Showing posts with label electronic. Show all posts
Showing posts with label electronic. Show all posts

Schematics Multi-Mode Beacon & Blogger Image Upload Failure PCB

Circuit Some more programming for the PIC 16F628 in its hi-rise accommodations has seen my 50mW 30m beacon go truly "multi-mode". It now transmits WSPR, QRSS and Sequential Multi-tone Hellschreiber in a 10 minute cycle.

I have stayed with the basic timing framework offered by Gene Marcus w3pm's excellent audio WSPR generator code, but added my own routines for the QRSS and Hell. This was easy-enough to do, as I'd already hacked the code to run with my VXO-based architecture and all three modes are just FSK.

Here's a screen-shot from Argo, captured locally, showing all three modes...

You can see the closing "d" of my call sign in QRSS, a S/MT Hell version of my call and (most of) my WSPR message. The frequency difference between the QRSS/Hell and the WSPR signals exercises pretty much all the range of my VXO - I have to work the bottom of the WSPR band, which places the QRSS/Hell emissions around 10.140050 MHz.

I turned the beacon on late yesterday afternoon and got good WSPR spots through the night (once again bucking the trend that had been established last week). Ususal dx to Douglas w3hh and very solid propagation to Al, ra6as...

OK - I give up - Image Upload isn't working. It is producing garbage like this (which I'll leave to shame the providers of this "service")...

I would like to have shown you the WSPR spots, but Blogger disagrees. I've tried different image formats, uploading from different browsers (I usually use Chrome), re-starting the computer, uploading from another computer - all to no effect.

It is now three hours later and - guess what - everything is working FB now. No change this end - of course. Just working now when it wasn't before. So here's the WSPR spots I wanted to show you earlier...

In between each of the 5.6 Joule flashes from WSPR, there are now also the other modes to entertain me. Here's a nice spot of the QRSS from pa3tab's "Tabber" grabber..

Here's Joachim's spot of the Hell (preceded by some of my QRSS) ...

I wonder if anybody else is running multi-mode?

...-.- de m0xpd


WSPR spots coming in at a pleasing rate (more overnight spot stats to follow) and I was particularly pleased to receive a report from Pierre, on5sl, through the knightsqrss mailing list...

Thanks Pierre!

To:- the people at "Blogger" (/Google)
The point of blogging is diluted if the supporting infrastructure doesn't work (as in my image upload issues above). We didn't turn to our paper diaries and journals to make an entry, only to be frustrated by a book that wouldn't open or a page that wouldn't accept ink.

Blogging needs to work NOW in real-time.

Forget all the "too-clever-by-half" facilities you're trying to add and just make the system WORK reliably, please.
read more "Schematics Multi-Mode Beacon & Blogger Image Upload Failure PCB"

Schematics Improving a new Quad 909 PCB

Circuit One of our French customers, who is working in professional audio, bought a new Quad 909 to drive his Tannoy studio-monitors.

He has always used Quad 303 monoblocks with Dada High-end boards and was very pleased with the result so, as he needed more power for another project he bought a 909.

The Tannoys are very sensitive and transparent (as studio monitors should be). When he connected the 909 he heard a hiss and distortion in the mid-tones.He brought back the amplifier to the reseller and it was tested by Quad. They said everything was working within specifications so there was nothing they could do.

So he sent the amplifier to Dada Antwerp and asked us to find the reason of the problem and to see what we can do about it.

Joost and me took an afternoon to do some tests with Virtins Multi-instrument Audio analyser and the other lab-equipment.

First we did a listening-test. The sound was rather "harsh" and "metalic" compared to other (revised) Quads.

We measured a Total Harmonic Distortion of 0,8854% (!) and a Signal-to-Noise Ratio of 81,4dB at full power with 8 Ohm load. The total power before clipping was 120W RMS. Very bad figures for a high-end amplifier... And much worse than the "classical" 606 the 909 is based on.

We decided to take the amplifier apart and to concentrate on 3 possible sources of distortion:

  • The power-supply
  • The amplifier-boards
  • The input-board for the Quadlink

The power-supply board is the "classical" board known from the 606-II and the 707 with a Toroïdal transformer and 4x 15000µF capacitors in a dual-mono design. Only, the original BHC Aerovox capacitors have been replaced by Chinese CapXon capacitors.

