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16  Using Arduino / Networking, Protocols, and Devices / Re: Simple question about PIN usage on: August 28, 2014, 10:31:31 am
Using a reed switch on such a high frequency signal will be ineffective.
To use a technical term, the signal will piss straight through it.
17  Topics / Product Design / Re: DIY CNC? on: August 28, 2014, 09:07:12 am
A cheap alternative for larger holes is the Q max punch
http://www.amazon.co.uk/Q-Max-Sheet-Metal-Punch-QMA20M/dp/B0055KJGW8
18  Using Arduino / Networking, Protocols, and Devices / Re: Simple question about PIN usage on: August 28, 2014, 09:00:08 am
What do you hope to achieve by this?

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without adding any voltage or interference.
Unlikely.
19  Using Arduino / General Electronics / Re: Connecting a 5V Arduino Pins to a 3.3V Raspberry Pi GPIO's pins on: August 28, 2014, 08:55:58 am
No those resistors are way too high.
I use a 1K and 510R.
Note this only works for Raspberry Pi inputs being connected to Arduino outputs.

For the other way round you need a transistor, FET or some other level shifting circuit.
20  Using Arduino / General Electronics / Re: HC SR04 not working with DC power supply on: August 28, 2014, 06:18:32 am
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the TX led don't blink .
They won't they are controlled by the PC.

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the led doesn't power on.
Suggest something is wrong. Measure the 5V pin and the Vcc pins on the arduino with your multimeter.

If you haven't got a multimeter then why are you doing electronics?
21  Using Arduino / Project Guidance / Re: HC-05 BTBEE + arduino on: August 28, 2014, 04:15:33 am
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but i couldn't get the LED to turn ON only when the BT module receives a specific word or command predefined.
So post that code, maybe we can spot the error.

Next time do not use the quote for posting code but the # icon next to the quote.
22  Using Arduino / LEDs and Multiplexing / Re: NEWBIE Q: Output power of Galileo per PIN on: August 28, 2014, 04:09:46 am
Just to wrap this up:-
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.I have observed that each pin outputs a decreasing amount of voltage every time I activate another output pin.

The port expander used is the CY8C9540A, the data sheet says that a voltage high from any one pin is only guaranteed to be 1V when sourcing 10mA.
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IOH = 10 mA for any one pin, Vdd = 4.75 to 5.25V.
40 mA maximum combined IOH for GPort0; GPort2_Bit3; GPort3; GPort5_Bit2, 3, 6, 7; GPort6.
40 mA maximum combined IOH for GPort1; GPort2_Bit0, 1, 2; GPort4; GPort5_Bit0, 1, 4, 5; GPort7.
80 mA maximum combined IOH.

On the other hand it is much better at sinking current, you can sink 25mA and still have the output voltage below 0.75V
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IOL = 25 mA for any one pin, Vdd = 4.75 to 5.25V.
100 mA maximum combined IOL for GPort0; GPort2_Bit3; GPort3; GPort5_Bit2, 3, 6, 7; GPort6.
100 mA maximum combined IOL for GPort1; GPort2_Bit0, 1, 2; GPort4; GPort5_Bit0, 1, 4, 5; GPort7.
200 mA maximum combined IOL.

That chip is a poor choice for a hobbyist development board. Especially as it is I2C and runs only at 100KHz.

The new  Galileo 2 uses a PCAL9555A chip which as the same current limits but on the high output the voltage will be 0.7 of the supply voltage ( for 5V that gives 3.5V ), so it is better but still poor.

It also can run faster but only at 400KHz so maximum toggle speed of an output has gone up from 200Hz to 800Hz.

The designers just don't get it, despite me telling them personally at the Rome Maker Fair last year that the I/O was far too slow to do anything interesting with the board.
23  General Category / General Discussion / Re: Arduino Newbie on: August 28, 2014, 03:10:49 am
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I was wondering about the Intel Galileo Gen 2. Would this be a good choice?
That is a no also from me as well.
While the processor is fast the I/O is painfully slow. Just toggling an output will only go at 800Hz, on the first version of the board it would only go at 200Hz. While on a simple 16MHz arduino this is about 90KHz.
The Intel designers just don't get real time.
24  Using Arduino / Programming Questions / Re: Help: how to break this while loop in my Arduino Leonardo code on: August 28, 2014, 02:49:52 am
If you want to read four bytes then in the if statement simply do not proceed until the bytes avaliable  is greater than three.
25  Using Arduino / General Electronics / Re: Okay to mount Arduino to Styrene? on: August 28, 2014, 02:42:25 am
There should be no problem but I would connect to ground any unused I/O pins just to be on the safe side.
26  Using Arduino / Project Guidance / Re: Expandir I/O Digital y PWM on: August 28, 2014, 02:00:51 am
Yes it is called RISC OS and it is not a form of Linux at all. smiley
27  Using Arduino / Programming Questions / Re: How to time a loop then move to the next? on: August 27, 2014, 05:36:12 pm
Yes it is possible.
How?
Use a finite state machine as shown inthe blink without delay sketch.
Only you are not blinking but changing the pattern.
28  Using Arduino / LEDs and Multiplexing / Re: Switch Matrix for Keyboard on: August 27, 2014, 05:32:40 pm
If it is for midi then don't you need a velocity measure? That involves a single pole changeover switch and measuring the time between the breaking of the normally closed connection to the making of the normally open one. The time gives the velocity which is the second midi parameter in the note on message.
29  Using Arduino / Project Guidance / Re: Different uses for serial communication on: August 27, 2014, 05:10:40 pm
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Is there a limit to how many devices we can communicate with using the wire library?
The protocol uses a 7 bit address so the number of devices you can get on a bus at one time is 128 plus a master.
After that you have to do some sort of bank switching between sets of addresses.


and then there is RS485 which covers lots of protocols
http://en.m.wikipedia.org/wiki/RS-485
At one place I worked we had door controllers communicating with each other using a protocol based on this system.
30  Using Arduino / Motors, Mechanics, and Power / Re: Solar heating with motorized satellite dish on: August 27, 2014, 05:07:24 pm
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Lets just say for a sake of the argument that code,  which says that sensors are activated every 10 minutes is implemented

The sun moves at 0.25 degree per minute. It subtends an angle of 0.5 degree, therefore the sun will drift right across the focal point in two minutes.
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