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196  Using Arduino / Sensors / Re: DHT11 and humidty, whats the extent of the problem? on: August 29, 2013, 06:27:26 pm
There are accurate humidity sensors.
Here is one.
They are not cheap though, $50+.
197  Using Arduino / Project Guidance / Re: How to make a robot follow you? on: August 29, 2013, 02:27:18 am
It depends on how far behind you , you want the robot to follow.
If its very close, like a meter or 2 , then some simple kind of proximity sensor on the robot that senses
something which you carry will work.
If its further away, it gets much harder, especially if you want the robot to be able to follow you around obstacles
or around a corner.
198  Using Arduino / Project Guidance / Re: Nation Crossing Quadrocopter? on: August 24, 2013, 09:56:35 pm
I suggest you join a RC group that specialises in building quadcopters and learn a lot about
power budgets, ie how much power is needed to lift a given weight.
As a very general rule , you need around 1 watt per ounce of weight.
Unless you can source Solar panels that weigh far less than 1 oz per watt
then you cant use Solar power.
199  Using Arduino / Project Guidance / Re: Nation Crossing Quadrocopter? on: August 24, 2013, 08:13:16 pm
Not a hope in hell.
Have a look at the power consumption of your average quadcopter.
Mines a relatively small one , but the 4  motors pull 6 amps from an 11V lipo battery and
Im using pretty good batteries, and that gives me about 10 minutes flight time.
My quadcopter weighs around 400 grams.
With the best batteries you can buy, you can push the limit to around 20 minutes, but thats about it so far.
You would have more chance with an electric powered plane , but even then it would be pretty big.

200  Using Arduino / General Electronics / Re: General Wireless Module Question on: August 24, 2013, 06:36:14 pm
The tranmsitter is simply a keyed oscillator, whose frequency is set by a saw resonater.
When you apply a logic 1 to the data pin , it produces an output at whatever frequency the saw filter is .
Usually 315 or 433.92 Mhz.
So data gets sent by rapidly turning the transmitter on and off.
As MarkT indicates, they are very simple and crude devices, but can be used successfully with the Virtualwire library
which does all the hard work in coding the data in such a way as to get the best results from them.
201  Using Arduino / Project Guidance / Re: Replicating an RF remote signal on: August 23, 2013, 06:37:52 pm
If the transmitter in the remote uses ASK (amplitude keying) you will be able to receive the data on your 315 Mhz receiver.
Unfortunately, thats the easy part.
Figuring out what it means is the hard part.
Without a CRO or logic analyser it will be very hard to go any further, unless you can somehow find out the data format the remote uses.
202  Using Arduino / Project Guidance / Re: Communicate (one-way) with simple sensors wirelessly. on: August 20, 2013, 06:14:41 pm
Why do you want to use hall effect sensors.
This makes the design of the entire transmitting arrangement difficult because you have to deal with analog voltages.
If you used reed switches which are just open or closed, its a lot easier.
You could then use reed switch > SC2262 encoder > cheap 433 Mhz transmitter.
203  Using Arduino / General Electronics / Re: Run motor from rc helicopter through Arduino on: August 19, 2013, 06:54:57 pm
What kind of battery are you using to power the motors.
You must use a lipo battery or a battery with a similar high current rating.
A 9V transistor radio battery has no hope .
204  Using Arduino / General Electronics / Re: Run motor from rc helicopter through Arduino on: August 18, 2013, 11:30:04 pm
If you want the helicopter to fly, you need to test the motor with the helicopter rotor attached.
Helicopter motors draw amps , not ma , which is one reason that model helicopters use lipo batteries.
Model helicopters also have ESCs on the control board to power the motors.
You need to use the hardware in the helicopter to power the motors.
It may be possible to use the arduino to control the ESC in the helicopter to control the motor speeds.
If you know the AH capacity of the helicopter battery , and the average flight time , you can work out
the average motor current.
205  Using Arduino / Networking, Protocols, and Devices / Re: 433 MHz RF problems - can't even get test program to work on: August 18, 2013, 05:32:32 pm
Possible that you have the receiver too close to the transmitter, causing it to overload when the transmitter transmits.
Try a minimum spacing of a few metres.
206  Using Arduino / Networking, Protocols, and Devices / Re: 433MHz transmiter for radio control on: August 17, 2013, 09:46:44 pm
Most of the small cheap radios are range limited because of the way they work.
The transmitters are power limited and the receivers are broadband.
This allows them to be used very easily, to be able to cope with multiple data rates
and makes them ideal for short range applications like garage door openers etc.
The 2.4 Ghz radios wont penetrate solid objects very well, and the 433 Mhz radios are too low powered
to get any decent range.
You could theoretically get to around 1 Km with high efficiency gain antennas at both ends, but thats not really
viable for model control.
207  Using Arduino / Project Guidance / Re: Get rid of PWM noise in brushless fan on: August 15, 2013, 12:05:50 am
What kind of fans are you using.
Brushless DC fans commonly used in PCs cant be speed controlled, unless they are specifically designed to be .
In which case the fan will have 4 wires going into it.
Supply voltage + - and speed detection and speed control.
Trying to PWM the supply voltage will simply destroy the internal electronics in the fan over time.
208  Using Arduino / Project Guidance / Re: USB Serial handshake problems on: August 13, 2013, 07:28:42 pm
Most PCs will support Xon - Xoff flow control, although you have to turn it on .
Some info here.
209  Using Arduino / Networking, Protocols, and Devices / Re: XD-RF-5V receiver and RCSwitch problem on: August 13, 2013, 06:09:20 pm
The RCswitch library is designed to decode transmissions from devices that use the SC2262 encoder chip.
If your garage door opener doesnt use this chip, then you wont decode anything.
Most garage door openers use rolling code transmitters to provide extra security, and dont use the SC2262 chips.
210  Using Arduino / Project Guidance / Re: Using a Satellite Dish in Projects on: August 12, 2013, 05:55:03 pm
Not much you can do with the dish Im afraid.
They are specifically designed for just one purpose and the electronics that comes with them
is usually just a low noise down converter which needs a special receiver to work.
If you had 2 dishes and lots of spare money, you could make yourself a microwave data link
but thats not a beginners project.

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