Barebones Arudino

I've been looking for a solid list of parts to run an absolute barebones atmega for finished projects. Would I be correct with the following list of required and optional components?

Required

1 x ATmega328 with Arduino bootloader
1 x 0.01µF Ceramic Capacitor (power)
1 x 10k resistor (auto-reset)
1 x 16MHz resonator/crystal

Optional

1 x 0.01µF Ceramic Capacitors (auto-reset)
1 x LED (Pin 13 indicator)
1 x 470 ohm resistor (LED)
1 x SWT10 Switch (reset)
1 x 6-Pin male header (Programming / USB Pwr)
2 x 14-Pin male headers (ATmega328 connectors)

On a side note, have any of you seen this: http://www.geocities.jp/arduino_diecimila/obaka/project-2/index_en.html

Looks OK. But if you use a crystal rather than a resonator, you'll need a couple of loading capacitors as well.

There have been several versions of an arduino on a chip I've seen.

Depends on how bare bones you want to go. If you run on the internal oscillator, use an ISP for programming (you have to add some entry in the boards.txt to do so). And if you do not mind about not so precise timing (this implies no reliable serial connection). Then you can run Arduino on the naked 328 chip without any external components whatsoever.

Udo

Besides the 22pF load capacitor, you might want to add an LDO 5V regulator so that you can use 4 AA batteries...

Thanks for the input everyone! My plan is to use my 'due' to program the chips with the final code and just use a socket for the chip itself. Power is obviously required as well, and I would likely use either a straight 5v psu, or wire up a regulator of some sort to handle things...

It really amazes me how little is required to make it work.. I am new to electronics, but I'm already feeling myself falling in love :wink:

I am new to electronics, but I'm already feeling myself falling in love

Another Arduino nerd falls victim to her charms. When is the wedding planned for :smiley:

Lefty

Just to revise my required list (and to ask a related question).

Two Choices... (all assuming suitable power will be available)

Absolutely Required:
1 x ATmega328 with Arduino bootloader
1 x 0.01µF Ceramic Capacitors (power)
1 x 10k resistor (auto-reset)

Crystal Option:
1 x 16MHz crystal
2 x 22pF Capacitors (crystal)

Resonator Option:
1 x 16MHz ceramic resonator

My Question: Is there a benefit to using a "real" crystal, as opposed to a resonator? (running with the internal does not impress me much, as timing would and could be important depending on the application). Is one more accurate over the other? or is it just down to cost...

Sorry for the constant questioning for what is probably a simple thing for most intermediate and above users. I have seen tons of breadboard/simple/basic/onchip/etc examples of arduino's and a large part variation, I just wanted to make sure I understand things before I order a dozen or so sets.

Thanks again!

What about a button for the reset?

Is there a benefit to using a "real" crystal, as opposed to a resonator? (running with the internal does not impress me much, as timing would and could be important depending on the application). Is one more accurate over the other? or is it just down to cost...

I don't think there is an issue with accuracy, but if I had to guess, the crystal would be the more accurate of the two. I think it mainly comes down to parts counts and probably availability, as well as parts placement on the PCB. For a custom PCB, you can probably get a smaller size using a resonator than a crystal+caps. However, I am not sure that a resonator has a standard 0.1 inch lead spacing, and so might not be easy to fit on a stripboard or the like for a simple prototype (this isn't an issue with a custom PCB, of course).

I am not sure that a resonator has a standard 0.1 inch lead spacing, and so might not be easy to fit on a stripboard or the like for a simple prototype (this isn't an issue with a custom PCB, of course).

The ones I have purchased in the past all had .1" pin spacing.

Lefty

What about a button for the reset?

If the application calls for one, I would add one of course, I am just looking at what would be the bare minimum to say, run the blink sketch. Basically, I want to know what bits I'd need to have on hand to "whip up" a second/third/etc arduino for completed projects or for off breadboard prototypes.

Thanks for the information about the crystal/resonator.

I would add a 28 pin DIP socket for the processor chip to the list. That would allow you to remove the chip and install it on a standard Arduino board for reprogramming, otherwise you will need to install ICSP pins or serial connections in your standalone construction. The odds are that some bugs will be discovered late in the project or new software functions will be desired or required, so don't assume that the chip will never have to be reprogrammed. It does take very little to build a standalone 168/329 chip to a project and frees up your Arduino board for further development on new projects.

