0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
INTRODUCTION
0-100°C electronic temperature controlled relay is a circuit using which the temperature can be controlled with the help of a LM35 temperature sensor. The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in? Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration. Using a precision reference (TL431) a temperature is set and an accurate comparator inorder to construct a simple thermal controlled switch. The temperature that is set is compared with the output of the LM35 which decides whether to energize or de-energize the relay. An LED and an alarm is used to indicate when the device crosses the set temperature. The circuit is very useful in practical areas like heater,iron box etc.
Dept. of Applied Electronics & Instrumentation Engg
1
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
BLOCK DIAGRAM
REFERENCE LM 35 COMPARATOR VOLTAGE
RELAY
Dept. of Applied Electronics & Instrumentation Engg
2
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
BLOCK DIAGRAM EXPLANATION
The functional block diagram is shown. It comprises of a LM35, comparator, relay and a reference voltage to set the reference temperature. LM35: Temperature sensor which is calibrated in the Celsius (Centigrade) scale with a linear degree>volt conversion. Comparator: An accurate comparator (A1 of LM358) in order to construct a complete thermal-controlled switch Reference voltage: The preset (VR1) & resistor (R3) from a variable voltage divider which sets a reference voltage (V ref) form 0V ~ 1.62V. The op-amp (A2) buffers the reference voltage so as to avoid loading the divider network (VR1 & R3). Relay: The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. When the LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is actuated. When the temperature falls below the preset temperature, relay is de-energized.
Dept. of Applied Electronics & Instrumentation Engg
3
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
LM35
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in? Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1?4?Cat room temperature and ±3?4?C over a full ?55 to +150?C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1?C in still air. The LM35 is rated to operate over a ?55? to +150?C temperature range.While the LM35C is rated for a ?40? to +110?C range (?10?with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package. Features ? ? ? ? ? ? ? ? ? ? ? Calibrated directly in ? Celsius (Centigrade) Linear + 10.0 mV/?C scale factor 0.5?C accuracy guaranteable (at +25?C) Rated for full ?55? to +150?C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4 to 30 volts Less than 60 µA current drain Low self-heating, 0.08?C in still air Nonlinearity only ±1?4?C typical Low impedance output, 0.1 ? for 1 mA load
Dept. of Applied Electronics & Instrumentation Engg
4
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
TL431
The TL431/TL431Aare three-terminal adjustable regulator series with a guaranteed thermal stability over applicable temperature ranges. The output voltage may be set to any value between VREF (approximately 2.5 volts) and 36 volts with two external resistors These devices have a typical dynamic output impedance of 0.2W Active output circuitry provides a very sharp turn-on characteristic, making these devices excellent replacement for zener diodes in many applications. Features ? ? ? ? ? ? ? ? ? Programmable Output Voltage to 36 Volts Low Dynamic Output Impedance 0.20 Typical Sink Current Capability of 1.0 to 100mA Equivalent Full-Range Temperature Coefficient of 50ppm/°C Typical Temperature Compensated For Operation Over Full Rated Operating Temperature Range Low Output Noise Voltage Fast Turn-on Response
Dept. of Applied Electronics & Instrumentation Engg
5
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CIRCUIT DIAGRAM
Dept. of Applied Electronics & Instrumentation Engg
6
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CIRCUIT WORKING
The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. When the LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is actuated. When the temperature falls below the preset temperature, relay is de-energized. The circuit can be powered by any AC or DC 12V supply or battery (100mAmin.) Remark : There are several versions of LM35 temperature LM35CZ & LM35CAZ (inTO-92case)?40°Cto+110°C LM35DZ (inTO-92case)0~100oC LM35H & LM35AH (in TO-46 case) ?55°C to +150°C sensors :
The one we supply with this project is the -DZ version with temperature detection range from 0 ~ 100oC. The heart of the circuit is the LM35DZ temperature sensor which is factorycalibrated in the Celsius (or Centigrade) scale with a linear Degree>Volt conversion function. The output voltage (at pin 2) changes linearly with temperature from 0V (0oC) to 1000mV (100oC). This greatly simplifies the circuit design as we only need to provide a precision voltage reference (TL431) and an accurate comparator (A1 of LM358) in order to construct a complete thermal-controlled switch. The preset (VR1) & resistor (R3) from a variable voltage divider which sets a reference voltage (Vref) form 0V ~ 1.62V. The opamp (A2) buffers the reference voltage so as to avoid loading the divider network (VR1 & R3). The comparator (A1) compares the reference voltage Vref (set by VR1) with the output voltage of LM35DZ and decides whether to energize or deenergize the relay (LED1 ON or OFF respectively). The purpose of R2 is to provide a bit of hysteresis which helps to prevent relay chattering. Hysteresis is inversely proportional to the value of R2. Lower value of R2 gives higher hysteresis.
