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1  Using Arduino / Project Guidance / Re: Switching from 12v to 9V on: April 18, 2013, 09:57:48 pm
OK thanks for your taking your time to help with my doubts.  smiley-cool
2  Using Arduino / Project Guidance / Re: Switching from 12v to 9V on: April 18, 2013, 02:49:55 pm
ORing diodes is sufficient.
Are you expecting the Arduino to source a lot of 5V current to a shield, LEDs, anything?
If so, an external regular to bring the 9/12 down to 7.5V before feeding into the barrel jack connector, or 6V to feed into Vin, would be a good idea.

how can I brig down both bot voltages? 

A this moment I'm planning to interface a temp sensor(LM35) and a RN42 bluetooth module but maybe I'll add a gsm/gps + sd card, but I'm not sure if I can interface everything at the same time.

3  Using Arduino / Project Guidance / Switching from 12v to 9V on: April 18, 2013, 01:42:33 pm
If I'm going to use 12v and 9v to supply an arduino.  Do you think is secure to switch  does two voltages during operation using ORing diodes?
Should I place a voltage regulator or something for protection?
4  Using Arduino / Project Guidance / Re: Bluetooth for proximity on: April 15, 2013, 10:54:15 am
Do you guys know anther way to do this?  I mean, to trigger an alarm once a person carrying some portable device walk out of range.  Or comes in range, we could  use some logic to deal with that.
Yes that is easy, what is hard is knowing what this "range will be", it will not be very well defined.
Basically you need a transponder, that is just a transmitter and receiver that keep exchanging messages. When the exchanges stop you know you are out of range. However that range could be variable depending on a large number of factors.

That's basically what I need.  I don't mind range. I'm looking to trigger an alarm once the system is left unattended.  Do you know any transponder easy to manipulate with a microcontroller or microprocessor?  I've been reading about bluetooth and its hard to manipulate,  we have to deal with the lower layers of the bluetooth software stack to be able to get the RSSI values.
5  Using Arduino / Project Guidance / Re: Bluetooth for proximity on: April 13, 2013, 08:24:09 pm
I really don't mind distance if its going to be on average more than 10 ft.  And if it is out of range the alarm should stay on.   I also found 2 similar projects with some code here:
http://blog.bluetooth-smart.com/2012/09/16/programming-the-ble112-using-bgscript/
http://blog.pothoven.net/2008/05/bluetooth-proximity-monitor-improved.html

is this helpfull?
6  Using Arduino / Project Guidance / Re: Bluetooth for proximity on: April 13, 2013, 06:48:51 pm
Do you guys know anther way to do this?  I mean, to trigger an alarm once a person carrying some portable device walk out of range.  Or comes in range, we could  use some logic to deal with that.
7  Using Arduino / Project Guidance / Bluetooth for proximity on: April 13, 2013, 06:15:20 pm
HI everyone.  I've been looking for info on how to use a Bluetooth module to trigger an alarm if it goes out of range or at a certain signal threshold. Something like this http://www.engadget.com/2010/09/28/blue-watchdog-bluetooth-proximity-alarm-100-decibels-of-aural-t/

What i want its a fixed control unit and a portable transceiver to trigger the alarm the fixed control unit. So I'm going to need to Bluetooth modules.

So far I have found info about using it as a communication module but nothing related to what I'm looking for.

How to pair the two devices?
How can I manage to read it's signal level?

8  Using Arduino / Project Guidance / Re: Is arduino ok for the job?? on: April 05, 2013, 08:28:22 am
At first glance, it looks like the Arduino could do it.    The Arduino Uno has 14 digital I/0 pins plus 6 analog input pins.   The Mega has more.

The RFID, GPS, and GSM/Ethernet should be possible with additional hardware ("shields"), but you'll have to do some research and determine if they can all be  used together on the same Arduino.

Thanks for your answer. I'll work on that. I read that shields can be stacked but i think is better to work on a bread board and then concet the shields to whatever pins i need, but ill have to take care with the code when programing.
9  Using Arduino / Project Guidance / Is arduino ok for the job?? on: April 04, 2013, 10:43:28 pm
Hi everyone,

I have in mind a project with different sensors or switches at same time.  I'm going to use a RFID to monitor proximity, a temperature sensor, an infrared sensor (like those used in garage doors), a GPS to verify location, GSM to send text, a sd card to log info and save info, a limit switch.

Is there enough space to interface all this parts with the arduino or Do I have to look toward a microprocessor based system.
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