In many tutorials (e.g. http://playground.arduino.cc/learning/4051 or http://bildr.org/2011/02/cd74hc4067-arduino/) it is recommended to connect the multiplexer's enable pin to ground. So the IC is "switched on". When set to high all channels are disabled.

Is the enable pin only for controlling the channels together or has it something to do with power saving? Background of this questions: I want to use four 16 channel multiplexer on an battery powered project. Atm the circuit is designed with enable to gnd. I need the multiplexer only in the daytime so does it have any influence respective power consumption to switch enable high vs to ground at night, when I do not need any channel? Or is the enable pin only an additional switch to control / disable all channels together and not a general on/off switch for the chip?

Lars, what resolution do you have with your scale? We had some ideas and came to the solution not to use an amp but instead an external ADC with a higher resolution than the 10bit Arduino, do you use an other board (e.g. the DUE has a 12 bits resolution)?, see http://hackerbee.com/2013/03/18/100-hive-losses-this-year/ or did we forget something? and a resolution of max load / 1024 is with the INA333 possible? I think it amplifies only the signal or does it do any digitalization?

Btw. do you know the GBoard? http://imall.iteadstudio.com/development-platform/arduino/arduino-compatible-mainboard/im120411004.html I do not know what Arduino board template was used and I think the GSM part was not the new official - the GBoard is a longer time at the market.

And I think it is not battery optimized??! On the other hand "Current Consumption: Type:100; Max: 500 mA (s. http://ftp://imall.iteadstudio.com/IM120411004_GBoard/Documents/DS_IM120411004_GBoard.pdf) wouldn't be too bad if the GSM part can be disabled. Unfortunately the documentation is not too large, so if anybody has information about that, a short note here is appreciated!

About the Uno: You can find some critical parts (and advanced software settings) that should be omitted by optimizing for battery use:

http://www.gammon.com.au/forum/?id=11497

The initial outcome is that, to save power, forget about using a development board. Further savings (like reducing clock speed) would be overshadowed by the huge overhead of the voltage regulator and USB interface chip.

A bare bones Arduino-"Board" without USB interface and also a GSM "shield" without additional voltage regulator and a 100% power disabling option would be really great. If this board can be driven by the new GSM lib (included in the official 1.0.4 IDE) this would be really great.

I can not understand that people developing GSM shields that are intended to be used without Ethernet or Wifi but are still depending on a power jack. A lot application that have no direct internet access will also have no wall outlet. So please share your experiences and findings.

Have a look at this thread:
http://arduino.cc/forum/index.php/topic,148708.0.html

What GSM Shield do you use? Has this any power saving feature or are you planing to switch the whole board on and off?

2. upload the measurements to Cosm.com using a gprs-module. (I just smoked my gprs-shield so this can take some time )

Thanks for this update! May be this combined board is usable: http://imall.iteadstudio.com/im120411004.html It is an Arduino, GSM, XBee, SD-Card on one board. It is cheap, but I do not know how power saving can be done.

Perhaps the new Arduino GSM shield is more power saving and battery compatible but there are some inconsistent information atm:
http://arduino.cc/forum/index.php/topic,148708.msg1156939.html#msg1156939

When <400 mA peak current is correct this would be an interesting board. But you have to pay nearly 100 Eur for the board only!

I found some inconsistent information about the current consume of the new Arduino GSM shield http://store.arduino.cc/eu/index.php?main_page=product_info&cPath=11_5&products_id=244

And for me even more interesting: Is there a power saving mode or can I deactivate / switch off / disconnect power the whole device via software commands or is this only doable via an external hardware switch (MOSFET, Relay, ...)


On the product page http://arduino.cc/en/Main/ArduinoGSMShield you can read

It is recommended that the board be powered with an external power supply that can provide between 700mA and 1000mA. Powering an Arduino and the GSM shield from a USB connection is not recommended, as USB cannot provide the required current for when the modem is in heavy use.

The modem can pull up to 2A of current at peak usage, which can occur during data transmission. This current is provided through the large orange capacitor on the board's surface.

But in a blog post http://blog.bluevia.com/2013/03/11/meet-the-new-arduino-gsm-shield/ is much less current mentioned:

Peak current < 400mA

A tutorial shows also powering the shield via USB, no extra or external power!

The Telefonica / Arduino GSM Shield is now available: http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_5&products_id=244

Unfortunately a bit more expensive than I expected. I heard in an interview that the price would be well below already sold GSM modules, but it is rather more expensive than existing shields. I am also a bit disappointed that the power consumption seems to have the level of already existing shields.