Dept. of Applied Electronics & Instrumentation Engg
7
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
Calibration : No special instrument is required. The relay can be set to "trip" (change state) at any temperature form 0 ~ 100oC. For example: To set a 70oC trip point ( switch over temperature) : 1. Connect a precision digital volt meter or multimeter across the test points "TP1" & "GND". 2. Slowly Adjust VR1 until you get a exact reading of 700 mV ( or 0.7V) on your voltmeter or multimeter.
Dept. of Applied Electronics & Instrumentation Engg
8
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
PCB LAYOUT
Fig 3
CB Layout
Dept. of Applied Electronics & Instrumentation Engg
9
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
Fig4CB Layout
Dept. of Applied Electronics & Instrumentation Engg
10
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
PCB DESIGN
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially-produced electronic devices. PCBs are inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire wrap or point-to-point construction, but are much cheaper and faster for high-volume production; the production and soldering of PCBs can be done by totally automated equipment. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.
MATERIALS
A PCB as a design on a computer (left) and realized as a board assembly populated with components (right). The board is double sided, with through-hole plating, green solder resist, and white silkscreen printing. Both surface mount and throughhole components have been used. A PCB in a computer mouse. The Component Side (left) and the printed side (right). The Component Side of a PCB in a computer mouse; some examples for common components and their reference designations on the silk screen. Conducting layers are typically made of thin copper foil. Insulating layers dielectric are typically laminated together with epoxy resin prepreg. The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue, black, white and red. There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known prepreg materials used in the PCB industry are FR-2 (Phenolic cotton paper), FR-3
Dept. of Applied Electronics & Instrumentation Engg 11
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
(Cotton paper and epoxy), FR-4 (Woven glass and epoxy), FR-5 (Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven glass and polyester). Thermal expansion is an important consideration especially with BGA and naked die technologies, and glass fiber offers the best dimensional stability. FR-4 is by far the most common material used today. The board with copper on it is called "copper-clad laminate". Copper foil thickness can be specified in ounces per square foot or micrometres. One ounce per square foot is 1.344 mils or 34 micrometres.
ETCHING
Chemical etching is done with ferric chloride, ammonium persulfate, or sometimes hydrochloric acid. For PTH (plated-through holes), additional steps of electroless deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes the resist leaving the bare copper to be etched away.
LAMINATION Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are formed by bonding together separately etched thin boards.
