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16  Using Arduino / General Electronics / Re: A way to measure current in the battery holder: on: February 09, 2014, 07:12:24 am
The simplest ideas are often the best. Guess what I'll be making later?  smiley-cool
17  Using Arduino / Microcontrollers / Re: running out of memory - bigger ATMega? on: February 08, 2014, 09:30:19 am
You might possibly look at your code first as is often a lot of initial optimisatiom that can be done to save Flash and SRAM.

If you post the code then I'm sure a lot of people could suggest ways to make it more efficient.

Is it SRAM or Flash you currently need more of?

If you do genuinely need more of either then the 1284P is a great step up.
18  Using Arduino / General Electronics / Re: Current flow + to - on: February 08, 2014, 06:40:37 am
Electrons are negatively charged so, when a potential difference is applied, they 'flow' (jiggle would be more descriptive at quantum level) from negative to positive.

In order to reconcile with conventional current then you consider the elctron holes to be positive and hence conventional current is the flow of positive holes towards a negative potential.

Atoms with excess electrons are negatively charged. Atoms with electron deficit (excess 'holes' in their valence shells) are positively charged

To understand properly then you need to read up on some chemistry and electron shells and valence electrons.
19  Using Arduino / Project Guidance / Re: Test Soil Voltage Using Aduino Error on: January 15, 2014, 09:19:34 am
Your diagram shows the voltmeter in series with your circuit. You take voltage measurements in parallel.

I'm not clear what you are trying to do here. If you measure voltage then you would do so with a lead attached to each probe, and just read 5v.

The resistivity of the soil may have some effect, depending on how high it is, due to the soil resistance and voltmeter resistance being in parallel. Good soil woild have a resistivity of below 50 ohm meters. Bad soil coild be several thousand ohm meters.

Can you clearly explain what you are actually trying to do, and why.

You also need to be aware that you could have other ground currents present, such as supply fractional neutral return currents in a PME system, that will show a step voltage between any probes inserted in the soil. This could be non-existent to quite signicant, again, depending on the soil resistivity, test postion and magnitude of those currents.
20  Using Arduino / General Electronics / Re: Waterproof Connectors on: January 05, 2014, 07:12:28 am
I have a unit with LED indicators. I want an auxillary connector to add an extension box with just more LEDs. The extension LEDs are controlled by transistors and power will be local, so the lead just needs to carry a signal to transistor base (RGB) and a commom Gnd.

This may end up being LED strips, such as WS2801, so I guess I should look at whether those connectors are waterproof.

The other option is connectors internal with something like a stuffing gland to pass through to keep moisture out.

Thanks for the suggestions. It's good having IP65 enclosures until you want to connect things together!
21  Using Arduino / General Electronics / Waterproof Connectors on: January 04, 2014, 03:35:41 pm
I need some connectors that are waterproof, for use outdoors when it may be raining.

They only need to be 5v rated as they would be signal wires only, 2 pin and 4 pin panel/chassis female and an inline male.

Normal RJ45 and CAT5 would do what I need if there are waterproof versions.

I'vd hunted so far without luck. Could just be rubbish search terms.

Any pointers would be very much appreciated.
22  Community / Local Groups / Re: Anyone near Derby, UK ? on: January 01, 2014, 08:41:01 pm
I am Corby, Northamptonshire, just south of Leiecester.

There is Nottingham Hackspace not too far from you. There is an open hack night every Wednesday forbvistors to go and see what it's all about and look round the place. The Arduino 101 workshop is one of the most popular workshops run at the 'space.
23  Using Arduino / Networking, Protocols, and Devices / Re: RF24 Library: Driver for nRF24L01(+) 2.4GHz Wireless Transceiver on: January 01, 2014, 11:02:48 am
Do you have this set up on a breadboard or just sticking jumpers into Arduino headers?

I experieced similar symptom with ethernet shield initially, which cleared up when I mounted the nRF on a proto shield with better connections.

