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MS Power usage
Posted: Mon Jan 08, 2007 1:31 pm
by czb83
Any idea how much power a V3 MS1 board uses? I have it wired up to constant power source. Any idea how much current it draws, or how long it would last on a battery. I figure the stock EFI PCM always has power, maybe Megasquirt can too?
Thanks.
Posted: Wed Mar 28, 2007 9:23 pm
by JustinGray
How can the power requirement be for 2 amps when the regulator is not rated to that level?
The U5 regulator is only speced to provide 500 mAs directly. Does anyone have a good number for the actual usage of the MS board itself. I am trying to determine the available current to drive another board using the MS u5 regulator
Posted: Wed Mar 28, 2007 10:59 pm
by Glen Hoag
I threw an ammeter on a v3 a while back and got around 200mA running on a stim. Note that most of the MS outputs merely provide a ground path for the devices they control, so power for them doesn't go through the regulator.
If you provide constant power to the MS, you would have to change the code to create a different strategy for cold start. MS currently reads ambient barometric pressure by reading the MAP sensor at startup.
There is a 1A version of the regulator specified for the MS. It is LM2940T-5.0. I have provided this part in all my v3 kits, and most of my v2.2 kits. On the v3 board, you need to make sure that you don't try to draw too much current downstream of the polyfuses; they are rated at 0.55A.