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Old 10-28-2015, 04:56 PM   #2259 (permalink)
e*clipse
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Quote:
Originally Posted by P-hack View Post
fwiw, silabs has integrated their isolation technology into an isolated shunt monitor Si8920, signal delay measured in nanoseconds.

http://www.mouser.com/ds/2/368/Si8920-766188.pdf

-100 to 100mv range

shunts are what tesla uses for fast and accurate.

It is conceivable to run an op amp and an isolator off the high side driver supply as well and blast out a digital current shunt reading back to the controller, or do other distributed gate logic stuff (i.e. hysteresis current control, shoot through protection, saturation detection, "formal" digital protocol between gates and controller, etc). I mean if you can have an attiny just to make a square wave, you can throw a $1 arm 24mhz 12bit adc on the high side gates and slave the low sides to them with another isolator, and even capture leg vs "neutral" voltages between pulses, or?? for pennies (shunts are cheap)

the controller basically then is the clock/position source plus user demands, and reporting back to user.

just my $0.015
I like that - if I understand the data sheet correctly, this part isolates small analog signals. This could be a really good solution for a lot of isolation challenges. In fact it may be wise to put these on all analog signals to protect the ECU... hmmm...

I have messed around with digital signal isolation a bit. I was trying to come up with a very robust rotary position sensor setup for the throttle. There are really good sensors out there for position and current sensing that put out pwm and/or pulse frequency modulated signals. They have the advantages of easy isolation and an easy failsafe checks, and are less susceptable to noise. I was able to get them to work using the PIC's input change notification feature with interrupts. The main thing that bugged me about it in the end was the large amount if interrupts I ended up using. Perhaps a better programmer could find a better solution?

- E*clipse
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