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151  Using Arduino / Project Guidance / Re: Cost Effective Proximity sensing on: September 13, 2012, 02:54:48 am

Placing an RFID/NFC reader below the board and placing passive RFID tags on the objects will work just fine for both proximity and identification. Certain models of reader (with their corresponding compatible tags) allow a range as much as several cm.

You might want to tweak the vertical positioning of the reader if you want to mark the detection exactly when the object actually touches the surface (as opposed to 1-2 cm above the surface).

The RFID reader cost might be a little high (> 30 USD) if you buy from a hobbyist shop or in small quantities, but you can very likely get the price < 20 USD if you buy from manufacturer.

What are you trying to design, i.e., what's the application?

Look through the following pages to get some perspective:
152  General Category / General Discussion / Re: ARM-based Arduino Due - where?? on: September 12, 2012, 12:42:28 am
Good point on the Maker Faire. I'm not gonna get my expectations up, but the timing does seem to be about right! And they do have this on the 2012 Program schedule for Sept. 29:

"1:00PM » The Arduino Hour with Massimo Banzi (co-founder of the Arduino Project) & Alf-Egil Bogen (Atmel Corporation)"
153  General Category / General Discussion / Re: Arduino Commercialization on: September 10, 2012, 06:37:48 am
On the page suggested by @dxw00d, the relevant section is the one titled: " Can I build a commercial product based on Arduino? "
154  General Category / General Discussion / Re: ARM-based Arduino Due - where?? on: September 10, 2012, 06:35:19 am
This is Galago:

And the Teensy 3.0 looks pretty exciting too:
155  General Category / General Discussion / Re: ARM-based Arduino Due - where?? on: September 10, 2012, 06:32:59 am
The simplicity is what's got me sticking with (hopes on) the Due too (as with the past Arduino boards), versus RPi and Beagleboard, etc.

And the already established Arduino user community, and the body of work that has already been done -- there are a lot more users, and lots of code, project ideas, and libraries that are already existent that one can work with and tweak to create further new things.

I agree RPi is getting there but for simpler, one-thing-at-a-time applications -- that need the horsepower but not the extra HDMI output for instance -- I'm still waiting for the Due.

Plus after using the Due board as a prototype, I can then easily use the design to make my own tailored version of it when I need to adapt things to my final application.
156  General Category / General Discussion / ARM-based Arduino Due - where?? on: September 09, 2012, 10:47:33 am
There are certain applications I'm developing for, which could benefit greatly from the more powerful specs of a 32-bit ARM running at 96Mhz.

(I know there are alternate boards already fitting that bill, but...)
Does ANYone have any authoritative information on what is going on with the Arduino Due??

It's nearly a year delayed past what was the expected date ("by the end of 2011").

I realize of course that the engineers working on the design don't owe us anything, and frankly they might even be hard at work on this as I speak, but I'm just fascinated that there have been absolutely minimal UPDATES on the progress of this! I'm sure I am not the only one who would be interested to hear the Arduino team or anyone's update on what is going on with the release date of this.
157  Using Arduino / General Electronics / Re: Measure current draw with high precision (not necessarily accuracy) on: August 31, 2012, 11:42:40 pm
@ Nick:
Thanks for the clarification!

I read the self-discharge section of your article, but forgot to consider it in context. In fact, the self-discharge might only be greater if you consider the running of the built-it protection circuitry that Li-ions and Lipos have on board when we buy them in the safe form they're usually sold in (e.g., from Sparkfun or Adafruit, etc.).

So in this context I suppose even about 100 microamps of precision should be more than good enough. Although of course for RELATIVE comparison (where the change from one case to another might be on the order of a few microamps), it would be useful to use a high-precision multimeter as you listed. But again, that's not an issue either, because going by your webpage, when a certain power-saving factor is put into place, it is more likely to create a difference/reduction on the order of nearly milliamps (as opposed to one or two microamps).
158  Using Arduino / General Electronics / Measure current draw with high precision (not necessarily accuracy) on: August 31, 2012, 02:02:33 am
Inspired by Nick Gammon's comprehensive writeup on low-power methods (, I'm now trying to create a barebones Arduino with extremely low-power consumption.

