Arduino Uno R3 Purchasing

For the time being, i'm just need Arduino Uno R3 for testing the circuit. It is cost RM60 + RM6 for the USB cable. I bought it from Online Component, Jalan Pasar.

 Port that i used are 5V, GND, A0, 12, 11, 5, 4, 3 and 2. More information about the product, you can view at here http://www.myduino.com/index.php?route=product/product&product_id=271.

PCB Etching and Soldering Semi Mounted Device Component

Hi everyone,

This week will be etching process for PPG circuit. Actually this is forth etching, since the etching is not too good before. I've been learn how to etch a PCB by just watching video from youtube, you can view it here http://www.youtube.com/watch?v=RfelrrZyCYQ, it is quite easy if you just watch the video, actually it is really  trivial works. The works is as below:

1. Put on the goggles and gloves. Always remember safety first because it is deal with acid chemicals.
2. Make sure the area is well ventilated before mixing. The chemicals will produce hazardous fumes.
3. Exposed your PCB with the transparent plastic PCB layout at the UV light box for 60 minutes.
4. Mix two parts hydrogen peroxide for every one part hydrochloric acid. When mixed, they form a substance that is a severe skin irritant, and will produce toxic chlorine gas.
5. In a non-metallic basin pour enough of the solution to completely submerge the circuit board.
6. Drop in the circuit board and agitate it for about ten to fifteen minutes. Continue stirring until all copper has dissolve, and the solution has taken on a slight green tinge.
7. For cleanup, make sure you are wearing gloves. Wash the board off in cold water to remove any etching solution. Then use a paper towel or rag to dry it off completely. Set it aside. Assure that there is no solution in the workspace or containers then remove the gloves and googles.
8. Mix a one to one ratio of acetone and rubbing alcohol. Take a paper towel, dip it into the solution, and gentle rub it over the surface of the board. The permanent marker will begin to come off. Continue rubbing until all marker is gone. You should see that the circuit is now inscribed in the copper.

Below are my PCB after the etching process.

Next is the assembly process, it is include drilling and soldering as below:

1. Before drilling locate all the positions of the through hole components.
2. Drill through the board with a bit wide enough to accommodate whatever part must be placed at that location.
3. Place the components on the circuit board at their designated locations.
4. Soldering is a skill that requires practice, although it is not inherently difficult.

You can view this video http://www.youtube.com/watch?v=b9FC9fAlfQE for tutorial of soldering SMD components. Soldering SMD component is hard, that's why i need some items to make the job easier. The item is listed below:

1. Tweezers
2. Magnifier
3. Flux liquid
4. Solder wick
5. Solder wire 0.8mm
6. Solder iron with 0.5 mm tip

Below are my circuit that is still on soldering process.

Finish with the etching and soldering this week, let's go for the testing of the circuit. See you next week.

Bluetooth Research

I'm deciding to use Bluetooth as the wireless data transmitting and receiving to the Smartphone. First of all, i already decided the hardware that i should used. Below are the bluetooth hardware that used for my PPG interface with the smartphone:

1. Arduino Uno R3, which you can find here, http://www.myduino.com/index.php           route=product/product&path=37&product_id=271
2. Xbee Shield for Arduino, which you can find here as well, http://www.myduino.com/index.php?route=product/product&path=40&product_id=108
3. Bluetooth Bee, this is the link, http://www.myduino.com/index.php?route=product/product&path=50_56&product_id=105

Thanks for keep updating my blog.

     

PCB Design

Hai there,

After few weeks keep researching on how to etch a PCB, this week is my first time designing a PCB using Proteus software. Designing a PCB quite difficult, because i have to draw back all the circuit at the Proteus software then convert it to ARES. When it comes to ARES format, i have to arrange all the component and avoid wire jumper as possible. Below are my Proteus (ISIS) and ARES that already converted to the PCB layout.

Notice the circle mark, it is supposed to be LT1932, but its not available at Proteus. So, to solve this problem is, i just have to make footprint at the ARES which you can see at figure below.

Before etching the PCB, make sure all the component is fit at each soldering point or solder resist. On the left side is the upper and the right is bottom of the PCB. That's all for this week, see you guys next week.

Current Stabilier and Operational Amplifier OPA2350

Good Evening everyone,

Finally, my LT1932 current stabilizer and Op-amp OPA2350 have arrived. For your information, this is very rare components, its hard to find unless ordered or purchase online.

LT1932
In the previous post, i have post the datasheet of LT1932. At this post, i will summarize the LT1932. The function of LT1932 is used for stabilized the IR LED current to obtain the visible light output gain accuracy. LT1932 Constant Current DC/DC LED Driver in Thin SOT is used for the purposed of stabilizing the current that drives the LED and the appropriate resistor values a shown in Table below

LED Current (mA)	Resistor Value
40	562Ohm
30	750Ohm
20	1.13kOhm
15	1.5kOhm
10	2.26kOhm
5	4.53kOhm

So, the desired value that we expected is 20mA and i should used 1.13kOhm resistor at pin Rset or pin no 4 of LT1932.

The results of IR LED resistor current test is shown in table below.

I LED (mA)	R set Value
25.4	1kOhm
18.2	1.3kOhm
15.7	1.5kOhm

Figure below shows the actual component of LT1932.

OPA2350
This component also is the rare component, and i ordered it together with the LT1932. The datasheet of OPA2350 can be found here http://www.ti.com/lit/ds/symlink/opa2350.pdf. Actually, OPA2350 have 2 input and 2 output. In the circuit diagram, it is label by A and B for example OPA2350 U1:A and OPA2350 U1:B. Figure below shows the OPA2350 diagram.

It is show that for output A is using terminal 1,2,3,4 and 8. For the output B is using 4,5,6,7 and 8.