DRILLING Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill(NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB. Most common laminate is epoxy filled fiberglass. Drill bit wear is partly due to embedded glass, which is harder than steel. High drill speed necessary for cost
Dept. of Applied Electronics & Instrumentation Engg 12
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
effective drilling of hundreds of holes per board causes very high temperatures at the drill bit tip, and high temperatures (400-700 degrees) soften steel and decompose (oxidize) laminate filler. Copper is softer than epoxy and interior conductors may suffer damage during drilling. When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Laser-drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias. It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried vias when they connect two or more internal copper layers and no outer layers. The walls of the holes, for boards with 2 or more layers, are made conductive then plated with copper to form plated-through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. Removing (etching back) the smear also reveals the interior conductors as well. EXPOSED CONDUCTOR PLATING AND COATING PCBs are plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper. After PCBs are etched and then rinsed with water, the solder mask is applied, and then any exposed copper is coated with solder, nickel/gold, or some other anticorrosion coating. Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air
Dept. of Applied Electronics & Instrumentation Engg 13
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface.[6] This solder was atinlead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium. It is important to use solder compatible with both the PCB and the parts used. An example is Ball Grid Array (BGA) using tin-lead solder balls for connections losing their balls on bare copper traces or using lead-free solder paste. Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold plating (over nickel). Edge connectors, placed along one edge of some boards, are often nickel plated thengold plated. Another coating consideration is rapid diffusion of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating and/or leaving voids. Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias.[7][8] Silver, zinc, and aluminum are known to grow whiskers under the influence of an electric field. Silver also grows conducting surface paths in the presence of halide and other ions, making it a poor choice for electronics use. Tin will grow "whiskers" due to tension in the plated surface. Tin-Lead or Solder plating also grows whiskers, only reduced by the percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress lowers whisker incidence. Another coating issue is tin pest, the transformation of tin to a powdery allotrope at low temperature.
SOLDER RESIST Areas that should not be soldered may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and creating short circuits. Solder resist also provides some protection from the environment. Solder resist is typically 20-30 micrometres thick.
Dept. of Applied Electronics & Instrumentation Engg 14
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
SCREEN PRINTING Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board. Screen print is also known as the silk screen, or, in one sided PCBs, the red print. Lately some digital printing solutions have been developed to substitute the traditional screen printing process. This technology allows printing variable data onto the PCB, including serialization and barcode information for traceability purposes.
DESIGN
? ?
?
?
?
?
?
Schematic capture or schematic entry is done through an EDA tool. Card dimensions and template are decided based on required circuitry and case of the PCB. Determine the fixed components and heat sinks if required. Deciding stack layers of the PCB. 4 to 12 layers or more depending on design complexity. Ground plane and Power plane are decided. Signal planes where signals are routed are in top layer as well as internal layers.[15] Line impedance determination using dielectric layer thickness, routing copper thickness and trace-width. Trace separation also taken into account in case of differential signals. Microstrip, stripline or dual stripline can be used to route signals. Placement of the components. Thermal considerations and geometry are taken into account. Vias and lands are marked. Routing the signal trace. For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes as power plane behaves as ground for AC. Gerber file generation for manufacturing.
Dept. of Applied Electronics & Instrumentation Engg
15
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
APPLICATIONS
Here is a practical example showing how the circuit can be incorporated in an automatic temperature control system which maintains the temperature of water in a container at 70 oC.(Fig5)
Dept. of Applied Electronics & Instrumentation Engg 16
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
COMPONENTS REQUIRED
Slno: Components Specification 1 Resistors ? R1 -- 10K ? R2 -- 4.7M ? R3 -- 1.2K ? R4 -- 1K ? R5 -- 1K ? R6 -- 33? 2 3 4 5 6 7 8 9 IC 1 IC 2 IC 3 Transistor Diode Diode Pot Capacitor LM35DZ Precision Celsius (Centigrade) Temperature sensor TL431 +2.5V precision voltage reference LM358 Dual single supply Op-amp Q1:General purpose PNP transistor ( A1015,...) with E-C-B pin-out) D1;D2:1N4148 silicon diodes (or 1SS133) D3,D4:1N400x (x=2,,,,.7) rectifier diodes ZD1:Zener diode, 13V, 400Mw 2.2K (Temperature set point) ? C1 -- 0.1 µF ceramic or mylar cap (# 104 or 100n) ? C2 -- 470 µF or 680 µF electrolytic cap. (16V min)
Dept. of Applied Electronics & Instrumentation Engg
17
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
COST ESTIMATION
SL NO:
COMPONENTS SPECIFICATION
QUANTITY
PRICE
Dept. of Applied Electronics & Instrumentation Engg
18
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
FUTURE SCOPE AND ENHANCEMENTS
0-100°c electronic temperature controlled relay is a simple whereas a useful circuit with which the temperature can be controlled with the aid of a LM 35 temperature sensor. As explained the circuit can be made useful in practical area where the circuit can be connected to a device whose temperature has to be controlled at a particular limit say a water tank with a heater whose temperature can be set to a particular value. Similar another application is that the circuit attached with a buzzer which can be connected to a device like an iron box so that it would help to save electricity by avoiding overheating of the device. In future the circuit can be enhanced by connecting a GSM Module to the circuit so that in industrial area when a machine crosses the set temperature, we can inform the control room by sending a message,or else a call to control room manager so that damages to the machine can be avoided by disconnecting the equipment with GSM technology.
