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346  Using Arduino / General Electronics / Re: Decoupling shift registers on: January 30, 2013, 07:22:10 am
You can buy sockets with a pre-wired decoupling cap that is connected diagonally across pins 8 and 16.

You could easily do this on a PCB, perfboard or stripboard and site the cap inside the socket and laying flat directly underneath the chip. For SMD it's even easier as the space under the IC is often spare real estate that can sometimes be utilised if you're struggling for room and you are using a socketed DIP.
347  Community / Products and Services / Re: Cheap Fusion PCB Service(Color Free) !! on: January 29, 2013, 07:51:15 pm
I've placed an order for 10 Off 100mm x 100mm boards, so I'll report back here once they arrive.

The total price to the UK was $23.90 + $6.34 shipping, equating to a total payment of £18.91 Sterling.

I've had some smaller boards via Seeedstudio, which is the same Fusion PCB service, so I'm expecting these back at the same quality, which was very good.
348  Using Arduino / Programming Questions / Re: help with ENC28J60 on: January 29, 2013, 11:34:14 am
It won't work with the standard Ethernet library. You need to go search for the ENC28J60 library.
349  Using Arduino / Audio / Re: New library for PWM playback from SD cards: SimpleSDAudio on: January 29, 2013, 06:22:35 am
@tack: have you looked inside the new version? I think I've put your stuff in, but it would be nice if you can try if also autoworker works on your platform as it needs additional stuff in those hardware-settings.

OK, I've now had time to test it and I can report that it works perfectly 'out of the box'. Many thanks for adding those mods to the definitions as it will save re-applying them in future.

I've also tested the Autoworker mode and that also works fine on the 1284P. It has been tested with a 3 minute music file of 27Mb size and it played perfectly in 8 bit stereo full rate, sounding good through a set of hacked active PC speakers.

At the moment this is just running with a 100R in series with each channel. I want to use this now with a little 3W stereo amplifier as an onboard solution. -

Any thoughts on input filtering/control prior to the amp? At the moment I'm thinking of a .1uF capacitor in series and a 10k trimmer to control the input level, as per attached schematic. I don't need to be able to adjust volume by the user, just set it and leave it.
350  Using Arduino / Project Guidance / Re: Lower the voltage comming into the Arduino Pins? on: January 28, 2013, 09:58:46 pm
500 to 700V?
500-700 value for analogRead is what he means, I would guess.

That corresponds to about 2.5-3.5v.
351  Using Arduino / Displays / Re: HD44780 LCD with pre-defined segments on: January 27, 2013, 04:15:40 pm
It sounds like a display from a 3 phase electricity meter or metering/protection relay display panel. L1, L2 & L3 are the three phases. kWh and KvArh are Kilowatt Hours and KiloVoltAmpsReactive Hours/ The upside down circle sounds like a Delta winding symbol. UK low voltage system is from a Star wound secondary, so it could be from another country OR relating to a primary side metering/protection at 11kV or 33kV.
352  Using Arduino / Programming Questions / Re: Problem with shift register on: January 27, 2013, 04:05:09 pm
Maybe it's that the comments say connected to pins 2, 3 & 4 but the sketch actually uses 8, 11 & 12.
353  Using Arduino / Project Guidance / Re: Running out on pins on my Uno ...... !! on: January 27, 2013, 03:55:18 pm
I suspect that this topic has arisen before !!  (Apologises in advance !!)

I'd like to multi-purpose the pins in my current Arduino project.  In essence, can I define a pin TWICE and safely use that definition within it's own "enviroment"


int pinPP_nAddrTag = 12;        // Parallel port nAddrTag
int pinLED = 12;                    // The output LED pin (Also pinPP_nAddrTag)

In Setup()
  pinMode(pinPP_nAddrTag, INPUT);
  pinMode(pinLED, OUTPUT);

Question 1 :  
     Is the attribute of INPUT specified in pinMode associated with the variable pinPP_nAddrTag or with pin 12 ??

As it says it is 'pinMode'; it acts on the pin. In your example code you set Pin 12 to INPUT and then you set it to OUTPUT. Therefore it is no longer an input. You need to be careful what you are doing here as you could damage the pin. Let's say you thought it was an input and set it high; that would turn the pullup resistor on, and you'd be expecting something to pull that pin low, with perhaps a direct short to Ground, against the pullup. If you did that when actually your pin was an output then you could short the pin to ground, exceeding it's current rating and destroy it.

Another way of looking at this is as follows ....

In function 1:
       digitalWrite(pinLED, HIGH);

In function  2:
       int iDataRead;
       iDataRead = digitalRead(pinPP_nAddrTag);

Question 2:
       Should I use pinMode(....) in the above functions to establish whether INPUT or OUTPUT) ?

