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1  Using Arduino / LEDs and Multiplexing / Re: Bring New Life to Elektor Jumbo clock on: July 27, 2014, 11:49:06 pm
Yes 74HC595 and NPN transistors will drive the LED strips.
I am sure there is existing code to run a clock and read/display a thermal element,
Try looking in the arduino playground
http://playground.arduino.cc/
2  Using Arduino / LEDs and Multiplexing / Re: seven segment display help on: July 27, 2014, 10:43:25 pm
They will if your code is multiplexing properly.
3  Using Arduino / LEDs and Multiplexing / Re: seven segment display help on: July 27, 2014, 10:33:02 pm
Like so. Arduino drives PNP base low to turn it, and segment cathode low to turn the segment on.
PNP used is not particularly sensitive. Must be able to supply 160mA Id, so a >=200mA continuous on part will do.
4  Using Arduino / LEDs and Multiplexing / Re: seven segment display help on: July 27, 2014, 09:46:48 pm
No, with common anode, you need PNP to switch 5V on & off.
5  Using Arduino / Programming Questions / Re: Basic master slave. 3 X Mega boards on: July 27, 2014, 09:44:09 pm
Ok, first, don't go scattering your topics - one discussion, one topic.

Let the boards communicate over the serial ports.
Board 1 sends a message to Board 2 "Hey, send me your data"
Board 2 replies "Okay, here's some data.
Board 3 sends a message to Board 2 "Hey, send me your data"
Board 2 replies "Okay, here's some data".

Now each slave has some data bytes they can work with to do whatever.
6  Using Arduino / LEDs and Multiplexing / Re: seven segment display help on: July 27, 2014, 09:38:47 pm
You need 220 ohm resistor between Arduino pins and the segments,  and PNP transistors between each device's common anode and +5. The Arduino will drive each PNP one at a time so that only one digit lights up at a time, for 2mS or so, the eye will see them all being on together thru "persistence of vision".
7  Using Arduino / LEDs and Multiplexing / Re: Bring New Life to Elektor Jumbo clock on: July 27, 2014, 08:36:11 pm
Arduino + 4 TPIC6B595, very easy to do.
8  Using Arduino / Programming Questions / Re: Basic master slave. 3 X Mega boards on: July 27, 2014, 06:25:08 pm
Why complicate it with I2C? Mega has 4 hardware serial ports, use a dedicated port from master to each slave.
9  Using Arduino / Networking, Protocols, and Devices / Re: Assign communication SPI in another pins Arduino mega 2560? on: July 27, 2014, 05:21:23 pm
SPI comes from dedicated internal hardware, so it can't be re-assigned.
You can do things like add wires from the 50-51-52 (or 51-52-53) pins to other pins to access them, and treat the new pins as inputs only in the sketch so there is no interference.

You would connect the two displays in parallel to MISO-MOSI-SCK and send data to one or the other using separate slave select for each one.

With a 2560, you can also use the USART as SPI, so you can have 2 SPI ports.
I don't know if there is a library for this.

"22. USART in SPI Mode
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) can be
set to a master SPI compliant mode of operation. The Master SPI Mode (MSPIM) has the following
features:
• Full Duplex, Three-wire Synchronous Data Transfer
• Master Operation
• Supports all four SPI Modes of Operation (Mode 0, 1, 2, and 3)
• LSB First or MSB First Data Transfer (Configurable Data Order)
• Queued Operation (Double Buffered)
• High Resolution Baud Rate Generator
• High Speed Operation (fXCKmax = fCK/2)
• Flexible Interrupt Generation
22.1 Overview
Setting both UMSELn1:0 bits to one enables the USART in MSPIM logic. In this mode of operation
the SPI master control logic takes direct control over the USART resources. These
resources include the transmitter and receiver shift register and buffers, and the baud rate generator.
The parity generator and checker, the data and clock recovery logic, and the RX and TX
control logic is disabled. The USART RX and TX control logic is replaced by a common SPI
transfer control logic. However, the pin control logic and interrupt generation logic is identical in
both modes of operation.
The I/O register locations are the same in both modes. However, some of the functionality of the
control registers changes when using MSPIM."
10  Community / Local Groups / Re: Boston, Lincs, UK i.e. the original ? on: July 27, 2014, 05:11:04 pm
What a wimp! Must not have been from one of the bigger cities here.
11  Using Arduino / Programming Questions / Re: Setup executed multiple times?! on: July 27, 2014, 05:08:33 pm
int Poti [19];
elements are 0 to 18

for (int i=0;i<20;i++)
this goes 0 to 19

Going one too far, as Jack points out.

12  Using Arduino / Installation & Troubleshooting / Re: Arduino Uno, USB port case is under electricity? on: July 27, 2014, 12:53:29 pm
If you look at the schematic
http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf
at the lower left you can see the case is separated from Gnd by inductor L1, BLM21.
Digikey shows this as a ferrite bead with numerous values available.
http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&keywords=blm21

The FTDI datasheet, used in the Duemilanove, does not show the shield being connected to anything
http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf
nor does the pdf schematic in this example design file
http://www.ftdichip.com/Support/Documents/Schematics/FT232R/USB232R1.zip

One would expect the shield to be grounded only at  the PC end to prevent ground loops.
In my designs with MIKROE483 modules for USB interface, the shield is connected to Gnd:
http://www.mouser.com/ds/2/272/usb_uart_manual_v100-32094.pdf

Why did Arduino put an ferrite chip there? I don't know.
13  Using Arduino / Microcontrollers / Re: Standard Fuse Settings for 16Mhz ATMega328p on: July 27, 2014, 11:48:05 am
Yes, that one will do.
In the IDE, select Tools:Programmer:USBasp
I have one but never set things up to use it, might be some driver setup needed as well.
14  Using Arduino / Microcontrollers / Re: Standard Fuse Settings for 16Mhz ATMega328p on: July 27, 2014, 01:38:31 am
No, you need a programmer - the programmer connects to the SPI pins for programmer the bootloader in. The IDE can do that, but you need a programmer.
An Arduino can be used as  a programmer:
http://www.gammon.com.au/forum/?id=11635
15  Using Arduino / General Electronics / Re: PWM, Low Pass Filter, Transistor, & P Channel MOSFET on: July 27, 2014, 01:36:05 am
So like an automated guitar with harpsichord kind of sound, that's pretty neat.
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