FYP Week 5 - LM35 circuit

Hi,

 

Ni hao ma.....? Hehe...Just a lil mandarin to spice up the mood.....huhu. Okay, now for this week 5, I'm focusing on the construction of the LM35.

What is LM35

The LM35 series are precision integrated-circuit LM35 temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 sensor 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 sensor does not require any external calibration or trimming to provide typical accuracies of ±¼°C at room temperature and ±¾°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 sensor 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 sensor is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.
 

LM35 Sensor Circuit Schematic

Figure 1: Schematic diagram for LM35

LM35 Sensor Pinouts and Packaging

Figure 2: LM35 pinouts

Implementation of LM35

I did some research on the most appropriate and simplest form of circuit to be used for this project. Below I have attached the schematic diagrams of the circuits I will be using. As you can see below, the temperature sensor circuit shows that the sensor is simply connected straight to the conditioning circuit as in Figure 3.

The temperature sensor (LM35) is connected to the operational amplifier (LM358) in order to amplify the output signal received from the sensor. The output signal (labelled as signal in the diagram), will be connected to the input of the PIC main board.

Figure 3: Schematic diagram for the temperature sensor by using LM35

I've mentioned from the previous post that I will be constructing the PCB board for the temperature sensor and relay switch circuit. So, I went to the Pasar Road again to purchase some components to begin making the circuits.

First of all, after I've purchased the necessary components, I went to the lab to do some circuit constructing on the breadboard to see whether the circuit works or not. For this circuit, I'm using LM35 as the sensor and LM358, 5k variable resistor and 100k resistor for the conditioning circuit.

 Figure 4: Components use for the LM35 circuit

 Figure 5: Soldering process

So, here is the complete board for the temperature sensor circuit (Figure 6). The 3 pin sticking out will be connected to the PIC board, ground and 5V supply.

 Figure 6: Component placement on the temperature sensor PCB board

So, that's it for now...! Let's stop here..it's already lunch time. Gotta go now. Hope you enjoy this  entry. Have a great day.!   :)  <3



Bye & XOXO

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Quote of the day...!!

I would not waste my life in friction when it could be turned into momentum.  ~Frances Willard

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p/s: I really love purple..... :)

Regards,



Idriah Safriza :P

FYP Week 4 - Switching relay circuit

Bonjour,

Comment s'est passée ta journée (How was your day)? Hahaha.... Mine was awesome and just amazing... But I'm a lil tired with all the delayed work load......So many things to do, yet so little time left before due date. Okay, enough with the babbling.... :p

Let go straight to the point... Next week we will discuss on the LM35 circuit construction. So, now let's look at the relay switch circuit first.

Principle of Relay

A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. Relays are found hidden in all sorts of devices. Relays are amazingly simple devices. There are four parts in every relay:

• Electromagnet
• Armature that can be attracted by the electromagnet
• Spring
• Set of electrical contacts

The following figure shows these four parts in action:

Figure 1: Construction of Relay

In this Figure 1, you can see that a relay consists of two separate and completely independent circuits. The first is at the bottom and drives the electromagnet. In this circuit, a switch is controlling power to the electromagnet.

Operation of Relay

• When the switch is on, the electromagnet is on, and it attracts the armature (blue). The armature is acting as a switch in the second circuit.

• When the electromagnet is energized, the armature completes the second circuit and the light is on. 

•  When the electromagnet is not energized, the spring pulls the armature away and the circuit is not complete. In that case, the light is dark.

Consideration on purchasing a Relay

When you purchase relays, you generally have control over:

• The voltage and current that is needed to activate the armature
• The maximum voltage and current that can run through the armature and the armature contacts
• The number of armatures (generally one or two)
• The number of contacts for the armature (generally one or two -- the relay shown here has two, one of which is unused)
• Whether the contact (if only one contact is provided) is normally open (NO) or normally closed (NC)

Source taken from http://en.wikipedia.org/wiki/Relay

Source taken from http://electronics.howstuffworks.com/relay.htm 

The relay that I am using consists of 3 pins, the change-over (com), normally-open (n/0) and normally-closed (n/c) respectively. The relay is use for switching purposes to control the motor use in the Blood Pressure circuit. So how to do the connections....It's very simple! First of all, we use an NPN transistor (C547) where the base (B) is connected to the signal pin as below and straight to the PIC main board, Emitter (E) is connected to the ground and the Collector (C) to the relay. Please refer Figure 2 for better understanding.

Figure 2: Schematic diagram of the relay switch circuit

Component you need to make the relay switch circuit are IN4007 diode, two 1kohm resistors, 1 LED, 1 NPN transistor and a relay, exactly as you can see in Figure 3.

Figure 3: Components used for the relay switch circuit

After designing the PCB layout on the PCB, I proceed with drilling holes on the PCB.

Figure 4: Drilling the PCB

Next, I place the components accordingly by referring to Figure 2 schematic diagram and solder the components to the PCB neatly. 

Figure 5: Soldering result

So this is how I place the components........ and It's done.........TADA....!

 

Figure 6: Component placement on the relay switch PCB board

Yeay...! We are done with the switching relay circuit. Therefore, next week we can begin to discuss on the LM35 as the temperature sensor circuit..... Wait for me k.....C ya..........  (o','o )v


Bubye peeps
XOXO

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Quote of the day...!

