davebmw wrote:Any suggestions/observations please fire away.
A great start. Here are some general notes.
-- You can print both schematic and the board layout to post script, then use a program called ps2pdf to make it a pdf. If you don't want to install ps2pdf you can also use
http://ps2pdf.com/convert.htm with out having to install software. My home computer came with Acrobat, I use that to merge the pdf together, but I know there is another way to do it, I had a solution, so I did it that way.
-- I encourage you to not use the power ports, but feel free to try them. I still don't quite under stand the rules that follow them. I found the nets on the PCB were a bit mangled up. If you figure them out, please let me know, I would like to be less ignorant on that topic.
-- Perhaps I should have used a revision sequence like this freeEMS 1.(official release)_(version).(minor release)_(P is for PCB).(minor release) So mine is freeEMS 1, version A, minor release 19 like this freeEMS_1.00_A.19 yours would be something like this freeEMS_1.00_B.01. Hmmm, not sure I like the A and B thing. Your right it does have implications that it's a newer version of the same, which is miss leading because it's completely different. Perhaps we should change that to our initial or something. Kind of hard to change mine, perhaps we can change yours to freeEMS_1.00_TypeB.01. I'm flexible here, thoughts?
Now for specifics.
In, 3wirePWM, I see a 2 pin connector, I'm guessing the third wire goes from the battery straight (or relayed) to the injector. Just wondering where the third wire is. I'd say the NPN's are controlling the current through FET's. However it appears this isn't PWM anymore, perhaps has migrated as time went on. I've got an idea of how to use a hall sensor and VCO for a switching current control, but haven't gotten to sketch it up yet.
The idea I've been thinking about does switched current control, using a hall to create an analog voltage based on current, connected to a VCO that creates a square wave going to the switching FET charging and discharging the injector coil very quickly. So when current is getting lower then the threshold, the top side FET turns on saturated. The injector coil at this point is not fully charged so it starts to charge at the normal LR curve. After about .5ms, current will be above the threshold and the top side fet will turn off. I guess current then would flow through a snubber diode, until the current dropped again. Then on the switch would go, restarting the cycle. If done right, you could have a bit of over shoot on the start up allowing for a current curve very similar to a peak and hold curve. I was thinking of using this hall
http://www.allegromicro.com/en/Products ... e/3506.pdf however it's discontinued. I don't plan on making progress on sketching this idea up, so feel free to take a stab at it.
In coil drive I'm seeing the VR is you coil input? I don't quite follow. Is the MOSFET an over voltage protected device like the PIP? Perhaps the bus is for snubber caps or diodes. I don't fully understand diodesch.
In injector drive, what's the bias voltage of the NPN. It might require the resistor to be to large for the 1 amp (plus) to run through it. I'm seeing that NPN with two possibilities. One is to shut off in an over current situation, another it to perhaps help increase isolation attempting to keep the digital signal in spec. The function depends on the resistance value chosen for the low side resistor.
In power, I think you may want a P channel not an N channel on the input. Also the P channel is typically put in 180 from how you have it. If that was the intent, I would see it protecting against reverse voltage. As I see it now, you would have to signal it with a voltage above 12 - 14 V to turn it on. You may want to add the third output cap, I know many folks put it closer to the CPU or what ever chip, but I feel it really helps keep RF off the board when put at t reg, then the one at the CPU is less needed. Still installed but not needed as much.
Looks like, you're like me, and confused about the second switched 12V. I think that was intended to separate the dirty switched 12V and clean switched 12V. However, the dirty switched 12V should run directly to the injectors, coils ect. I think Fred was thinking about that for some of the more unique vehicles where you might not have it switched that way.
In XDP CPU I got an error, then it popped up with out the symbols. Not sure what happened there.
I had a couple that didn't work, appeared like a couple blank pages for future growth / plans.
All in all, I'd say it's a great start and a splendid work in progress. Keep it up.