details about hardware

8/7/2019 Details About Hardware

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y What Does an LM35 Do? How does it work?

o It has an output voltage that is proportional to the Celsius temperature. o The scale factor is .01V/oC

o The LM35 does not require any external calibration or trimming and maintains

an accuracy of +/-0.4 oC at room temperature and +/- 0.8 oC over a range ofoC to +100 oC.

o Another important characteristic of the LM35DZ is that it draws only 60 micro

amps from its supply and possesses a low self-heating capability. The sensor

self-heating causes less than 0.1 oC temperature rise in still air.

The LM35 comes in many different packages, including the following.

y TO-92 plastic transistor-like package,

y T0-46 metal can transistor-like package

y 8-lead surface mount SO-8 small outline package

y TO-202 package. (Shown in the picture above)

y How Do You Use An LM35? (Electrical Connections) o Here is a commonly used circuit. For connections refer to the picture above.

o In this circuit, parameter values commonly used are:

Vc = 4 to 30v

5v or 12 v are typical values used. R a = Vc /10-6

Actually, it can range from 80 K;to 600 K;, but most just use 80 K;

.

o Here is a photo of the LM 35 wired on a circuit board.



The white wire in the photo goes to the power supply. Both the resistor and the black wire go to ground. The output voltage is measured from the middle pin to ground.l

y What Can You Expect When You Use An LM35?

o You will need to use a voltmeter to sense Vout.

o The output voltage is converted to temperature by a simple conversion factor

o The sensor has a sensitivity of 10mV / oC. o Use a conversion factor that is the reciprocal, that is 100 oC/V.

o The general equation used to convert output voltage to temperature is:

Temperature ( oC) = Vout * (100 oC/V)

So if Vout is 1V , then, Temperature = 100 oC

The output voltage varies linearly with temperature.

How Do Solenoid Valves Work?

By an eHow Contributor

How Do Solenoid Valves Work?

1. Overview of Solenoid Valves

o Solenoid coil



A solenoid valve is an electromechanical valve that is controlled by an electric current. The electriccurrent runs through a solenoid, which is a wire coil wrapped around a metallic core. A solenoid

creates a controlled magnetic field when an electrical current is passed through it. This magnetic fiaffects the state of the solenoid valve, causing the valve to open or close. Solenoid valves are used

transport gases or liquids and have a wide variety of applications, including irrigation, sprinkler systems and industrial uses.

2. Mechanics of a Solenoid Valve

o A -- Inlet; B -- Stopper; C -- Spring; D -- Metal Bar; E -- Solenoid and Pin; F -- Outlet

The mechanical force in a solenoid valve is the solenoid coil, which converts electrical energy into

magnetic energy that is used to modulate the valve. A solenoid valve contains an inlet pipe, whichtransports the gas or liquid into the solenoid valve. The valve consists of a rubber or plastic stopper

that is held against the inlet pipe to seal it closed. The front end of the stopper contains a rubber O-ring, which seals the inlet pipe and prevents the gas or liquid from entering the solenoid valve. The

stopper is held in place by a metallic spring attached to the back end of the stopper. The stopper isalso attached to a metallic pin via a metal bar that runs perpendicular from the pin to the stopper. T

pin is located near the solenoid coil. When the solenoid coil is activated, the magnetic field draws tpin back, which pulls the stopper back and breaks the seal with the inlet pipe, allowing the gas or

liquid to enter the solenoid valve. When the solenoid coil is deactivated, the force of the springpushes the stopper back into place against the inlet pipe.

3. Importance of Pressure in Solenoid Valveso Solenoid valves are different from pumps in that there is no mechanical device to force the liquid o

gas through the valve. As a result, it is important for a solenoid valve to have a pressure differentia

between the outlet pipe and the inlet pipe. Specifically, the inlet pipe must have higher pressure thathe outlet pipe to force the gas or liquid through the solenoid valve. Equalized pressure within a

solenoid valve will prevent a substance from flowing though the valve, regardless of the state of thsolenoid and the stopper.

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