Sanity check: inverted primary trigger required for JimStim?
#21
Boost Pope
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by default I tend to assume that any signal can have an unexpected voltage on it eventually, especially one that comes from the engine bay and passes near the spark plug wires.
In the OEM design, these circuits are not optoisolated within the ECU- they drive the input of an opamp-based comparator.
In the MSExtra manual, the instructions for wiring the second trigger on the 4G63 do specify the use of a second 4N25, however in the traditional MS1 build for the Miata (including the MSPNP, so far as I'm aware) the second input does not have any isolation whatsoever- the CAS's CMP output is directly connected to the CPU pin through a current-limiting resistor. Lots of cars running around this way, and I've never heard of one blowing a CPU on account of the CAS.
Like everything else, there's more than one way to skin this cat.
#22
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I wouldn't recommend that. While it's not going to start fires, the output of a VR sensor can easily reach 10-20 volts or more peak-peak, depending upon RPM and gap. Microprocessors really don't like having voltages greater than Vdd (or lower than Vss) applied to their inputs
#24
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In '95.5, they added a crank sensor, but it was a raw VR device. This stayed until '99, when the crank sensor went open-collector and became a primary trigger, instead of just a misfire detector.
#29
Surface mount is really not hard with the right technique, even with just a normal iron. I'd rather do an 0805 resistor than a through-hole one now...
The displays I'm using now take a synchronous serial input. Just a big shift register. But those too would be different in a kit, since they cost $40 per 8 characters. (I bought a few tubes of them surplus a long time ago...)
The LEDs on the bottom are bicolor red/green. The idea is those are for warning indicators -- e.g. coolant temp / oil temp / oil pressure. Red=bad, orange=cold, green = normal. There is a small AVR on the back of the center display board which PWMs the LEDs on behalf of the big AVR.
For a kit I would use something like a 20x2 OLED display and it wouldn't fit nicely in the cluster. But it would be $20 instead of 9*$40.
#30
That's really impressive stuff! I'm actually gonna be graduating as an Electronics Engineer in May so SMD stuff doesn't bother me. What software did you use to develop the schematic/PCB? I don't have a ton of experience designing PCB's yet, but the custom footprints for the ECU connectors and such would be nice to have. This project looks really neat and whenever you get more time, please elaborate on it!
#33
I don't know anything about KiCAD. I do know that sometimes free can be expensive
Incidentally these boards are the first ones I had done at Gold Phoenix. The quality is good and they are hard to beat price-wise. I paid less than $150 for all the boards above (4 large, 12 small of the center display, 8 of the left/right) I've used a number of vendors (Olimex, PCBFabExpress, Advanced Circuits, etc.) and GP is higher quality than Olimex and much cheaper than the other two if you have more than one design.
Incidentally these boards are the first ones I had done at Gold Phoenix. The quality is good and they are hard to beat price-wise. I paid less than $150 for all the boards above (4 large, 12 small of the center display, 8 of the left/right) I've used a number of vendors (Olimex, PCBFabExpress, Advanced Circuits, etc.) and GP is higher quality than Olimex and much cheaper than the other two if you have more than one design.
#34
Personally since I'm at school I get a crazy discount on software so I use the NI Circuit Design Suite that has MultiSim (schematic) and Ultiboard (PCB design). Professors of mine use Eagle, never had experience with it though. We only use Advanced Circuits too, I think mainly because of student discounts and such.
Seeing this makes me want to do something similar....
Seeing this makes me want to do something similar....
#35
Boost Pope
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I'm with you on the SMD. 0805 or 1206 are pretty easy to do with some tweezers, a roll of .025" solder, and a regular iron with a clean tip. And no leads to trim on the backside.
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