Dept. of Applied Electronics & Instrumentation Engg
19
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CONCLUSION
0-100°C electronic temperature controlled relay is a simple and useful circuit which can be used to control the temperature above a set value using LM35, a temperature sensor. Initially,circuit was selected and components where purchased and the circuit was verified in bread board. Then we designed the PCB and the circuit was soldered onto the PCB. Output was verified by setting the temperature at different levels and it was found that the LED turn ON with an alarm when the device crosses the set value.
Dept. of Applied Electronics & Instrumentation Engg
20
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
REFERENCE
? ? ? ? ?
www.escol.com www.national.com www.scribd.com OPAMP AND LINEAR INTEGRATED CIRCUITS-GAYKWAD Software used: Livewire
Dept. of Applied Electronics & Instrumentation Engg
21
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
DATASHEET
Dept. of Applied Electronics & Instrumentation Engg
22
doc_297929525.docx
ASIET, KALADY
INTRODUCTION
0-100°C electronic temperature controlled relay is a circuit using which the temperature can be controlled with the help of a LM35 temperature sensor. The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in? Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration. Using a precision reference (TL431) a temperature is set and an accurate comparator inorder to construct a simple thermal controlled switch. The temperature that is set is compared with the output of the LM35 which decides whether to energize or de-energize the relay. An LED and an alarm is used to indicate when the device crosses the set temperature. The circuit is very useful in practical areas like heater,iron box etc.
Dept. of Applied Electronics & Instrumentation Engg
1
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
BLOCK DIAGRAM
REFERENCE LM 35 COMPARATOR VOLTAGE
RELAY
Dept. of Applied Electronics & Instrumentation Engg
2
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
BLOCK DIAGRAM EXPLANATION
The functional block diagram is shown. It comprises of a LM35, comparator, relay and a reference voltage to set the reference temperature. LM35: Temperature sensor which is calibrated in the Celsius (Centigrade) scale with a linear degree>volt conversion. Comparator: An accurate comparator (A1 of LM358) in order to construct a complete thermal-controlled switch Reference voltage: The preset (VR1) & resistor (R3) from a variable voltage divider which sets a reference voltage (V ref) form 0V ~ 1.62V. The op-amp (A2) buffers the reference voltage so as to avoid loading the divider network (VR1 & R3). Relay: The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. When the LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is actuated. When the temperature falls below the preset temperature, relay is de-energized.
