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121  Using Arduino / Networking, Protocols, and Devices / Re: Making a wireless transceiver on: March 18, 2014, 12:51:55 am
Its not generally viable to build your own radio tranceivers.
You need specialised test gear that most people dont have, and its far easier to simply buy
the assembled radios.
122  Using Arduino / Project Guidance / Re: RF Transmitter Not Working on: March 17, 2014, 02:43:56 am
Im still trying to understand what the LM386 does, given that its an audio amplifier.
123  Using Arduino / Project Guidance / Re: RF Transmitter Not Working on: March 16, 2014, 12:27:07 am
What you have built isnt a transmitter.
To generate 136 Mhz at sufficient power to light the globe, you need a stable frequency source, usually a crystal oscillator.
You then need a series of frequency multiplier stages to multiply the crystal frequency up to 136 Mhz, and then an RF power amplifier to raise the power level sufficiently to light the globe.
None of this is easy stuff for a first project.
If you really want to learn how to build transmitters, then this book is a good place to start.
http://www.arrl.org/arrl-handbook-2014
Be warned though, its a steep learning curve.
124  Using Arduino / Project Guidance / Re: RF Transmitter Not Working on: March 15, 2014, 05:39:40 pm
This type of experiment needs a substantial amount of transmitter power, at least 5-10 watts, and both the
transmitting and receiving antennas must be resonant with the transmitters frequency.

125  Using Arduino / Project Guidance / Re: Arduino + PIR + ATX Power Supply + LED Light Strips on: March 12, 2014, 10:40:11 pm
Theres nothing wrong if you dont need a regulated supply.
The 12V rail will vary depending on what load you connect to it, It will be low , ie less than 12V , and its not easy to know how much power it will supply before you cook the diode bridge for that rail.
If you keep the total power demand well below the supply maximum rating, say half its rating, it will work OK.

126  Using Arduino / Project Guidance / Re: Arduino + PIR + ATX Power Supply + LED Light Strips on: March 12, 2014, 01:05:26 am
More information is needed about what voltage and current the leds need.
ATX power supplies only directly regulate the 5V rail, and the 3.3 and 12V rails are indirectly regulated,
but need a load on the 5V rail for any regulation to work at all.
Because the supply is rated at 280W doesnt mean it can supply 280W on a single rail.
The power rating is the sum of all the rails added together in the typical proportion that a computer motherboard  needs.
If you want to use just one of the supply voltages, and not the others and want the one voltage regulated, you will have to modify
the supply and change the values of the sense resistors that control the PWM to the primary switcher.
Unless you have had previous experiance at doing this , I wouldnt use an ATX supply.


127  Using Arduino / General Electronics / Re: Line voltage (0-177v) variable power supply, feasible? on: March 10, 2014, 05:24:18 pm
You will still need a transformer.
The only differance is that instead of using a iron core transformer you will need a ferrite core transformer.
Such a power supply is feasable, but it sure isnt a beginners project, and a real lot can go wrong.
I would get some experiance in building small lo power switch mode power supplies first.
Theres a lot of math involved in building switch mode supplies that has to be well understood, otherwise you will end up
with a lot of dead fets.
128  Using Arduino / General Electronics / Re: Smallest DC-DC converter? on: February 25, 2014, 12:26:18 am
Whats is supplying the 5V?
USB ports are limited to 500ma , and some in laptops can only supply 100 ma.
You may find the DC - DC convertor wont start.
129  Using Arduino / General Electronics / Re: To supply power to Arduino WI Fi sheild Using 9V Battery on: February 23, 2014, 05:43:03 am
how long do you want the batteries to last
WiFi shields are power hungry,drawing around 130 ma on both receive and transmit.
Those little 9v batteries went last long,even if they work at all.
You need a bigger battery like a 7.4v lipo battery,or a 12v sealed lead act battery.



130  Using Arduino / Project Guidance / Re: Large Radio Network ? on: February 21, 2014, 04:55:23 pm
Powering the radios could be a problem, depending on how long you want the batteries to last.
If the radios have to be listening all the time, that represents a sizeable power component.
What sort of batteries are you going to use.
131  Using Arduino / Sensors / Re: Solar Radiation Sensor By Campbell Scientific on: February 21, 2014, 02:01:16 am
From the information about the Sensor, its impossible to tell.
You really need to contact the manufacturer and get better specs on the output data format.
132  Using Arduino / Project Guidance / Re: DHT22 (or equivalent) over long distance. on: February 21, 2014, 01:57:20 am
The DHT22 needs a dedicated data line for each sensor.
You cant have multiple sensors on the same data line.
The maximum recommended line length is 30M.
133  Using Arduino / Motors, Mechanics, and Power / Re: Balancing Batteries on: February 20, 2014, 05:24:52 pm
Voltage regulators in parallel wont current share, and can oscillate uncontrollably..
The only way you can make such an arrangement work, is to disable the voltage sensing from one of the regulators
and connect the sense voltage to the other via a summing network.
But its just not good practice.
134  Using Arduino / Networking, Protocols, and Devices / Re: newbie question on interfacing with a mobile phone. on: February 15, 2014, 10:29:06 pm
The issue is how are you going to connect the Mobile phone to the Arduino?
Most mobile phones only have a USB connector designed to connect the phone to a computer.
To connect a USB device like a phone to an Arduino, you need a USB host shield for the Arduino.
But this only allows the phone to be connected.
You then have to somehow get the Arduino to recognise the phone so you can talk to it.
Its far easier to junk the mobile phone and use an Arduino GSM shield.
Why do you want to use a mobile phone?
135  Using Arduino / Networking, Protocols, and Devices / Re: newbie question on interfacing with a mobile phone. on: February 15, 2014, 06:49:22 pm
What kind of mobile phone are you using.
Does it have a serial port?
Most mobile phones usually only have a USB port, and need a custom driver for whatever they are being connected too.
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