I'm starting with a minimal Atmega328-based setup on stripboard, powered by a Li-ion battery. I want to measure the current draw of the circuit load each time I change something.

What are some methods of measuring the current draw with high PRECISION, ideally with around 1 uA (one microamp) resolution?

I'd prefer to use standard electronics tools: DMM, or oscilloscope, or resistors, etc. But otherwise, pretty flexible on the method since I am measuring draw of entire circuit load (e.g., measured in series with the battery+), as opposed to just a specific part.
159  Using Arduino / Storage / Re: New fast data logging sketches on: August 24, 2012, 04:21:53 am
Fefas, You are more likely to get help on your problem, if you post your programming question (about bit-shifting) in the Programming Questions section of the forum:,4.0.html
160  Using Arduino / Networking, Protocols, and Devices / Re: WIRELESS communication on: August 23, 2012, 08:54:11 am
802.15.4/Zigbee (for example, Xbee Series 1 and Series 2 respectively)
Wifi 802.11

If you're asking only for wireless comm, the above four pretty much cover the main well-defined wireless specifications that are popular in most sensor applications or manufactured products these days, and certainly those are the most popular ones available to hobbyists, to my knowledge.

However, there are some variants of different frequency-transmission, including basic RF transmitter/receiver pairs; e.g., at Sparkfun, you can search for RF Link Transmitter and RF Link Receiver). I've also seen  nRF24L01 modules as well as RFM12B modules used in some Arduino projects.
161  Using Arduino / Networking, Protocols, and Devices / Re: Can a XBEE pro both send and receive serial data? on: August 23, 2012, 08:42:15 am
Yes, Xbee and Xbee Pro are completely equal and pin-compatible, except the transmission power/range (and thus the corresponding power consumption)

And yes, both Xbee and Xbee Pro can be used to both send and receive data. In the simplest scenario, they can be thought of just as direct replacements for RX and TX wire connections between two microcontrollers.

For learning in detail about Xbee modules, I suggest you read the following in the order you prefer (listed here in order of ease of reading):
1) The main page of xbee-arduino library:
2) The book "Building Wireless Sensor Networks with Zigbee, Xbee, Arduino, and Processing" by Rob Faludi:
3) The PDF "Unofficial Xbee Cookbook" by John Foster:
4) The Xbee/Xbee-Pro datasheet (available from Digi website or Sparkfun, Adafruit, etc.)
162  Using Arduino / Networking, Protocols, and Devices / Re: Bluetooth v4 LE HowTo on: August 22, 2012, 08:56:01 pm
@jareriks and everyone else,

Here are a few details regarding Bluetooth 4.0 (or BLE) modules and the status of various projects interfacing them with the Arduino. In my experience, there appear to be currently two main BLE modules being checked out in the Arduino community: the nRF8001 and the BLE112.

(1) The nRF8001
A couple of other hobbyists and I are working on interfacing Arduino with nRF8001 (software and breakout board). I particularly like the nRF8001 because it is a very low-cost ($4-5), tiny 5X5mm chip. Of course it has to be appended with some external circuitry like crystal, etc., but still I was able to do an Eagle layout where I fit the whole circuit within the equivalent area of a CR2032 coin cell -- I really like the fact that I'd be able to make a wireless sensor so tiny and for a fairly low cost, while being able to communicate with my iPhone or Android.
We just yesterday created a github repo for the Arduino interface with nRF8001:
Rigth now, it is empty, but in the next couple of weeks hopefully, the github page will contain both the Eagle schematics for a simple breakout board as well as the Arduino-library side of things, as progress ahppens. Everyone is welcome to contribute to this project; if you want to, just reply here or shoot me a PM, so you can be added.

(2) The BLE112
The Arduino interface with the second module, which is the BLE112, seems to be currently being worked on by Dr. Michael Kroll and independently by Jeff Rowberg (to see their pages, you can google either of their names along with BLE112). The BLE112 is a $15-16 module with an 18X12mm area. It's larger and slightly more expensive, but I really like the fact that the module (which is based around TI's CC2540 chip) is readily packaged, i.e., to interface with an external MCU, Arduino, etc without further part additions.