We took them out to test them with the Hameg LCR meter.

The BHC Aerovox was the ALP22A 63Volt, the CapXon has no type-indication, it is a plug-in two pin 80Volt 105° type.

We measured the capacitance at 100Hz, 1KHz, 10KHz and 25KHz with a 1V DC bias voltage. Both were within specifications (15mF or more) up to 1KHz. At higher frequencies the BHC scores better with 3x higher capacitance, for example 1100µF at 10KHz instead of 300µF for the CapXon.

The measured internal resistance is about the same and around 10mR at 1KHz.

This leads us to the conclusion that both capacitors are very comparable with a slight advantage for the BHC specifically in the higher frequencies. Of course this test doesn't say anything about the ageing of the capacitors after several hours of usage. The BHC has an excellent reputation for ageing. We decide to replace the 4 CapXon in the power-supply with BHC Aerovox.

Then we take a look at the amplifier boards. We replace the low-cost capacitors as usual, the electrolytes with Nichicon, the range between 1nF and 1µF with Wima MKS and the range below 1nF with Silvered Mica.

We also recalculated the bridge and used the exact values for the bridge components. Joost will comment on this later.

We connect the driver-boards to the power-supply. Now we measure a THD of 0,025% and a S/N Ratio of 87dB which is a lot better yet. A listening test gives the rich and transparent sound we are used to with Quad amplifiers.

Finally we take a look at the input-board that also contains the switch-on delay and the symmetric -> asymmetric conversion for the Quadlink.

The asymmetric signal from the RCA-inputs also passes through the output-stages of the preamplifier and again we find some low-cost capacitors on board. At a low input voltage the THD of the board is 0,003% but increasing the input-voltage increases the THD of the board. Around 10V we have 0,4% THD.

As the customer won't use the Quadlink we decide to remove the board from the signal-line and to connect the RCA-inputs directly to the amplifier-boards like in the 606.

The conclusion is that every detail has it's importance for the final sound-quality, specially the quality of the components and that it is best to avoid the Quadlink if you don't need it.


Practical: Component list

The 909 PCB is a thhrough-metalised PCB. You should use a good desoldering-pump or a desoldering-station to remove the old components.

For soldering on the PCB's only use lead-free solder. Tin/lead solder won't mix with the solder on the board.

You can click on the components below to go directly to the Webshop for ordering or for seeing more technical information or price and availability.

This way we have replaced all electrolyte capacitors with the best quality and we have adapted the bridge to the optimum value.

The specifications of the 909 transformer are: 2x 80,5 Volt 500VA

Measurement of a 606 MKII (my own) as a reference:

Vout is 32.2 V, no load, left and right channel:

THD 0.0009 and 0.0010

IM Din 0.0045 and 0.0041

Vout is 32.2 V, load is 8 Ohm:

THD 0.0129 and 0.0059

IM Din 0.0342 and 0.04

So the left channel is out of spec, THD should be lower than 0.01 some work ahead!

Joost Plugge
read more "Schematics Improving a new Quad 909 PCB"

Schematics Fully Automatic Emergency Night Light PCB

There are already published diagrams for automatic emergency lights but this fully automatic led base emergency light has the following special advantages.

1. Fully automatic - The name suggests its character. The emergency light charging is fully controlled and you don't have to worry about over charging of battery.

2. The emergency night light - This circuit is designed to glow leds where there no light in the room and only when there is no mains supply available. If one of them are available, the leds will not glow and the power is saved. This is achieved by using LDR and a PNP transistor.So we can plug the emergency lamp on the mains socket overnight without the fear of overcharging or waste of energy.

The working of this design is very simple by the way we can divide this emergency light circuit into two sections.

Circuit Diagram of : Click  to enlarge

1. Charging section

The charging section consist of a the input 9vdc from the adapter transformer (not shown in the circuit) is fed to the input of the adjustable voltage regulator LM317. By adjusting the preset RV1, we can adjust the output voltage of the regulator IC. The output voltage can be adjusted to deliver the charging voltage. When the battery gets charged above 5.2 volt, the zenar diode ZD1 conducts and the LM317 IC stops deivering charging voltage.