Dept. of Applied Electronics & Instrumentation Engg
3
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
LM35
The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in? Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1?4?Cat room temperature and ±3?4?C over a full ?55 to +150?C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it has very low self-heating, less than 0.1?C in still air. The LM35 is rated to operate over a ?55? to +150?C temperature range.While the LM35C is rated for a ?40? to +110?C range (?10?with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package. Features ? ? ? ? ? ? ? ? ? ? ? Calibrated directly in ? Celsius (Centigrade) Linear + 10.0 mV/?C scale factor 0.5?C accuracy guaranteable (at +25?C) Rated for full ?55? to +150?C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4 to 30 volts Less than 60 µA current drain Low self-heating, 0.08?C in still air Nonlinearity only ±1?4?C typical Low impedance output, 0.1 ? for 1 mA load
Dept. of Applied Electronics & Instrumentation Engg
4
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
TL431
The TL431/TL431Aare three-terminal adjustable regulator series with a guaranteed thermal stability over applicable temperature ranges. The output voltage may be set to any value between VREF (approximately 2.5 volts) and 36 volts with two external resistors These devices have a typical dynamic output impedance of 0.2W Active output circuitry provides a very sharp turn-on characteristic, making these devices excellent replacement for zener diodes in many applications. Features ? ? ? ? ? ? ? ? ? Programmable Output Voltage to 36 Volts Low Dynamic Output Impedance 0.20 Typical Sink Current Capability of 1.0 to 100mA Equivalent Full-Range Temperature Coefficient of 50ppm/°C Typical Temperature Compensated For Operation Over Full Rated Operating Temperature Range Low Output Noise Voltage Fast Turn-on Response
Dept. of Applied Electronics & Instrumentation Engg
5
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CIRCUIT DIAGRAM
Dept. of Applied Electronics & Instrumentation Engg
6
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CIRCUIT WORKING
The circuit switches a miniature relay ON or OFF according to the temperature detected by the single chip temperature sensor LM35DZ. When the LM35DZ detects a temperature higher than the preset level (set by VR1), the relay is actuated. When the temperature falls below the preset temperature, relay is de-energized. The circuit can be powered by any AC or DC 12V supply or battery (100mAmin.) Remark : There are several versions of LM35 temperature LM35CZ & LM35CAZ (inTO-92case)?40°Cto+110°C LM35DZ (inTO-92case)0~100oC LM35H & LM35AH (in TO-46 case) ?55°C to +150°C sensors :
The one we supply with this project is the -DZ version with temperature detection range from 0 ~ 100oC. The heart of the circuit is the LM35DZ temperature sensor which is factorycalibrated in the Celsius (or Centigrade) scale with a linear Degree>Volt conversion function. The output voltage (at pin 2) changes linearly with temperature from 0V (0oC) to 1000mV (100oC). This greatly simplifies the circuit design as we only need to provide a precision voltage reference (TL431) and an accurate comparator (A1 of LM358) in order to construct a complete thermal-controlled switch. The preset (VR1) & resistor (R3) from a variable voltage divider which sets a reference voltage (Vref) form 0V ~ 1.62V. The opamp (A2) buffers the reference voltage so as to avoid loading the divider network (VR1 & R3). The comparator (A1) compares the reference voltage Vref (set by VR1) with the output voltage of LM35DZ and decides whether to energize or deenergize the relay (LED1 ON or OFF respectively). The purpose of R2 is to provide a bit of hysteresis which helps to prevent relay chattering. Hysteresis is inversely proportional to the value of R2. Lower value of R2 gives higher hysteresis.
Dept. of Applied Electronics & Instrumentation Engg
7
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
Calibration : No special instrument is required. The relay can be set to "trip" (change state) at any temperature form 0 ~ 100oC. For example: To set a 70oC trip point ( switch over temperature) : 1. Connect a precision digital volt meter or multimeter across the test points "TP1" & "GND". 2. Slowly Adjust VR1 until you get a exact reading of 700 mV ( or 0.7V) on your voltmeter or multimeter.
Dept. of Applied Electronics & Instrumentation Engg
8
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
PCB LAYOUT
Fig 3
CB LayoutDept. of Applied Electronics & Instrumentation Engg
9
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
Fig4
CB LayoutDept. of Applied Electronics & Instrumentation Engg
10
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
PCB DESIGN
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially-produced electronic devices. PCBs are inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire wrap or point-to-point construction, but are much cheaper and faster for high-volume production; the production and soldering of PCBs can be done by totally automated equipment. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.
