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1936  Community / Products and Services / Re: Arduino Cases, Machined aluminum and Walnut on: October 16, 2012, 08:18:24 pm
Pretty! Walnut makes anything look better!
1937  Development / Other Hardware Development / Re: 5V supply help needed on: October 16, 2012, 08:13:05 pm
Sounding like a pretty good size battery. I'd design for at least 2A and an 8-hour runtime, to give some headroom and allow for battery aging. Total energy the battery needs to deliver to the 5V load is 80Wh. Assuming a 3.7V LiPo, that'd be about 21.6Ah. Then figuring 90% efficiency for a boost converter to bring it up to 5V and we're at just slightly over 24Ah. Time to start studying datasheets for batteries, charge controllers, and boost controllers/regulators.
1938  Using Arduino / Project Guidance / Re: Lighting Lots of 1.2v Bulbs...or Bright LEDs on: October 16, 2012, 03:21:39 pm
There are hybrids of the various suggestions as well, e.g. multiplex the LEDs as a 7x5 matrix, use a shift register for the 7 columns, and drive the rows via MCU pins.

Populate the entire 7x5 matrix, add a real time clock, and with a little extra code, the thing could be laid out like a calendar and work fine from year to year. Not sure if that's the look you're after though, and I'd probably explore simpler solutions first smiley-grin

Merry Christmas!  (Now that's really rushing the season isn't it!)
1939  Using Arduino / Networking, Protocols, and Devices / Re: XBee to XBee on: October 16, 2012, 03:14:46 pm
If the router is sending and the coordinator is receiving, which is what I understood earlier, then DH and DL can remain at their default values of zero, this causes the traffic to go to the coordinator.

But glad you got it working.
1940  Using Arduino / Networking, Protocols, and Devices / Re: XBee to XBee on: October 16, 2012, 09:47:15 am
I think the code looks fine now. IF or WHILE does not matter.

I'm not terribly familiar with those XBee shields, I just use adapter boards. I know there are jumpers that need to be set up correctly, they will need to be different for programming the XBees vs. operating. In addition to the associate LED, is there another one, possibly labeled RSS or similar? This would illuminate when data is transmitted.

I'm assuming the XBee "AT" firmware is loaded, as opposed to the "API" firmware.
1941  Using Arduino / Networking, Protocols, and Devices / Re: XBee to XBee on: October 16, 2012, 08:50:30 am
I see two issues with the receiver code. First, it will attempt to read data when none is present. Second, it will potentially miss data while it delays for 15 seconds.

The receiver code should not have delay() in it, and should test for the presence of an incoming byte before reading/printing it. See Serial.available(). Note that it is not reasonable to expect that the two Arduinos stay in sync by virtue of the delays being the same.
1942  Using Arduino / Project Guidance / Re: Lighting Lots of 1.2v Bulbs...or Bright LEDs on: October 16, 2012, 08:38:34 am
There are 20 pins, but still not enough, 0-13 and the analog inputs A0-A5 can function the same as the digital pins as well.

Several choices here:

1. Use shift registers to provide more outputs. 74HC595 shift registers have 8 outputs and can be cascaded, so four would be needed.

2. Use a multiplexing chip like the MAX7219 or MAX7221.

3. Multiplex the lamps directly with the Arduino.

(1) Will be the simplest code, but lots of wires, (3) Will be the least complicated electrically, but the code will be more difficult, (2) is somewhere in between.

FWIW, if it were me, my preference would be LEDs over 1.2V incandescent bulbs. Current drawn from Arduino pins should be limited to 20mA.
1943  Using Arduino / Microcontrollers / Re: Is there Brown-out detection for Arduino Uno? on: October 16, 2012, 07:28:25 am
Page 54 of the datasheet shows that I can read a brown-out reset flag. And also the watchdog reset flag. That's nice to monitor.

I hope someone else can confirm, but I think the bootloader may get in the way of that.
1944  Using Arduino / Project Guidance / Re: Counting on: October 15, 2012, 10:56:04 pm
First, please don't cross-post. I'd go delete the other post.

This is indeed a straightforward project. With a Mega there are enough pins to drive the displays directly, they wouldn't even need to be multiplexed. I'd think most optical interrupters could be treated as a digital input signal as opposed to analog.

So yeah, simple, but we all have to walk before we run. What have you tried so far? Check around for tutorials, GIYF.
1945  Development / Other Hardware Development / Re: 5V supply help needed on: October 15, 2012, 10:29:28 pm
Just wanted a general feel for the circuit complexity, didn't mean for you to make a career out of reverse engineering it. LM358s are op amps, maybe doing voltage or current sensing of the battery or load. Not familiar with that MCU but I figured there'd probably be one at least. Wouldn't be surprised if there were a dedicated LiPo charge controller and then regulators for the output too. Did you get a current reading on your circuit?
1946  Development / Other Hardware Development / Re: 5V supply help needed on: October 15, 2012, 07:45:05 pm
Hmmm, well I'm not that up on LiPo battery prices, but assuming similar capacity is required, I wonder if just the batteries wouldn't rival the cost of the Anker. But I get the third-party concern. Of course if the plan is to build dozens, hundreds, etc., then lower prices could be had. But to build in some of the other bells and whistles, low current cutoff, etc., will involve extra engineering effort. How complex did the Anker circuit seem to be?

But we're still working in the dark, without knowing the actual current requirements, it's hard to know how much battery is needed.
1947  Development / Other Hardware Development / Re: 5V supply help needed on: October 15, 2012, 07:13:46 pm
I don't really know anything about the Ankers. Could you tell if the four batteries were connected in parallel? Sounds like it does everything you want, so why not just use it? It's pretty much gotta be a fancy version of what I described earlier, probably with some intelligence built into it to do the soft switch etc.
1948  Development / Other Hardware Development / Re: 5V supply help needed on: October 15, 2012, 05:46:21 pm
Sounds good. The switching supplies are much more efficient whether they are boost- or buck-type (i.e. lowering voltage). Efficiencies of 90% or higher are common.

Edit: Do you know how long the Anker 10Ah will run the circuit?
1949  Using Arduino / Microcontrollers / Re: Is there Brown-out detection for Arduino Uno? on: October 15, 2012, 05:02:57 pm
The brown-out detector can be set for 1.8, 2.7 or 4.3V via the extended fuse byte. Arduino Unos are set for the 2.7V level. I'm currently working on a project where it was beneficial to change it to 4.3V.

Isn't 2.7V a bit low? At 16 MHz the processor requires 3.78V. So it would become unreliable before the brown-out reset kicked in.

Agree completely, but it is what it is!
1950  Development / Other Hardware Development / Re: 5V supply help needed on: October 15, 2012, 05:00:07 pm
I figured the max current would be something less than 1A if it's running on a 5V/1A supply now. So that's USB, not a wall wart or something?

For starters, I'd definitely measure/know the current requirements. Linear voltage regulators do nothing but waste power, so not good for battery powered circuits. You mentioned 3.7V, I assume that's LiPo. I might look to a circuit like this which can charge the battery and power the load simultaneously, or run on just the battery. I'd then follow that circuit with a switching boost regulator to take the 3.7V up to the required 5V. That will be a lot more efficient than a simple (linear?) regulator to drop 7.4V to 5V.

Just select a 3.7 battery that has a mAh capacity compatible with the load and run time requirements.



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