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46  Using Arduino / Networking, Protocols, and Devices / Re: Just a quick question on logging (Leonardo) on: February 14, 2013, 07:20:09 pm
I don't know what causes that, sorry. I noticed myself that the keyboard emulation is sometimes slower than expected.

You could run a test with a very simple text editor. To see if that is a lot faster.
Perhaps you can let the Arduino (with keyboard emulation) write to a file that can be imported in Excel.

For logging, you could also add a SD card shield, and write the data to a file on the SD card. Afterwards you plug the SD card in the computer to read the data.
47  Using Arduino / Networking, Protocols, and Devices / Re: Just a quick question on logging (Leonardo) on: February 14, 2013, 06:43:45 pm
Did you use the serial output via the usb ? or the keyboard emulation.
That serial communication is a software serial port. It is not very fast.
I don't know about different speeds with different computers. Did one have a slow usb 1.1 hub ?
48  Using Arduino / Project Guidance / Re: arduino to record and play back voices? on: February 14, 2013, 02:54:28 pm
You need extra hardware for that, like a wave shield or voice shield.

Here are a few:
http://www.adafruit.com/products/94
https://www.sparkfun.com/products/9799
http://spikenzielabs.com/SpikenzieLabs/VoiceShield.html
https://www.sparkfun.com/products/10963

But you could also use a digital voice recorder, and connect (reed)relays to the buttons. So the Arduino can operate the voice recorder.
49  Using Arduino / Programming Questions / Re: Constant vs. #define Macro on: February 14, 2013, 12:58:35 pm
A "#define" could be overwritten without error.
A "const int" can not be overwritten with a different value.
And the compiled sketch has the same size.
50  Using Arduino / Networking, Protocols, and Devices / Re: Mixed Parity Odd and Even in Serial Protocol on: February 14, 2013, 09:41:17 am
I think it is allowed to call Serial.begin() multiple times.
Receiving data is probably interrupted, but I assume that you are not receiving data at the same time.
http://arduino.cc/en/Serial/Begin

Using Serial.end() stops the serial port.
So I would try this:
Use Serial.begin() with baudrate and SERIAL_8E1
Write the 3 bytes.
Wait until the 3 bytes are transmitted with Serial.flush().
Use Serial.begin() once more with SERIAL_8O1
Write the next 3 bytes.
And wait again for those bytes to be transmitted with Serial.flush().

Or do you use SoftwareSerial ?
51  Using Arduino / Sensors / Re: Differential pressure sensor on: February 14, 2013, 05:26:35 am
WARNING: The output is not 100mV ... 150mV. It is a bridge sensor. The 100mV ... 150mV is the difference between the output pins. Since the sensor needs 12V the output pins are near 6V, and this is too high for the Arduino.

ADVICE: Buy an other pressure sensor. Look at the sites of Sparkfun and Adafruit to see what kind of pressure sensors can be used with the Arduino. You first have to know if you want a baromic, absolute pressure sensor or a relative pressure sensor.

OPAMP: If you want to use this sensor, you have to use an opamp. But you have to use a good regulated 12V for the sensor and a good 5V for the Arduino. Opamps like the INA128 can be used as opamp. I think they operate at a low voltage like 5V and allow the inputs to be a higher voltage.

This is a simular pressure sensor : http://playground.arduino.cc/Main/SPX3058D
That pressure sensor uses 5V, which is okay for the Arduino. By connecting it directly to the Arduino inputs, the calculated pressure is very inaccurate. But the sensor was inaccurate anyway, so it was still usable for me.
52  Using Arduino / Sensors / Re: Is it possible to use the Sensors for this on: February 13, 2013, 09:18:49 pm
Yes, that's possible.
You have to use a light or led and a light sensor.
It is a very simple task and the Arduino can do that very quick.

You have to try a few things to learn what the best sensor and light is.
53  Using Arduino / Sensors / Re: LuminOx oxygen sensor on: February 13, 2013, 07:34:16 pm
You can use the 5V pin of the Arduino to power the sensor.
The term "3.3V TTL level RS232" indicates that the serial connection is with digital signals of 3.3V.
The Arduino Uno uses 5V digital signals, so you have to adapt them to 3.3V.

The conversion of RS232 5V to 3.3V is not hard to do, I can't find it right now. Hopefully someone else knows.