I then moved to custom PCB's with plug in ENC28J60 and everything works fine together.

You could also investigate what speed each library sets the SPI bus, to see if there is any issue there. If a device sets SPI speed and then it is left at a speed the next device doesn't expect then that could cause issues.
24  Using Arduino / General Electronics / Re: New PCB production tool on: January 01, 2014, 09:03:38 am
....  Just missing easy PTH, soldermask, and silkscreen for finished boards.  (Is that all...)
See a post I made on another forum which shows soldermask and silkscreen achievable.

I sell tinning solution and dry film solder mask on eBay. I also have the foil for white silkscreen but haven't got round to writing the instructions yet to list it.

I now use a mix of toner transfer via vinyl and laminating dry film photoresist for UV method. Which I use depends on urgency and trace size/board detail. A laminator is still required for the photoresist, soldermask, silkscreen application and white silkscreen foil application, so sometimes it's just easier to toner transfer via vinyl and laminator.
25  Using Arduino / General Electronics / Re: New PCB production tool on: December 30, 2013, 11:15:12 pm
I used something I bought a while back that printed onto paper, you heat-transfer the results (the toner) to a PCB board, and then put it into acid. That part all worked, what I stumbled on was the holes. Drilling (say) 28 holes of the correct size, the exact distance apart and in a straight line, totally defeated me. How did you solve that?
I use a mini rotary tool and the etched holes to center and drill fine by hand. It's one of those things that gets easier with practice.

One trick you can use is a piece of strip board or vero board as a template. Line up over DIP holes and drill through as a jig.
26  Using Arduino / General Electronics / Re: New PCB production tool on: December 30, 2013, 11:12:10 pm
The vinyl works fine. I've run loads of it through HP laser and modified laminator (180-200 dec c) with no problems.
27  Using Arduino / General Electronics / Re: New PCB production tool on: December 30, 2013, 08:11:53 pm
I've seen it referred to before 'Press n Peel Blue' but not used it myself.

When I was using toner transfer I ended up using self adhesive vinyl, which seems to have the same properties but is a lot cheaper.

Print to a normal sheet of paper first to get a position for your design. Cut a patch of self adhesive vinyl a bit bigger than the print area. Run the paper back through so the design is printed on the vinyl patch. Iron/Laminate on then let cool and peel off. You can achieve 100% transfer with vinyl.

I was buying 10 A4 sheets on eBay Uk for the equivalent of about 5USD.

See the following thread for examples of quality.
28  Using Arduino / Programming Questions / Re: Someone can tell me why this LED doesn't blink a regular time ? on: December 29, 2013, 02:30:05 pm

What is the value of T1 when you first add 1 to it, and then what is it's value after adding 1 each time? At what point do you give it an initial value, or 'initialise' it?
In the sketch shown, T1 is defined outside of a function, and therefore it is a global variable.  All static and global variables that are not otherwise initialized, are set to 0 before the sketch runs.
Always good practice to explicitly initialise a variable, or assign a value, prior to first operations though, would you agree?
29  Using Arduino / Project Guidance / Re: Control Arduino with iPad locally on: December 29, 2013, 02:26:44 pm
I'm not sure about the WiFi shield as it all depends on having an Access Point for your iPad to connect to. I am waiting on a couple of WiFi modules to arrive from China to play with myself as I currently use ENC28J60 + WR7-2N to convert ethernet to WiFi, but I am connecting outwards to a router/AP, rather than inwards like you want to.

It's a shame it's not an Android tablet as you could have done it very simply with a Bluetooth adapter for less than £10.

See the following link for web server on Arduino -
30  Using Arduino / Networking, Protocols, and Devices / Re: NMEA protocol decoding on: December 29, 2013, 08:28:25 am
Look for TinyGPS and TinyGPS++ libraries as they will take all the grunt work away and you can then pull out whatever data you need from the GPS very easily.
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