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16  Using Arduino / Sensors / Re: GY-521 gyroscope/accelerometer breakout board on: March 08, 2013, 11:53:45 am
They are the raw values from the sensor. So the values you get are normal.

17  Using Arduino / Programming Questions / Re: Time and TimeAlarms Libraries – Ask here for help or suggestions on: March 07, 2013, 09:09:18 am

Hello Michael,
I placed this code in a class:
And I could add the 'get', 'set', 'read' and 'write' functions.

But I don't understand the difference between the 'sysTime' and the time in the RTC.
Are they synchronized with the 'syncInterval' ?
If the Arduino is running a little slow, it is no problem.
If the Arduino is running a little faster, it could cause a glitch for the number of seconds.

How is this handled ?
I do not know how this is done in a PC or other embedded system. I was just wondering what would happen.
18  Using Arduino / Sensors / Re: Drift of values read by Arduino MPU6050 sensor on: March 03, 2013, 07:41:47 am
Sorry, but I can't help with this.
I would assume that the raw values would drift, and using the DMP would reduce that.
Perhaps some timing is not right in the libraries of Jeff Rowberg. He is also on this forum:;u=30149

Perhaps you can tell more, what values ? which library function ? how much drift ? do you use the example code, or your own code (please upload your sketch).
19  Using Arduino / Programming Questions / Re: Creating a library for MPU-6050 using KRODAL's code on: February 27, 2013, 08:56:29 am
There are two pages for a library:

I can't help with the library. My sketch is only the basic interface, following closely the datasheet.
20  Using Arduino / Sensors / Re: trouble reading two accelerometers sharing same pins on: February 18, 2013, 02:57:46 am
It looks like a normal SPI interface. So with two pins for CS, it should be possible.

The best way to make this work, is to create a class. If the class is created the pin for CS is copied into a variable in that class.
But I don't have a H48C sensor, so I can't make that class.

Can you please upload your code ?
(Use the button with the '#' above the text field for tags around your code).
21  Using Arduino / Programming Questions / Re: RX TX programming and map function on: February 16, 2013, 07:59:18 am
The Leonardo has two serial ports.
One for the serial monitor on the PC.
And one on pin 0 and 1.

A library is used for those.

You should try some examples with the 'Serial' library.
And send some strings to the serial monitor.

After that, try Serial1 on the pins 0 and 1. And use that for the bluetooth module.
22  Using Arduino / General Electronics / Re: bridge rectifier problem on: February 16, 2013, 07:53:43 am
Did you add a capacitor at the DC output  of the bridge rectifier ?
If so, this is how it is calculated:
The top of the sine wave is 1.4 * the measured AC voltage.
The diodes have a voltage drop of perhaps 0.7V each.

The output is ( 11.3 * 1.4 ) - ( 2 * 0.7 ) = 14.42 V
Since you are measuring 12.3 V, pehaps that is with a load.
23  Using Arduino / General Electronics / Re: High Voltage Monitoring on: February 16, 2013, 04:44:15 am
A 100k pot could have less good contacts in a number of years.
That would cause the 500V to go to the Arduino.
In such situations I always use fixed resistors, and the correction can be done in the Arduino with a calculation.

It is very dangerous indeed. 500V is dangerous, and 500V in a capacitor is extremely dangerous because there is no current limit.
24  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Mega 2560 with servo controller CM700 on: February 16, 2013, 03:11:45 am
Is this the servo controller : ?
Do you have the USB adapter to connect it to a PC ?
Do you use the RXD and TXD signals to communicate ? Are those 3.3V or 5V level signals ?
How did you connect them to the Arduino Mega, you have to connect RX<->TX and TX<->RX.
25  Using Arduino / General Electronics / Re: High Voltage Monitoring on: February 16, 2013, 02:49:30 am
Yes, the 10-bits (0...1023) have by default a range of 0 to 5V.
By selecting the internal reference, the 10-bits have a range of 0 to 1.1 V.

That is roughly 1mV resolution.
With the resistors I mentioned, the resolution to measure the 500V is 0.7V.
So you can measure the 500 with 0.7V precision.
However, due to the high impedance, and resistor inaccuracy, it is not that accurate.
26  Using Arduino / Installation & Troubleshooting / Re: Toasted??? on: February 16, 2013, 02:42:12 am
I bought the cheapest USBasp programmer on Ebay.
Well, actually I have two of those cheapest, since one of them has timing problems on the USB to my computer.

If you mention something, like the fuse detector, please add a link to it (just copy the url in the text).
If you use another Arduino board to test that, you can use the other Arduino also as a programmer.

Reading 0xFF could be that the value is 0xFF or it could be that nothing could be read.
27  Using Arduino / General Electronics / Re: High Voltage Monitoring on: February 15, 2013, 06:05:51 pm
You could use a voltage divider, if it is okay to connect the grounds.
For example two resistors of 22M in series to reduce the voltage and a third resistor in series of 68k for the voltage to the Arduino.
Perhaps adding 1nF parallel over the 68k to reduce noise and perhaps some protection diodes.

The resulting voltage will be : 68k / (22M + 22M + 68k) * 500 = 0.77V
If you set the voltage reference of the Arduino to 1.1V, you can measure the voltage.

I have done something like that with my Geiger counter, and it is doing well.
I measured the voltage with my multimeter and adjusted the calculation in the Arduino to that.
This is my post with the schematic for my Geiger counter:,120390.msg907435.html#msg907435
28  Using Arduino / Networking, Protocols, and Devices / Re: Mixed Parity Odd and Even in Serial Protocol on: February 15, 2013, 01:47:32 pm
Serial.println will add a CR LF, but Serial.print and Serial.write don't.

If you set the last Serial.begin(), the data can be received. But only in the same format. So after you sent the last byte, the device starts responding and that data can be received in a normal way.

CrossRoads, 9-bit data ? Is that even possible ?
29  Using Arduino / Motors, Mechanics, and Power / Re: How to run motor in both directions, using just 2 output pins on: February 15, 2013, 11:23:18 am
nop, will not spend so much on a shield

5 or 6 dollars (inclusive shipping) on Ebay.
Search for "motor shield", it is the same as the Adafruit shield, but an older version with cheaper components.
30  Using Arduino / Programming Questions / Re: Using PROGMEM data on: February 15, 2013, 10:40:11 am
PSTR is the same as declaring a string in flash with PROGMEM.
So you can use sprintf_P() and strcpy_P() with PSTR and also with PROGMEM strings.

The Serial.println() uses the 'stream' class. The 'F()' macro is for that class.
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