PCB layout - JHarvey

[Fred]

Having pads for LED's for all the outputs and selected inputs would be a bonus particularly for troubleshooting/debugging in the early stages, certainly would not hurt to have that built in, a user could choose whether to fit the LED's or not.

I'm all for LEDs to be attached to existing outputs for a visual indication of what is actually happening (as opposed to what the PC SAYS is supposed to be happening), however I'm 50089489% AGAINST any special purpose LEDs that are only LEDs with the exceptions of maybe one coded flashing trouble light and one or more shift lights etc. Wasting IO on LEDs is a bad idea when an external device could be networked to read the data and display appropriate stuff from it's IO. I'm sure that you agree with me on that anyway though. Just stating it explicitly :-)

They don't have to be on the edge of the board, they can just be parallel across the outputs with the load. Each injector could have one LED and one resistor across it. Ditto each coil. This gives a nice visual strobe effect that is really easy to detect strangeness by watching. I have this on my COP setup on my MS and it was useful in the short amount of time I played with it. They don't have to be exposed either, if you are trouble shooting it's fine to have the case lid off and in that case they could just be where ever the FETs etc are for a visual indication of which FET is giving trouble also.

Obviously if there is a space shortage then it is low priority, but having a visual on these things is very worth while. I've also found piezo speakers invaluable on the outputs of the tach circuit for trouble shooting, what you can't see on the LEDs at all is very easy to hear lack of smoothness on the piezo. I'm not saying we should have dedicated piezos, but they could be paralleled with the IO channels for testing purposes quite easily.

Fred.

[gearhead]

12 ignition and injector drivers? minimum would be 2 and 4. I thought maximum for now was going to be 6 and 6 or 8 and 8?

It would be 'nice' if these unused injection and ignition could be easily repurposed as high current drivers for those of us with reasonable cylinder counts i.e. 4.

I am fully on board with the need for sequential injection as well as the need for individual coil drivers (sequentially fired or waste spark fired). I apologize for not paying attention, but is the initial board going to be designed around an I4, V or I6, V8 or V12? I would think a V8 would be a reasonable 'size' for the initial board. I understand that V10 and V12 are out there and that the code can support them, but the numbers of people wanting FreeEMS for one of these installs have to be unbelievably small. Size does matter, here, and smaller is better.

Gearhead

[Fred]

12 + 12 is the maximal configuration. The outputs should be reusable as general stuff easily enough.

12 + 12 comes from 12 COP + 6 semi + 6 staged semi

A maximal 4 cylinder setup would be 4 COP + 4 seq + 4 seq staged
A maximal 6 cylinder setup would be 6 + 6 + 6
A maximal V8 setup would be 8 + 4 + 4

I think minimal should be 4+4 and that 6+6 would be better 8+6 would cover COP/semi for v8 guys and sequential for all 4 and 6 cylinder guys. Those needing higher counts and or staged injection can add another board. Then again, if we can fit it all, why not put it in?

What size board would you be looking for Gearhead? If you went silly you could make it up in 2 boards 60x90 each and put one on top and one under the cpu board. it would be about 30 - 50mm high though and the circuitry on each would have to be somewhat independent.

Fred.

[gearhead]

I would vote for 4j+4g (4 injection + 4 ignition) as that is all I need for my COP sequential 4 cylinder. Even on my buick/rover v8, I will want 4j+4i as it will be crank triggered only. My preference is but 1 data point, I understand that. I also understand that there are some people that favor 6s. I do not understand *why* mind you, but just that there are people that favor them. Regardless of cylinder count, I think any engine will benefit from sequential injection in turbo form. NA, not so much of a factor. Large injectors and tiny idle PWs benefit from sequential. So, if there are a number of us with with needs for V6/I6 (probably with the plethora of I6 BMWs and V6 nissans), it would need to be 6j+6g for the initial board. Regardless, I would ask for a vote to see what the desires/needs actually are, though, as opposed to providing 12j+12g as the initial layout. Now, staged is another question. These are guys that have huge turbos that need huge injectors to support WOT but have low displacement and need tiny idle and cruise PWs. I feel that if staged injection is needed, it should be on another stacked board as it just adds a lot of stuff that will be seldom used. I'd like a compact 'base' board.

Gearhead

[gearhead]

oh, yeah.. I forgot. The leds. Sure. Just keep them small/ compact.

Gearhead

[davebmw]

There is an onboard eeprom for writing state data for the next run, otherwise the board could be constant powered and code written to place it into sleep mode where the only draw would be quiescent current from the regulator and a tiny ram holding current for the cpu.

Sounds good!

You forced me to think about the serial connection. After thinking I've realised that it's not at all a big deal to desolder the db9 from the TA board and run a ribbon to a suitable convenient location. Same goes for those wanting USB connectivity (me included). Not caring about facing the DB9 outward opens up a bit more scope for rearranging things.

Sorry didn't mean to twist your arm but the main board will have a DB9 for comms mounted on the back edge probably a header for a ready made USB module wouldn't go amiss either.

