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1  Using Arduino / Project Guidance / Re: long range wireless link to arduino on: March 26, 2014, 03:44:55 pm
You coukd try using nRF24L01+ 2.4Ghz transceivers.

For the distance and conditions you'll need the high power amd pre-amped ones with external antennas. Use some commonly available wifi directional antennas; waveguide, yagi or dish, and you might be able to punch through the signal. Also run them at 256kbs for maximum sensitivity and range.

You could probably get some cheap yagi antennas for less than £30 and the radios wojkd be about £15 the pair. Potentially get it going for around £70 with some pigtails and gender adapters factored in.

If you can get hold of some old satellite dishes then you could even try making your own biquad element to mount and do some diy antennas of about 20dbi gain.

There is plenty of info about on extending 2.4Ghz for normal wifi, which would be applicable.
2  Using Arduino / General Electronics / Re: MOSFET Recommendation on: March 15, 2014, 06:57:19 pm
Thanks CrossRoads

I've not used any FETs before now.
3  Using Arduino / General Electronics / Re: MOSFET Recommendation on: March 15, 2014, 12:32:41 pm
The voltage reaching the 'match' is irrelevant, so I can't see any issue with low side switching.
4  Using Arduino / General Electronics / MOSFET Recommendation on: March 14, 2014, 05:39:16 am
Looking for someone with a bit more experience to recommend me a logic level, SMD (could be through hole if required) MOSFET, for the following application:-

Source voltage would be 7.2-12V, more than likely form AA's, but could be from a 12V SLA or a LiON.

I need to switch that directly across a thermo igniter, essentially an electric match. These igniters are then used to fire pblicly available pyrotechnics, such as a smoke grenade or flashbang.

Now, with AA's in series, maximum current should remain the same so they should not be able to deliver more than a couple of Amps, and it will be for fraction of a second, maybe 200-500ms transient. The igniters are essentially self destroying and go open circuit anyway, but I'll still pulse the output.

I could insert a resistor into the circuit, but I'd need one that could cope with the current, voltage and transient time and continue to operate for 1000's of operations.

My initial thoughts are that a well rated MOSFET could just switch these from AA's, but the complication comes if a battery is being used which can source a higher maximum current.

Measured resistance of e-match is 1.5 Ohms, so a 12v source would give a maximum transient current of 8A, then dependent on the batteries ability to actually deliver that.

It would more typically be 9v (via 6 x AA in series), so theoretical maximum 6A.

The datasheet on Duracell Procell AA's doesn't state maximum discharge, but just says that it could deliver 1A with a discharge curve indicating less than 1 hour. (Datasheet link attached).

Does anyone know typical short circuit currents for different battery types and can you advise on a suitable MOSFET or supplementary circuit to switch this type of transient load?

The same power source will provide 5v and 3.3v to AVR and other items, via linear regulators, so my other concern is voltage dip affecting BOD. Could this be mitigated a little with some large reservoir caps on the input to the regs?

Thanks in advance for any help.
5  Using Arduino / LEDs and Multiplexing / JST SM 2.5 4 Pin Connectors - PCB Headers? on: March 08, 2014, 07:21:14 am
Does anyone know a supplier of a PCB header for the JST SM 2.5 connectors that are commonly used on WS2801 LED strips and strings?
6  Using Arduino / Audio / Re: Playing a music with an arduino uno on: February 22, 2014, 07:47:21 am
SimpleSDAudio.

You'll need an SD Card and reader, or make one yourself using some male pin headers. Then use the supplied converter to convert your audio file and copy to SD. I find the quality to be very acceptable.
7  Using Arduino / Networking, Protocols, and Devices / Re: What library is best for the ECN28J60 on: February 22, 2014, 07:42:45 am
UIPEthernet is a direct replacement  for the standard ethernet library, meaning you can use many code examples that already exist.
8  Using Arduino / General Electronics / Re: Antenna for 315MHz RF on: February 17, 2014, 08:39:14 am
Glad the suggestions helped.

Another reason I use the nRF is that they have FIFO buffers and interrupt pin. It will receive into the input buffer and then you periodically check and read any packets, rather than have to have your sketch worry too much about the criticiality of timing for send and receive.
9  Using Arduino / General Electronics / Re: Antenna for 315MHz RF on: February 16, 2014, 09:21:04 am
That seems like very poor range. Are you sure your drop out is hardware related and not software related, i.e. could it be your code missing incoming packets?

If it really is the hardware then you may find you only need a higher gain antenna on the master device, rather than all your slaves. That will give you better receive and transmit gain, without having to equip every device.

I use nRF24L01+ devices (2.4Ghz) and they get across the house with just the onboard trace antennas, and the wavelength is shorter. With just the base device with antenna, I get about 100ft range from devices with low power units and PCB trace antennas.

You could actually find that having them too close can be detrimental. Have you tried with them further apart. If a 1/4 wave (@ 315Mhz) is 23.8cm then you need around 4 inches for a single wavelength separation even.
10  Using Arduino / General Electronics / Re: analogRead not showing expected results on: February 14, 2014, 11:32:35 am
What exactly are your resistor values and the input voltage Vcc?

You say you don't have anything larger than 10k so would it be a corect assumption to believe you are using 3 x 10k, aiming for a 20k/10k divider?

To calculate the analog input value accurately you need to know the actual Vcc and account for all resistance in the divider, including the pin input impedance.
11  Using Arduino / Microcontrollers / Re: 16-bit handles 32/64-bit weirdly on: February 11, 2014, 03:25:28 pm
Why did you show a serial.Print example in your first post then and quote certain outputs from the sketch you posted?

BECAUSE I am not wondering how to fix my serial shit. I gave you the principal and the question on how to fix this problem. Please stay related to my main question here!

I gave you the answer. You are in error. word() is a cast, nothing to do with strings. You cast your variable to word datatype (16 bit) before output, so why would it be anything else?

With that attitude, I'm outta here. Good luck with any future help. I don't owe you my free time so I will donate it to someone more appreciative.
12  Using Arduino / Microcontrollers / Re: 16-bit handles 32/64-bit weirdly on: February 11, 2014, 03:19:30 pm
Why did you show a Serial.print example in your first post then and quote certain outputs from the sketch you posted?
13  Using Arduino / Microcontrollers / Re: 16-bit handles 32/64-bit weirdly on: February 11, 2014, 03:15:26 pm
Word(num) casts your variable to a word datatype, the same as an int on Arduino.

It's nothing to do with strings.

Well ok wtf, I have no clue what I am doing. I am a noob to C++; how do I get this to work?!

Code:
Serial.println(num);

Where did you get that code from? What made you think word () is anything to do with converting to strings?

I would suggest starting with the Arduino Language Reference.
14  Using Arduino / Microcontrollers / Re: 16-bit handles 32/64-bit weirdly on: February 11, 2014, 03:10:48 pm
Word(num) casts your variable to a word datatype, the same as an int on Arduino.

It's nothing to do with strings.

Your code is working perfectly. It's you who are in error. ;-)
15  Using Arduino / Microcontrollers / Re: Wireless Ethernet connectivity for RasbPi on: February 10, 2014, 04:46:08 pm
Wireless USB Dongle?
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