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1  Using Arduino / General Electronics / Re: Unconventional/alternative battery recharge? on: August 19, 2014, 09:47:40 pm
Thats a very small capacity battery.
How much power does your robot need?
2  Using Arduino / Project Guidance / Re: Multiple arduino's sending information via 2.4ghz or 433mhz? on: August 17, 2014, 06:02:36 pm
Its preferable for a setup like this to try and avoid having bi directional transmissions, as it requires having receivers
running all the time at the sensors, which eats up the power.
Outdoor sensors are easier to install if they can run on batteries.
A common technique that a lot of weather stations use, is to transmit their data at regular intervals, that are differant
for each sensor.
eg 1st sensor sends data every minute, 2nd sensor sends every 70 seconds, 3rd sends every 80 seconds etc.
This avoids data corruption from sensors interfering with each other.
If the sensors use a 32.768 khz watch crystal as the clock, then you can get accurate timing for the data sending.
3  Using Arduino / Project Guidance / Re: House plant watering bot on: August 16, 2014, 05:22:53 am
You still need a failsafe system , regardless of when the last watering happened.
What happens if the Arduino crashes whilst the water pump is running.
4  Using Arduino / General Electronics / Re: Old Computer Power Supply on: August 15, 2014, 09:16:31 pm
CD drives draw most of their power from the 12V rail.
Only the low level logic uses the 5V rail, so if the drive isnt doing anything , like reading or writing
it wont draw power from the 5V rail , which is what you need.
5  Using Arduino / Project Guidance / Re: Easy to use rf transceiver chip. on: August 15, 2014, 06:34:40 pm
Your question makes no sense.
What do you mean by , you dont want to use a pre made module.?
Do you want to build your own module , in which case forget it, its too complex a task.

6  Using Arduino / Project Guidance / Re: House plant watering bot on: August 15, 2014, 06:25:32 pm
Why do you need to know if watering has happened x days ago.
Surely, if the soil moisture sensor is showing inadequate moisture, then you need to water.
7  Using Arduino / Networking, Protocols, and Devices / Re: 2 rf modules on: August 13, 2014, 06:33:38 pm
OK, you will have to look at whether VirtualWire can operate in full duplex mode .
I dont think it can.
The problem with those cheap modules, is that you have to pre process the data with some program running in the Arduino to make them work reliably.
Most people use Virtualwire, but only for 1 way transmission.
8  Using Arduino / General Electronics / Re: MC34063 buck with large variable input? help on: August 13, 2014, 06:28:14 pm
The limiting factor apart from the chips voltage and current limits, is the inductor saturation current.
If you design the circuit based on the highest input voltage at maximum output current , then it will be Ok at lower input voltages.
9  Using Arduino / Networking, Protocols, and Devices / Re: 2 rf modules on: August 12, 2014, 07:59:25 pm
Your question makes no sense.
If what you mean is can I have a system where I can send data and receive data at the same time using those types of modules
the answer is no, you cant.
If you want to send data in both directions , you need better radio modules , such as Xbees or NRF24l01 .
10  Using Arduino / Project Guidance / Re: Arduino Oscillator on: August 12, 2014, 06:00:16 pm
Normally using a standard CRO probe to measure the frequency of a pierce type crystal oscillator will pull the crystal
and lower its frequency as the probe adds parallel capacitance.
Most Micros use pierce type oscillators.
If you have an active FET probe then its OK .
11  Using Arduino / Networking, Protocols, and Devices / Re: I cannot get SoftwareSerial to work on: August 07, 2014, 06:26:38 pm
Are you using 2 Arduinos.
Software Serial is 1/2 duplex and cant send and receive at the same time .
12  Using Arduino / General Electronics / Re: Regulation of water flow on: August 03, 2014, 09:57:14 pm
A cheap source of rotary ball valves, which is what the OP needs can be found in battery operated garden hose timers
which you can buy at any hardware store.
You have to pull the timer apart, and remove the ball valve.
They usually run off 3V or 6V, depending on the type of timer.
13  Using Arduino / General Electronics / Re: RR3 RF receiver on: August 03, 2014, 08:17:07 pm
Those 433 ASK radios generate a lot of noise , as you are seeing.
To determine what the keyfob is sending, its much easier to pull the keyfob apart
and connect the Arduino to the data pin of the transmitter in the keyfob.
That way, all the noise is removed, and you get a clear indication of the transmitter data
which makes it easier to decode.
14  Using Arduino / Project Guidance / Re: MPPT Solar controller - based on Tim Nolan's ideas on: August 01, 2014, 07:15:50 pm
MPPT controllers are expensive , but theres no reason why they need to be .
Theres not much in them in the way of electronics.
I would guess its the small market.
As to why MPPT controllers make a differance, you need to understand how Solar panels work.
For example , a 12V solar panel isnt really a 12V panel at all.
Its really a somewhere in between 12V and 21V panel depending on what load is connected to it and how bright the sunlight is.
Solar panels will only deliver their rated power at one specific voltage and load, and this voltage and load moves around as the
sunlight intensity changes.
The ones Im using are rated at 100 watts STC , 18V at 5.5 amps.
What does this mean?
The STC means that panels power rating is measured at 25D cell temperature with a irradiating intensity of 1000w/sq meter.
The 18 V @ 5.5 amps means that the Solar panel wants to see a load of 3.2 ohms.
With any other load the panel will deliver less than 100 watts.
If the load is a 12V battery, the panel will only deliver 66 watts as the battery clamps the solar panels voltage to 12 V , but the current stays the same at 5.5 amps.
This happens because Solar Panels behave like current sources, so the current is determined by the available sunlight.
The Solar panel is now  behaving like a 66 watt panel.
All a MPPT controller does, is fools the Solar panel into thinking its still connected to a 3.2 ohm load, so the battery gets the full 100 watts.
At differing levels of sunlight, you get less improvement, so if you live somewhere, where you never get 1000w/sq meter, there wont be as much differance.
All grid Tie Inverters, which are the type that are used by roof top solar systems to feed power back into the grid have MPPT trackers in them , as the improvement gets better economically the bigger the installed panel capacity.

In its simplest format , all a MPPT controller needs is a small micro, 1 Power FET, one inductor,a couple of transistors,one or 2 diodes ,one opamp,a current shunt, and a small number  of resistors and capacitors.

15  Using Arduino / Project Guidance / Re: Project parameters r/t a wireless greenhouse controller on: July 31, 2014, 10:55:40 pm
Everything you want to do is possible, but you would be much better looking at one of the larger processors like the Mega or even a Duo, to make sure there is enough memory to handle your code.
The requirement to control everything via a web browser, will really chew up memory .
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