Cadsoft Eagle is quite popular, due to the huge library of parts available. Many supplier provide Eagle libraries of their inventory.

The free version is limited to PCB of 100mm x 80mm but fine for most needs.

It's a bit counter intuitive and takes some perseverance to learn, but I've just done so in a few days to a decent standard.

The Sparkfun Eagle tutorials are a perfect place to start.

There is also Fritzing, but I actually didn't get on with it as well as I am now doing with Eagle, even though it was easier to pick up and use straight away.

I tried looking at this yesterday but, unfortunately, it only seems to work with a particular implementation of LiquidCrystal_I2C, the same one as compatible in the New LiquidCrystal Library.

My I2C backpacks work with the other I2C implementation, the one that controls the backlight through the I2C bus, rather than a dedicated arduino pin.

Are thee any plans to make MENWIZ compatible with more than one LCD connection method, as it rather limits scope for take up in this guise, but otherwise looks like it could be an excellent library.

If it were to be included as core library then it would need to work with any LCD connection, certainly with the shields available.

Many thanks.

I've been using the standard LiquidCrystal library to a while with both LCD shields (DFRobot) and standalone LCD, both in 4 bit mode. These are 16 x 2 displays.

I have just received some I2C backpacks to convert these to I2C.

My first thought was to move to the New LiquidCrystal Library as it uses all the same Classes and Methods but supports different interface methods, including I2C.

When looking to set it up I noticed there is no option to set the data line connections, as there is with the stabard parallel constructor. Also it wants a #define for the backlight pin, where my backpacks control backlight through the I2C chip (PCF8574).

I finally got it working with a standard LiquidCrystal_I2C library from the main Arsuino site, which controls the hackling with a setBacklight() call, rather than needing a separate Arduino pin to do so.

There appears to be two different LiquidCrystal_I2C libraries, one which controls the backlight through I2C and the other that requires backlight control via a separate Arduino pin. The I2C implementation in New LiquidCrystal Library seems to be based on the latter.

For full backwards compatibility it would need to support both methods and also have the flexibility to define whether backlight is on a pin or I2C (and which expanded bit) plus able to define the expanded bits for the other LCD lines.

Another really good idea for flexibility would be to have an optional declaration for contrast, leave it hardware via a trimmer or control in software via PWM/Analog pin.

I see that the I2C pin configuration is planned for v1.13.

Of course, if I'm missing something here and it already does the above then I welcome any pointers in the right direction.

Many thanks.

You'd definitely want some kind of isolation. If you connect a battery source to the same neutral/earth of a power system then there are things that can kill your electronics. Under fault conditions on the power system you will get a voltage rise on a neutral earth, called a transfer potential. This is transient in nature but could potentially last long enough and rise high enough to take the ground connection above a small battery positive voltage. Typical safe values for touch and step potentials her in the UK on power Athens is 400v. Similar voltages can be transferred to a neutral earth system for fractions of a second.

Transformers in consumer equipment also serve the purpose of isolation, as well as stepping dowon voltage before rectification.

I've not seen the mini personally, but I would make an educated guess that you need a USB>TTL breakout/adapter to connect to the RX/TX pins for upload via bootloader, OR use an ISP programmer to just upload via SPI without the bootloader.

I'm sure someone else will come along to confirm or correct.

I placed my first order with seeed last night. Just a test batch of I2C backpacks at the default options.

10 boards for just over $13 with shipping.

For the next ones I'll get the size down slightly with SMD components and panelise to get 2 per panel.

It was very straightforward, with uploading before you add to cart. You just need to raise you can only send one file so need to zip or rar. It would be useful if they stated this on the page.

Will post photo's and commens when they arrive (and see if I designed a working board; LOL)

Do a search here and on google for 'standalone ATMega328' , 'Standalone Arduino' or 'Breadboard Arduino'.

Doing what you want is very easy. All you need is an ATMega328P-PU with Arduino Bootloader, a 16Mhz Crystal, 2 x 22pF Capacitors, a 10k resistor and a 5v supply. Add your LED and resisted and you have the hardware to run the Blink sketch.

There are plenthy of UK eBay sellers that do the components in kit form for a few pounds and deliver within two days.

If doing anything more then you'd want to add some 0.1uF decoupling capacitors at each pair of Vcc/Gnd pins.

How much more 'accurate' are you expecting things?

A couple of percent looks pretty good really. There are a number of things that are going to affect the readings you get between your multimeter and the analog ports via voltage divider.

Your Arduino analog ports have 8 bit resolution. Your multimeter most likely has better than 8 bit resolution.

Your multimeter has limits. It will have accuracy fingures given in both percentage and digits (if digital).

Your reference voltage may not be exactly 5v, and will vary slightly with the load on that supply line.

Your resistors have a tolerance. Are you using 5% or 1% resistors. They will also vary as they will have a temperature coefficient.

You are measuring the resistances too, which again will be within the measuring tolerances of your meter AND at a specific temperature that can change.

Combine all of these and what you are seeing is actually pretty good as far as I can see.

You're measuring with two different instruments, in different ways, with various things that have errors and tolerances.

What is the purpose of JP1, JP2, JP3, JP4?

They don't appear to connect to anything on the board, just JP1 > JP2 and JP3 > JP4, unless I'm missing something.

I'm planning on having a play with this as it could be the solution to a manu system we need to provide user settings saved to EEPROM.

Reading through it seems that it can use a 4 button or 6 button set up.

6 Buttons - Up, Down, Left, Right, Select, Back
4 Buttons - Up, DOwn, Select, Back

What about 5 Button option, like what you'd have on some default shields:-

5 Buttons - Up, Down, Left, Right, Select

This doesn't have a specific button for the Back option, but couldn't the library incorporate a visual replacement. When in Menu's or on items you'd have a last option of 'BACK' which you just Select as with any other.

Actually, I guess this could also provide you a 3 button option too, along the lines of your existing 4 button plus the 'BACK' display for selection.

I'm guessing he meant to quote it and was agreeing, but it didn't go to plan. LOL

You'll need to keep two delays, timers and a state record

E.g.

delayBlinkOn
delayBlinkOff
timerBlinkOn
timerBlinkOff
stateBlinkOn
stateBlinkOff

1) Turn your LED on and set stateBlinkOn to True and timerBlinkOn to the current millis().
2) While stateBlinkOn is true then you want to check timerBlinkOn each loop until it's equal or greater than millis() + delayBlinkOn.
3) Once the condition is met, turn your LED off and set stateBlinkOff to True and timerBlinkOff to current millis().
4) While stateBlinkOff is true then check the timerBlinkOff each loop until it's equal or greater than millis() +  delayBlinkOff.
5) Once the condition is met, you're back to turn your LED on at Step 1 above and the sequence repeats.

Now, go code that up. ;-)

I've seen these on eBay recently and they are a tempting buy. There is a YouTube video showing someone using with an ATMega128 but I can't turn up any code examples at all.

Make sure you fully understand what you are doing before using CT's. Open Circuit CT's, under Primary load, can be extremely dangerous and generate several thousand volts and extensive arcing. CT's should NEVER be open circuit under load. Worrying about how to connect to, and possibly killing, your Arduino would be the least of your concerns.

The cheap ones from china work out at about £1.50 each. I've had a fair few of these without problems and they take a couple of weeks to arrive, on average.

If you want I2C then you can either buy a backpack for about £4 on eBay OR get yourself some PCF8574 expanders and wire it yourself. There are plenty of examples if you Googke.

Finally, use the New LiquidCrystal Library and it will support various methods of connecting the display, all using the same common methods. You simply declare which type at the beginning of the sketch.