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61  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?

62  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.
63  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?
64  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?
65  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.

66  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.
67  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.
68  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.

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.

69  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.

70  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.
71  Topics / Device Hacking / Re: Opinions on intercepting 433MHz from Oregon Scientific WMR200 Weather Station on: December 10, 2013, 07:58:24 pm
You can cut the costs of OS sensors down by buying them directly from the US.
The prices in Australia are extremely high compared to the US prices.
I use a company called Price USA to do this , as OS in the US wont ship to Australia..
Ive managed to build a clone of a THGR810 temp / Hum sensor which does get decoded Ok on my OS weather stations
and also by a weather shield Arduino based decoder.
Ive got a WMR100 & a WMR80, but its not Arduino based.
Made it long before I learnt about Arduinos.
Its based on a Microchip 16F88 and is written in basic , not C .
Ill eventually get around to a C version.
OS do some funny things to the data that their Sensors transmit, to make it hard for people to make the sensors.
Guess they want to protect their product.
72  Topics / Device Hacking / Re: Opinions on intercepting 433MHz from Oregon Scientific WMR200 Weather Station on: December 10, 2013, 04:51:31 pm
Depends a lot on what you are trying to do.
Its easy to decode the data thats transmitted from Oregon sensors so that you can receive them using an Arduino and then display them on a PC which is connected to the Arduino.
Have a look here.
The weather shield is an Arduino based program that can decode the WMR100, 200 series of sensors.

If however , you want to make your own sensors and have them displayed on a Oregon console , then thats a lot harder to do
as there is information in the data that is sent from genuine OS stations that is not fully understood as to its function.
Ive built 2 Arduino weather shield decoders and they work fine .
Ive also made some of my own sensors, mainly temp / humidity ones and they also work fine when used with the Weather shield.
73  Using Arduino / Project Guidance / Re: Another smoking Leonardo on: December 08, 2013, 05:00:10 pm
Many Walwarts are unregulated power supplies which return a rated voltage when plugged into the device they were intended for
so a walwart rated at 12V which is designed for a modem / router will produce 12V when powering the router.
Routers draw far more current that a Arduino does, so using such a power supply on a Arduiono or Leonardo will result in more than 12V being delivered.
The Leonardo is rated at 12V max , and thats the board itself, not including any extra devices plugged in , such as LCD displays etc.
If the LCD display has a backlight, then theres a good chance the on board regulator is fried.

74  Using Arduino / Networking, Protocols, and Devices / Re: 433 Mhz RF signal cloning on: December 04, 2013, 06:34:31 pm
The RCswitch library relies on the encoder using a particular type of chipset which are listed here.
You will need to pull the key fob apart and see what the encoder chip is.
If its not one of the SC2272 type encoders, then using that library wont work.
75  Using Arduino / Sensors / Re: Capacitive Touch Piano on: December 04, 2013, 01:35:28 am
I cant see any sensing plates in your diagram.
The capsense library relies on a fairly large area of sensing plate to work properly.
If the plate is too small, the capacitance change becomes too small to detect.
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