, and decrementing pwm if current is greater than throttle. I think I could barely feel a hint of the variation in the current sensor, and I do mean BARELY. It could have been in my imagination, actually.

Am I missing something: Like 2 lines of code to get perfectly smooth driving. OR... Like 200 lines of code and an endless search for P and I IN THE DANG RAIN, WORKING WITH HIGH VOLTAGE!!! just to get the same result! Man, that makes me mad. But surely the ghetto increment, decrement way wouldn't work on a larger motor??????

Well, Ian of Zero Emissions Vehicles Australia uses that method, and he has an 11 inch Direct Drive monstrosity! It works great for him... I feel some rebellion coming on... hmm.....

Power to the people Marty. Power to the People, Coz... (Sneakers. 10th Best movie ever).

Also, for the first time, I could detect the 16 KHz tone, since the car is dead silent, and the controller is in the back seat, and the ceiling acts like a parabolic dish, with my head at the focus. hehe. Also, I was really scared again (always after changing code to drive the car), so my senses were heightened like a puma.

MOSFETS AND DIODES:
STTH6002C
IRFP4668pbF

STTH6002C's can be gotten cheap from Nu Horizons.com if those bozos ever order more! I emailed them, and they won't write me back. They ran out, and don't want to order the minimum 390 to replenish their supply. I need a business name! No respect! Geeze.

Both can be gotten from Digikey.com or Mouser.com.
__________________
kits and boards

Last edited by MPaulHolmes; 03-29-2009 at 08:31 PM..
  Reply With Quote
Old 03-29-2009, 09:00 PM   #698 (permalink)
EcoModder Student
 
esoneson's Avatar
 
Join Date: Nov 2008
Location: Youngsville, NC
Posts: 117
Thanks: 11
Thanked 13 Times in 12 Posts
Paul,

Here is my 2 cents for Version 2.

Cent one: Drop the atmega8 and go atmega16 or 32. I believe that the pins you are using in the atmega8 are a subset of the 16 and 32, so it should be easily accompished. The development envrinment supports all three microprocessors. With a change like this at the transition from Version 1 (the Ben memorial, I mean Ben Tester version) and the Paul Version 2, it will not impact any major design issues at this time. The 16 or 32 will allow for incremental software features to be added (just look at the list of features over the past several posts) on a as needed basis without having to change the processor in the middle of feature adds.

Cent 2: Go with the Power Wheel design for the mosfets. Easily done with hand tools for DIYer, adds gobs of safety for up to 1300 amps without damage and still allows for the normal 144v 500amp original design goal. Speaking as a person looking to keep costs low, I would gladly pay for an additional 5 mosfets in order to get the flexability that the Power wheel provides. Also, the cool temperatures that the article states is a real plus without having to install a gigantic copper bar to carry the heat away. How much did that bar cost anyways?

That's my vote for minimum changes for Version 2.

Thanks,

Eric
__________________
1995 BMW 318i EV in the making
  Reply With Quote
Old 03-30-2009, 12:42 PM   #699 (permalink)
EV Converter
 
Join Date: Mar 2009
Location: Saugerties, NY
Posts: 51
Thanks: 0
Thanked 1 Time in 1 Post
Paul,

If your simple code works, then great you’re done! There is no need for a fancy PI loop if everything is working nice and smooth. The question is will it work just as smooth for other motors and other voltages.

I believe Einstein was quoted saying something like “the simplest solution is the best solution, as long as it’s not too simple.”

I think frequency of your iterative loop plays a key role in how stable and smooth the controllers response is to accelerator pedal input. A physics teacher once told me if you have trouble understanding the dynamics of a multivariate problem take the variables to their limits and see what happens.

So, let’s look and the extremes. Say your loop takes just a nanosecond to increment the PWM duty cycle. Your foot calls for 10% current to the motor. The motor has inductance, so it can’t respond that fast. In 1024 nanoseconds the PWM duty is up to 100%. It stays there until the current sensor feedback tells it that 10% has been achieved. You lurch forward at full torque. Then blam, in another 1024 nanoseconds the PWM duty is back to 0. The response is to fast, and the controller goes from 100% to 0 to 100% and so on. It’s an unstable system that results in a really jerky ride.

Now let’s look at the other extreme. It takes a full second for the loop to make on 1/1024th increment. Your foot calls for power, but the controller says hold on there, let’s not rush this. You get really slow response and a sluggish EV.

So, somewhere in between there is an iterative frequency that gives just the right response without significant overshoot. You may have found the “sweet spot” already for your motor and voltage just by accident. It will be a bit different for an 11” motor at 144V, but maybe it will be fine.

If you find that you get a jerky start, just decrease the iterative frequency. If you want quicker response, increase the frequency. Could it be this simple? Maybe so.

What PID logic would essentially do is slow down the rate at which the increments or decrements occur as you get closer to the target current. So, if you want to get more complex, you could calculate the difference between the target current and the actual current and slow down the iterative frequency as feedback from the LEM sensor gets closer to the target current. Its been years since I have wrote code, but this doesn’t sound to hard. Just have a delay in the loop that is inversely proportional to the difference between the target and actual. Is this simpler than the code you were trying to make work in the rain?

Do you need this extra bit of code? Only way to find out is to experiment. Not only with your EV, but in others. That’s the beauty of an open source design. We can all work together to make this the best darn controller out there.

Roger
  Reply With Quote
Old 03-30-2009, 01:13 PM   #700 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,316

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)
Thanks: 3,846
Thanked 6,723 Times in 3,486 Posts
Quote:
my senses were heightened like a puma
Oh, man. That stuff keeps me coming back.

---

A non-technical but important issue: Paul, you (we?) need to namethis controller. It'll help in spreading the word. Branding!

Any ideas? I'm partial to Little Miss Mosfet.

__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Paul and Sabrina's Cheap 3 Phase Inverter (AC Controller) with Field Oriented Control MPaulHolmes Fossil Fuel Free 3477 05-24-2021 04:28 PM
Paul & Sabrina's Cheap EV Conversion MPaulHolmes Fossil Fuel Free 542 11-12-2016 10:09 PM
Three Dirt Cheap DIY Electric Cars - Part 5 SVOboy EcoModder Blog Discussion 0 12-12-2008 05:10 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com