Power control of the EMS system

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Fred
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Re: Power control of the EMS system

Post by Fred »

gearhead wrote:With all the noise an IGBT coil driver generates, the coil drivers need to have their own gnd.
Then you are going to LOVE this :

EDIT : see next post instead of this : http://i260.photobucket.com/albums/ii15 ... iring4.png

I can't see any ways of improving on this off the top of my head. There needs to be a separate grounding diagram made though. It was just too much stuff to try and fit in one diagram. I always hated the MS wiring diagram and now I can see that it was because they tried to put too much on one drawing.

Power and primary connections
Grounding connections
Accessory connections

Perhaps 3 diagrams?

Just realised that I didn't include a power feed for accessory items. Those should be supplied either from an extra relay in parallel with the key, or an extra relay in parallel with the fuel pump stuff depending on which items they are and when they need to operate/whether they will cook if left on etc.

Fred.
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Fred
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Re: Power control of the EMS system

Post by Fred »

Image

Main Key :
  • B - Battery
  • C - Coils
  • E - Engine Management System
  • F - Fuses
  • I - Injectors
  • K - Ignition Key
  • L - Lambda Controller and Sensor Heater
  • P - Fuel Pumps
  • R - Relays
EMS Connections :
  • Constant fused power in
  • Battery reference switched power in
  • Noisy switched power in
  • Fuel pump, injector and coil relay control out
  • Injection ground
  • Ignition ground
  • Accessory ground
  • Signal ground
  • 4 (up to 12) coil control lines out of the EMS
  • 4 (up to 12) injector control lines out of the EMS
Relay Functions :
  1. Wide Band Lambda Controller and Sensor Heater
  2. Battery Reference
  3. Noisy Power Feed
  4. Accessory Power Feed
  5. Injector Power Feed
  6. Ignition Coil Power Feed
  7. Main High Pressure Fuel Pump
  8. Secondary Low Pressure Lift Pump
Fuse Functions and Values :
  1. 10 Amps - Wide Band Lambda Controller and Sensor Heater
  2. 2 Amps - Battery Reference
  3. 10 Amps - Noisy Power Feed
  4. 10 Amps - Accessory Power Feed
  5. 15 Amps - Injector Power Feed
  6. 30 Amps - Ignition Coil Power Feed
  7. 25 Amps - Main High Pressure Fuel Pump
  8. 15 Amps - Secondary Low Pressure Lift Pump
  9. 2 Amps - Ignition Key Feed
  10. 2 Amps - EMS Constant Power Feed
Hierarchy Of Control :
  1. The ignition key switches the main relays which have constant power to them.
  2. The main relays feed the wideband controller and heater, the switched noisy power, the switched battery reference power and any accessory devices like idle solenoids etc.
  3. The EMS switches the fuel pump, injector and and ignition coil control relays.
Now we need a sensor connection diagram and grounding diagram to go with it :-)

Fred.
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jharvey
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Re: Power control of the EMS system

Post by jharvey »

2 switched feeds for freeEMS?

Another thought, instead of constant power, how about a large cap or battery in freeEMS, that can keep it on for a couple seconds after it's shutdown? Just a thought, I don't object to constant power, I just thought the large cap might help keep noise down for the ECU.
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Fred
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Re: Power control of the EMS system

Post by Fred »

Yeah, 2, at least. 1 for the battery voltage reference and sensor 5 volt supply so that it is off when the key is off and one for all the other stuff. The constant one will purely feed the CPU power supply. "all the other stuff" could *possibly* (though unlikely) require more than one independent feed. For each independent feed you need an extra relay to ensure they are separated the entire way back to the source. If you put the relay on the battery then you could cut this back to 2 from 8 quite reasonably.

If we go with a cap we need circuitry to fill it in a controlled way and then bridge to the reg solid afterwards. If we go with a battery it needs to be 5v. I think constant is the best bet in that light. It will draw next to nothing when shut down into sleep anyway, so it's no different to the clock ticking away or the alarm brain listening etc.

Also, although earlier I said that we don't need a full sized FET for driving the fuel pump relay, I've changed my mind (again). If I want to drive 4+ relays with that pin, it needs to be fairly durable so make it a to220 please.

Fred.
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thebigmacd
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Re: Power control of the EMS system

Post by thebigmacd »

I'd personally like to see the main ATC fuse(s) for the ECU onboard (in the edge of the case), like alarm and ICE systems have. It makes for nice packaging.

