Help making bare minimum standalone arduino.

Using Arduino Project Guidance
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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?

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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

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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().

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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)

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Thanks for the help so far. I've looked at those sources, and they still seem to be have more components than necessary for a bare minimum setup. They did help though, I think i might have been able to figure it out, and I made a crude schematic. Does it all look correct and problem free?

I've seen different places use either 20pf or 22pf capacitors on the crystal, does it make a difference?

Also as far as if a voltage regulator is desired, well I bought the 3 parts that were mentioned in the arduino reference

  • 7805 Voltage Regulator Jameco# 51263
  • 10?F Electrolytic Capacitor Jameco# 94220
  • 1?F Electrolytic Capacitor Jameco# 94160
    However I have been unable to find a simple schematic for this part, trying to do a search results in multiple different schematics, all containing more than just those 3 parts (such as diodes, extra capacitors, etc). Can anyone explain, or point me in the right direction how to make the voltage regulator with those 3 parts only?
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Here is quick overview of wiring up a 7805 type regulator. Wire the larger of your two caps to the input and the smaller to the output. The actual values of the caps is not too critical, but without any input and output caps your regulator will tend to break out into oscillation.

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The arduino reference uses 2 10uF capacitors with the 7805. They are laid out as the RBBB schematic without the resistor led and diode. The 47uF capacitors on the RBBB are probably better values to allow for more current capability and a less well behaved power source.. You want some decoupling capacitors (.01 uF ceramic work well) between GND & VCC close to the ATmega on your own schematic. It would work without (probably) providing you're not connecting anything to the Atmega chip. (Kind of defeats the object). If you have plans to connect anything remotely electrically noisy you may well need more decoupling above the 2 .01 uF capacitors.

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To be picky (but not disrespectful, I hope) you are not making a standalone Arduino. You are making a standalone microprocessor. You won't be able to do anything with it until you connect it to the outside world. But that is also true of any Arduino unless you just want to see a LED flashing. At some point you may need to reprogram the chip so I would suggest you use a header in your project. Your schematic looks OK, but you will probably find it easier to get 22pF caps, as they are standard values, where 20pF are not AFAIK. Anyway, good luck.

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This could confuse. A transformer doesn´t have polarity ( + or - ).
A rectifier does. The schematic should read "+ from rectifier OR battery , - from rectifier 0R battery" . You can use a 9 or 12 volt battery.

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My thread covers this same exact thing.. (with some trouble shooting) that Lefty already pointed out in here and helped me..

http://arduino.cc/forum/index.php/topic,52707.0.html

to keep things even cheaper..

1.) buy Ateml chips pre-loaded with bootloader (unless you have a real/true Arduino around to flash).. keeps cost down

2.) to keep cost down even more.. use one of the tuts outlining how to use an old cell phone data cable as an FTDI cable to upload sketches to your Arduino circuit.

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Thanks for those diagrams of the voltage regulator. I'm still getting 2 different stories about the capacitor sizes though, I had copied and pasted from the reference and it said a 10uf and 1uf, and "retrolefty" mentions a big and small cap, but "pluggy" said he read in the reference somewhere that its 2 10uf ones, I've also heard other sources seemingly using 2 identical ones. Does it work both ways, or is one method better?

Also, voltage regulator aside, does the schematic I posted above look all correct and problem free?

As far as the issue "selby96" mentioned about programming it. Well I plan to just program it with a duemilanove board, and then take it out and put it in its permanent spot in its own circuit. The purpose of me making the minimum standalone is for permanent installation. I do all the prototyping on the duemilanove board, but once a project is done and needs no more changes, I'd like to just pop the chip out, install it permanently to the project, and pop a fresh atmega328 with bootloader into the duemilanove and move to the next project.

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Thanks for those diagrams of the voltage regulator. I'm still getting 2 different stories about the capacitor sizes though, I had copied and pasted from the reference and it said a 10uf and 1uf, and "retrolefty" mentions a big and small cap, but "pluggy" said he read in the reference somewhere that its 2 10uf ones, I've also heard other sources seemingly using 2 identical ones. Does it work both ways, or is one method better?

The capacitor sizes for the regulator input and output are very non-critical. However, rather then expecting someone on the web to give you the 'perfect & exact' (or even a correct answer for that matter), you should do what most of us do, get a copy of the chip's datasheet and see what it says and recommends. That is always the reference one should go by.