MATERIALS
A PCB as a design on a computer (left) and realized as a board assembly populated with components (right). The board is double sided, with through-hole plating, green solder resist, and white silkscreen printing. Both surface mount and throughhole components have been used. A PCB in a computer mouse. The Component Side (left) and the printed side (right). The Component Side of a PCB in a computer mouse; some examples for common components and their reference designations on the silk screen. Conducting layers are typically made of thin copper foil. Insulating layers dielectric are typically laminated together with epoxy resin prepreg. The board is typically coated with a solder mask that is green in color. Other colors that are normally available are blue, black, white and red. There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known prepreg materials used in the PCB industry are FR-2 (Phenolic cotton paper), FR-3
Dept. of Applied Electronics & Instrumentation Engg 11
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
(Cotton paper and epoxy), FR-4 (Woven glass and epoxy), FR-5 (Woven glass and epoxy), FR-6 (Matte glass and polyester), G-10 (Woven glass and epoxy), CEM-1 (Cotton paper and epoxy), CEM-2 (Cotton paper and epoxy), CEM-3 (Woven glass and epoxy), CEM-4 (Woven glass and epoxy), CEM-5 (Woven glass and polyester). Thermal expansion is an important consideration especially with BGA and naked die technologies, and glass fiber offers the best dimensional stability. FR-4 is by far the most common material used today. The board with copper on it is called "copper-clad laminate". Copper foil thickness can be specified in ounces per square foot or micrometres. One ounce per square foot is 1.344 mils or 34 micrometres.
ETCHING
Chemical etching is done with ferric chloride, ammonium persulfate, or sometimes hydrochloric acid. For PTH (plated-through holes), additional steps of electroless deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with tin/lead. The tin/lead becomes the resist leaving the bare copper to be etched away.
LAMINATION Some PCBs have trace layers inside the PCB and are called multi-layer PCBs. These are formed by bonding together separately etched thin boards.
DRILLING Holes through a PCB are typically drilled with tiny drill bits made of solid tungsten carbide. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill(NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB. Most common laminate is epoxy filled fiberglass. Drill bit wear is partly due to embedded glass, which is harder than steel. High drill speed necessary for cost
Dept. of Applied Electronics & Instrumentation Engg 12
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
effective drilling of hundreds of holes per board causes very high temperatures at the drill bit tip, and high temperatures (400-700 degrees) soften steel and decompose (oxidize) laminate filler. Copper is softer than epoxy and interior conductors may suffer damage during drilling. When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Laser-drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias. It is also possible with controlled-depth drilling, laser drilling, or by pre-drilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried vias when they connect two or more internal copper layers and no outer layers. The walls of the holes, for boards with 2 or more layers, are made conductive then plated with copper to form plated-through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with 4 layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. Removing (etching back) the smear also reveals the interior conductors as well. EXPOSED CONDUCTOR PLATING AND COATING PCBs are plated with solder, tin, or gold over nickel as a resist for etching away the unneeded underlying copper. After PCBs are etched and then rinsed with water, the solder mask is applied, and then any exposed copper is coated with solder, nickel/gold, or some other anticorrosion coating. Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air
Dept. of Applied Electronics & Instrumentation Engg 13
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface.[6] This solder was atinlead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium. It is important to use solder compatible with both the PCB and the parts used. An example is Ball Grid Array (BGA) using tin-lead solder balls for connections losing their balls on bare copper traces or using lead-free solder paste. Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), and direct gold plating (over nickel). Edge connectors, placed along one edge of some boards, are often nickel plated thengold plated. Another coating consideration is rapid diffusion of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating and/or leaving voids. Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias.[7][8] Silver, zinc, and aluminum are known to grow whiskers under the influence of an electric field. Silver also grows conducting surface paths in the presence of halide and other ions, making it a poor choice for electronics use. Tin will grow "whiskers" due to tension in the plated surface. Tin-Lead or Solder plating also grows whiskers, only reduced by the percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress lowers whisker incidence. Another coating issue is tin pest, the transformation of tin to a powdery allotrope at low temperature.
SOLDER RESIST Areas that should not be soldered may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and creating short circuits. Solder resist also provides some protection from the environment. Solder resist is typically 20-30 micrometres thick.
