Puma board for FreeEMS

[Fred]

Well, in future some sort of constant power setup will be part of that standard too :-)

Fred.

[nitrousnrg]

Well, in future some sort of constant power setup will be part of that standard too :-)

Yep, I'm aware of that. Its implemented in mine. btw, low power consumption should be a goal for hardware designers too.

FT232 is externally powered to save some power, and no led is showing the regulated 5v status. I wrote down the max analog circuits consumption, it was something like 60mA in the worst case. Most of those mA came from the air pressure sensors. I have to think a little more about reducing those mAmpers.

[Fred]

None of the sensors etc should be supplied when the power is off, just the cpu, nothing else. One pin, undecided, will control the software to sleep or wake, but other than the cpu, nothing should be on. When it comes to on-state power consumption, within reason, who cares?

[nitrousnrg]

Damn.
If I shut down the regulated 5.00v for the analog circuits, then I must shut down the regulated 5.0v for the cpu. VanalogRef must be VCC+-0.3v or so.

I can shutdown the analog parts if a reference zener is used for the cpu. I've to think a way to power down injector drivers, xor, and rpm circuits. I don't like to have so many regulators but I might have no choice.

Would it be reasonable to put the maximum power consumption during the off-state in the Standard? For example, 800uA max.

[Fred]

Hmmm, re the standard, I don't know, worth discussing, seems like designer choice, though?

As for the vref and the difference, interesting! I wonder if that applies during sleep or not? If so, you have a good point. I hadn't thought about that.

[nitrousnrg]

Hmmm, re the standard, I don't know, worth discussing, seems like designer choice, though?

Its to give the designer more flexibility. "One regulator dedicated to the cpu" seems like a tight constraint if the purpose is just to keep the power low while off.
Besides, the board can have leakages in other circuits. A maximum power consumption would be a more standardized way to say "it must not discharge the battery"

As for the vref and the difference, interesting! I wonder if that applies during sleep or not?

I guess it does, you can poweroff the ADC module by putting everything into sleep, but I think you can't left its Vcc not powered.

[nitrousnrg]

News!:

(note to myself: never, ever again upload a full resolution photo)

I've been building a BDM programmer, if it works I should create a thread about it. That would be once the S12 is soldered, in the pcb I didn't finish yet.
Also, I'm making a temperature controller, to put it in an oven/hot plate, although I don't a thermocouple yet. I have the thermocouple driver (just unpacked, DIP8), the microcontroller (it has been working for a while, arm cortex-m3), and the triac driver (I soldered that board yesterday).

wow, now I have lots to do.

[jharvey]

Awesome and I like your box.

About the hot plat controller, is that a project you can post? I think I have some rework to do on some board I have, and a hot plate reflow would make that easier to do.

[nitrousnrg]

Of course, If you are interested then I'll put it in github.

I'll let you know when I get the time to do it

[nitrousnrg]

Now I have a little more time to elaborate

I'm implementing the temperature controller with an mbed board, using gcc to compile (I truly hate their web compiler license). Imagine a breadboard, pcb with thermocouple driver, mbed, pcb with triac driver.
Once this sloppy thing works, I can start playing with smt. The real oven controller will be FreeEMS itself. It have a thermocouple driver, and plenty of outputs to drive the triac. Plus, there is a proven communication protocol already implemented, and I can tweak/fork ECU manager to act as a temperature controller. It'll take some time.

Back to the board design:

This is what I'll do with the regulators:
One 250mA regulator for the cpu (analog and digital vcc), and one 500mA regulator for everything else (both analog and digital). I'm keeping in mind all the considerations to not mess analog signals/power rails with digital stuff).
Both regulators are powered from the constant 12v from the battery, the 500mA reg (LM2937) can be powered off.
When the switched 12v are off, the big regulator is powered off.
I simulated a simple switch with a pnp and a npn to do it. If it works in the breadboard, I'll try it with a mosfet instead of the pnp. With this, the 5v circuits shutdown can be cpu-driven too.

The idea is to don't use the switched 12v to drive digital/analog circuits; it must drive power circuits only. Those 12v are noisy, and prone to create unwanted behaviors.

Am I making sense?