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2026  Using Arduino / Project Guidance / Re: internet of things project on: February 16, 2013, 02:42:00 pm
http://bit.ly/UrWkXe
2027  Using Arduino / LEDs and Multiplexing / Re: Power supply questions for the Max7219 on: February 16, 2013, 02:38:25 pm
As long as everything runs on 5V, it can be supplied by one common supply and the current will flow as required. The LEDs are controlled, but not powered, by the Arduino. The MAX7219s actually supply all the current for the LEDs. The SPI interface by which the Arduino communicates to the 7219s consists strictly of logic signals involving very little current or power. So I would not expect the Arduino to consume more than 40mA or 50mA (assuming an Uno) if there are no additional loads connected to it.

Be sure the power supply is able to supply the total current required. It would be good engineering to have some headroom, so I might size the power supply so that it can deliver at least 125% to 150% of the maximum expected load.

Since the LEDs consume a relatively large amount of current, good bypassing is also called for. Check the MAX7219 datasheet, but IIRC, it recommends a 10µF electrolytic in parallel with a 100nF ceramic capacitor on each chip.
2028  Using Arduino / LEDs and Multiplexing / Re: Power supply questions for the Max7219 on: February 16, 2013, 01:42:11 pm
I'm not sure what it means to split a transformer. (I am aware of split windings but assume those would not be accessible in a wall wart even if they are present.)

You are aware that the Arduino can be powered directly from 5V by connecting it to the 5V pin? The single wall wart can do the whole job, assuming it has sufficient current capacity to run everything. The 7-12V input jack is convenient for higher voltage and/or unregulated supplies, but is not the only way to power it. In that scenario, I'm not sure I'd try to draw 600mA through the Arduino's on-board regulator, it would probably get quite warm and maybe even shut itself down.
2029  Using Arduino / Sensors / Re: How to measure the frequency of an ac signal and convert it to a voltage on: February 16, 2013, 10:52:29 am
Try one of the frequency counter sketches, use the measured value to drive a PWM output, and integrate it?
2030  Community / Exhibition / Gallery / Re: First OSH Board and surface mount project. on: February 16, 2013, 10:45:18 am
Nice job, and welcome to the dark purple side!
2031  Using Arduino / Networking, Protocols, and Devices / Re: mesh network between xbee pro s2b on: February 16, 2013, 10:38:44 am
I just shut down my coordinator, and sure enough, the other devices kept working.  Then I shut down one of the other devices (a router) and turned it back on, it couldn't connect.  I let it try while I crawled back up into the attic and turned on the coordinator and the disconnected router hooked up in a few seconds.  There was an end device sleeping and waking up the entire time that kept working just fine through the whole episode.  WTF??

Sorry to make you crawl through the attic smiley-eek  When you say the router couldn't connect after being turned back on, what was the specific symptom? Are JV or NW set to non-default values?

Quote
...the network doesn't come back up until the coordinator does...

When is the network considered "up"?

Most of my XBees have an "associated" LED, the meaning of which I misinterpreted for some time. What it doesn't mean is that "I am actively connected to a network and can transmit and receive." Consider a two-node network, a coordinator and a router. Configure them and get them talking. Then power both off. Now power up the router only. The "associated" LED will still blink, indicating that the router is still associated to a network, and when it can again connect to that network, it will then be able to transmit and receive.

What the associated LED does mean is more like "I joined a network (coordinator required for that) and nothing has happened to cause me to leave it." It's just an internal status in the individual module that doesn't necessarily reflect the current ability of the device to actually function on the network.
2032  Using Arduino / Networking, Protocols, and Devices / Re: mesh network between xbee pro s2b on: February 16, 2013, 10:11:48 am
Oh yeah! I just noticed that the mesh network documentation was written by you Jack. Good work! You are a "mesh network" saver!! smiley-lol

And sometimes I'm just a mesh. But glad to help in some small way smiley-grin
2033  Using Arduino / Networking, Protocols, and Devices / Re: mesh network between xbee pro s2b on: February 15, 2013, 09:57:59 pm
When you get ready to add your third XBee, think carefully about where you're going to put the coordinator.  For example if you choose to hook it to a laptop, the network dies (yes, it quits working entirely) when you close the lid on the laptop.