I would also like to see separate pigtails/connectors for internal and external curcuits. IE one bundle of wires goes to the firewall and one bundle goes towards the steering column. In the end it's a simple matter of implementation on a per-install basis but I think it would be good to group the PCB pads with such an end-goal in mind:

Interior Harness:
+12 Battery (Reference/Backup)
+12 Battery (Flyback)
+12 Ignition Relay
GND Main
GND Signal
Tach Out

Exterior Harness:
+12 Fuel Pump
+12 Injectors and Coils
+5 Sensors
GND Sensors
Driven I/O
Signal I/O

Like I say, just a suggestion on simple groupings. I find EMSs of all types both OEM and aftermarket tend to have the pins all intermixed.
Keith MacDonald
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Fred
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Re: Power control of the EMS system

Post by Fred »

thebigmacd wrote:I'd personally like to see the main ATC fuse(s) for the ECU onboard (in the edge of the case), like alarm and ICE systems have. It makes for nice packaging.
The trouble is that when you have a car amp with a pair of 25A fuses hanging out of it and then you run 5 metres of cable to the battery, you had better be sure you fuse it at the battery too otherwise you are probably going to end up with something like this one day :

Image

What I'm getting at is that although we could fuse the 3 power inputs at the device, an intelligent install would also fuse the wires at the source. At which point the on device fuses serve no purpose really. Regardless of that, I wouldn't necessarily be against it, I just don't 100% see the point.
I would also like to see separate pigtails/connectors for internal and external curcuits. IE one bundle of wires goes to the firewall and one bundle goes towards the steering column. In the end it's a simple matter of implementation on a per-install basis but I think it would be good to group the PCB pads with such an end-goal in mind:

Like I say, just a suggestion on simple groupings. I find EMSs of all types both OEM and aftermarket tend to have the pins all intermixed.
This makes sense, however there could potentially be a trade off with how nice the layout on the board is. If that was the case (and it may not be) I'd keep the board sweet and allow the user to bundle the wires as they wish.

Additionally, some of the wires you have listed as "inside" I would DEFINITELY not be running inside. I'd be sending them straight to the battery or other power distribution point such as starter motor or BMW bus bar. I've not seen a vehicle yet with a properly separated power system inside the cab. Most/all share the smallish trunk wire with fans and lights and all sorts. Notoriously noisy really. Grounding is the same, if you want a demo, ground your head deck to the inner dash chassis and see what happens :-)

I think such grouping is definitely worth considering though. I might be more tempted to group clean stuff together and noisy stuff together and just pluck inside/outside stuff out of the loom as it made sense to do so.

Fred.
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Re: Power control of the EMS system

Post by Fred »

thebigmacd wrote:I'd personally like to see the main ATC fuse(s) for the ECU onboard (in the edge of the case), like alarm and ICE systems have. It makes for nice packaging.
You know, I saw a thread yesterday or the day before on another board where a guy fried his whole board, burned the traces off and the whole shooting match. I thought to myself "If the fuses were on the board, he couldn't have done that". Which is true, but at the end of the day, it cost him his board not us. And he should have fused the wiring anyway to prevent fires. If it was a commercial product it would make sense so that warranty claims didn't occur based on idiot installs. Given that it's home brew by definition I'm still wondering if it's worth it.

Just a thought.
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Re: Power control of the EMS system

Post by jharvey »

I think I'll have this covered, when I make my version of the board. I'm planning for a fuse pad (or via), and a trace that will connect them. I seem to recall normal PCB's run 2oz copper per some area, that means the copper is X thick. So if you layout a trace that is X wide and keep all other traces wider then that, then you have a fuse. If you break your natural fuse, you can replace it by adding one to the pre-made pads/via's.

Under normal conditions, you simply don't care about it. In the past I've done similar for current sensing resistors, but we'll stear clear of my thoughts about current sensing for now ;)
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Re: Power control of the EMS system

Post by Fred »

jharvey wrote:I think I'll have this covered, when I make my version of the board. I'm planning for a fuse pad (or via), and a trace that will connect them. I seem to recall normal PCB's run 2oz copper per some area, that means the copper is X thick. So if you layout a trace that is X wide and keep all other traces wider then that, then you have a fuse. If you break your natural fuse, you can replace it by adding one to the pre-made pads/via's.
That seems to me to be a bloody good idea young Jared! Good work :-)
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ababkin
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Re: Power control of the EMS system

Post by ababkin »

my 2 cents:

- perhaps the discussion about power persistence (after shutoff or other causes of power off) should be clearly separated to: a) MCU controlled: the intentional delay for various reasons before power is shut to the MCU and/or other devices , and b) MCU uncontrolled: a protective circuit that will ensure there is power available for the MCU to react and prepare itself for the inevitable 'coming power-down'. The latter is basically a brownout detection circuit with a largish cap that allows MCU to run for several milliseconds longer to save stuff and shut everything down properly. I've seen some discussions on these circuits on forums discussing flash file systems on embedded devices (like EFSL). Quite useful for on-board datalogging.

- Not sure what power supply freeems is using (pardon ignorance, linear?), but i've discovered that a buck supplies like ones based on lm2678 (5A) or lesser current ones don't require much components, and give over 90% efficiency (free sample chips).

- I would use one or two of those cute through-hole solder-in mini-fuses (look like 1/2W resistors) to protect the board. Easy to unsolder/resolder a new one and doesn't take up much space.

Alex
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