Lefty

I would add a 28 pin DIP socket for the processor chip to the list. That would allow you to remove the chip and install it on a standard Arduino board for reprogramming, otherwise you will need to install ICSP pins or serial connections in your standalone construction. The odds are that some bugs will be discovered late in the project or new software functions will be desired or required, so don't assume that the chip will never have to be reprogrammed.

VERY good point... I will certainly add a socket to the list.

It does take very little to build a standalone 168/329 chip to a project and frees up your Arduino board for further development on new projects.

And this is pretty much the point. Now that issue #146 has been fixed (in lastest svn revision) I can finally put the finishing touches on my pan-tilt application, but I would never want to be without a dev board to continue to play with :slight_smile:

How about an Ardweeny...
http://www.solarbotics.com/products/kardw/

I saw that actually.. (in fact, i just ordered a bunch of stuff from them -- mostly rfid stuff). I will likely pick a couple up just to have them around, but I was looking for a non-breadboard solution, DIY style :wink:

I would change the 0.01uF capacitors (at least the power filter cap) to 0.1uF
ceramic capacitors. Depending on how far away your power source
is from the board you may also want to add some larger filtering caps (10-50uF).

As was suggested I would add local regulation to the board. I like the MC33269.
Be careful with the capacitor selection for this device.

I also would add a protection diode on the reset pin. There is no internal protection diode on the uC for this pin.

Your board is very similar to my new PICO board. The schematic and BOM
for the PICO are in the datasheet at Loading...

(* jcl *)


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Could you explain the reasoning for the cap change? I only ask to learn. I pretty much pulled the parts list from the ardweeny, so your suggestion makes me wonder.... why oh why? :smiley:

If the MCU is destined for it's own board, I would most certainly add onboard regulation. However, if it is just part of a larger board (say a led matrix with half a dozen ic's, resistors, etc, etc.) Would I be better off with multiple power supplies (possibly driven from a single input) or would a single regulated supply (of sufficient current) be suitable?

(mental side track: assuming a single power supply, would the use of optocouplers (or similar) be required to keep things "separate"? As I have said, I am just getting into electronics from 15 years in I.T. so while I know the barebones basics (120v hurts, 220v hurts even more, etc ;)), I am pretty much a blank slate and love to know the why behind how things work, not just... Thats just the way it is...)

Thanks to everyone for your help in this thread, not to mention the rest of the board!

Nick

Could you explain the reasoning for the cap change?

The 0.1uF capacitor is the typical size recommended in this
application. Some applications could require more some less. The
downside of larger ceramic capacitors would primarily be size and
cost.

If you want to quantify the value you could (1) measure the voltage
ripple in your application or (2) estimate the ripple using the
formula I = C dv/dt. You would need to determine the switching currents.

0.1uF is a good comprimise of capacitance/size/cost. Since this local
filtering the placement is almost as critical as the value. Keep this
capacitor close to the uC and keep the pin length short.

If the MCU is destined for it's own board, I would most certainly add
onboard regulation. However, if it is just part of a larger board
(say a led matrix with half a dozen ic's, resistors, etc, etc.) Would
I be better off with multiple power supplies (possibly driven from a
single input) or would a single regulated supply (of sufficient
current) be suitable?

Unless the microcontroller is switching large loads (which usually
isn't the case) I would usually not add a separate regulator. I have
built systems where the unregulated bus was distributed and local
regulation was used for different sections.

If the distance between the uC and regulator is large you may want to
add some larger filter capacitors near the uC. I place the 0.1uF
withing a 100-200mils of the uC. The larger filter caps within a few
inches or so.

On my boards like the ZB1 and NBx I have output pins for the
regulated voltage and the unregulated bus. This enables each
application to provide additional voltage regulation.
The schematics are in the datasheet.

(mental side track: assuming a single power supply, would the
use of optocouplers (or similar) be required to keep things
"separate"?

If you are interfacing to line voltages you should have isolation.
You should be powering from an isolated supply (like a wall-wart)
and be using solid-state or mechanical relays. Almost all solid-state
relays have internal optical isolation. Mechanical relays are isolated
by the driving coil.

(* jcl *)


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