He who is not courageous enough to take risks will accomplish nothing in life 

- Muhammad Ali -

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Regards,

Idriah Safriza :P

FYP Week 3 - Component placement, board drilling and soldering for the PIC mainboard

Hello there,

It's time for me to update my latest progress...  :)    I'll continue from my previous post, I've did some drilling and soldering for my PCB. Just to show you guys how the PIC main board looks like..check it out below!

The first attempt was a silly mistake as I have forgotten to mirror the image before printing out the PCB layout on the PCB iron-on paper. So, I have to reproduce the PCB once again following the same procedure as before.

Furthermore, I've also bought a new set of components for the second attempt to make the PCB in order to make sure the components are all in good condition. Sometimes, when we solder and desolder components, we might not realize whether we damage the component by accident. Therefore, to play safe I just bought a new set of components for the 2nd attempt to make the PCB board for the PIC.

 Figure 1: Components used for the PIC main board construction

I did some soldering and a little circuit constructing with my friends at the lab and to be honest the first etching is not much of a success, so I have to redo the PCB for the second time. The first PCB turn out inverted than the original PCB layout image due to my carelessness. So, I redo it again for the second time. So, here's the result.

Figure 2: The first attempt to make the PCB for the PIC main board..it doesn't turn out well

 Figure 3: So I redo the PCB and it looks more organized than the 1st.

  

Figure 4: Soldering process (back view)

 

Figure 5: Finished PCB (front view)

So, that's it! The PIC main board is done! For my next post I am thinking on focusing on the temperature sensor (LM35) and relay switch circuit. So, keep in touch and keep on waiting for my updates! See you soon people...... <3

Bye

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Quote of the day....!!

Don't ever take a fence down until you know why it was put up.  ~Robert Frost  <3 <3 <3

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Regards,  

Idriah Safriza  :)

FYP Week 2 - Microcontroller main board (PCB designing and etching)

Ape khabar,

Hope everyone is doing just fine. First of all, Happy Chinese New Year to everyone. May this year of dragon brings more prosperity and happiness to everyone.

This week I am going to discuss on how I designed my PCB for the PIC mainboard. Furthermore, I will also explain on the procedure on how to do the etching process for the PCB board. Hope you enjoy it.....!!  :)

Part 1: PCB Design

Okay, so let me begin, Hmmmm.....I did some PCB designing using the PCB express software where I have downloaded it from the internet for free...hehe. There are many other similar software where you can use to design your PCB layout such as the FreePCB, Eagle, PCBArtist, WinQCad, DipTrace, Altium and etc. I am more familiar with the ExpressPCB because I used it before when I designed my PCB board for my Diploma projects. Therefore, for this Degree project, I will also use the same software as I am already familiar with it. 

Download ExpressPCB for free here!

What is ExpressPCB

Step 1: Draw Schematics using ExpressSCH

Begin your project by drawing a schematic. While not required, it will save you time when designing your PCB. Drawing a schematic with the ExpressSCH program is as easy as placing the components on the page and wiring the pins together. The schematic can then be linked to your PCB file, so that the PCB knows what needs to be connected together.

Click here to read more on ExpressSCH

Figure 1: ExpressSCH screenshot

Step 2: Design PCB using ExpressPCB

Designing 2 or 4 layer boards using the ExpressPCB program is very simple. Start by inserting the component footprints, then drag them into position. Next, connect the pins by drawing the traces. If you link your schematic file to the PCB, the ExpressPCB program will highlight the pins that should be wired together in blue. 

Click here to read more on ExpressPCB

Figure 2: ExpressPCB screenshot

This is just a brief introduction on the ExpressPCB. So here are my designs for the PIC mainboard..........  ('', )v  

Figure 3:PIC mainboard schematic diagram

Figure 4: Top view of PIC mainboard PCB layout

Figure 5: Back view of PIC mainboard PCB layout

Part 2: Etching process

For the etching process, I did it manually. First I print out the mirror image of the PCB layout to the PCB-Iron- on paper. Then, I iron the PCB-Iron-on paper onto the PC Board and next I soak the PCB into the acid to etch out all the unwanted cooper from the PCB. Below are the steps of the etching process, simply follow this 5 easy steps. :)

 Figure 6: Print out of PCB layout on PCB-Iron-On paper

 Figure 7: Iron the PCB-Iron on paper on the PCB

Figure 8: Soak the PCB into the Ferric Chloride acid for etching purposes

 Figure 9: Clean the excessive marks with thinner

 Figure 10: Finished PCB

There you have it.....! It is half way done...Now that the PCB is almost done...next I will proceed with the board drilling, component placement and soldering of the components. Yeay..!

Don't forget to catch me next week okay! Gonna miss you guys...

Bubye...

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Quote of the day.....!

The greatest personal limitation is to be found not in the things you want to do and can't, but in the things you've never considered doing 

- Richard Bandler -

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p/s: Gong Xi Fa Cai Xian Nian Kuai Le to everyone. Hope this year will be a blast!!

Regards,

Idriah SafrizaBte Idris Chin <3