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16  Using Arduino / General Electronics / Re: Help with building simple RF module. Please help on: March 30, 2014, 12:41:18 am
The difficulty is building a simple receiver that will work for receiving data.
Low power FM transmitters generally assume you already have some kind of FM receiver, as building an FM receiver is anything but trivial.
As you can buy already built 433 Mhz Transmitters and receivers for less than $4 each , its silly to even consider building your own.
17  Using Arduino / General Electronics / Re: Measuring crystal frequency - HELP! on: March 29, 2014, 04:47:14 am
Crystal oscillators in PICs and AVRs are supply voltage dependant for a given crystal frequency , and also very dependant of the value of the capacitors from either side of the crystal to ground.
The crystal itself is also important, as it needs to be a parallel mode crystal.
Usually, the datasheet for the Pic or AVr will tell you what the optimum capacitor values should be .
You can measure the frequency with a X10 Cro  probe connected to the output pin of the oscillator, but the best most reliable way
is to use the CLKOUT option which most PICs and AVRs have and simply measure the freqency on the CLKOUT pin.
18  Using Arduino / General Electronics / Re: Measuring el. consumption non-contact? on: March 28, 2014, 01:23:04 am
Whats the nature of the load that is being supplied and how accurate do you want the result to be.
Current clamp type measurements generally arnt all that accurate , and they assume constant voltage and unity power factor.
19  Using Arduino / Project Guidance / Re: Lowest power method for 2 digit LCD on: March 27, 2014, 06:03:00 pm
Have a look at one of these.
http://ww1.microchip.com/downloads/en/DeviceDoc/41250F.pdf
Inbuilt LCD driver which runs even when the Micro is in sleep mode..
20  Using Arduino / General Electronics / Re: Serial communication question on: March 25, 2014, 07:56:00 pm
Try sending the data slower, lower baud rate , or leave a pause between the characters being sent.
Software Serial doesnt have a receive buffer, so data can get corrupted if data is coming in , but the CPU is doing something else
like writing to a display.
21  Using Arduino / General Electronics / Re: Wireless sound from one arduino to another on: March 24, 2014, 01:41:58 am
This is by no means a trivial project.
You will need some kind of audio amplifer which also provides a Dc offset so that the microphone output
falls within the range of the Arduinos A/D converter.
You will also need some kind of simple audio codec to convert the sampled audio into a digital bit stream to feed to the radio.
At the receiving end you will have to do the reverse, and then somehow recover the audio and feed it to an audio amplifier and then a speaker.
Hope you are an experianced Arduino programmer.

22  Topics / Device Hacking / Re: car fm radio antenna hack on: March 21, 2014, 12:36:03 am
AM means Amplitude Modulation.
FM means Frequency Modulation.
In either case, you need some hardware that can function as a modulator.
The Arduino cant, as theres nothing in it that can perform this function.

23  Using Arduino / General Electronics / Re: AC Freq Measurement on: March 18, 2014, 07:00:08 pm
How accurately do you want to measure the frequency?
Thats what determines the complexity needed.
24  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.
25  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.
26  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.
27  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.

28  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.

29  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.


30  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.
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