You shouldn't have any problems running the AVR processor at 16Mhz @ 4.5vdc, the chip is rated at 20mhz max @ 5.0vdc. The Amtel datasheet shows a graph of speed Vs Vcc voltage.

What you will have problems with is trying to power all those loads with standard 9 volt batteries. They are not designed to supply that kind of current and are very expensive to use as their mah and internal resistance are not very good for more then a few 10s of ma continuously. Rechargeable AA cells wired in series is a better bet if you must have portability.

Lefty

Sounds interesting. My favorite points:

1. And it could still be a full functional arduino...
2. It could be as small as a stamp

Lefty

Yes no one uses Fahrenheit for scientific stuff not even Americans.

Correct, any true nerd, including Americans, know that one should use the Rankine scale, much better range (Yes no one uses Fahrenheit for scientific stuff not even Americans.)  

Lefty

I've heard people say that the Wire library activates the internal pullups.

I believe it does, and seems to work fine with a single close by device. However a stronger external pull-up is normally recommended according to spec and the number of devices on the net.

Lefty

My only comment would be about the 'hardwired' I2C pull-up resistors. Many people use multiple I2C devices in a daisy chain arrangement and it would be better IMO to have jumper clips so one could disable the pull-ups if they wished to have the pull-ups located on a different board in the daisy chain. Just food for thought.

PS: Are you not also missing a ground connection to the external interface connect pads on the far right side of the board?

Lefty

I'm working in a board for Arduino and now the problem is to give the correct volts in the Vin pin from 24volts. Now I'm using a 7810 voltage regulator but....

is this correct?
Vin uses the internal voltage regulator?

Thanks in advance

That will work, the 24vdc is being regulated down to 10vdc, wired to the Vin pin and then the on-board regulator regulates it down to the +5vdc required for the board. However depending on how much current your board and external components draw that external 7810 regulator may be very hot and require a large heat sink.

Lefty

if I understand things right, a logic-level MOSFET has a gate-threshold voltage of 5V or below, right?

No. The gate threshold voltage spec is the voltage where the mosfet just starts to conduct, it's a more useful spec when using the mosfet as a linear amp rather then as a switching device. A normal mosfet might have a typical gate threshold rating of 4-5 vdc, but requires a full +10vdc gate voltage to fully turn on.

Logic level mosfets mean the the device can conduct full rated current at a logic voltage (4-5v)on it's gate. One really should look over the device's data sheet at a graph that shows gate voltage Vs source/drain current flow to see if the device will work with the load you will be using, with the gate voltage avalible.

Lefty

Well the spec sheet for that actuator recommends protecting the actuator with a 10 amp fuse, so that implies that your external +12vdc power supply should have a simular or higher current rating. The solenoid valve most likely takes an amp or less as a guess, but no spec sheet was shown. Look around E-bay or surplus on line vendors for a large enough power supply.

One way to control these with an Arduino is to use a LOGIC LEVEL N-channel MOSFET transistor. The one for the actuator should be rated at least for 50vdc or more and 25 amps or more.

Lefty

But wouldn't also the bootloader have to be recompiled and burned into the chip to keep the baud rate correct for the IDE?

Lefty

I want to control the deliver of eletricity to a device plugged in the eletricity network.

Certainly possible using either a simple relay (electromechanical) or a SSR (solid state relay). It would be necessary to know what the wattage load (voltage AC and current draw) is of what you wish to control so the proper relay or SSR can be specified.

Lefty

Seen on E-bay, a Mega board with ATmega2560 processor chip. Does anyone know if the Arduino IDE support this chip directly (bootloader, signature number, AVRDUDE, etc) ?

http://cgi.ebay.com/Arduino-Mega-ATmega2560-Free-USB-Cable-/280489587581?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item414e7b737d

Lefty

There is more  to designing a good electromagnet as crosh has implied. Seems I recall it requires a 'soft iron' core for best results. Also if the coil is embedded into a cup shaped core it has tons more strength then just a iron rod. The finish and mechanical coupling to what you are trying to lift is also very important. Good luck finding accurate information.

Lefty

I have 4x 328s here.
I can't get ANY of them to work with a three pin resonator or a crystal with two caps.

They only work when I have the two pin crystal plugged in.

If other people have other results, I can't explain the phenomena

It's possible the fuse settings for your 328  chips are set such as not to be proper for the standard oscillator settings. Check out an AVR datasheet for the fuse options offered for oscillator function and if you have the means to read your fuse settings, see if it is set up correctly.

The standard fuse setting for an Aduino 328 are:

low_fuses=0xFF
high_fuses=0xDA
extended_fuses=0x05

Lefty

This is of note and should be made into a sticky: the 328 has internal caps on the clock inputs.
It works with a a 16mhz crystal installed between the two pins. There is no need for caps and a ceramic oscillator doesn't work.

While you may have got yours to work, we shouldn't let this statement stand for others to use in the future, let alone make it a sticky.

1. While the 328 AVR pins 9 & 10 each do exhibit some amount of capacitance to ground, it is not generally enough to let crystals work accurately at their specified frequency, and may cause fail to start up or sluggish starting. Even if a crystal will oscillate without using external padding caps, accuracy will suffer somewhat without the use of external padding caps such that the total capacitance (internal + external) are what the crystal was specified to work with.

2. Three pin ceramic resonators do work with the 328 processor, and yes they have internal padding capacitors wired from the outside pins to the middle pins, just be sure to ground the middle pin. I have at least two 328 processors using ceramic resonators and they work just fine, they just don't quite have the accuracy of a crystal resonator, but in most cases that is not an important issue.

Lefty

I kept coming up a few pins short for my projects.

Buy a Seeduino mega. $1.50 cheaper ($46.50) then a Arduino standard board + your assembled expander ($30 + $18).  

http://www.seeedstudio.com/depot/seeeduino-mega-fully-assembled-p-438.html?cPath=27&zenid=9f6118c193cee9f8b7337d4df91a2eca

Lefty