How to make a remote controlled fan at home?
in
Is it possible to turn an everyday plug-in fan into a remote controlled fan, and if so how? What would be the materials needed for a project like this? Any helpful websites?
This is for a project we are going to show at a science fair at a local middle school, so it would be great if we could use common house-hold items.
Any help is appreciated. Thanks.
Answer:
This product was existed ten years ago and I bought one from local store cost $39 ,made in China product. It has a remote to control speed,swinging,timer and cycling wind speed. It has one main ac motor for fan and one small motor for swinging. It used Triac as its main motor output control.
Buy one from your local store. open it and tear it down to study the circuit.
How to calculate the pressure and volume of a tank full of steam and water?
in
A tank contains 10kg of water at 98(degrees Celsius) in the ratio:
- 8kg in liquid form
- 2kg in vapour form
What is the pressure within the tank and appropriate volume of the tank?
(Worked solutions in metric units would be much appreciated!)
Thank you in advance!
Answer:
The working is only reading values off a steam table. The mixture is saturated therefore, at 98 C the pressure will be around 0.93 atmospheres and the volume of the steam fraction will be:
27.84 x 2 x 0.453 / 33 = 0.76 m^3. The volume of the water, at 8 liters, is pretty negligible in comparison
How to use the light dependent resistor properly?
in
I know that you supposed to use it inversely, but how to do it? I looked it up on youtube and google, but it didn't help. I have the 2N3904 NPN transistor, LDR, LED, 9V battery and 330Ohm resistor. I put it together but it didn't work. I also directly wired the LDR to LED, but it still works the opposite of what I wanted.
Answer:
The first link shows how to use an LDR with a transistor and LED giving basic operation. As the light increases, the LDR resistance reduces.
To operate an led as it gets darker, the LDR resistance increases and allows the voltage between the base and emitter to increase. The current through the base to the emitter increases sharply when the voltage reaches about 0.7V, turning the transistor on. This allows current to flow from the battery, through the led and the collector to the emitter and back to the battery. The resistor shown as 500 ohms can be 470 or 560 ohms, the nearest standard values. It might help to add a 2.7K resistor between the base and the junction of the LDR and potentiometer.
At the bottom of the article there is a link to another design using an op-amp, which is more accurate considering just how much light operates the switch. A 100K resistor (or other value like that) between pin 6 and pin 3 will improve the operation by adding some positive feedback and hysteresis. The op-amp works as a voltage comparator. When the voltage at pin 2 is less than the setting at pin 3, the output at pin 6 is close to the + supply, and turns the transistor on. When the voltage at pin 2 is slightly greater than the setting at pin 3, the output at pin 6 is close to the - supply, and turns the transistor off.
When used with fluorescent lamps the light is pulsating, so this leads to confusion over the setting. Connect the capacitor shown across the LDR itself so that these pulses are averaged/smoothed more completely, but also add a 10K resistor in series with pin 2 and another in series with pin 3, to protect these inputs.
How to calculate the force of a caulking gun?
in
What is the equation to find the APPLIED FORCE and the PRODUCED FORCE of a caulking gun?
Thanks!!
Answer:
Applied force is just the force you input. So if you grip it with 10 lbf grip, then Applied force is 10 lbf. Produced force is a moment equation. You need the distance from the pivot point to your hand, and the distance from the pivot point to the point where the handle pushes on the rod in the middle of the gun.
For the distance of your hand, you can consider your hand an evenly distributed load over the distance of your fingers, and so the distance of the force will be 2/3 of the width of your hand plus the distance from the pivot to the top of your pointer finger. If that's to abstract, just measure from the pivot point to somewhere around the middle of your ring finger.
The math is Applied_Force x Distance_Hand = Produced_Force x Distance_Rod
Roughly I would say it's about 20lbf x 4in = Produced_Force x 1.75in, so the Produced Force would be about 45.7lbf
how to cool a transformer to prevent it from overheating?
in
i saw that in many industries machines get heated up due to relentless work.they use water somehow to cool them.i want to know the process.please tell me.
