gemellocattivo.com

Which means "Evil Twin". Lets see your projects where you change boring into fun or create the fun from scratch.
It is currently Thu Mar 28, 2024 7:12 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 30 posts ]  Go to page Previous  1, 2, 3
Author Message
PostPosted: Thu Dec 17, 2015 11:40 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
Its 8A-10A when the throttle is moving

50% throttle was 3-4 A with me manually PWMing it before I lightened the springs.....so it might be ok with a single driver if I do something to limit throttle rate of change like clamp the duty cycle to 50-60%. That is an option so I'm thinking I'll run it with dual internal drivers and see log map the current, then make the final call on what to do.

Pololu has thorough holes where they want the cap but the guidance it just "For good performance, it is very important to install a large capacitor across the motor supply and ground close to the motor driver. We generally recommend using a capacitor of at least a few hundred μF and rated well above the maximum supply voltage;"

Soooo......VDC I assume they mean but 60V? 250V?
and at least a few hundred means...400-500μF? or is 1000 better? Is 2000 better? I have no idea. This is not at all my area of expertise making me lean toward just using the internal driver(s) that were designed by someone who does understand this.


Top
 Profile Send private message  
 
PostPosted: Thu Dec 17, 2015 2:51 pm 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
For 12v nominal, 60v is probably adequate.

The exact capacitance isn't really important either, this cap is connected in parallel to the battery so it's only to deal with transients. Since the input is DC, you could go infinitely large for infinite filtering without problems, except the inrush current when you turn the circuit on would get infinitely high (and probably blow the fuse). You could also go without one at all, then at high PWM frequencies you might have problems if the inductance of the supply wires is high, so having something is good. Anything in the 10 to 1000 uf range would be adequate, so if you have any caps in the uf range lying around they will probably work (but be careful of polarity with electrolytics!).

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Fri Dec 18, 2015 9:25 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
The board came with a 150 on it I think.....which they say is ok for testing but a larger should be added??? The prevision generation board they sent you one so I'm not understanding why on earth they sent the board out with a missing component. Its going to cost me 10x the cap price in shipping to get it.


Top
 Profile Send private message  
 
PostPosted: Fri Dec 18, 2015 11:27 am 
Offline

Joined: Sun Oct 11, 2015 2:07 pm
Posts: 134
The value of the cap isn't that important, 150 uf would be fine.

I usually order from DigiKey a lot, so I tack things like this onto my next order.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke


Top
 Profile Send private message  
 
PostPosted: Fri Dec 18, 2015 11:31 am 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
apalrd wrote:
The value of the cap isn't that important, 150 uf would be fine.

I usually order from DigiKey a lot, so I tack things like this onto my next order.


They say this:
Quote:
The driver includes an on-board 150 uF capacitor, which might be sufficient for brief tests and limited low-power operation, but adding a bigger capacitor is strongly recommended for most applications.


not sure why if they think it needs a bigger one they didn't install a bigger one......very strange.

I tand to work on what I'm working on and like to finish it....so I place a plot of orders and pay a lot of shipping :(


Top
 Profile Send private message  
 
PostPosted: Fri Dec 18, 2015 9:19 pm 
Offline

Joined: Sat Jan 03, 2015 5:40 am
Posts: 208
mk e wrote:
I tand to work on what I'm working on and like to finish it....so I place a plot of orders and pay a lot of shipping :(


And wind up with a big scrap pile :) My projects always cost 3x what I figure, but I sure do have some interesting bits left over.


Top
 Profile Send private message  
 
PostPosted: Sat Dec 19, 2015 5:24 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
mk e wrote:

I can't test anything on the real HW at the moment because I broke the ECU somehow....it no longer responds on the USB connection. Jim is going to talk me through connecting and re-loading the FW via serial and see if that sorts it out. I'm not sure what I did exactly but I sure made it angry :(


ECU fixed. The serial connection and reload of the low-level stuff went fine which restored the USB connection and I was able to load the FW with no issue. No idea what wrong but it's fixed now.


Top
 Profile Send private message  
 
PostPosted: Sat Dec 19, 2015 5:25 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
cribbj wrote:
mk e wrote:
I tand to work on what I'm working on and like to finish it....so I place a plot of orders and pay a lot of shipping :(


And wind up with a big scrap pile :) My projects always cost 3x what I figure, but I sure do have some interesting bits left over.


It's not scrap it's a head start on the next project :)


Top
 Profile Send private message  
 
PostPosted: Sun Dec 20, 2015 6:16 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
mk e wrote:
Yesterday I tested (on the simulator) a model that uses both internal H-bridges in parallel to get me 10A and it seems to work. The down side here is I'm doing the PWM in the model itself instead of using the HW feature. The full engine model seems to run in about 150usec so that limits the PWM frequency to about maybe 500hz before there could be substantial error.....there are some things I could do with model optimization to get the throttle serviced more frequently, but 1khz is probably the practical limit on this path. I think it will work but is a poor use of fancy software.


On the actual HW the full model runs in about 3.5msec as it so 200hz is the limit until I optimize a bit.


Top
 Profile Send private message  
 
PostPosted: Mon Oct 17, 2016 12:09 pm 
Offline

Joined: Thu Jan 01, 2015 6:47 pm
Posts: 4250
A little update here. I stopped all the nonsense about trying to use the 2 internal drivers....the external pololu driver work great and doesn't require bizarro programming.

What I'm doing now is coding some safety into this. So comparing the 2 TPS sensors and 2 pedal sensors to make sure they mostly match and then comparing TPS to desired TPS top make sure that mostly matches or in idle mode desire RPM to actual RPM. This is getting close to ready to try I think.


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 30 posts ]  Go to page Previous  1, 2, 3

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group