OBD MPGuino gauge

[Magister]

Thanks for the testing, guys!! I will take a look at it.

[cmags]

Originally Posted by KJSatz

Would an iDuino work with this?

I'm planning on using the iDuino too. Looking over the schematic, the only trouble I see is that the Arduino is powered by the OBD connector's 12V line. This is convenient for having one less plug to come into the circuit, but the iDuino does not have a built-in regulator, and requires a regulated 5V.

Question: Can we power the iDuino from a separate 5V source, allowing the 12V line from the car to power only the MC33290 on pin 1?

It would be the same 12V from the car's system as it is coming in over the OBD line, so I don't see why not.

I could put a regulator on the aux. board (requires 4 components: 7805, .1uf cap, 330uf electrolytic cap, 1n400x diode), but I'm trying to save board space for a small enclosure. Plus I was running into heat issues with my MPGuino so I'd like to keep the reg out of the box if possible. My plan is to build an external 5v regulator and run it into the USB port of the iDuino, and use that to power the board and the VDD of the MC chip. Seems viable, anyone see a reason this won't work? The MC already has a separate ground (signal GND vs chassis GND) so it already looks power isolated.

[RussEnterprises]

Originally Posted by cmags

I'm planning on using the iDuino too. Looking over the schematic, the only trouble I see is that the Arduino is powered by the OBD connector's 12V line. This is convenient for having one less plug to come into the circuit, but the iDuino does not have a built-in regulator, and requires a regulated 5V.

Question: Can we power the iDuino from a separate 5V source, allowing the 12V line from the car to power only the MC33290 on pin 1?

It would be the same 12V from the car's system as it is coming in over the OBD line, so I don't see why not.

I could put a regulator on the aux. board (requires 4 components: 7805, .1uf cap, 330uf electrolytic cap, 1n400x diode), but I'm trying to save board space for a small enclosure. Plus I was running into heat issues with my MPGuino so I'd like to keep the reg out of the box if possible. My plan is to build an external 5v regulator and run it into the USB port of the iDuino, and use that to power the board and the VDD of the MC chip. Seems viable, anyone see a reason this won't work? The MC already has a separate ground (signal GND vs chassis GND) so it already looks power isolated.

There should be no problem with using a separate 5v source, as long as the 5v source shares a ground with the 12v source. Chances are if your 5v source is powered from the cars electrical system, that will be the case, but I'd probably connect the ground from the iDuino to the MC33290 ground just to make sure.
For my prototype, I'm using 3 wires from the obdii plug (+12, gnd, K-Line) to a small piece of perfboard with the 33290, pullup resistor, and a 7805, then 4 wires to my arduino clone (tx, rx, gnd, +5). If I do a final version, I may be able to build the perfboard into the hood for the obdii plug, or I may just put it in a small box and leave it inline.

Russ

[electromike]

I am curious about the power drain for the OBDuino. If i am correct, the device doesn't take advantage of any power saving code right?

I know my car doesn't cut the power to the device when the car is off. Is that normal for most?
I want to make sure that I don't kill the car battery specially since it is winter.

Will we be seeing some power saving code in the project soon, or is my best bet to run an extra line and power the device off of the Car's ACC connection?

Thanks.

[Magister]

For the moment I have a small switch to shutdown the gizmo before leaving the car, but each time I go into the car I have to switch it to on before starting the engine, and it's annoying.

I am testing an "ignition sense interface" (2 transistors, 2 diodes, 2 resistors) that will require a wire from the accessory (like the cigarette lighter).

The OBD2 plug always has the +12V even when there is no key in the contact. A pin will be used on the atmega as a "keepon".

[Nevyn]

Someone tested it and with the backlight off it was like 20 milliamps I guess they got. Don't remember the thread. "Does the MPGuino turn off" or something like that.

[dcb]

I would leave the extra wires out of it (complicates installation, so NOT what obduino is about), just use a timeout if RPM and speed are zero for a bit, or in some cars I would imagine the network stops responding when not in "run" and that would be a pretty good clue that it is time to turn off the backlight.

[electromike]

I tried googling to come up with some numbers to see how much of a worrie this should be.

Civic battery is a 51R ranging in capacity from 41 down to 28 depending on quality.
We wouldn't want to drain more then 10% in Three Days.

which means
28AH*10% = 2.8 AH's.
2.8 / 72Hrs = 39mA
39mA / 2 ~= 20ma Safty factor.

So with the backlight off.. it looks like there wouldn't be much to worry about if you use your car every other day, and a switch to shut it off if you know you will be away (or just unplug it) for an extended period of time.

Any comments on the math? That was just a quick guess..

[Magister]

I tried to play also with sleep mode in the AVR but I can not make it work well.

[americasfuture2k]

hmm, wonder if a button cell like a 2032 (off the top of my head) can be incorporated into the MPGuino to keep the memory.