Is the GSM lib included in the Arduino IDE 1.0.4 only for the new Arduino shield or is it also usable with the GBoard?? http://imall.iteadstudio.com/im120411004.html

Btw there is a service similar to Telefonica's from Cumulocity, her is the GBoard bundled with a Deutsche Telekom SIM
http://www.heise.de/hardware-hacks/meldung/Arduino-funkt-in-die-Cloud-1810096.html

Now available: http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_5&products_id=244

Now available: http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_5&products_id=244

Thanks a lot! The delay between switching the multiplexer and reading the pin made it work as expected. In my case 400 µs made the difference! Many thanks!

I like to set up some QRE1113 Reflective Sensors to count bees and copy this project http://www.instructables.com/id/Honey-Bee-Counter/ The disadvantage of the documented setup is that you need with 44 QRE1113 also 44 input pins. So I decided to use a Mux (or more precisely 3 x 16-Channel) to reduce the number of required input pins. This posting is about the sensor part of the QRE1113 not the IR-LED element.

First I set up the QRE1113 referred to this schematic http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Proximity/QRE1113-Analog-Breakout-v11.pdf and did some test. All worked great! You can also use the ~20K internal pullup from the Arduino or a 100K pulldown as described in the original Instructables what leads to different sensitivities, but all worked smooth without the Mux.

In the final version I will use some 16-Channel Analog Multiplexer, CD74HC4067, http://www.sparkfun.com/datasheets/IC/cd74hc4067.pdf. But for testing i grabbed this 8-Channel chip: MC14051B, http://www.produktinfo.conrad.com/datenblaetter/150000-174999/172901-da-01-en-4051_4052_4053.pdf in a local store (the CD74HC4067 was not available).

With the internal pullups enabled I got a enormous sensitivity fare above the spec and not usable (it switches in a range of 70 mm, spec is around some mm, also a halogen bulb in the room "fires" the sensors). Now I tried to replace the internal pullups of the Arduino with external pullups. But I can see only different values on the input with different pullups (1K, 10K, 20K, 100K) but the sensors do not switch by approximation.

I noticed that the MC14051B has a 250 Ohm Typ. “ON” Resistance (I measured a resistance of 100 to 110 Ohm between in and out pin of the Mux when the channel is switched). Could this be the problem with my poor readings? Is this “ON” resistance the reason, or other stuff? How can I fix the problem? Is the CD74HC4067 better (datasheet says 70 Ohm Typ. “ON” Resistance). Or is there a general problem with such sensors as the QRE1113 and multiplexing?

First there is an initial project and some usefull stuff under
http://arduino.cc/forum/index.php/topic,113534.0.html

I think the project is quite good doable with some professional load cells. This cells have temperature compensation, so this problem is done.

Here is a description how to wire a load cell to an Arduino:
- http://cerulean.dk/words/?page_id=42
- http://edg.uchicago.edu/tutorials/load_cell/

I would not develop an own web interface. You can use cosm for beginning.

Thanks for the numbers! 70 mA sounds ok when you're using the GSM part-time only. I wonder why GSM shields need an additional MOSFET to switch the power on or off. Perhaps I'm wrong but I would expect that many will use GSM in a battery powered setting, so power saving or switch off should be a main property. But it seems that I'm wrong. ;-)

Has anyone a project for a longer time (more than a week) with a battery powered GSM shields running and can share some experiences?

Any GSM shield can be powered by batteries. As long as they are big enough. Getting 2A out of small batteries isn't likely.

Yes that's true of course! ;-) So let me specify it. What battery do I need, if will run the GSM module once a day and this for six month: 2 minutes x 30 days x 6 month: means 6 days permanent on.

I think this http://www.ebay.de/itm/SIM900-GSM-GPRS-Shield-module-development-board-IComSat-kit-for-Arduino-/150872501603 is not the way to go:

Current Consumption(pulse) 2000 mA
Current Consumption(Continues) 500 mA

The problem is all data is in the "max" collumn, not data in "Type". So I do not know if this values are overrate the real consumption.

5V @ 500 mA means 2.5W So I would reach about 3.6h permanent on or for a 2Ah battery--for my application--about 100 days

When you do, though, you need the full 2A capability. The shield only sucks that much current in transmit mode.

Yes and I have reservations that this peak corrupts my calculation. Also I do not know what this peak for a Battery means. Is for 2A max. a 3Ah battery sufficient or must it be more or is there an other parameter beside the "Ah" to respect.