Pocket Signal Visualizer (Pocket Oscilloscope)

Hello every one,

We all are doing so many things in every day. For every work there where need some tools. That's for making, measuring, finishing etc.. So for electronic workers, they need tools like soldering iron, multi-meter, oscilloscope, etc. In this list the oscilloscope is a main tool for seeing the signal and measure it characteristics. But main problem with the oscilloscope is that it is heavy, complex and costly. So this make, it to be a dream for electronics beginners. So by this project I change the whole oscilloscope concept and make a smaller one which affordable for beginners. That means here I made a pocket sized portable tiny oscilloscope named " Pocket Signal Visualizer ". It has a 2.8" TFT display for draw the signal in the input and a Li-ion cell for making it to be a portable one. It is capable of viewing up-to 1MHz, 10V amplitude signal. So this act as a small scaled version of our original professional oscilloscope. This pocket oscilloscope make all people accessible to the oscilloscope.

How is it ? What is your opinion ? Comment to me.

For more details about this project visit my BLOG,

https://0creativeengineering0.blogspot.com/2019/06/pocket-signal-visualizer-diy-home-made.html

This project get an initiation from a similar project in the given website named bobdavis321.blogspot.com

• ATMega 328 micro-controller
• ADC chip TLC5510
• 2.8" TFT display
• Li-ion cell
• ICs given in the circuit diagram
• Capacitors, resistors, diodes, etc given in the circuit diagram
• Copper clad, solder wire
• Small enameled copper wires
• Push butt switches etc.

For detailed component wise list, observe the circuit diagram. Images are given in the next step.

Here the project mainly concentrated on the electronics side. So the tools mainly used are the electronic tools. The tools used by me is given below. You choose your favorite tools.

Micro soldering Iron, SMD desoldering station, Multi-meters, Oscilloscope, Tweezers, screw drivers, pliers, hack-saw, files, hand driller, etc.

The tools images are given above.

My plan is to make a portable pocket oscilloscope, which is capable of displaying all type of waves. First I prepare the PCB and then it enclose in an enclosure. For the enclosure I use a small foldable make-up box. The foldable property increase the flexibility of this device. The display is in the first part and the board and control switches in the next half. The PCB is divided into two pieces as frond end PCB and main PCB. The oscilloscope is a foldable one, so I use an automatic ON/OFF switch for it. It switch ON when it open and it automatically OFF when it closes. The Li-ion cell is placed below the PCBs. This is my plan. So first I make the two PCBs. All the components used is the SMD variants. It reduce the PCB size drastically.

The full circuit diagram is given above. It is divided into two separate circuits as frond-end and main PCB. The circuits are complex, because it contain lot of ICs and other passive components. In the frond-end the main components are the input attenuator system, input selection multiplexer and the input buffer. The input attenuator is used to convert different input voltage to a desired output voltage for the oscilloscope, it create this oscilloscope capable in working at wide range of input voltages. It is made by using resistive potential divider and capacitor is connected parallel to each resistor to increase the frequency response (compensated attenuator). The input selecting multiplexer is work like a rotary switch to select one input from different input from the attenuator but here multiplexer input is selected by digital data from the main processor. The buffer is used to boost the input signal power. It is designed by using an op-amp in voltage follower configuration. It reduce the loading effect of the signal due to the remaining parts. These are the main parts of the frond end.

For more details, visit my BLOG, https://0creativeengineering0.blogspot.com/2019/06/pocket-signal-visualizer-diy-home-made.html

The main PCB contain the other digital processing systems. It mainly contain a Li-ion charger, Li-ion protection circuit, 5V boost converter, -ve voltage generator, USB interface, ADC, High frequency clock, and the main micro-controller. The Li-ion charger circuit used to charge the Li-ion cell from the old mobile phone in an efficient and intelligent manner. It uses TP 4056 IC to charge the cell from the 5V from the micro-USB port. It explained in detail in my previous BLOG, https://0creativeengineering0.blogspot.com/2019/05/diy-li-ion-cell-charger-using-tp4056.html . The next is the Li-ion protection circuit. It is used to protect the Cell from short circuit, over charge etc. It explain in my one of the previous BLOG, https://0creativeengineering0.blogspot.com/2019/05/intelligent-li-ion-cell-management.html . The next is the 5V boost converter. It is used to convert the 3.7 V cell voltage into 5V for better working of the digital circuits. The circuit details are explain in my previous BLOG, https://0creativeengineering0.blogspot.com/2019/05/diy-tiny-5v-2a-boost-converter-simple.html. The -ve voltage generator is used to generate a -ve 3.3V for the op-amp working. It is generated by using a charge pump circuit. It is designed by using a 555 IC. It is wired as an oscillator to charge and discharge the capacitors in the charge pump circuit. It is very good for low current application. The USB interface connect the PC with our oscilloscope micro-controller for firmware modifications. It contain a single IC for this process named CH340. The ADC is convert the input analog signal to the digital form suitable for the micro-controller. The ADC IC used here is the TLC5510. It is a high speed semi-flash type ADC. It capable of work at high sampling rates. The high frequency clock circuit is work at 16 MHz frequency. It provide necessary clock signals for the ADC chip. It designed by using a NOT gate IC and the crystal of 16 MHZ and some passive components. It explain detailed in my BLOG, https://0creativeengineering0.blogspot.com/2019/06/simple-16-mhz-crystal-oscillator.html. The main micro-controller used here is the ATMega328 AVR micro-controller. It is the heart of this circuit. It is capture and store the data from the ADC. Then it drive the TFT display to display the input signal. The input controll switches is also connected to the ATMega328. This is the basic hardware setup.