Dept. of Applied Electronics & Instrumentation Engg 14
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
SCREEN PRINTING Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board. Screen print is also known as the silk screen, or, in one sided PCBs, the red print. Lately some digital printing solutions have been developed to substitute the traditional screen printing process. This technology allows printing variable data onto the PCB, including serialization and barcode information for traceability purposes.
DESIGN
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Schematic capture or schematic entry is done through an EDA tool. Card dimensions and template are decided based on required circuitry and case of the PCB. Determine the fixed components and heat sinks if required. Deciding stack layers of the PCB. 4 to 12 layers or more depending on design complexity. Ground plane and Power plane are decided. Signal planes where signals are routed are in top layer as well as internal layers.[15] Line impedance determination using dielectric layer thickness, routing copper thickness and trace-width. Trace separation also taken into account in case of differential signals. Microstrip, stripline or dual stripline can be used to route signals. Placement of the components. Thermal considerations and geometry are taken into account. Vias and lands are marked. Routing the signal trace. For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes as power plane behaves as ground for AC. Gerber file generation for manufacturing.
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
APPLICATIONS
Here is a practical example showing how the circuit can be incorporated in an automatic temperature control system which maintains the temperature of water in a container at 70 oC.(Fig5)
Dept. of Applied Electronics & Instrumentation Engg 16
0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
COMPONENTS REQUIRED
Slno: Components Specification 1 Resistors ? R1 -- 10K ? R2 -- 4.7M ? R3 -- 1.2K ? R4 -- 1K ? R5 -- 1K ? R6 -- 33? 2 3 4 5 6 7 8 9 IC 1 IC 2 IC 3 Transistor Diode Diode Pot Capacitor LM35DZ Precision Celsius (Centigrade) Temperature sensor TL431 +2.5V precision voltage reference LM358 Dual single supply Op-amp Q1:General purpose PNP transistor ( A1015,...) with E-C-B pin-out) D1;D2:1N4148 silicon diodes (or 1SS133) D3,D4:1N400x (x=2,,,,.7) rectifier diodes ZD1:Zener diode, 13V, 400Mw 2.2K (Temperature set point) ? C1 -- 0.1 µF ceramic or mylar cap (# 104 or 100n) ? C2 -- 470 µF or 680 µF electrolytic cap. (16V min)
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
COST ESTIMATION
SL NO:
COMPONENTS SPECIFICATION
QUANTITY
PRICE
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
FUTURE SCOPE AND ENHANCEMENTS
0-100°c electronic temperature controlled relay is a simple whereas a useful circuit with which the temperature can be controlled with the aid of a LM 35 temperature sensor. As explained the circuit can be made useful in practical area where the circuit can be connected to a device whose temperature has to be controlled at a particular limit say a water tank with a heater whose temperature can be set to a particular value. Similar another application is that the circuit attached with a buzzer which can be connected to a device like an iron box so that it would help to save electricity by avoiding overheating of the device. In future the circuit can be enhanced by connecting a GSM Module to the circuit so that in industrial area when a machine crosses the set temperature, we can inform the control room by sending a message,or else a call to control room manager so that damages to the machine can be avoided by disconnecting the equipment with GSM technology.
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
CONCLUSION
0-100°C electronic temperature controlled relay is a simple and useful circuit which can be used to control the temperature above a set value using LM35, a temperature sensor. Initially,circuit was selected and components where purchased and the circuit was verified in bread board. Then we designed the PCB and the circuit was soldered onto the PCB. Output was verified by setting the temperature at different levels and it was found that the LED turn ON with an alarm when the device crosses the set value.
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
REFERENCE
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www.escol.com www.national.com www.scribd.com OPAMP AND LINEAR INTEGRATED CIRCUITS-GAYKWAD Software used: Livewire
Dept. of Applied Electronics & Instrumentation Engg
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0-100°C Electronic Temperature Controlled Relay
ASIET, KALADY
DATASHEET
Dept. of Applied Electronics & Instrumentation Engg
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doc_297929525.docx