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61  Using Arduino / Project Guidance / Re: Detect interference from power lines on: January 02, 2014, 04:26:41 pm
110KV transformers you will only find in zone sub stations .
You wont find them anywhere along  the power line.
To measure interferance at 2.4 Ghz , you need a receiver that is designed for operation at this frequency.
This means an antenna designed for 2.4 Ghz and a receiver with a RF amplifier also designed for 2.4 Ghz.
Id be very surprised if you measure anything at 2.4 Ghz from a power line as theres no obvious mechanism to create it.
62  Using Arduino / General Electronics / Re: Morse Code Tx and Rx on: December 27, 2013, 06:40:54 am
Decoding morse code is hard to do, unless its generated by a machine which maintains constant timing.
ie the length of the dots and dashes dont change.
If its being sent by hand, you will have a very hard task decoding it.
63  Topics / Home Automation and Networked Objects / Re: light switch rf control on: December 26, 2013, 05:29:53 pm
The rc switch library relies on the remote being controlled having a Sc2272 or similar decoder chip inside it.
Whilst this chip is pretty common, its not universal.
You may have to pull the remote switch apart to see what it uses.
64  Using Arduino / General Electronics / Re: Calculating inductance on: December 19, 2013, 02:51:25 am
Will the inductor have any DC flowing thru it?
If yes, then you also must consider the maximum DC current that the inductor can handle before it saturates.
65  Using Arduino / Sensors / Re: Wind Speed Sensor WH2080 on: December 17, 2013, 06:44:08 pm
Buying Wind Sensors by themselves to use in an application differant to what they were intended for is risky
for 2 reasons.
If its a wireless sensor as this one appears to be , then you will either have to dismantle the sensor to figure out
how the wind speed direction and speed are detected, or you will have to reverse engineer the radio protocol that the sensor uses.
Even if you can get this all working, you will have to figure out the relationship between the spin rate of the anemometer and the actual wind speed, and this is not easy to do.
Unless the Wind Sensor comes with a calibration chart which shows the relationship, then you will have to calibrate the wind sensor to get the wind speed correct.
Try and buy a wind sensor from a reputable supplier who will provide the calibration data if you want accuracy.

66  Using Arduino / Motors, Mechanics, and Power / Re: GSM Shield battery power supply? on: December 17, 2013, 04:45:05 pm
The voltage of a battery doesnt tell you how much electrical energy the battery holds, and although the little 9v batteries
are nominally 9 volts, their capacity is only around 100 - 200 mah, so they cant power very much.
Running a GSM shield where it transmits every 20 seconds will be very hard to run off a battery unless there is some mechanism for
charging the battery on a regular basis, or regularily replacing the battery.
Whats the application involved?

67  Using Arduino / General Electronics / Re: how to convert digital trasmission to analog? on: December 17, 2013, 06:02:15 am
Yes that's correct, but those simple 433.92 transmitters only support 2 binary states, on and off.
they don't support multiple amplitude states, or the ability to transmit  multi byte symbols.
68  Using Arduino / General Electronics / Re: how to convert digital trasmission to analog? on: December 16, 2013, 09:46:24 pm
Whats that means is that the Transmitter sends data by the amplitude modulation of the transmitters carrier wave,
ie turning it on and off.
They cant be linearly modulated, which is what is needed for true AM transmission.
But what is your goal here, why do you need AM transmission?
69  Development / Other Hardware Development / Re: How long can my arduino work continuosly? on: December 16, 2013, 05:59:48 pm
Reading the OPs post, the Arduino is going to be controlling a motor and a small fan.
Do you think they will last longer than the Arduino will?
70  Using Arduino / Motors, Mechanics, and Power / Re: GSM Shield battery power supply? on: December 16, 2013, 05:52:05 pm
You need a much bigger battery.
Those little 9v batteries have very limited current capacity, and wont power a GSM shield, especially when it transmits.
To determine what sort of battery you will need, depends on many things, but the main one is how often will the GSM shield be used, as its usually the most power hungry component.

71  Using Arduino / Sensors / Re: Deriving True Power with ACS712 on: December 16, 2013, 01:42:13 am
What are you intending to power with this set up?
Determining RMS volts is easy, but RMS amps is difficult if the load has any kind of active devices in the
power supply , like switch mode regulators, as the current waveform then is not sinusoidal.
You then need a true RMS converter to get the correct result.
Something like this.
http://www.analog.com/en/special-linear-functions/rms-to-dc-converters/ad636/products/product.html
72  Using Arduino / General Electronics / Re: Circuit Design Help? rectifier-voltage peak detector. on: December 14, 2013, 08:31:19 pm
The basic theory behind Joule Thief converters, requires a minimum voltage of approx 0.5V to get them to oscillate.
They use a single transistor as a self oscillating converter and with only 85 mv for input  , its extremely difficult to make a DC - Dc converter that will work.
73  Using Arduino / Project Guidance / Re: Decoding RF help on: December 13, 2013, 07:46:15 pm
That Nexa article does suggest its using some variant of the Sc2262 encoder, so all is not lost.
It will help you understand  whats being sent, but you will still have to figure out what the data being sent actually does.
A CRO is very useful for figuring this sort of stuff out.
Heres the datasheet for a SC2262 Encoder.
http://www.escol.com.my/Datasheets_specs/pt2262_1.pdf

The data encoding format is described about 1/2 way in the article.
You may be able to spot the data patterns in your transmission.
Note, there is no timing standard as to how long the short bit or the long bit is , as both are set by a RC oscillator on the chip which can be changed by the user.
Note that the encoder is a trinary encoder, in that it can send 3 states, 0 , 1 and floating.
Quite often though the floating state is not used.


 
74  Using Arduino / Project Guidance / Re: Decoding RF help on: December 13, 2013, 04:47:07 pm
Decoding RF signals requires some knowledge of what is being used to generate the signal in the first place.
You need to know what type of data coding is being used, but Manchester coding is fairly common, but there are others.
In this type of coding , 1s and 0s are transmitted as positive to negative , or negative to positive transitions, which means the
data is self clocking and has no DC component.
Whilst not universal, a common approach is send a sequence of flag bits , which usually are represented as a sequence of 10101010 data pulses which last for 10 - 20 ms , followed by a unique and constant sync byte or nibble, which will be in some way always differant and easy to detect than the flag bits.
The purpose of the flag bits is to provide time for the receivers AGC loop to adjust to the incoming level of the RF signal
and the 1010101010 transitions allow the receivers data slicer to adjust to the 50% point of the incoming data.
Many common transmitters use one of the family of SC2262 / SC 2272 encoder , decoder chips , so if you can determine whether your transmitting device has one of these, then it makes the process a lot easier, otherwise you will have a difficult task.
The SC2262 encoder sends data as a sequence of short pulses or long pulses, with the data being conveyed by the pulse length.
Usually a logic 1 is a short pulse followed by a long pulse, a logic 0 is the reverse, ie a long pulse followed by a short.


75  Using Arduino / General Electronics / Re: Double RC circuit on: December 11, 2013, 05:50:15 pm
Simplest way to understand whats going on is to measure the leakage current of the capacitors.
I presume they are both electrolytics.
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