2. Automatic light and mains detection

This emergency light circuit design can behave automatically to switch off the LEDs when there is power supply available on the mains. So a BC558 PNP transistor done this job of shutting down the power supply to further circuit elements when there is mains available. The transistor BC548 is usually turn on during day time because the resistance of LDR is low when there is light in the room. When outside light falls, the LDR resistance will become high, this turn off the transistor Q3. So a positive voltage is fed to the base of LED driver transistor SL100 and the transitor turned on by completing circuit through white LEDs on its emitter terminal.  

Bread board assembly

  • The zenar diode can be chosen accoring to battery charctersitics
  • The preset RV2 can be varied to get the right LDR light sensing.
read more "Schematics Fully Automatic Emergency Night Light PCB"

Schematics Scrolling LED sign based on Atmel ATtiny2313 AVR microcontrolle PCB

On this page you will find a scrolling LED sign based on the ATtiny2313 AVR microcontroller, which you can build yourself (when finished) Other names for this device can be: Moving message sign, Message crawler, Scrolling message, message display, etc.
The idea is to let a text scroll over the LED dot-matrix displays. A dot-matrix display is a display which contains 5x7 dots (LEDs) in one case, the LEDs are connected like a matrix, there are two types CC and CA, the LEDs are simply put the other way around, here the drawings (inside and front):
If you put 1.8 Volt e.g. at the lines 4 and 10, that LED (dot) will lit, the trick of multiplexing is to scan the columns (5) and set the data on the rows (7) (or visa-versa), the multiplex-frequency must be greater than approx. 40Hz else you will see the flickering of the LEDs to much (take about 5 msec per column, thats about 25 msec for one frame)
The scanning goes as follows, first set the rows data on the 7 rows e.g. 1010010, then activate (0 or 1 -> depends on which type CA = common cathode, or CC = common anode) the first column, now these LEDs (dots) will lit, wait 5 msec, then switch the column off, now load the next rows data, and set the second column on, wait 5 msecs again, and switch it off again, if you repeat this sequence very fast, you will see the data (character data) appear on the display (refresh frequency 40 - 70Hz is ok, don't take twice or half the artificial light-frequency of 50/60 Hz)
The rows data comes e.g. from the EEPROM or flash memory of the AVR, you can also take an external EEPROM/flash IC, the ATtiny2313 has 128 bytes EEPROM and 2k of flash memory, what you can do is put the character data (ASCII) into the flash memory (read below for more details) Next the test-diagram:

The 74HC595 is an 8-bit shift-register IC, with this IC you can shift 8 bits to the outputs with only 3 wires, that are Data (Ds), and 2 shift inputs (SHcp, STcp), connect like the diagram. How does the 74HC595 works? First shift the 8 bits into the stages with SHcp, then shift the stages to the outputs with STcp, this causes the outputs to switch in one go, with e.g. a 74HCT164 you can only shift the bits into the outputs, the advantage of the 74HC595 is the storage register. Don't forget that multiplexing causes the LEDs only lit up for a fraction, so if you want the same intensity you must put more current through them, this diagram is for practice and programming, wants you have it working you can put transistors and resistors on. Here I put the letter R on the display as you can see, using a little breadboard: (next: How the scrolling is done...)

How to scroll a character accross the display ? The trick is to build one character on the display by scanning the columns very fast, and let say each 20 times (20 frames) scroll it one position to the left, this will give the effect of a walking text accross the dot-matrix display. So first build one frame, repeat this 20 times, and after that, read the data one address later, if you do this 5 times (5 columns) the character scroll from right to left from the display. (the refresh goes so fast that your brain can't keep up, and what you see is the R scrolling over the display) Btw, I will take five 74HC595's shiftregisters IC's, that are 5 x 8 bit = 40 bits / 5 columns = 8 dot-matrix displays, making it a nice tiny message sign.

