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46  Using Arduino / General Electronics / Re: battery charging... on: May 05, 2014, 12:23:43 am
What do you mean by 0.5v above its charge level?
How are you going to measure the charge level whilst charging?
47  Using Arduino / General Electronics / Re: Power supply from ATX PSU on: May 04, 2014, 08:06:45 pm
The 12V rail resistance reading is wrong.
It should read around the same as the 5V rail resistance.
It looks like either a shorted capacitor or a shorted diode for the 12V rail.
48  Using Arduino / General Electronics / Re: Cheap digital radio receiver WITHOUT demodulation on: May 04, 2014, 06:31:48 pm
When you say accurate measurements, what do you mean .
How accurate.
Measuring the signal strength of radio signals accurately is quite a hard thing to do , and theres no cheap way to do it.
You need a commercial field intensity receiver to do this type of thing accurately.
What exactly are you trying to measure?
49  Using Arduino / General Electronics / Re: help with battery capacity on: May 04, 2014, 06:21:09 pm
Hobbyking sell a range of chargers primarily for charging batteries for RC models, but you can use them as general purpose
battery chargers for Lipo,NIMH,Nicad and Lead Acid.
They can charge and discharge at a fixed rate which is user presettable, so are useful for measuring a batteries capacity as they have a timer , and you can program them to stop charging and discharging when a given voltage is reached.
http://www.hobbyking.com/hobbyking/store/__5548__IMAX_B6_50W_5A_Charger_Discharger_1_6_Cells_GENUINE_.html
50  Using Arduino / Motors, Mechanics, and Power / Re: AC Motor Control with Arduino on: April 29, 2014, 02:29:08 am
You need a device called a VFD (variable frequency drive.)
Some info here.
http://www.phaseconverterinfo.com/phaseconverter_vfd.htm
Building these devices is highly specialised , and you need a thorough background in power engineering.
No way I would be doing this as a first project.
51  Using Arduino / Project Guidance / Re: PIC16F628 transmit to Arduino UNO~~~helppp!! on: April 28, 2014, 01:58:56 am
You cant use those cheap RF modules to send async data, because they wont emulate a hard wired link.
The receiver is totally dumb, and in the absence of any input signal produces garbage on its data pin which is fed into a hardware usart will cause massive overrun and framing errors, and in the worst case will cause the usart to lockup.
You need , as a minimum some form of data coding like Manchester, and some form of pulse position modulation to transmit the data.
Have a look at how the Virtual Wire library works to achieve what you want.
http://www.airspayce.com/mikem/arduino/VirtualWire/

52  Using Arduino / Networking, Protocols, and Devices / Re: PIC16F wireless transmit 433Mhz to arduino UNO on: April 26, 2014, 08:32:27 am
If the PIC can support SPI, then Id use a better radio like
http://www.nordicsemi.com/eng/Products/2.4GHz-RF/nRF24L01
otherwise , you will need some preprocessing in the PIC and likewise in the Arduino.
If you can compile Virtualwire for the PIC and also use it in the Arduino, then this will work OK.

53  Using Arduino / General Electronics / Re: Buck converter inductor current calculation - Am I doing it right? on: April 24, 2014, 06:15:14 pm
This site provides good instructions on designing switch mode power supplies and allows you to simply enter
the input output requirements, and it will give you the component values.
http://www.daycounter.com/Calculators/Switching-Converter-Calculator.phtml


54  Using Arduino / General Electronics / Re: DC-DC Converter Step Up Down problem, Gets Very Hot! on: April 24, 2014, 03:12:43 am
The article is very vague about a lot of things.
For example, the type of peltier used.
Most PC USB ports can only supply 500 ma, so a peltier that tries to draw more than 500 ma will cause the USB hub to current limit
or worse, possubly damage it.
5V at 500 ma is only 2.5 watts ,and the normal efficiency of a peltier is around 50% when cooling, so at best the total cooling power available would be only 1.25 watts, which is next to none.
Assuming a 375 ml can of coke and wanting to cool it from 25C to 10C.
The specific heat of water, which coke mainly is , is 4.2 J/G/C needs 4.2 X 375 X 15 = 23625 joules or 23625/1.25 = 5.25 hours to cool the coke down.
This assumes also that the cabinet is perfectly insulated.

You can make peltier coolers, but you need far more power than a USB port can provide, and you need an extremely good
heatsink on the hot side to keep the temperature down.
55  Using Arduino / General Electronics / Re: Schottky Diode on: April 23, 2014, 06:36:48 pm
Are you really sure you mean 30 Mhz ?
What is the application?
56  Using Arduino / General Electronics / Re: DC-DC Converter Step Up Down problem, Gets Very Hot! on: April 23, 2014, 06:34:04 pm
Your project is not possible, simply because the output power of a PCs USB port is far too low to run
any kind of peltier based cooling system.
Peltier coolers are power hungry, the particular model you are using pulls 60 Watts which is far beyond the capacity of any
USB port.
Your DC - DC converter is being grossly overloaded.
57  Using Arduino / General Electronics / Re: Need a battery source on: April 18, 2014, 03:02:02 am
Another source of 18560 cells is dead laptop computer batteries.
Ive pulled apart 4 dead laptop batteries recently (2 from HP laptops,2 from Asus laptops ) all of which had 6 X  18560 cells in them.
In every case, and I dont know why, 2 of the cells were totally dead and the other 4 were fine.
Most people simply throw away dead laptop batteries, as the manufacturers dont make them so that individual cells
can be easily replaced.
Its very hard to get the plastic casings apart without damaging the plastic.
The cells in these types of laptop batteries are usually 2200 mah.
58  Using Arduino / Networking, Protocols, and Devices / Re: What rf to use? on: April 17, 2014, 07:40:38 pm
For distances like this, its important to know whats in between the transmitter and receiver.
Do you have line of sight, ie can you see from one end of your path to the other.
Most of the low power transmitters that claim distances like this also need line of sight.
59  Using Arduino / General Electronics / Re: What happens if you have too little voltage? on: April 17, 2014, 01:40:04 am
What is it that you are trying to charge.
Generally, trying to power something off solar power directly is always problematic
due to the fact that Solar panels are essentially current sources and work best if they are directly charging a battery.
You can then regulate the batteries voltage , and use the regulated voltage to power whatever you like.
The battery ensures that in the absence of sufficient sunlight, the powered device still works.
Without a battery, all that will happen when there is insufficient sunlight, is that the supplied voltage will be less than 5V
and how that affects what you are powering depends on what it is.

60  Using Arduino / Motors, Mechanics, and Power / Re: Speed Control of 230 Vac motor with Arduino on: April 13, 2014, 04:08:07 am
It depends on what type of motor the ventilator uses.
There are 2 common types of AC Motors, Universal or Brush type and Induction Motors.
The first type can be speed controlled with Triacs , but the 2nd type cant.
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