Here is a link to the original national LM7805 fixed +5vdc regulator. On the very first page there is a picture showing input and output caps with notes about there usage. That input cap is shown as .22ufd, but larger is fine. The output cap is shown as not required, but .1ufd suggested. For use with digital components like the 328 chip, It's common practice to wire .1ufd caps between +5vdc and ground at various spots on your board, best location being right at the +5vdc power pins for your AVR chip, pins 20 & 22. Digital circuits create noise on the +5vdc power bus and power bypass caps are your best friend to help prevent strange problems.

http://www.national.com/ds/LM/LM340.pdf

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I know that others have posted the usual (and very good) how-to's, but just thought I would pitch this one in just to throw in the bucket. It's the most thorough one I have seen thus far (but it's on a breadboard, but it's easier to see the concepts by this)

http://itp.nyu.edu/physcomp/Tutorials/ArduinoBreadboard

BTW, FTW -
(http://www.adafruit.com/adablog/wp-content/uploads/2009/05/one-chip-arduino-v2-0.jpg)]http://arpro.posterous.com/one-chip-arduino![](http://www.adafruit.com/adablog/wp-content/uploads/2009/05/one-chip-arduino-v2-0.jpg)

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Capacitors in many (most ?) applications are very non critical. The reference I was looking at for the 2 10uF capacitors around the 7805 is http://www.arduino.cc/en/Main/Standalone
If your power supply isn't particularly clean bigger is often better. In my opinion any simpler than the RBBB is too far, you soon get sick of swapping chips when you're debugging sketches and the simple programming interface and reset switch makes life bearable.

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Does this help any (click through to get a readable version)

Eventually, there's supposed to be a bunch of explanatory text to go with this.

This is the Freeduino v1.19 schematic, just rearranged into "boxes."
The "bare minimum" is the stuff inside the pink box. Add the other boxes "as needed."
(This is a diecimila-era schematic. For duemilanove, the "power select" box gets more complicated.
For Uno, the "USB/Serial Converter" changes. But it stays basically the same.

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Thanks for all the input, very helpful.

One thing I noticed though is on many of the rather minimal arduinos, people are hooking them up similar to my schematic (which I'm not 100% sure is right). ImageShack - Best place for all of your image hosting and image sharing needs , however they are also applying voltage to the AREF pin, sometimes direct, and sometimes through a resistor. Is this necessary or not? I've never used the aref pin on my duemilanove for anything.

Also, some are not using a pull resistor on pin 1 reset, and others are. Is the resistor pretty important, or not really?

And I don't get why, if the voltage regulator can by made with just the chip and 2 capacitors, why is the rbbb kit (and others) using 3 capacitors, and a diode? (plus an led, but I understand the point of that).

All the info just varies so greatly from different sources.

I hate asking so many questions, but I'm just baffled by how hard of a time I've been having finding this basic info. I've searched for "minimal", "standalone", " bare minimum", and others, and read at least 50 pages of so called minimum arduinos, and none of them are minimum. They all have tons of extra parts for programming, and generally are pretty full fledged programmable arduinos. I mean, thats good for a diy arduino that you can work on, and those are very cool. But if you already have a working project with all the bugs worked out, then it shouldn't need any extra programming. If you want to make it permanent, or make multiple permanent copies of it to give to family, or other situations like that then there is no point in wasting time and components, using anything more than the bare minimum components, and minimum connections. Seems like something 95% of the arduino users would want to do this. Make permanent minimal installations of successful projects. Yet info such as a simple accurate schematic of the bare minimum for a stable working chip, without anything extra, has been near impossible to find.

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carl1864:
ImageShack - Best place for all of your image hosting and image sharing needs , however they are also applying voltage to the AREF pin, sometimes direct, and sometimes through a resistor. Is this necessary or not? I've never used the aref pin on my duemilanove for anything.]

It is only necessary when you are going to be using analog in. It's the Analog REFerence pin. I don't know much about it but I don't use it either. Unless you know your going to use it just don't hook anything to that pin.

carl1864:
Also, some are not using a pull resistor on pin 1 reset, and others are. Is the resistor pretty important, or not really?]

If you use a switch to reset the chip then yes it is very important to make it work. If you are only unplugging/plugging power to it (or using an on/off switch) then all you need to do is wire reset to +.

The way the reset works is like this: The resistor ties reset to +. If the pin goes low (or rather has - charge instead) then it will reset the chip. When you press the reset button, the resistor stops the flow of + to reset, and - flows, thus resetting the chip.

