Show Posts
Pages: [1] 2 3 ... 28
1  Using Arduino / General Electronics / Re: Buck converter inductor current calculation - Am I doing it right? on: Today at 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.

2  Using Arduino / General Electronics / Re: DC-DC Converter Step Up Down problem, Gets Very Hot! on: Today at 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.
3  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?
4  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.
5  Using Arduino / Project Guidance / Re: How can one controll peltier and fan with Arduino Uno? on: April 21, 2014, 05:01:29 am
The Peltiers capacity to pump heat falls as the temp differance between the cold and hot side increases.
You need to measure the actual temp differance between the hot and cold side, and then consult the data sheet
of the peltier to find out what its pumping capacity is , at this temperature differance.
Generally , the maximum capacity is measured at either a hot side temp of 25C , or a maximum differential
between hot and cold of 10C.
6  Using Arduino / Project Guidance / Re: How can one controll peltier and fan with Arduino Uno? on: April 20, 2014, 07:41:58 pm
Using peltiers as coolers is tricky unless you have a very good understanding of the thermal load that being applied to the peltier
and a good understanding of the heat pumping capacity as a function of the cold side - hot side temperature differance,
Check the datasheet of the particular model of peltier you are using for the heat  pumping capacity as a function of hot side - cold side temp differance, to see if its even possible to do what you want.
The few times Ive played around with peltiers, the only way I could keep the hot side cool enough was by using a heat pipe which had a very big water cooled heat sink on the other end.
You also need to know the heat loss of the box that you are trying to cool, under worst case temperature differance between inside and outside.
These types of projects wont work just by slapping components together..
You will usually do better by using multiple smaller peltiers , that one big one.

7  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.
8  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.
9  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.

10  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.
11  Using Arduino / General Electronics / Re: Need a battery source on: April 12, 2014, 07:23:23 pm
Its a 18560 cell, very common type of LIPO battery.
They can be sometimes hard to buy though, as most of the suppliers are in China.
Try googling for a source near where you live.
12  Using Arduino / General Electronics / Re: Power consumption on: April 09, 2014, 07:04:55 pm
If the batteries are the little rectangular type with the terminals on the top, then typically capacities are around
110 - 150 mah.
Very poor value on a $ per watt hour basis.
13  Using Arduino / General Electronics / Re: How can I find out why a small DC motor won't work? on: April 06, 2014, 06:04:26 pm
Could be worn out brushes in the motor, especially if its fairly old.
Usually you can pull small DC brush type motors apart and that will allow access to the brush assembly.
If the commutator is open circuit then its unreparable.
14  Using Arduino / Motors, Mechanics, and Power / Re: Motors used in car thermatic fans. on: April 01, 2014, 08:23:26 pm
Thanks, most of the current fans for cars so far that Ive seen in car shops  are the 2 wire models, so brush type motors still.
Seems that they arnt designed to be repairable if the brushes wear out,as they sure dont come apart easily.
15  Using Arduino / Motors, Mechanics, and Power / Re: Motors used in car thermatic fans. on: April 01, 2014, 04:09:45 pm
Thanks for the pictures.
I guessed brush type motors also, but fan motors because they have to run for long periods of time usually dont have brushes
as the brush life would be pretty bad.
Maybe brush life has been improved .
Pages: [1] 2 3 ... 28