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1  Using Arduino / Project Guidance / Re: Arduino easy power saving on: December 25, 2013, 08:36:05 pm
How's this one work as an easy replacement for delay()

http://hwstartup.wordpress.com/2013/03/11/how-to-run-an-arduino-on-a-9v-battery-for-weeks-or-months/
2  Using Arduino / Project Guidance / Re: Using two arduinos for more processing power on: December 22, 2013, 02:09:10 am
Quote
how can we get two arduinos communicating with very little overhead.
That probably depends a lot on the nature of the comms required, pulsing a single pin may be enough, hardware parallel FIFOs are good if you need some real throughput. On a chip with a hardware FIFO on the UART there's almost no overhead in sending some bytes. And you can exchange a single byte using SPI in no time at all with almost no cost to either CPU. And then there's dual-ported RAM memory-mapped into the address space of each processor.

Hi Rob,
You've presented some interesting options there.
1. UART hardware FIFOs
2. SPI
3. Memory mapped dual-ported RAM.

At first glance, I would think that memory mapped RAM would be the fastest and most complex option. Do you have any suggested reading to learn more about it when it comes to AVRs?

SPI seems to be popular with Arduino and associated shields, so I should be able to read up on that easily.

UART hardware FIFOs would be similar to serial communication no? Any links you could suggest for me to learn more about this would also be appreciated.


Thanks in advanced!
3  Using Arduino / Project Guidance / Re: Using two arduinos for more processing power on: December 21, 2013, 11:43:16 pm
The problem with using multiple MCUs in a system is that the task of communication itself on each device requires substantial resources - code space, interface pins (2) and CPU cycles (lots!).

If you are driving the WS single-wire bus chips, then you cannot interrupt the part of the code which dumps the data to them, but they do not require to be refreshed regularly so you alternate this function quite separately with whatever else you need to do to determine the patterns to be displayed.  That "whatever else" is likely to be just as easy to define in full, as to communicate with another module to be told the pattern and replicate it in local storage as an intermediate step.

Hmm I figured this might be the case.
Basically the overhead from the extra communication is too much.

So I guess the real question is, how can we get two arduinos communicating with very little overhead.
4  Using Arduino / Project Guidance / Re: Using two arduinos for more power on: December 21, 2013, 05:24:51 pm
Hi,

If it's just power you're running low on, and there's no need for additional processing you'd also be able to provide that by using a second power supply for the addressable LEDs.  Do you have an idea of the current required for your project yet?  That will determine what you can use - just remember to connect the GND from the external supply to your Arduino even if it doesn't directly supply the Arduino too.

Cheers ! Geoff

D'oh!
I meant power in the colloquial sense, as in processing capacity/speed.
5  Using Arduino / Project Guidance / Re: Using two arduinos for more power on: December 21, 2013, 04:29:54 pm
You aren't exactly giving us much to go on.
How many LEDs? What, exactly, is "everything else"? What sort of display commands?
I was using that as an example. What comes to mind is bitbanging a long string/grid of WS2811 based RGB LEDs.

Have one Arduino responsible for that, and it receives display commands from the "Master" unit that is doing the rest of the work. (Whatever that may be, just brainstorming here)

I'm really just looking for ideas on how to expand the power of an arduino.

For a master-satellite processor setup like this I'd suggest using Arduino Pro Mini's
for the satellites as they are small and cheap
That was exactly my thought. Third party Pro Minis can be had for under $4 each now. So putting two together for a processing power boost seems like a good idea!
6  Using Arduino / Project Guidance / Using two arduinos for more processing power on: December 21, 2013, 03:37:29 am
Hey guys,

I was thinking of spanning a project over two Arduinos.
One will run the LED strip code, and the second will run everything else and issue display commands to the first.

That's an example that comes to mind, but I'm open to discussion about any projects/applications of two Arduinos for more processing power.

It's probably better to use a faster chip (something like an ARM based Teensy comes to mind) when you have a lot of processing to do, but I thought i'd ask anyways.
7  Using Arduino / General Electronics / Re: Lithium cells / batteries. More efficient to step-up or step-down on: December 19, 2013, 03:23:27 am
My gut reaction is that having a single cell is going to simplify things(*) even if it doesn't
bring any efficiency improvement - at the expense of less endurance.

(*) no charge balancing needed, fewer mechanical connections, simpler to monitor
one cell.

Cells are being charged in a balanced charger anyways. None of your other points are concerns of mine. Mostly looking at efficiency here to prolong usable battery life.
8  Using Arduino / General Electronics / Lithium cells / batteries. More efficient to step-up or step-down on: December 18, 2013, 07:50:48 pm
Hey guys,

I'm building a battery powered LED project.
I need a maximum of 1A @ 5v. Current draw will typically be less.
I want to use "14500" lithium cells.
I plan to use a separate regulator board (to meet my current demands) and bypass the onboard regulator of the arduino.
Size/weight are issues. Through-hole components preferred for ease of prototyping.