One more difference (for me, a minor one) is that BLE112 modules can be both host and slave whereas nRF8001 can be slave-only, but for my general hobby projects, slave-only on the Arduino side would be just fine.

Also, above, I mentioned COIN CELL in particular because Bluetooth LE of course seems to be targeted toward low-power, occasionally-transmitting-sensor-type applications, and I think the general cliche statement from these various manufacturing companies appears to be that the module can run off a coin cell for years (but of course, this should depend on the duty cycle). I think the point is that the BLE modules tend to be small in size and can run off coin cells which are usually designed for low current draw (although they allow slightly larger pulse discharge).

Here you can find the links to the datasheets for these two modules:
163  Using Arduino / Project Guidance / Re: Power consumption of the leonardo on: August 20, 2012, 08:09:28 pm
In that case, if you run your design and code like the following, I think you should have no problem reaching well below your desired average 5 mA current draw:

2) WAKEUP once every X seconds/minutes/hours
3) TAKE sensor measurements (sensor = light, etc., whatever you want)
4a) If sensor measurements within desired range, go back to SLEEP
4b) Else If sensor measurements above/below certain threshold, then POWER-ON motor/servo, then send CONTROL signal to motor/servo, thus OPEN/CLOSE door, then POWER-OFF motor/servo, then go back to SLEEP
5) => LOOP

This way, the Atmega and Sensors have a very small duty cycle (depending on how often you set the period of waking up and monitoring), and the Motor/Servo have an even less frequent time of operation. So overall your power savings should satisfy your target

On your board, to allow programmability, you could even include an FTDI 6-pin header or an FT232 chip (which by default will be powered only when USB connected, so that won't be a problem), or you could just use ISP.
164  Using Arduino / Project Guidance / Re: Power consumption of the leonardo on: August 20, 2012, 08:44:40 am
Jantje, I think two points are relevant in your case:

1) Clearly, the Atmega chip is NOT the most power-consuming part, so working on optimizing it (or its clock) won't be as important as optimizing the rest of the circuit. In particular, you said at one point that the motorshield takes 90mA and at another that it averages only 1.2 mA. Which is it?

2) What exactly are you using the motorshield for? It would help if you clarify exactly what its role is (I've read your earlier post but still not clear), because perhaps if it's only a one-time/occasional action on the motorshield, then it is possible to apply this type of power optimization, which obviously is the most ideal implementation for a device (and which you suggested yourself halfway through your post):
Atmega wakes up, Sends out X signal on I/O pins, XYZ part receives signal and does its job, then the WHOLE circuit goes to sleep (i.e., including powering-off/sleep of XYZ part).
Here XYZ part, e.g., could be your sensors and your motors.

By the way, what exactly do you mean when you say the Leonardo is not supported with the Motorshield? Hardware wise, or software? If the former, I would be surprised, unless it has something to do with the geometric pin layout of the shield. If the latter, perhaps we can fix it by looking at the code.
165  Using Arduino / Project Guidance / Re: Power consumption of the leonardo on: August 19, 2012, 08:25:40 pm
You are running off a 7Ah battery.
So, if you play this right using a self-made breadboard Arduino or a stripboard Arduino (which should take an hour at most), and choose the minimal number of correct components, you can get the circuit working for thousands of hours (especially if you use sleep mode judiciously). But that is excluding the power draw from the motor shields and peripherals you have of course. Also, for the self-made circuit, you can simplify things by even completely leaving out the FT232/USB-interface-chip; you can just put a male six-pin header, and use an FTDI cable when you need to upload code from the computer.

Or if you want to use the official Arduino board, from my understanding (looking at the schematic), the FT232/Atmega16U2 won't even be powered when there is no USB connected, so you should have minimal/zero power consumption by it. The voltage regulator's current draw - yes, this is a problem, but you can either mess around by replacing it with a different regulator, or find some way (as Nick suggested) of directly powering the microcontroller/main-circuit with batteries.

By the way, what is the full list of additional peripherals/components/shields you are using outside of the main Arduino circuit? I am curious how much they contribute to the power draw, and if that needs to be looked into first.
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