If you want to have a stepper driver, would it not be best to use full sized FETs backed by a driver chip? Or can you get suitably powerful and reliable chips to do this? I know for a fact the MS chip is unsuitable and unreliable in real world use most of the time, just like vb921s suck.

I personally don't need a stepper for my app but thats why the stepper chip is right next to the heatsink rail with enough room for 8 MOSFET's should the need arrise for a meaty drive circuit its there ready and waiting or like me probably only fit 2 for the 3 wire push pull IACV.


I like your dual cpu socket idea. I can't see any problems with it at all actually, but there could be something. One thing is for sure, you couldn't have it TA compatible for the purposes of main CPU (leaving the cpu bits on board unpopulated) AND have it TA compatible with respect expansion to two CPUs. I think standardising around the TA footprint is a good thing for expansion though. It provides I/O connectivity to nearly all the CPU pins, is compact, and can be made durable with suitable components.

I like the idea of a seperate CPU card to start with but i will more than likely want to fit to the main PCB as a settled design. Leaving the headers with access to the I/O ports allows for serious expandability maybe i'll need to fit another header for the 144 pin MAG devices extra IO ports.


Why only 4 drivers in the high current section? I assume you intend to have only high Z capability on this board? I can't be sure, but I suspect that there will be excess power dissipated if you run 12 low Z injectors in PWM mode on that small a heat sink. Speaking of heat generation, do you intend that these bars will just hang like that or be fixed to the case for further dissipation?

There is room for plenty more just shuffle things along the bar a bit, the heatsink bars will be supported from below in 4 places. I think a 10mm T section bar will have enough area along its top edge to get rid of all the heat generated into an ally lid/case.

Nice drawing
Ta!

Fred.

[Fred]

I think 6+6 is a good place to be at if we can. or 8+6 perhaps for COP on V8 setups. After I redo my utes management my next project will almost certainly be an RB30DET why? because it means I can have the same 500hp as the ute, but with much better reliability and bottom end/torque linearity. Can't argue with that :-)

There is nothing to stop Dave doing a bmw drop in right out of the stops in parallel with Jared's base board either. Freedom is good :-) We do want a generic solution first up though, something that enough of us want that we can do a small bulk buy for them and get started trying to use them.

So for me it would be :

Settle for 4+4+spares
Prefer 6+6+spares
Don't mind 8+6+spares

4+6 also makes sense for wasted spark on 6, 8 , COP on 4, and sequential for 4, 6 with semi on 8.

I think we should be aiming for a generic case for the base board, not something OEM specific.

Fred.

PS, while I was writing this, Dave posted again, Dave, fix your post :-p It's so hard to read without some sort of quote marks or boxes...

[davebmw]

PS, while I was writing this, Dave posted again, Dave, fix your post :-p It's so hard to read without some sort of quote marks or boxes...

Ha done it!

[Fred]

Perhaps I don't understand steppers, but don't you only need four drivers ? pull up and pull down on each side? why 8? with resistors for current sharing and mega load driving?

Fred.

[gearhead]

I think 6+6 is a good place to be at if we can. or 8+6 perhaps for COP on V8 setups. After I redo my utes management my next project will almost certainly be an RB30DET why? because it means I can have the same 500hp as the ute, but with much better reliability and bottom end/torque linearity. Can't argue with that

There is nothing to stop Dave doing a bmw drop in right out of the stops in parallel with Jared's base board either. Freedom is good We do want a generic solution first up though, something that enough of us want that we can do a small bulk buy for them and get started trying to use them.

So for me it would be :

Settle for 4+4+spares
Prefer 6+6+spares
Don't mind 8+6+spares

4+6 also makes sense for wasted spark on 6, 8 , COP on 4, and sequential for 4, 6 with semi on 8.

I think we should be aiming for a generic case for the base board, not something OEM specific.

Fred.

PS, while I was writing this, Dave posted again, Dave, fix your post :-p It's so hard to read without some sort of quote marks or boxes...

So, how do we determine desired configuration for a first cut board layout... Benevolent dictator? Poll? My vote is 4+4+2 spares (which can b either ignition or injection). I think we should conceptually lay out how you would do those other configurations that are more 'common' as well.

so, if you have a 4 cyl and you need staged, you could use the base board, but you would have 2 drivers for primary (ganged) and 2 for secondary. i.e. you could not do staged sequential fuel. All would work just fine, including COP ignition. If you want/have a 'stacker board' you can do sequential staged injection with 4 cyl and COP.

I would define this 'stacker board' as a stackable, generic high current output board (to-200 or dpak) outputs that you could jumper to the appropriate pins I and O. If you are doing injection, populate the snubber diode and ensure that one of the pins fed through is the 12V dirty 'supply' to dump the spikes to. Add jumpers to the appropriate pins to drive these channels and back to the board to feed out the main connector. I thinbk we need to think through how this would work. This concept has the advantage of it being very useful for many installs and has the ability to be small foir most installs