1. Is it more efficient to step up a single 3.7v cell or step down two cells in series (7.4v)?
2. Will I run into issues using 14500 cells in parallel to increase my capacity?
3. Will I run into issues using 14500 cells in series? (They have onboard protection circuits)



Possible equipment options:
Batteries: (upto 2C discharge rate) http://dx.com/p/trustfire-protected-14500-3-7v-900mah-rechargeable-lithium-batteries-2-pack-26124
Voltage Regulator:
Both: http://dx.com/p/mini-dc-dc-voltage-stabilizer-regulator-module-red-126106
Step up (TDFN package): http://www.maximintegrated.com/datasheet/index.mvp/id/5770
Step up (TDFN package): http://www.maximintegrated.com/datasheet/index.mvp/id/5127
Step up (SOT23 package): http://www.maximintegrated.com/datasheet/index.mvp/id/2451



9  Using Arduino / Microcontrollers / Re: Ebay switching power supply. 5.32v with no load. Safe? on: December 13, 2013, 04:44:19 pm
The 5V atmega mcus are rated at 6V absolute maximum, and I'm not aware of any other components on an Arduino that are rated at a lower voltage. So 5.32V should be OK. You will probably find that the output voltage drops somewhat when you connect the Arduino to it.

As I quick test, I connected a Nano and didn't see any voltage drop. But with an additional load on top of the Arduino I might.
10  Using Arduino / Microcontrollers / Ebay switching power supply. 5.32v with no load. Safe? on: December 13, 2013, 04:37:46 pm
Hey guys,
Bought a cheap switching power supply off of ebay, and it's putting out 5.32v with no load on it.

Food for thought: The spec for USB is +-5%, so USB ports could be putting out up to 5.25v

Is it safe to use directly on the 5v arduino pin? I think I remember up to 5.5v is safe, but i'm unsure.
11  Using Arduino / Project Guidance / Arduino easy power saving on: December 12, 2013, 02:57:35 am
Hi guys,

Just starting to explore power saving options for my battery powered projects.

I think a good place to start would be a simple replacement for the delay() function, that uses less power.

Here's what I've found so far:
http://www.rocketscream.com/blog/2011/07/04/lightweight-low-power-arduino-library/
http://www.reddit.com/r/arduino/comments/o5443/so_you_want_an_easy_way_to_save_power/
http://code.google.com/p/narcoleptic/

Are those still valid options, or should I be using something else?
12  Using Arduino / Project Guidance / Re: "Funduino" pro mini clone - running at 3.3v and 16mhz on: December 11, 2013, 07:29:01 pm
Quote
've got a Pro Mini clone that was labeled as 5v, 16mhz when I ordered it. Only paid $6 for it too!

Ummm.  I have ordered over time more than 50 of these
http://www.ebay.com/itm/Arduino-PRO-MINI-ATMEGA328-5V-16M-MWC-avr328P-Development-Board-/271251071444
And have NEVER gotten a 16MHz version with a 3.3V regulator.  Since they use pick & place automation on these boards, an entire 3.3V reel of regulators would need to have been substituted accidentally ...
Are you putting 7 - 9 Volts on the RAW power pin?

Ray

Thanks for that link ray! Those are super cheap!
I got mine from Dealextreme.

With 12v on vin I'm getting 3.3v as a digital high. So definitely 3.3v regulator.
13  Using Arduino / Project Guidance / Re: "Funduino" pro mini clone - running at 3.3v and 16mhz on: December 11, 2013, 05:07:43 pm
D'oh! I guess I should have checked the datasheet!

That looks perfect. I'll give it a shot when I have some time and report back!
14  Using Arduino / Project Guidance / Re: "Funduino" pro mini clone - running at 3.3v and 16mhz on: December 11, 2013, 04:36:31 pm
Is there an easy way to get the chip to run at 8Mhz?
The crystal is SMD and there's no way I can solder something that small.

Yes, you can use the "Burn Bootloader" function to set the fuses to run on the 8MHz internal oscillator. At that point, the external crystal will be ignored.

You may be able to find an existing entry in the boards.txt file that comes with the Arduino IDE that suits your needs. If not, there's this: http://www.engbedded.com/fusecalc/

Note, you will need an AVR ISP or an Arduino as ISP to use the Burn Bootloader function:

http://arduino.cc/en/Tutorial/ArduinoISP

Ah, I was aware of the internal crystal, but I thought it was considered inaccurate?
As I mentioned above, my reason for wanting to run the chip in-spec was for timing sensitive projects.
15  Using Arduino / Project Guidance / "Funduino" pro mini clone - running at 3.3v and 16mhz on: December 10, 2013, 04:41:11 pm
Hey guys,
I've got a Pro Mini clone that was labeled as 5v, 16mhz when I ordered it. Only paid $6 for it too!

Turns out, I'm getting 3.3v as a logic high and the chip appears to be running at 16mhz.
I know this is out of spec for the chip, which requires a minimum of 3.6v @16mhz.
From what i've read, people have success overclocking the 328p, but I'd rather run the chip in-spec for any timing sensitive projects.


Is there an easy way to get the chip to run at 8Mhz?
The crystal is SMD and there's no way I can solder something that small.

Can I perhaps set a fuse or hack the bootloader to use a divider of two for clock speed?

Thoughts?
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