Actually not! The coordinator is only needed for new devices to join the network. The coordinator can go offline and other devices that are already associated to the network keep operating.
See: http://arduino.cc/forum/index.php/topic,146089.msg1099076.html#msg1099076

Of course this still doesn't make hooking the coordinator to a laptop a good idea! (except maybe for testing purposes)

2034  Using Arduino / Installation & Troubleshooting / Re: Windows 8 incompatibility ? on: February 15, 2013, 07:05:01 pm
The signed drivers have been tested and approved for inclusion in the next releases. The only thing that's new is the cat containing the signature. The driver is still the same old non-included usbser.sys so there's not much to test.
I'd say it's safe to use it.

Like I said, I wouldn't lose any sleep over using it.
2035  Using Arduino / Microcontrollers / Re: Interesting. on: February 15, 2013, 06:10:29 pm
We've come a long way, eh. I read that the ARM6 processor only has about 35K transistors. I've always wondered about the AVRs but haven't found anything very authoritative. With a µC, it'd be nice to see the memory and peripherals broken out.
2036  Using Arduino / Installation & Troubleshooting / Re: Windows 8 incompatibility ? on: February 15, 2013, 05:56:42 pm
There's a hoop that needs to be jumped through to install unsigned drivers:
http://windows.microsoft.com/en-US/windows-8/windows-startup-settings-including-safe-mode

Wouldn't it be better to install the signed drivers than to modify your OS to accept unsigned drivers?

Perhaps so. But it's not an OS mod per se, it's a one-time setting that gets reset with the next boot. OTOH the signed drivers are in test status. In this case I wouldn't lose sleep either way though. You pays your money and you takes your chances.
2037  Using Arduino / Networking, Protocols, and Devices / Re: mesh network between xbee pro s2b on: February 15, 2013, 04:37:01 pm
The XBees automatically create the mesh network, you don't need to do anything special to have it happen. Be sure to get a copy of the Digi Product Manual and become familiar with it. This is one of the best sources of information.

Here is the simplest way that I have found to get them talking in AT (transparent) mode.
2038  Using Arduino / Installation & Troubleshooting / Re: Windows 8 incompatibility ? on: February 15, 2013, 12:11:50 pm
There's a hoop that needs to be jumped through to install unsigned drivers:
http://windows.microsoft.com/en-US/windows-8/windows-startup-settings-including-safe-mode

It's working like a champ here. Actually, I'd modify those steps slightly:

1.   Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. (If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, click Settings, and then click Change PC settings.)

2.   Under PC settings, tap or click General.

3.   Under Advanced startup, tap or click Restart now.

4.   On the Choose an option screen, tap or click Troubleshoot.

4a.   On the Troubleshoot screen, tap or click Advanced options.

5.   On the Advanced options screen, Tap or click Startup Settings.

6.   Tap or click Restart.

7.   On the Startup Settings screen, choose Disable driver signature enforcement.

8.   Sign in to your PC with a user account that has administrator rights.

2039  Using Arduino / Programming Questions / Re: help with getting CTC Timer1 clock out of chip on: February 14, 2013, 11:52:26 pm
Here's an example. A couple of good intros to AVR timers:
http://fourwalledcubicle.com/AVRArticles.php
http://www.gammon.com.au/forum/?id=11504

Code:
//Output a 1250Hz signal on Arduino pin 9
//Toggles the pin based on dividing the 16MHz system clock
//frequency by 6400. Toggling the pin effectively adds another
//factor of two, so the resultant frequency is 16MHz / 100 / 64 / 2 = 1250Hz

void setup(void)
{
    pinMode(9, OUTPUT);
    TCCR1B = 0;                                     //stop the timer
    TCCR1A = _BV(COM1A0);                           //toggle OC1A on compare match
    OCR1A = 99;                                     //divide by 100 (timer counts from 0 to 99)
    TCCR1B = _BV(WGM12) | _BV(CS11) | _BV(CS10);    //start timer, CTC mode, prescale factor 64
}

void loop(void)
{
}
2040  Using Arduino / Programming Questions / Re: help with getting CTC Timer1 clock out of chip on: February 14, 2013, 11:33:26 pm
Or tell us what you're trying to do.

But I'll make a guess: Are you trying to divide the system clock frequency by 6400 and output the result on a pin so it is observable with a scope? Not sure why the interrupt would need to be enabled.

If so, try using compare match by setting TCCR1A appropriately. The resulting signal will then be output on the OC1A pin (Arduino pin 9) or IC1B (Arduino pin 10).

Don't assume register values are the initial values as documented in the datasheet, as the Arduino core does some initialization for PWM, etc. So if I want to use the timer for my own purposes I usually start with

Code:
TCCR1B = 0;    //stop the timer
TCCR1A = 0;
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