What I am going to do is putting ASCII data (thats 128 x 5 bytes = 640 bytes) into the 2k flash memory of the ATtiny2313, then I have 704 words left for my program, that can really be a huge program!, because I used only 69 lines (69 instructions) of program so far, and that scrolls characters fluently accross the dot-matrix display. I made the program so that you can set the scroll-speed, from 0 - 255, so 256 speeds, 25 fps (frames/second) is a nice speed. On one of my pages (this page) I am using a 2-bit Gray code rotary encoder, with this encoder I will make an edit function in the software, so you can edit messages, without a keyboard, this save space, this type of rotary encoder has a push-function in the shaft, so e.g. after you select a character you can store that in memory.
read more "Schematics Scrolling LED sign based on Atmel ATtiny2313 AVR microcontrolle PCB"

Schematics A Digital, Up / Down Counter PCB

Origionally I designed this for use on my Metal Laithe to Aid in winding coils.
But it can be adapted for many other applications.

This Circuit uses a CD40110BE, Up/Down Counter IC's.
The CD40110BE is Available from Digi-Key
Digi-Key Part Number "296-3506-5-ND"


This IC is able to Source Each Segment with 25 mA, Giving a Very Nice Bright Display.
The 7 Segment Displays MUST be a Common Cathode Type, as I have used here

NOTE Also : All the UnMarked Resistors should be at least 680 Ohms for Up To 12 Volts Supply Voltage.

For Higher Supply Voltages up to 18 volts or Reduced Currents, I would suggest Increasing these Values to 1500 Ohms.

Or if you want "Reduced Power" and "Brightness", Adjust the resistor values as appropriate.
Basically the Approximate Current is Supply voltage Minus 2, Divided by the Resistor Value.

The Schematic posted here Only shows the First, Second, Third and Last Stages.
And This board is for a counter of up to 9999.

However: Since All Stages between the Third and Last, Would be the same,
So you could make a display with as many digits as you wish, by expanding the circuit board.

Additionally: You can just put in 1, 2, 3, or all 4 IC's and the Appropriate Displays.

Other Options:
  1. Adding a Clock Circuit with a Frequency of 1 Hz in place of the Reset Switch will create a Frequency counter in Hz/Sec.
  2. Adding a Clock Circuit with a Frequency of 1 Hz into one of the Inputs can create an up or down counter type of timer.
  3. Although Not Highly Accurate, a Simple 555 circuit will work as a Simple Clock.

read more "Schematics A Digital, Up / Down Counter PCB"

Schematics Simple Audio Amplifier Circuit Using LM386 PCB

Here is a simple low power audio amplifier circuit that can produce a power output of 1W. This mono amplifier circuit is build on LM386 IC which works great on low voltages even below 9V. This low voltage amplifier is useful to amplify weak sound signals from your soundcard to amplify it to give to the headphones  or high power amplifiers for maximum sound effect.

Circuit Diagram of  Simple Audio Amplifier Using LM386 : Click  to enlarge

You will need to assemble two identical circuit to connect  stereo input from sound card in your PC.

  • Supply Voltage (LM386N-1, -3, LM386M-1) 15V
  • Supply Voltage (LM386N-4) 22V
  • Package Dissipation (Note 3)
  • (LM386N) 1.25W
  • (LM386M) 0.73W
  • (LM386MM-1) 0.595W
  • Input Voltage ±0.4V
read more "Schematics Simple Audio Amplifier Circuit Using LM386 PCB"

Schematics elektronika itu tanpa batas^^ 2010-05-17 15:10:00 PCB

Robot Mikro yang Mampu Bekerja Dalam Tubuh

Ilmuwan di Korea telah membuat robot-robot yang cukup kecil untuk bisa menjelajahi tubuh manusia dan digerakkan oleh otot jantung.

Sukho Park di Chonnam National University, Korea, dan rekan-rekannya telah merancang sebuah robot-mikro yang digerakkan oleh sel. Tim Park membuat robot tersebut dengan menumbuhkan jaringan otot jantung dari sebuah tikus pada kerangka-kerangka robot kecil yang dibuat dari polidimetilsiloksana (PDMS). PDMS merupakan polimer biokompatibel sehingga membuat robot tersebut cocok digunakan dalam pengaplikasian biomedik.

Yang istimewa pada robot-robot ini, kata Park, adalah mereka tidak memerlukan suplai energi eksternal. Tetapi sel-sel otot jantung yang berelaksasi dan berkontraksi yang memberikan energi. Sel-sel otot jantung sendiri mendapatkan energinya dari sebuah medium kultur glukosa. Sel-sel yang berdenyut sendiri ini memungkinkan robot tersebut menggerakkan keenam kakinya.

