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Old 08-20-2008, 09:06 PM   #1 (permalink)
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How to Power the MPGuino???

Hey, I've got a freeduino v1.20 with an integrated 7805 voltage regulator.

Can I just plug the mpguino setup directly to the car's 12v accessory circuit, or do I need to use a cell phone charger.

I've got a 9v output dc cigarette charger rated at 1 amp

But I read somewhere that you should only use chargers rated from 100 to 500 mA

I thought current has to be drawn in so I don't know why it would matter to have it limited to 500mA

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Old 08-20-2008, 09:20 PM   #2 (permalink)
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Don't use a cell phone charger, there's no way to tell what your gonna get. SVOBoy needs to get that verbiage corrected in his blog.

DO connect to constant battery power, your trips exist in volatile memory and will get lost every time you turn the key if you do not.

I've used a freeduino directly connected to car voltage with no apparent ill effects. The custom versions also use a 7805 with some extra capacitance to help with reliability/transients. There is one person on the arduino forum who uses a 7812 prior to the 7805 but his writeup didn't quite make sense to me, haven't seen the issues he was reporting. If you are able to replace the components on your freeduino with a soldering iron then I'd just hook it up to system voltage myself. This has been an area of much discussion but so far I've not heard that plugging it straight in has been an issue, not to say it won't ever be.
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Old 08-20-2008, 09:55 PM   #3 (permalink)
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I still don't see what's wrong with the cell phone charger...
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Old 08-20-2008, 10:27 PM   #4 (permalink)
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Yeah, my alternator produces negative voltage sometimes when I get it tested, it's really bad, but I don't know if I want to replace it since the car's on it's way out

So I think I may want some extra protection, could I wire the cell charger directly to the main power source?
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Old 08-20-2008, 10:42 PM   #5 (permalink)
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svoboy, the charger is a complete variable, I do not know anything about random cell phone charger x or its current capacity or any other issues it might introduce, nor if the cigarette lighter it plugs into is constantly powered or if it loses power when the key is in start and/or off. I aint supporting random cell phone charger x. If anyone wants to use a cellphone charger, that is svoboys idea and department, talk to him

For powering the iduino, I recommend at least the following circuit (note, you can replace the 7805 with a 7812 and power a freeduino or other board with an onboard 7805 with no ill effects except maybe a minor wallet dent and have some extra protection):

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