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16  Using Arduino / Audio / Re: Why the Sparkfun Si4735 radio shield is all wrong on: May 17, 2013, 03:28:47 am
Did you read the document about the antenna circuit.
The 180nH and the 18pF are for a 'tuned' antenna circuit.
It could increase the sensitivity, but if there is a mismatch, the reception gets worse.

I would like to see protection diodes for the antenna input.

Why is the green led on the SCK pin ?
You have so many unused pins, you might as well use another.

I think that sometimes a diode is used at the reset circuit. Parallel to R1. See the schematic of the Arduino Uno.
17  Using Arduino / Sensors / Re: GY-521 gyroscope/accelerometer breakout board on: May 10, 2013, 06:33:17 pm
You can read the datasheet for the sensitivity.

Or use the i2cdevlib and read about the functions. You still have to read the datasheet to understand how much 'g' the acceleration value is.

About the distance and position, I don't know. Sorry. I never tried to calculate that.
18  Using Arduino / Sensors / Re: MPU6050 SparkFun Breakout to Arduino Uno - No Communication on: May 03, 2013, 01:55:58 pm
That is the Sparkfun breakout board,

Connect it as written a few posts earlier.
Vcc and Vio to 3.3V
SDA and SCL are the I2C bus. The Sparkfun board has already 10k pull-up resistors.
Gnd to Gnd.

I don't know PIC microcontrollers. Do they have a I2C bus ?
19  Using Arduino / Audio / Re: Why the Sparkfun Si4735 radio shield is all wrong on: March 25, 2013, 06:36:12 pm
I don't know if I can make a good RF board.
If perhaps 5 people will use it, it is not worth it.

The breakout board (not the shield) of the SI4735 is good for making your own design.
The link in my first post is to someone who used the breakout board.

But the SI4735 still lacks SSB for the shortwave. And it can't receive the CB band (27Mc).

I bought a used radio with SSB and and was going to connect the buttons to an Arduino. But to do that I would have to take the radio completely apart and it still looked as if it was new. So I don't have an Arduino controlled radio at the moment.
20  Using Arduino / Sensors / Magnetometer HMC8553L undocumented registers on: March 09, 2013, 04:55:00 am

I'm testing the HMC8553L magnetometer.

The documented registers are from 0 (0x00) to 12 (0x0C).
I found undocumented registers at 13 (0x0D) to 59 (0x3B).
Some are Read/Write or Read Only or Write Only.
Some are to change the sensitivity or to invert an axis.

Where can I find more information about this ?

Please don't try to write to those registers, some undocumented registers make the sensor unusable.

21  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.

22  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.
23  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).
24  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.
25  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).
26  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.
27  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.
28  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.
29  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.
30  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.
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