Answer:
The government might see that you have real transformers. They must be coming for you. Run.
How to increase torque in an electric motor, without increasing the voltage?
in
@billrussell42: This can be done through placing a load on the motor, right?
Answer:
As an induction motor slows due to directly applied load the torque produced by the motor will increase, but so will the amperage. This increased current will cause excessive heating of the windings. If a way can be devised to keep the internal temperature of the motor within the design limits, then higher than normal sustained torque can be achieved.
Some motors are constructed with high temperature insulation for operation in locations designated as hotter than normal. These motors should be able to operate with higher torques at their rate speeds when installed in normal temperature environments.
Some motors have designated design service factors ( 10-15%) wherein they can operate for short periods at torques higher the design load.
A significant increase in delivered torque will usually be done through the incorporation of speed reduction devices such as gears, V-belt sheaves, chain drives, etc. This is most likely what Billruss was referring to in his answer. There are gear-motor drives where the gear has already been included within the power unit package.
How to control the speed of my motor?
in
The motor turns pretty fast, and i want to decrease its RPM. Can I use a dimmer? Will it work? What else would you suggest that is guaranteed to work and has a low cost?
Answer:
It depends on what type of motor it is.
How to build a Motorized base to rotate my project?
in
My project is very light, not more than a circular cardboard that i want to rotate. I want it to be rotating very slowly, something like 4 rotations per minute. What kind of motor do I need to use? and What is the cheapest way to achieve what I'm seeking?
Answer:
Battery, DC motor and a potentiometer (for variable resistance), available at any radioshack, ebay, electronics shop, etc depending on where in the world you are. An AC to DC converter if has to run for too long coz the battery will wear out pretty soon.
How to calculate the pressure and volume of a tank full of steam and water?
in
A tank contains 10kg of water at 98(degrees Celsius) in the ratio:
- 8kg in liquid form
- 2kg in vapour form
What is the pressure within the tank and appropriate volume of the tank?
Thank you in advance!
Answer:
Whenever you've got liquid water in equilibrium with gaseous water, the gas's pressure equals the vapor pressure of water, which is a function of temperature. So, first thing is to look up the vapor pressure of water at 98° C:
P = (vapor pressure of water at 98°C) <== Look it up.
Next, figure out "n", the number of moles of water in vapor. You can do that knowing that the molecular weight of water is 18, and there are 2 kg of water. (Hint: 1 mole of water has a mass of 18 grams. It's a division problem.)
Next, use the ideal gas law to figure out the volume of the water vapor:
V_vapor = nRT/P
Plug in "n" and "P" that you figured out above; and set "T" to the ABSOLUTE temperature (convert 98°C to Kelvins).
That gives you the volume of the vapor.
The volume of the liquid is easier; it is essentially uneffected by pressure and temperature. So all you need to know is the density of water (ρ = 1000 kg/meter³), and use the formula:
V_liquid = (mass of liquid) / ρ
How to calculate the pressure and volume of a tank full of steam and water?
in
A tank contains 10kg of water at 98(degrees Celsius) in the ratio:
- 8kg in liquid form
- 2kg in vapour form
What is the pressure within the tank and appropriate volume of the tank?
Thank you in advance!
Answer:
The quality, or mole % vapor is 0.20, since 2 kg / (2 kg + 8 kg) = 0.20
The vessel contains water at its vapor pressure at 98 degrees C.
From vapor pressure correlation: mole% vapor = Psat / Ptotal
0.20 = Psat / Ptotal
From vapor pressure charts: Psat (90 C) = 707 mmHg
0.20 = 707 / Ptotal
Ptotal = 3535 mmHg, or 4.65 atm
Using PV = nRT and solving for volume (at this pressure):
V = (10 kg * 2.2 lb / kg / 18.02 lb / lb*mole) * (1.314 cf * atm / K / mole) * (371 K) / 4.65 atm
= 1.22 * 1.314 * 371 / 4.65
= 127 cubic feet for total vaporized water to remain at that pressure
