- Hoon.sch (Schematic Design).pdf
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Solid point! I contradicted myself...TonyS wrote:The reason I asked is because I initially assumed that an external box application was a given, but when I read "Configuration of the micro should be done over SPI or I2C by the primary micro (FreeEMS)" I wasn't sure, as these protocols are more typically used for intra-board communications, while board - board communications tend to use more environmentally "robust" protocols (485, CAN,...).Fred wrote:I don't think it matters much, does it?TonyS wrote:Is this to be an "add-on" board (remote?) or is to be a "populate parts" option on the main board?
I use a package called Easy-PC (terrible name - but works well in my opinion). I'm not sure how we can share at this point, but I will try to update the drawing as suggestions, requests, specs,... come in.jharvey wrote:Nice, I like hoon uC. I might like to add some stuff. Is the source file something that can be shared? If so what did you draw it in?
I really think that I will have to come up with a circuit simulation to explain/show why two levels of snubbing are needed. The "3rd line" is to show that this snubber function needs to be controlled so that it is "in-circuit" during pwm and "out-of-circuit" at injector shutoff.jharvey wrote:The D1 diode isn't required if using OV drive silicon. However it might be handy for those that are familiar with that snubbing technique. Hmmm I see that 3rd line from D1 to the uC, are you thinking of a pin diode? Those are typically used as RF switches.
Fred wrote:Is there any reason to go to 8 straight away? The circuit could be duplicated from 4 to 8 or 12. Probably 8 is more common anyway, though. If it made sense it could be one micro per channel, but that is unlikely.
The PWM could be software too (8 digital outputs), it would be easy to do with this little programmatic load.
I wonder what the sources of tolerances are. We may find the actual tolerance is tighter than we expect, or looser. For example, we'll probably have a fairly consistent temperature, so that source of tolerance is minimized. Either way, I suspect it's tight enough. I don't think it's all that important to measure the peak, and we can probably handle a fairly large tolerance in the 1 amp range. The big heat savings is when we go from 4 to 1 amp. If it's 1.01, it's not really the end of the world. So 8 bit is probably good enough, however if we have 10 bit, might as well get the better accuracy.TonyS wrote:The Allegro ACS714 is quite an interesting part (good find!). Because of the bi-directional current sensing capability (0 to +/-5A), it has a 185mV/A response centered at Vcc/2. I haven't dug deep into the data sheet to look for any "gotchas" (I did notice that it has a +/-40mV, 0A spec).
He actually explained it in an earlier post, have a read back through them, perhaps?jharvey wrote:I'd like to chat about the "bi-level snubbing" I can't seem to find that term in google. What advantages does it have from a normal snubber diode or just an OV drive?
With an 8-bit A/D, you will have resolution of about 1 count for every 100mA of current (based on using the ACS714). Is this enough?jharvey wrote: So 8 bit is probably good enough, however if we have 10 bit, might as well get the better accuracy.