Google Adsense

Saturday, September 22, 2012

How to make the simplest magnetometer ?

How to make the simplest magnetometer ?

There are many types of magnetometers such as Hall’s effect, fluxgate …etc.
But there is a disadvantage of that types of magnetometers, they are always EXPENSIVE!
So we designed a simplest circuit to measure the magnitude of magnetic flux, and it only cost $2 (USD)

Before we start to make the apparatus, we have to know how it works.

We use the original definition of Faraday’s law:

By this integral formula, we can figure out the flux of a magnet.
But because of our coil is very small, and the dt would be long, so the magnitude of eddy voltage would be very small.
So that we need to use an OP(operational amplifier) circuit for two proposes:

1.      To amplifier the signal
2.      To integrate the voltage with time

We used the integral circuit to amplify 100times and integrate the signals.

The OP integral circuit is driven by this formula:

Next, we designed an 85-turns coil(diameter= 14mm; length= 23.8mm;dia. of wire 0.23mm) as a sensor to produce eddy voltage to drive the apparatus.

Why we choose this size of coil? Because we are going to use a voltage meter to measure the output signal, and we want to show the voltage just as same as the value of ”Tesla”.

Following is our calculation of the coil through the OP circuit and then produce voltage as same as the value of tesla.

We can know


It is the complete circuit that we used.

 It is the simplest magnetometer

 Use an oscilloscope to track the interaction of output voltage and a magnet.

 Use a voltage meter to measure the magnitude of magnetic field of a magnet
V = Tesla

It is the magnetometer working.

Please subscribe, common, share.

Tuesday, September 18, 2012

Making Red Yeast Rice (Monascus purpureus)

Red Yeast Rice (Monascus purpureus) is a species of  mold that is purplish-red in color. 

This fungus is most important because of its use. It is usually added into foods, likes "char siu"(honey-roasted pork) , to be a stain in China.  Otherwise, red yeast is also used to make wine.

 Broth of wine

 There is the producing process of red yeast as follows:

Day 1: Inoculate, Load trays, and pile up

    Mix the red yeast with rice thoroughly , load it on bamboo plane and pile it up.

 Day 1

 Day 2: Stir

      The hyphae of the red yeast grow very fast. To protect its temperature from getting too high and maintain the humidity of the rice, we have to stir the rice.

Day 2

Day 3: First water immersion

      The rice lost a part of water. To let the red yeast grow readily, we have to soak the plane of rice into water to replenish sufficient water.

 Day 3

Day 4: Stir

      To protect its temperature from getting too high and maintain the humidity of the rice, we have to stir the rice. Just like Day 2.

Day 4

Day 5: Second water immersion

      At this moment, read yeast grow extremely fast so we have to replenish sufficient water again.

Day 5

Day 6: Post-mature

      After water immersion, we have to stir it often to maintain its humidity and temperature.

Day 6

Day 7: Dehydrate (Final product)


Day 7

From Segura and Brandy's (University of California, Los Angeles) article :

"Statin Content Insufficient to Explain Effect of Red Yeast Rice on Cholesterol

A multitude of studies show that red yeast rice and its preparation, Cholestin have
antihypercholesterolemic effects as well as antihypertriglyceridemic effects (3,5).
However, given that Cholestin has a 0.4% content by weight of statin, the highest
Cholestin dosage administered in these studies (2.4g/d) delivered only approximately 5
mg of lovastatin (monacolin K) per day. In comparison to efficacy evaluations of
lovastatin, comparable levels of cholesterol reduction were seen with dosages of
lovastatin ranging from 20 to 80 mg/d. This suggests that the results seen with treatment
of red yeast rice are likely the combined effects of monacolins, plant sterols, and other
substances in the red yeast rice supplement (1). However, the exact mechanisms by
which the individual components of Cholestin act to reduce cholesterol are unknown.
Nevertheless, as a result of the antihyperlipidemic effects of the Chinese red yeast rice
contained in Cholestin, this supplement has the potential to impact the process of
atherosclerosis (6) and serve as a potent therapy to reduce the risk of cardiovascular

There are more details inside

Thursday, September 13, 2012

From Calcium Metal to Enthalpy

Calcium metal is a silver white metal.

It is a little harder than sodium metal. When it reacts with water, it would produce calcium hydroxide , hydrogen gas and a lot of heat. That is because when calcium element during losing two electrons from the atom and form lattice this process, its enthalpy change is very high.

But why the reaction is not exciting as sodium metal that is because the high melting point of calcium metal. If the calcium would melt during the reaction, the surface of calcium to contact with water would become very large, so that the reaction would become exciting.

Ca(OH)2 deposit.

However, compared with sodium,calcium has much stronger covalent bonds between each atoms, so it has higher melting point.

Let's use thermodynamics to check how calcium metal emit heat into the surrounding. 

 First, we have to write out the reaction formula and figure out the enthalpy change in the reaction.

ΔfHm                         0.0       2 x (-285.8)                             -985.2             0.0            (kJ/mloe)

=>  ΔH = (-985.2+0) - (0.0+ 2 x (-285.8))
            =   413.6  kJ/mole 

 Second, we are going to do an experiment to measure the heat transformation from the reaction.

Calcium metal weight
0.12 g
Molar of calcium
3.00 x 10-3 mole
Water weight
20.22 g
Origin temperature of water

Theoretical ΔT of water:
ΔH = m x s x ΔT

 =>ΔT = ΔH / ( m x s)
           = (( - (-413.6 x 103 x (0.12/40.078))) / (4.186))  / (20.22 x 1)
           = 14.63
=>      T = 30.59 + 14.63
           = 45.22

Theoretical temperature
Measured temperature
Surrounding temperature
Lose heat
98.00 cal
Heat capacity of the beaker
2.87 cal/

Heat lose in the beaker:
(40.32 – 30.59) x (2.87)
= 27.93 cal
Energy lose in other forms(gas kinetic energy, radiation…):
98.00 – 27.93
= 70.07 cal
= 293.02 J

Total energy released
1238.32 J
Energy in heat form
945.30 J
Heat transform efficiency

We can know not all the enthalpy change would turn into heat that is why the water is only 40.32℃ in the experiment.