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136  Using Arduino / Networking, Protocols, and Devices / Re: newbie question on interfacing with a mobile phone. on: February 14, 2014, 05:21:43 pm
Your questions make no sense .
What are you trying to achieve here?
You will need as a minimum as Arduino with a GSM shield to be able to receive SMS messages.
What do you want the Arduino to do ?

How you create them is another matter altogether and probably beyond the scope of this forum.
137  Using Arduino / Motors, Mechanics, and Power / Re: Helicopter experiment on: February 14, 2014, 01:16:26 am
The most critical design parameter for a helicopter is its weight.
Without knowing that , its impossible to know what motors will be needed.
138  Using Arduino / Networking, Protocols, and Devices / Re: 433 MHz RF module increasing range on: February 08, 2014, 11:28:54 pm
There are many versions of those low power 433 modules.
The cheapest versions are only 1 mw and what you are seeing is pretty typical.
To get better range you will need either the 12 or 25 mw versions, which are claimed to be good for 1000m
You can improve the range also by soldering a proper SMA connector to the modules and connecting a better
139  Topics / Home Automation and Networked Objects / Re: How to build a wireless camera system with Arduino? on: February 07, 2014, 02:13:36 am
What kind of webcam?
If its a USB Webcam , then its not possible to do with Arduino as the USB data rate is too fast.

140  Using Arduino / Project Guidance / Re: making a Reciever on: February 05, 2014, 10:41:41 pm
Building your own Radio receivers, other than a simple crystal set, is simply not a practical proposition for anyone
other than an experianced RF designer.
The design calculations alone will swamp anyone , let alone actually building the circuitry.
Its best to simply buy the hardware already assembled and treat it as a module which does all the hard work
and all you need to do is feed data in and get data out.
141  Using Arduino / Networking, Protocols, and Devices / Re: What rf to use? on: February 04, 2014, 05:16:19 pm
You can use Xbees without an antenna, but the range will be very limited, 10 metres or less.
To get any decent range, you will need a good external antenna.
142  Using Arduino / General Electronics / Re: suggest me a good Power Supply and solar panels question on: January 29, 2014, 04:23:14 pm
Its very hard to answer your questions without knowing what you are going to use the Arduino for, as this determines how much power it uses, and this determines whether its feasable to use solar panels to power it.
Even with Solar panels , you will still need a battery of some kind.
Will the Solar panels be outside in the sun?
How many sun hours per day do you get.
This is related to your latitude.
143  Using Arduino / Project Guidance / Re: dual axis solar tracker for mobile/portable installation of solar panels on: January 28, 2014, 07:36:13 am
The fundamental problem with small wind turbines, which are the type that might be used in camping or erected on a short pole
is the swept area is simply too small to gather any usuable wind , unless the wind speeds are 40 kmh + .
As the power in wind is proportional to the cube of the wind speed, small drops in the wind mean really large drops in output power.
A good example is a popular small wind turbine called an Air X 400, which is a small 400 watt turbine with a rotor diameter of 1.5 Metres.
To get 400 watts , you need a wind speed of 45 kmh, and because of the cubed law, at half the speed you get 50 watts.
Ok if you live somewhere near the coast where the wind is always blowing a gale.
Then there is the cost, and small wind turbines are very expensive relative to the power they make.
You are much better off with Solar panels for the same cost.

144  Using Arduino / Project Guidance / Re: dual axis solar tracker for mobile/portable installation of solar panels on: January 27, 2014, 06:29:46 pm
Before you even think about any kind of vertical axis wind turbine , make sure you examine closely the
power output versus wind speed for the turbine you are considering.
All VAWTs fall into 2 categories.
They are either a Savonious rotor design, which are fairly common , but extremely inefficient as they are a drag rotor and need
hi wind speeds to make any usuable amount of power.
The other type is a Darrieus vane which do work well, but are extremely large and need very substantial mounting structures, so are not viable for most people.
145  Using Arduino / Project Guidance / Re: dual axis solar tracker for mobile/portable installation of solar panels on: January 26, 2014, 02:08:23 am
Why do you want to do this?
Have you looked at the economics of how much extra power you would get from a tracked array
and the economics of simply having a fixed array with an extra solar panel added.
Its generally easier and cheaper to add extra panels than to make a tracking array for a smaller number.
146  Using Arduino / Networking, Protocols, and Devices / Re: 433.92 Mhz garage gate opener on: January 25, 2014, 02:35:09 am
Very hard to help here, as more information is needed.
Just having a transmitter on 433.92 Mhz isnt enough, as the type of receiver in the garage gate is needed.
Garage door openers frequently use rolling code transmitters for security, and if this is the case, then simply
recording the transmission wont help, as it changes every time you open the door.
If you can read the IC type in the transmitter , it may help determine what type it is.
147  Using Arduino / General Electronics / Re: how to calculate the exact frequency of this FM transmitter? on: January 17, 2014, 05:17:57 pm
Get yourself a copy of this book.

It explains the basic theory of Radio Comm pretty well, and has constructional articles of how to build both transmitterss and receivers.
Dont expect to learn everything in 5 minutes though.
148  Using Arduino / General Electronics / Re: how to calculate the exact frequency of this FM transmitter? on: January 17, 2014, 01:38:35 am
I think the OP may be a bit confused re what is needed.
A few posts back, the OP indicated they wanted to make a walkie talkie.
Firstly, such radios dont operate in the FM band, but usually in the 433 - 434 UHF band , similar to UHF CB radios.
Such radios use narrow band FM , bandwidth limited to a 10 Khz channel, with typically 5 Khz deviation.
In this case its essential that the frequency stability of the both the transmitter and receiver is controlled by a crystal oscillator
which usually provides the clock for a fractional N dual modulus pre scaling synthesiser.
In my work life I used to design and make such things, and its not that hard to do , but sure isnt a beginners project.
Heres a bit of an article on how such devices work.
Its a bit old , and there are far better ICs around now , but the explanation is easy to understand.
149  Using Arduino / General Electronics / Re: how to calculate the exact frequency of this FM transmitter? on: January 16, 2014, 07:00:32 am
What are you trying to do with this transmitter?
The frequency is given by the formula 1 / 2 X pi X sqroot (L X C), but as
the circuit has the oscillator as the output stage , its frequency stability will be terrible.
You need some kind of crystal oscillator followed by a multiplier to get a stable frequency.
150  Using Arduino / Networking, Protocols, and Devices / Re: Super simple wireless on: January 14, 2014, 05:43:47 pm
Its unclear whether you want bi directional transmission capability or not , but if so you need radio modules
that are bi directional and that limits you to Xbees or the NRF series of modules.
If uni directional transmission is OK, then you can use the much cheaper and simpler 433.92 Mhz ASK modules.
Most remote light switches are uni directional.
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