The serial port is used to upload a sketch and for the serial monitor.
But if you use SoftwareSerial, you can create a second serial port for the sensor.
http://arduino.cc/en/Reference/SoftwareSerial
That way, you can still send messages to the computer, and have full control over the sensor.
54  Using Arduino / Networking, Protocols, and Devices / Re: /dev/ttyACM0 in bash on: February 13, 2013, 02:28:01 pm
You could set the settings for the serial port, with stty
55  Using Arduino / Project Guidance / Re: New to this. Need advice with USB mouse interface on: February 13, 2013, 12:58:18 pm
That is very interesting, but I can't open the Eagle schematics file.
Is the page more useful : http://fab.cba.mit.edu/classes/4.140/people/andy.bardagjy/input/index.html ?
The datasheet provides also example schematics : http://www.avagotech.com/pages/en/navigation_interface_devices/navigation_sensors/laserstream/adns-9500/
But it seems rather difficult.
56  Using Arduino / Project Guidance / Re: Lamp controller on: February 13, 2013, 08:11:30 am
It can be done.
The Arduino Mega 2560 has more serial ports, and the SoftwareSerial can create serial ports on normal pins on the Arduino Uno.
http://arduino.cc/en/Main/arduinoBoardMega2560
http://arduino.cc/en/Reference/SoftwareSerial

It can be done in (many) other ways.

For example the very cheap 433MHz modules could be used with VirtualWire.
Every slave has to be an Arduino.
http://www.open.com.au/mikem/arduino/VirtualWire/

An ethernet or wifi shield can turn the Arduino into a simple webpage.
So you could control the Arduino with any PC or a tablet.
57  Using Arduino / Sensors / Re: MQ8 H2 sensor on: February 13, 2013, 04:25:35 am
After the burn-in time, they are reasonably stable.
But still for just one type of gas and indoors and for a certain air humidity.

I can't find in the datasheet how sensitive the MQ-8 is to oxygen. You have to test that.
Perhaps you need also an oxygen sensor : http://en.wikipedia.org/wiki/Oxygen_sensor
It seems that a galvanic oxygen sensor is used for simple measurements and a lambda oxygen sensor is used in cars.

The MQ-8 sensor uses 5V for the heat element. The sensor could get 50 or 60 degrees celsius (the metal on the outside). That should be avoided. Ask anyone who works at a natural-gas processing plant, they might freak out.
58  Using Arduino / Sensors / Re: Sensing people standing around a piece of artwork. on: February 13, 2013, 04:03:40 am
You could start with the MLX90614, that's hard enough to detect the number of people.
The temperature you measure depends on the temperature around. On a cold day it is easier to detect people.

I suggest to combine a few sensors.

At least add a PIR motion sensor. You could even use two of them, on the left and right side of the art object. You could use more PIR sensors, like a row of 5 or 7, and shield the front with a small opening for a small beam.

Ultrasonic sensors can measure the distance. For example the ping))) modules. Perhaps you should use just one. I don't know if the ultrasonic sound will interfere if you use more than one.

Some radar motion detectors are not expensive. But you need the complete module with variable sensitivity, not the radar elements without amplifier (as sold on Ebay).

A theramin is something that senses if someone is very close : http://en.wikipedia.org/wiki/Theremin

Measuring the weigth of the people in front of the art object with a weigth sensor in the floor is out of the question ?
59  Using Arduino / Sensors / Re: MQ8 H2 sensor on: February 13, 2013, 03:46:54 am
I have made a page for those sensors : http://playground.arduino.cc/Main/MQGasSensors
But they are not very accurate, and you have to figure out the ppm for the value yourself.
60  Using Arduino / Interfacing w/ Software on the Computer / Re: Interfacing techniques: Help!!! on: February 13, 2013, 03:45:06 am
You can emulate a usb keyboard with the ATmega328 using V-USB : http://www.obdev.at/products/vusb/index.html
If the computer has a serial port or parallel port or PS/2 port or game port, you could use that.
Or using bluetooth, with a bluetooth dongle in the PC.
Perhaps using ethernet or wifi.

And beside those, you could open a device (like a keyboard or a usb audio stick) and connect your ATmega328 to the circuit board of that device.
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