For more details about the circuit and its design, visit my BLOG,

https://0creativeengineering0.blogspot.com/2019/06/pocket-signal-visualizer-diy-home-made.html

Here I only use SMD components for the whole circuit. So the design and further process are little bit complex. Here the circuit diagram and the PCB layout are created by using the EasyEDA online platform. It is a very good platform which contain all the component libraries. The the two PCBs are created separately. The unused spaces in the PCBs are covered with ground line connection to avoid unwanted noise problems. The copper trace thickness is very small, So use a good quality printer to print the layout, otherwise some traces get dis-continuities. The step wise procedure is given below,

• Print the PCB design (2/3 copies) into a photo/glossy paper (use good quality printer)
• Scan the PCB layout for any dis-continuities in the copper trace
• Select a good PCB layout which have no defects
• Cut the layout using a Scissors

The layout design files are given below.

For the PCB making I use single sided copper-clad. This is the main raw material of the PCB making. So select a good quality copper-clad. Step-wise procedure is given below,

• Take a good quality copper-clad
• Mark the dimension of the PCB layout in the copper-clad using a marker
• Cut the copper-clad through the markings using a hacksaw blade
• Smooth the sharp edges of the PCB using sand paper or a file
• Clean the copper side using a sandpaper and remove the dusts

Here in this step we transfer the PCB layout into the copper-clad using the heat transfer method. For the heat transfer method I use an iron box as heat source. The procedure is given below,

• First place the PCB layout in the copper-clad in an orientation in which layout facing the copper side
• Fix the layout in its position by using tapes
• Cover the whole setup using a white paper
• Apply the iron box to the copper side for about 10-15 minutes
• After heating wait some time for cool it
• Put the PCB with paper in a mug of water
• Then remove the paper from the PCB using hand with care (done it slowly)
• Then observe it and ensure that it has no defects

It is a chemical process for removing unwanted copper from the copper clad based on the PCB layout. For this chemical process we need ferric chloride solution (etching solution). The solution dissolve the non masked copper to the solution. So by this process we get a PCB as in the PCB layout. The procedure for this process is given below.

• Take the masked PCB which is done in the previous step
• Take ferric chloride powder in a plastic box and dissolve it in the water (the amount of powder determine the concentration, higher concentration fastening the process but sometime it damage the PCB recommended is a medium concentration)
• Immerse the masked PCB in the solution
• Wait for some hours (regularly check the etching completed or not)(sun light also fastening the process)
• After completing a successful etching remove the mask by using sand paper
• Smooth the edges ones again
• Clean the PCB

We done the PCB making

SMD soldering is little bit harder than the ordinary through hole soldering. The main tools for this job is a tweezers and a hot air gun or micro-soldering iron. Set the hot air gun at 350C temp. Over heating some time damage the components. So only apply limited amount of heat to the PCB. The procedure is given below.

• Clean the PCB by using PCB cleaner (iso-propyl alcohol)
• Apply solder paste to all the pads in the PCB
• Place all the components to its pad using tweezers based on the circuit diagram
• Double check all the components position are correct or not
• Apply hot air gun at low air speed (high speed cause misalignment of the components)
• Ensure that all the connections are good
• Clean the PCB by using IPA (PCB cleaner) solution
• We done the soldering process successfully

The video about SMD soldering is given above. Please watch it.

Here in this step I assemble the whole parts into a single product. I completed the PCBs in the previous steps. Here I place the 2 PCBs into the makeup box. In the top side of the makeup box I place the LCD screen. For this, I use some screws. Then I place the PCBs in the bottom part. Here also used some screws for fitting the PCBs in place. The Li-ion battery is placed under the main PCB. The control switch PCB is placed above the battery by using double sided tape. The control switch PCB is get from an old Walkman PCB. The PCBs and the LCD screen are connected by using small enameled copper wires. It is because it is more flexible than ordinary wire. The automatic on/off switch is connected near to the folding side. So when we folded the top side it is turnoff the oscilloscope. This is the Assembling details.

The above images shows my finished product.

It is capable of measuring sine, square, triangular waves. The oscilloscope trial run is shown in the video. Watch it. This is very useful for everyone who like Arduino. I like it very much. This is an awesome product. What is your opinion? Please comment me.

If you like it please support me.

For more details about the circuit Please visit my BLOG page. Link given below. https://0creativeengineering0.blogspot.com/

For more interesting projects, visit my YouTube, Instructables and Blog pages.

Thanks for visit my project page.

Bye.

See you again........