If you do NOT wire the pin at all, then that reset pin is floating. In other words, you may be ok, but you may not. If the pin floats and get's interference of any type then it may just start resetting itself constantly.

carl1864:
And I don't get why, if the voltage regulator can by made with just the chip and 2 capacitors, why is the rbbb kit (and others) using 3 capacitors, and a diode? (plus an led, but I understand the point of that).]

The two capacitors are needed if you are going to use a voltage regulator as opposed to usb power. The diode is to ensure you don't burn your chip by connecting ground and VCC backwards.thanks to WestFW for the info

carl1864:
All the info just varies so greatly from different sources.

I hate asking so many questions, but I'm just baffled by how hard of a time I've been having finding this basic info. I've searched for "minimal", "standalone", " bare minimum", and others, and read at least 50 pages of so called minimum arduinos, and none of them are minimum. They all have tons of extra parts for programming, and generally are pretty full fledged programmable arduinos. I mean, thats good for a diy arduino that you can work on, and those are very cool. But if you already have a working project with all the bugs worked out, then it shouldn't need any extra programming. If you want to make it permanent, or make multiple permanent copies of it to give to family, or other situations like that then there is no point in wasting time and components, using anything more than the bare minimum components, and minimum connections. Seems like something 95% of the arduino users would want to do this. Make permanent minimal installations of successful projects. Yet info such as a simple accurate schematic of the bare minimum for a stable working chip, without anything extra, has been near impossible to find.

I see what you mean, and I have been there. Don't need the regulator if you are running on usb as it's regulated already, you do need the capacitors and diodes, you don't need the crystal, you don't need an led, you do need a means to connect the chip to flash the firmware, but if you have another arduino, or have an icsp programmer (also these are easily makable with a serial port and a few odds and ends) to flash the application to the chip then just do it on a breadboard before you solder.

That's pretty much it. All you need is an Atmega chip, a usb power connection, two capacitors, a diode, a power switch, 6 wires to connect these (and 1 for + to reset) and Voila! :slight_smile:

As soon as I get home, I will make a simple schematic in fritzing that will help you tremendously as to what parts do what, and why or why you would not need them :slight_smile:

Till then, lemme throw you a schematic of my chip I am setting up right now. The Atmega32L

FYI THIS schematic is adaptable if you download the fritzing file (from here: http://fritzing.org/projects/the-atmega32l-programming-the-beast/so you can see which pins on the atmega32 are what so you can adapt to those pins on the Atmega328.
Things you can leave out of my schematic though: the breadboard with the 3 leds(and all connecting pieces on that breadboard), and the two ceramic capacitors and the crystal.

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you don't have to power the AVcc and ground, just the one side Vcc and ground.

This is WRONG. If a chip has multiple ground and power pins, they should ALL be connected to the appropriate supply rails. Otherwise you get (by definition) undefined behavior. Some things may work, others may not. There may or may not be an internal connection on the chip that is sufficiently low-resistance to insure proper operation of the other parts of the chip...

The diode prevents you from destroying the chip if you happen to plug in a wall-wart with the wrong polarity.
The capacitors each serve slightly different purposes; they may or may not make each other unnecessary. The regulator should have input and output caps (already discussed), and the AVR should have a "bypass cap" for each power pin. (missing bypass caps were one of the problems I noticed in your schematic.)

Personally, I think it's about time to get rid of the generic wall-wart jack and regulator, in favor of a USB connector, even if only for power. There are enough USB-like power supplies that put out a a nice regulated 5V that putting up with "random" seems ... unnecessary.

AREF is not connected on the official Arduino boards; it need not be connected on a "minimal" system either.

One reason that you're having trouble finding consensus on "bare minimum" is that a lot of people aren't going to consider a few resistors and caps (costing less than $0.01 each in bulk, and probably lying around in my "junk drawer") as "real components" in the sense of adding cost or complexity to a design. The voltage regulator is another open issue; I just said I thought it was no longer needed, but it is surely important (and needs its associated components) if you need to operate the resulting circuit from an over 5V supply...

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I was recently working on this type of thing as well. Two things I had trouble with -

  1. I burnt the bootloader on the new chip using another arduino. When doing this don't forget to disable by putting a 120 ohm resistor between 5v and reset on the arduino doing the burning.

  2. I never was able to upload a sketch onto my breadboarded arduino. I resorted to programming it in an arduino and then popping it out and putting it in my breadboard rig. Works but not very elegant.