Pages: [1]   Go Down
Author Topic: Atmega328 powered by a 3.7 volt battery?  (Read 9679 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 8
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Can an Atmega328 +oscillator run off of 3.7 volts without a regulator to be used for 7 channel pulse width modulation with mosfets to drive the leds?

I'm desiring to power it with an 18650 battery. (which charges to 4.2 volts and drains to 2.75 volts)

http://www.dealextreme.com/details.dx/sku.5790
Logged

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 206
Posts: 12851
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset


I believe 3.7 volts is below the threshold for 16 MHz.  Many folks have claimed that running a processor at 16 MHz / 3 volts works but it is outside of the Atmel specifications.

Do you need the processor to run at 16 MHz?
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 8
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

How do I know if I need it to run at 16Mhz? I'm going to be writing code similar to this: http://fritzing.org/projects/arduino-knight-rider-with-8-blue-12v-led-modules/


Do I even need an oscillator? I just know I'm going to make a persistence of vision display (POV).

will I need 16Mhz for this?
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 533
Posts: 26956
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

A 3.3V/8MHz Promini running on a 3.7V LiPo battery will control those LEDs just fine for you.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 206
Posts: 12851
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I just know I'm going to make a persistence of vision display (POV).  will I need 16Mhz for this?
I doubt it.  A 328 running at 8 MHz should do fine.  In which case, you will be able to run directly from the battery.

Quote
Do I even need an oscillator?
No.  But the answer to the next question has to be "yes"...

Do you have a way to change the fuses?
Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 8
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Code:
No.  But the answer to the next question has to be "yes"...

Do you have a way to change the fuses?

I honestly have no idea what you are telling me? Could you restate it? I'm new to all this. I feel like your information is valuable and I don't want to miss it.


Do I need to use anything more than just the naked atmega328 chip?

I'd really like to use just the chip from my arduino uno rather than the pro mini. is this possible?
« Last Edit: January 21, 2011, 02:31:54 am by SpiffyChee » Logged

Netherlands
Offline Offline
Sr. Member
****
Karma: 1
Posts: 290
(:-)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The bare chip needs to be loaded with a 8MHz boot loader and you will need a programmer for that.
The fuses can be changed with the programmer. You can see the fuses as the settings in the bios of a computer.
The fuse settings set things like if you use a crystal or not if the internal clock needs to be divided or not.

Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 533
Posts: 26956
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Sure - research fuses, internal oscillator, 8 MHz.
I've never done it, but I have read instances where others have, so it is possible.

Here's bunch of info on,
http://wolfpaulus.com/journal/embedded/arduino3
likely more than you will be able to use.

Do yourself  a big favor & get a 2nd arduino - then you can keep your deumilanove intact for programming & development, and download into something like  promini for embedding into your project.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0
Offline Offline
Newbie
*
Karma: 0
Posts: 8
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Mann.. there HAS to be an easier way? So I cant just use the external oscillator and the chip with an unregulated battery source??

those batteries charge to 4.2 volts and drain to 2.75

I'm so confused. I just know i need the smallest and lightest weight battery possible and this is discouraging :/
« Last Edit: January 21, 2011, 03:35:35 am by SpiffyChee » Logged

London, GB
Offline Offline
Sr. Member
****
Karma: 8
Posts: 332
Nothing works.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The Jeenode uses 16MHz at 3.3V.
Logged

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 206
Posts: 12851
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset


A word of caution on those batteries... they may require a cut-off circuit to ensure they don't "run dead".  It's my understanding that lithium batteries are damaged when they are run below a certain charge.  I can't tell from the description if those batteries have an internal cut-off.  From the comments, it appears most people use them in an existing device that presumably has a cut-off.

Quote
Mann.. there HAS to be an easier way? So I cant just use the external oscillator and the chip with an unregulated battery source??
Yes.  You can either take a chance and run at 16 MHz (which is very likely to work) or obtain an 8 MHz crystal (or resonator).  But you may have to change the fuse settings to adjust or disable the brown-out detector.  Or, if you go with AA cells, just add a third battery.

Standard AA alkaline batteries typically have more total energy (2700–2900 mAh per cell according to Wikipedia).  The draw-back to alkaline cells is the voltage drop (1.5 full to 0.9 dead).  The benefit is the ability to run-dead and lots of energy per cell.  I have a few gadgets running directly from two AA cells and I'm very pleased with the results.
Logged

Washington
Offline Offline
God Member
*****
Karma: 38
Posts: 790
Firefox & Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

My arduino works down to 2.5v before randomly resetting.
Logged

Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

Pages: [1]   Go Up
Jump to: