10-11-2009, 06:27 PM
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#2401 (permalink)
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EcoModding Lurker
Join Date: Jul 2009
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Certainly, Jack. The shunt needs to be in a line close to the controller ground, and the common mode rejection of the instrumentation amp has to handle whatever difference there is. Even large common mode voltages can be accommodated with transformer coupled guard shielded amps. If we can place the shunt in a part of the circuit that isn't switched (I guess that is the B+ line, and the conjterol board ground is at or near the B minus, right?) Would the shunt in the B minus lead give us the info we need for feedback? If so, the common mode voltage would be only a volt or so, being voltage drops in the busbar and cables. So the AD623 for example, which runs on +12 single supply and tolerates common mode as much as 150 mV below the negative supply, should handle getting the shunt voltage up to what the Hall ckt was giving.
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10-11-2009, 11:24 PM
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#2402 (permalink)
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EcoModding Lurker
Join Date: Jun 2009
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Bob,
The B- has to be completely isolated from the vehicle / controller ground for safety reasons. There is no easy way to use a shunt and keep the isolation requirements.
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10-12-2009, 01:23 AM
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#2403 (permalink)
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EcoModding Lurker
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The problem has been addressed with isolation amplifiers. My initial search turned up the Avagotech HCPL 7510, stocked by Mouser under $5. The application note is our exact application, and the description looks good. Need a +5 supply on each side of the isolation barrier. Three other possibilities I looked at, AD 215, AD204, and TI Iso 122 were all more expensive, though they allow different solutions to the isolated power supply problem. I have ordered a couple of the Avagotech 7510 pieces from Mouser, and lash up a test circuit.
Nearly 50 years ago, I was a test tech at Dynamics Instrumentation, which built isolated strain gauge amplifiers in a 3 by 5 by 12 inch package, with Russian doll shielding, and able to see a 10 mV signal in hundreds of volts of common mode. Now a fi'dolla chip does it if we tend to the power supplies.
A further search may turn up a better solution, but this should work. It will give 2 to 3.5 volts for 0 to 200 mV in on the shunt side.
As I read the sideways roadmap in the wiki, there are supplies on each side of U11, and the comparator U8A is what the current sensing feeds, so we can do level shifting there. What was the output of the Hall device? It may be best to have a little add on board that plugs in where the Hall device did.
Hey, if Avagotech did the job they claim, this IS easy! we will see.
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10-13-2009, 09:35 AM
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#2404 (permalink)
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Master EcoModder
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10-13-2009, 09:43 AM
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#2405 (permalink)
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PaulH
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Hi Jack! It depends on what voltage you will be running at. I would stay away from 144v if the max is 170v. There are some 200v schottkys (rated at 120 amps) in a TO247 package, and maybe others?
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10-13-2009, 09:45 AM
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#2406 (permalink)
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Master EcoModder
Join Date: Sep 2009
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I'm just looking at whats available. I did find this baby but its a bit expensive:
SindoPower | SKKE600F12 | quality online
Seems to be difficult to find a high power soft recovery diode beyond a few tens of amps. |
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10-13-2009, 10:00 AM
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#2407 (permalink)
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Master EcoModder
Join Date: Sep 2009
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10-13-2009, 10:13 AM
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#2408 (permalink)
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PaulH
Join Date: Feb 2008
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Awesome!!!
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10-13-2009, 12:44 PM
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#2409 (permalink)
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Master EcoModder
Join Date: Apr 2009
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Hey Guys
I just finished the initial release of a new windows program that my friend Kyle and I wrote. You can use this to graph all the data coming out of the new firmware in real time!! You can save this data to a CSV file for importing in excel if you want. The program has a built in terminal window that you can use to set settings of the controller such as loop and throttle min and max. We also added an interface to the bootloader to make it easier to flash new files onto the controllers. It also includes a built in updater.
Keep in mind that this is version 0.1 and is still a little buggy, but we are hoping you guys can help us out by finding bugs and reporting them here: https://rtdexplorer.fogbugz.com/defa...g=pgPublicEdit
You can download the program from here. RTD Explorer
I will be adding a link to the website shortly with the supporting files such as the boot loader.
Heres a video showing all in operation.
Please let us know what you think.
**I almost forgot, Joe, Do you think you could try it out on your controller? Fran told me you already have the bootloader loaded and the firmware installed. I think It might help you with the throttle thing.
-Adam
Last edited by adamj12b; 10-13-2009 at 12:55 PM..
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10-13-2009, 01:18 PM
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#2410 (permalink)
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Master EcoModder
Join Date: Sep 2009
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I have got to get me one of these! Where can i get the hex files for the micro?
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