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31  Using Arduino / General Electronics / Re: 433mhz Receiver on: February 15, 2013, 09:12:10 am
Do you have a flat bed scanner, perhaps that can make a good scan/photo.
32  Using Arduino / Programming Questions / Re: Using PROGMEM data on: February 15, 2013, 09:08:33 am
You have a mixture of Arduino and avr gcc code.
The Arduino uses the arv gcc compiler, and every low level function can also be used with the Arduino.

For the Arduino, the 'F()' macro is created:
Serial.println(F("Hello string in flash memory"));
But the 'F()' macro is something typical for the Arduino IDE only.

The sprintf_P() functions are avr gcc functions, they work with PSTR.
sprintf_P( buffer, PSTR("Hello number twelve: %d"), 12);

Perhaps this will be fixed some day. For now it is a little inconsistant.
33  Using Arduino / General Electronics / Re: 433mhz Receiver on: February 15, 2013, 08:54:46 am
I can't find it.
The pins are most of the times : Ground, Data, Vcc, Antenna.
If you look at the board with a magnifier, perhaps you can see which pin is ground and which is the antenna.
34  Using Arduino / General Electronics / Re: 433mhz Receiver on: February 15, 2013, 05:53:47 am
The only way is to buy an other one to compare them.

Was it powered via the Arduino with the USB bus or did you use an adapter with more current ?
35  Using Arduino / Motors, Mechanics, and Power / Re: Arduino mega with 2 dc motors on: February 15, 2013, 05:43:07 am
You need a H-bridge shield for the motors.
But which one depends on the maximum current (stall current) of the motors.
36  Using Arduino / Motors, Mechanics, and Power / Re: How to run motor in both directions, using just 2 output pins on: February 15, 2013, 05:41:34 am
You can use a H-bridge.

I think it is like this:
If you keep one pin low, the other pin uses PWM for forward speed.
To reverse, do it the other way around, the first pin for PWM and keep the second pin low.

If you build a H-bridge yourself, you need extra transistors. Perhaps the best way is to use a H-bridge with optocouplers. With optocouplers you don't have to worry about level shifting or inverting the signal for NPN or PNP transistors.

I like this kind of circuit:
It can be adapted for NPN transistors only.
37  Using Arduino / Motors, Mechanics, and Power / Re: Control 5 bidirectional motors with Arduino on: February 15, 2013, 05:35:26 am
Tell us more.

What kind of motors ? Do you know the type, or can you make a photo of it.
If you tested them for reverse rotation, that doesn't mean they are also manufactured for that.
Do you know the voltage of the motors ? Can you measure the stall current ?
How do you want to control them ? With speed control in both directions ?

To control a motor with speed and direction, a H-bridge is used.
There are many shields for the Arduino with a H-bridge, but some of them are only for 1 or 2 motors.

If you only want full speed in both directions, the DPDT relay could be used. That could even be used with a PWM output of the Arduino to have also speed control.
38  Using Arduino / Installation & Troubleshooting / Re: Toasted??? on: February 15, 2013, 04:24:56 am
To rewrite the bootloader you need a programmer, and use a cable to the ICSP header.
I use the USBasp programmer with an adapter from a 10-pin to a 6-pin header.
If avrdude can't open the device, it can't see the programmer, you have to fix that first.
39  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.
40  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 ?
41  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:

But you could also use a digital voice recorder, and connect (reed)relays to the buttons. So the Arduino can operate the voice recorder.
42  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.
43  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.

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 ?
44  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 :
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.
45  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.
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