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1  Using Arduino / Networking, Protocols, and Devices / Re: Ping to CC2540 Host Test App from Arduino? on: August 05, 2014, 06:30:39 pm
The above sketch is correct.
The mistake was mine, the crystal for the CC2540 was 16MHz and should have been 32Mhz.
2  Community / Products and Services / Re: IR Shield - feedback please! on: January 25, 2014, 03:09:54 pm
A few months after the Firelfy project I came across the Disney hats article, none of had remembered reading about it before but I wonder if it was tucked away in the subconscious, Firefly is really similar.
That Disney is always beating me to the punch, they have a great research department!
3  Community / Products and Services / Re: IR Shield - feedback please! on: January 25, 2014, 01:56:22 pm
That is awesome feedback!

I've used the TSSP4038 for continuous data transmission (bootloading over IR) but I wasn't aware it would work at 56kHz.
That's good to know, going to experiment with that.

The VS1838b parts from eBay have been great, but I haven't been pushing them over 32bits.
About 300 of them were in use for the firefly project ( ), where they would send a 32bit packet to set up a wearable social network.
Interestingly, in the firefly I 'detuned' the transmitters to reduce the transmission distance to about 3 meters.
First by reducing the duty cycle to the minimum (1 cycle on) and then by moving away from 38kHz.
Adjusting the transmit power allowed for range sensing but it wasn't implemented in the final build.
The LEDs used were PLCC2 package with 150 degree spread to get the most coverage and least distance.

I like the idea of using two different angles for the LEDs on the shield, probably I will rebag the kits to include that.


4  Community / Products and Services / Re: IR Shield - feedback please! on: January 24, 2014, 08:50:11 pm
AnalysisIR software looks great.
I have an SMD design of the shield as well (for a pre-assembled version) but am gauging interest with the kit first.
Do you have a suggestion for a variable frequency/clocked demodulator that works well with AnalysisIR ?

I normally use IRremote but thanks for the tip about IRLib, it looks good, will start using it.

That funny IR receiver pinout actually supports 3 different positions, only one at a time, they are all wired to the same pin.
The third position is a combination of the other two, to accommodate the larger IR receivers like this one on the right:

It will fit 56kHz as well as the continuous demodulation receivers like the TSOP58038.
Which I was using for IR bootloading an Arduino project that didn't have external access for USB.
That's here:

The IR receiver in the picture is the VS1838B, cheap as chips on eBay.
The IR LEDs are run of the mill 940nm, digikey or eBay.

5  Community / Products and Services / DC Servo Shield for Arduino Nano (underpants)! on: January 23, 2014, 04:34:06 pm
I really like the Nano and have hence created this DC servo motor driver.
The Nano is fully isolated from the power side, no ground loops, no chance of killing the USB port.
Any comments or suggestions?

More details here:

Michael Grant

6  Community / Products and Services / IR Shield - feedback please! on: January 23, 2014, 04:22:41 pm
Here are a couple of IR shields I have made, would like to hear any constructive feedback.

One has a joystick, the other has buttons.
Details are here:
And here:

Michael Grant
7  Using Arduino / General Electronics / Re: PCB Impedance Question on: August 13, 2013, 09:14:38 pm
TX-Line is a super handy free tool for calculating trace impedance...
8  Products / Arduino Due / Re: Floating Point Math? on: October 26, 2012, 12:42:07 pm
Fixed point is very handy for accumulating small bits to gain resolution.
An example using 16 bits, where the top 8 bits (H) are the integer component and the bottom 8 bits (L) are the fractional component.

It's quite easy if you define a new type using a union/struct...

typedef  union
      byte low;
      byte hi;
  };  unsigned  all;
} fixedPoint;

fixedPoint Accumulator;

Adding to Accumulator.all rolls from low to hi.
Access to the fraction component is by Accumulator.low
Access to the integer component is by Accumulator.hi

9  Products / Arduino Due / Re: Arduino Due Mini/Nano on: October 23, 2012, 10:37:29 pm
The SAM3A4C and SAM3X4C are the smaller (100pin/256k) cousins of the 144 pin SAM3X8E on the Due.
Being in the same family would make quick and dirty ...

10  Products / Arduino Due / Re: __FLASH__ attribute or other PROGMEM alternative on: October 23, 2012, 10:32:36 pm
Rob is correct, that is the case with ARM....
11  Using Arduino / Motors, Mechanics, and Power / Re: Problem with stepper motor and H-Bridge. on: July 09, 2012, 07:40:35 pm
Some steppers are 1.8 degree, 200 steps. Some are not...
The Epson steppers might be 3.6 degree, 100 steps.

You will need two H bridges to control a bipolar stepper, one for each coil.
What driver are you using, where is the schematic?

Is this it:
In this case the L293D is a dual H-bridge.

If it just vibrates then you have some motor wires mixed up...
Or you might be trying to move it too fast with too little current.

Try reversing one coil and slow it down...
12  Using Arduino / General Electronics / Re: Using Low votage audio amplifier with a piezo electric sensor. on: July 07, 2012, 07:58:05 pm
Sounds like the load cell is only half a Wheatstone bridge, a resistive divider, you can verify this with a multimeter..
It would be wise to add a divider for reference, that way small fluctuations in supply will be canceled...

13  Using Arduino / General Electronics / Re: Using Low votage audio amplifier with a piezo electric sensor. on: July 07, 2012, 06:28:13 pm
IIRC, all the legs were in series.
For hookup, you will want to research Wheatstone bridge, a couple of links:

The sensors should have four wires, with two active elements and two passive.
Essentially it is two resistive dividers where one is reference and the other changes.

The output of these two dividers is treated as a differential signal going into the AD623...
The instrumentation amp gives an output that is the difference between the two inputs...
14  Using Arduino / General Electronics / Re: Using Low votage audio amplifier with a piezo electric sensor. on: July 07, 2012, 05:27:18 pm
An instrumentation amp is a good start, the AD623 comes to mind, unlikely to find that at radio shack...
Also there are complete chips that include AC excitation for the load cell bridge if you want to get fancy...

Here's an example from 2008:

15  Using Arduino / Motors, Mechanics, and Power / Re: Question, do i need encoder for my project? on: July 07, 2012, 05:25:01 pm
Yes, the load during movement...
If the load/force is constant and the motor power is constant then the speed will be relatively constant given that the heat is negligible...
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