It doesn't matter, you can't use it in both modes simultaneously. If you use it as an output first in Function1 then as soon as you set it to an INPUT it will go high impedance and your LED will light only dimly.

OUTPUT is a Low Impedance state
INPUT is a High Impedance state

Hopefully, you will be understand what I DON'T understand (or what I need reassurance on !!!)

Thanks in advance !

If you were just using it to send a signal then you could manage it's state and use it for both input and output consecutively. That's exactly how something like the I2C bus works but, you can't keep an output high and driven if you're going to change to input. If you had some way of latching the signal out so it only needed a momentary high then you could do so and then re-use the pin.

It's safer just to use one pin for one thing unless you fully understand the limitations.
354  Using Arduino / General Electronics / Re: Small power source for one century on: January 27, 2013, 10:45:44 am
It's not just the power source you have a problem with, it's the whole device. There is no hard and fast data to prove that any electronics will actually last that long. At the very least you'd need some kind of hermetically sealed container to have a good chance of working preservation, IF you had confidence in a reliable power source.

The chances are that one of the crucial link components will fail way before that 100 year period is up.

Without some form of regular check and maintenance, I'm doubtful you'd get anywhere near the longevity you require.
355  Using Arduino / Installation & Troubleshooting / Re: Troubleshooting sketchy uploads to breadboard on: January 27, 2013, 10:38:30 am
Pin 1 is reset. In your picture it looks like you have one side of your switch going to pin4, with a resistor between the pin and ground. The other side of the switch then goes to Vcc on the other side of the board.

Pin1 should have a 10k resistor to Vcc. Then, from the pin side of that resistor you should go through a switch to ground. Your rest fromt he other Arduino then connects to that same point, onto the pin between it and the pullup resistor.

What is that large electrolytic capacitor in the bottom of the picture?
356  Using Arduino / Displays / Re: Do you have new LCDI2C4BIT Library? on: January 27, 2013, 06:54:42 am
You can get the 'New' LiquidCrystal Library, by fm, at

This replaces LiquidCrystal and LiquidCrystal_I2C in a single library (plus adds support for Shift Register expanders).

You'll need to determine the mapping of your I2C interface and set up the correct constructor though.

357  Using Arduino / Programming Questions / Re: LiquidCrystal_I2C_h not being recognised on: January 26, 2013, 05:37:00 pm
What version of IDE? Have you restarted IDE after copying the files into the libraries folder? You should have a LiquidCrystal_I2C folder inside libraries, with all thw files inside.

FYI, You might also like to consider the New Liquid Crystal Library from fm, as it is a replacement for both LiquidCrystal AND LiquidCrystal_I2C in a single library, with optimisations in speed -

358  Using Arduino / General Electronics / Re: im, running out of pins on: January 26, 2013, 03:38:49 am
Tyre are various options once you start using up all pins.

1) Move to another uC with more pins, such as 644P, 1284P or 2560.

2) Put other devices on shared buses, such as I2C and SPI, to free up other pins. This can require use of port expanders such as the PCF8574 which gives 8 input/outputs for 2 shared pins on the uC.

3) Use a voltage divided to read multiple buttons on an Analog pin. It needs tolerances building in and debouncing.

4) Matrix buttons and make use of the Keypad library to give you up to 9 buttons on 6 pins, 16 on 4 pins, 25 on 5 pins etc. Upto 4 x 4 (8 pins) can also be used together with a PCF8574 and Keypad_I2C to get 16 buttons on 2 pins. This can be repeated on the same two I2C pins to have 32, 64, 128 buttons or more.

5) Use cheap shift registers, such as the 8 bit 74HC595, and cascade to expand input/outputs using just 3 uC pins. limited only by the processing overhead to drive the number of shift registers you incorporate.
359  Using Arduino / Displays / Re: Unknown LCD - Longshot on: January 24, 2013, 11:00:56 pm
Making a guess that pin 1 and 2 might be a backlight connection?

A picture of the thing would be very useful ;-)
360  Using Arduino / Project Guidance / Re: The opposite approach to over internet control of arduino on: January 24, 2013, 05:32:53 pm
Use a normal web page to post data into your database.

Create a web service that exposes the data you want, in response to a specific GET request.

Have your Arduino running as a web client and periodically poll the web service. If there is data for the Arduino then it can parse the web service response and act on the data.

Decide on your polling interval based on how fast you need the Arduino to act to new commands posted into your database.

Once the Arduino has carried out the command you can even have it post back, again via a web service, into your database to confirm receipt and action to close the communication loop.

All nice and simple stuff for any web developer. :-)
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