Figure below shows the actual component of OPA2350

The cost of both components is list at table below.

Component	Quantity	Price
LT1932	1	20.00
OPA2350	1	25.00
Total		45.00

The price is quite expensive because the items is seldom and hard to find. But for the successful of the project, there are no other option to make its successful, one word for it SACRIFICE. See you next week.. :)

Purchasing Item

Welcome Back!

Everything is on schedule, i already purchasing component for my PPG circuit. Figure below shows the component that i had bought.

As can be seen in the Figure, the Surface Mounted Device (SMD) components is small. It is not more than 5mm width and 3mm length, and it is totally different with through hole components. This method for producing electronic circuits in which the components are mounted or placed directly onto the surface of Printed Circuit Boards (PCBs). There are no leads or either smaller leads and it may have short pins or leads of various style.

Why is choose SMD as component for the PPG circuit is

• Smaller components.
• Lower initial cost and time of setting up for production.
• Fewer holes need to be drilled.
• Small errors in component placement are corrected automatically as the surface tension of molter solder pulls components into alignment with solder pads.
• Lower resistance and inductance at the connection; consequently, fewer unwanted RF signal effects and better and more predictable high-frequency performance.
• Better EMC compatibility (lower radiated emissions) due to the smaller radiation loop area and the smaller lead induction

The cost of all the item purchased is shown on table below:

The cost of all the item purchased is shown on table below,. 

Components	Value	Quantities	Price (RM)
Capacitors (tantalum or ceramic, voltage rating?) below 50V	4.7uF 1uF  12pF 10uF	10 2 1 1	8.00 3.00 1.50 2.30
Inductor	6.8uH	1	2.80
Resistors	1kohm 1.3kohm 22kohm 1Mohm	10 10 10 10	1.00 1.00 1.00 1.00
Diode Schottky (20V 1 A)	1 A,40V	2	8.00
Diode Zener	5.1V	2 pieces	4.80
LED	5V	10	2.00
Total			36.40

The total for the components is not much and it is affordable. But, the LT1932 and OPA2350 i have to order because it is seldom used and the stock is not in the electronic shop. The ordered have been made, and i have to wait for 3 working days for the components to arrive. Below are the list of the electronic shop where is purchasing the item:

1. Online Component Sdn. Bhd. (www.online-components.com.my)
2. MSC Supply and Service 

Any rare components can be found at MSC Supply and Service, credit to this company because almost half day searching for the LT1932 and OPA2350 and it only be found and can be easily ordered at that electronic shop. That's all for now. Thank You.. See u Next Week..

Circuit Simulatioin

When its come to simulation, there's many things that i think how i should simulate the circuit. So, after keep asking Mr. Google, finally, its come to solution. The solution is i have to test the circuit 1 by 1. From the First circuit, the IR LED Current Stabilizer, Second circuit is Trans Impedance circuit and the last circuit is sallen key filter circuit. The result should be almost the same as theory result that i found in the article. Figure below shows the circuit and its result. I skipped the IR LED current stabilizer simulation, because i can't found LT1932 component, and plus, my supervisor assure the circuit will have no problem if the connection is right, because the circuit is original from the datasheet of the LT1932 which you guys can view here http://cds.linear.com/docs/en/datasheet/1932f.pdf.

Transimpedance Circuit 
Started with the trans impedance circuit simulation, you can see figure below:

Figure above shows the simulation circuit for trans impedance circuit. It is using Proteus for the simulation software. As can be seen it is 1.5V supply to the circuit and resulting 24.01mV. A transimpdance amplifier is an amplifier that converts current to voltage. Its input ideally has zero impedance, and the input signal is a current. Its output may have low impedance or in high-frequency applications, may be matched to a driven transmission line, the output signal is measured as a voltage. I assuming that the input voltage is 1.5V from the IR LED Current stabilizer and it is supposedly current. The noise gain for example the noninverting closed loop gain of this configuration determines the stability of the circuit. The reason for this is that any noise signal, no matter how small, can trigger an unstable circuit into oscillation. The DC gain is set solely by the resistors. The pole frequency is set by the feedback network, just as in the impedance function. Table below shows the current input and output for the transimpedance circuit.

Current Input (mA)	Voltage Output (V)
0.010	0.01
0.022	0.02
0.031	0.03
0.04	0.04
0.052	0.05
0.061	0.06
0.072	0.07

Sallen Key Low Pass FIlter
The second circuit is sallen key low pass filter. See figure below:

The circuit above is simulated using Multisim software. It is hard to simulate using Proteus, so i come with the solution by using Multisim. As can be seen, i'm not using OPA 2350 for the operational amplifier. Supposedly it is OPA 2350, but, i can't found it inside Multisim. As my supervisor advised, it is almost the same amplifier, as long as the result is there. So the function generator is set to 5V amplitude and the Frequency is set to 5Hz.
The sallen-key filter is a simple active filter based on utilizing op-amp stages, which is ideal for filtering analog frequencies. It is one of the most widely used filter topologies. One reason for its popularity is that this configuration shows the least dependence of filter performance of the performance on the performance of the op-amp. Another advantage of the configuration is that the ratio of the largest resistor value to the smallest resistor value and the ratio of largest capacitor value to the smallest capacitor value are low, which is good for manufacturability. A serious drawback is that the filter is not easily tuned. A low pass filter is a filter that passes low frequency signals but attenuates signal with frequencies higher that the cutoff frequency. Desire cut off frequency is 10 Hz which can be seen on the simulation, i get the 10 Hz cut off frequency.


As a summary, the both amplifier play important role to in very low frequency applications and it is commonly used in receivers for optical communications.

That's all by now.. Thank you.. Keep in touch..