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Topic: Help making bare minimum standalone arduino. (Read 6 times) previous topic - next topic

carl1864

So a long time ago, I had stumbled upon instructions for making the absolute bare minimum arduino, using nothing more than the atmega chip (with your sketch pre-uploaded), a 16mhz crystal, 5v regulator, and a couple capacitors or resistors.  In fact, I remember you could even omit the crystal (suffering a slight loss in timing, but functional for most things where timing isn't super important), and I'm pretty sure you could even ditch the 5v regulator too, as long as you were powering it by batteries that were roughly 5 volts.  Making it little more than just the plain chip itself, and maybe a resistor or two.

However I've been searching all over the place, and can't find the details how to do this anymore.  Searching for standalone arduino, or bare minimum arduino gets hundereds of results, that are far from what I'd call bare minimum.  Can anyone point me in the right direction for some good instructions on how to use the absolute bare minimum with only the chip, crystal, and regulator w/ caps (and also without the crystal and regulator).

Also one other question, what is the safe range of voltage you can power arduino from without using a regulator?  Like is 6v from 4 aa batteries fine?  What about 4.8v from 4 rechargeable AA batteries?

pluggy

You could do a lot worse than looking at the instructions and schematic of the RBBB for a minimalist Arduino :

http://shop.moderndevice.com/products/rbbb-kit

mrtaylor


MarkT

Quote
Also one other question, what is the safe range of voltage you can power arduino from without using a regulator?  Like is 6v from 4 aa batteries fine?  What about 4.8v from 4 rechargeable AA batteries?


The ATmega328 datasheet is your reference here (all 20MB of it!) but I think the 328P does 1.8V upto 5.5V.  HOWEVER you won't get an Arduino-bootloaded chip to work as low as 1.8V without reprogramming the fuses to reset the low-voltage brown-out detector threshold and the clock options to work with a much slower crystal.  So the practical limits are about 3V (with 8MHz clock) upto 5.5V abs. max (16MHz).   

6V is too much (although a battery-polarity-protection diode will drop enough voltage to help work with 6V battery).  NiMH rechargable batteries are 1.3V, not 1.2V, contrary to popular belief, and 4 fully charged NiMH's provide a nice 5.4V or so (convenient).  4 NiCd's give 4.8V which will work nicely.  Lithium cells are 3 to 3.7V and probably need the slower 8MHz crystal (some people report using the chip at 3.3V and
16MHz but that's outside the specifications.)

Note that the accuracy of analog->digital conversion depends on the accuracy of the supply voltage, so working without a regulator will be a big issue if calling analogRead().
[ I won't respond to messages, use the forum please ]

eried

This is my minimum approach!

(I am using the atmega8 firmware... so it runs at 8 mhz but without an external oscilator, just an stable 3.3v power and the reset button)
My website: http://ried.cl

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