Robot ini memiliki tiga kaki depan yang pendek (panjang 400 mikrometer) dan tiga kaki belakang yang lebih panjang (panjang 1200 mikrometer), semuanya terpasang pada sebuah badan segiempat. Pada saat sel-sel jantung berkontraksi, kaki belakang yang lebih panjang menekuk ke dalam. Ini menghasilkan perbedaan gesekan antara kaki depan dan kaki belakang, yang menekan robot bergerak maju. Para peneliti mengukur kecepatan rata-rata robot ini sekitar 100 mikrometer per detik.

Park mengatakan robot-robot yang mirip kepiting ini bisa digunakan di dalam tubuh untuk membersihkan rongga atau pembuluh yang tersumbat, dengan melepaskan sebuah agen pelarut untuk membersihkan penyumbatan yang mereka lalui.

Disadur dari:
read more "Schematics elektronika itu tanpa batas^^ 2010-05-17 15:10:00 PCB"

Schematics Touch Plate Circuit With High Sensitivity PCB

Here is a high sensitive touch plate circuit using NE555 which turns on a buzzer when anyone touches the metal plate or by hovering his hand over the plate. From the previously published touch control switch circuit, this circuit has an advantage of high sensitivity that it can detect an input voltage as low as 1 micro volt. This circuit is attachable to various designs such as touch plate lightning or motor control with necessary alterations.

Circuit Diagram of  Touch Plate With High Sensitivity : Click  to enlarge

As i said before, the main component of this circuit is a 555 IC which triggers when the pin no. 2 gets a voltage about 1 micro volt. The relay connected at the output will allow you to use this as a switching circuit. In this specific circuit, a UJT is connected through an output transformer to produce a sound.
read more "Schematics Touch Plate Circuit With High Sensitivity PCB"

Schematics Hard Disk Temperature Controller PCB

Many of us have had a problem of over heating computer hard disk while in long use. Here is a temperature controller circuit that switch on a DC fan to reduce temperature of your hard disk drive when it increases abnormally. The metal plate sown in the circuit should be screwed tightly with your hard disk to work it as a temperature sensor. When the temperature on hard disk increases than a preset level, the relay is activated and the fan connected to it will be start running to reduce the temperature.

 Circuit Diagram of  Hard Disk Temperature Controller: Click  to enlarge


Yes, this circuit is a simply modified version of the fire alarm circuit which is ever popular. the heart of this circuit is a transistor BC177 which has a metal case. this transistor is actually fixed on a metal plate which is held at the top heat emitting portion of the HDD. When the temperature increases, the leakge current in the transistor BC 107 will be changed to increase the bias. This small current at the collector of the heat sensor transistor will drive the transistor BC 108 further activates the relay. A DC 9 volt fan is connected to the relay will protect the HDD from over heating.

  • Assemble the circuit on a common PCB
  • Adjust the preset to get the relay turn ON when temperature increases more than 40degree
  • Make sure that the temperature sensor metal plate is well attached to the HDD

read more "Schematics Hard Disk Temperature Controller PCB"

Schematics Infrared Burglar Alarm Using Remote control PCB

There are so many circuits available for infrared Burglar alarm but transmitter  section of these burglar alarm circuits are complicated and you may have assemble it yourself. But here is burglar alarm circuit that uses the ordinary DVD remote as the transmitter. So not only the cost also the man power will be saved.  You only need to press and hold any switch of the remote control to allow flow of IR signals to outside. This can be done by grafting any key of the remote using insulation tape. This house alarm is very useful and doesn't require much components.

Circuit Diagram of  Infrared Burglar Alarm: Click  to enlarge


The transmitter and receiver circuit must be fixer either two side of the gate or door.Now the IR signal from the remote control recieved by the sensor TSOP 1738 and give it to the 555 IC input. The output of the 555 IC will be high only when it recieves the signals and this biases the transistor BC107 so the relay is activated. Whenever any obstructives come between the transmitter and receiver, the 555 output become low and the transistor SL100 that connected to the relay will be on and the UM66 will produce an alarm sound.

  • Assemble the circuit in a common PCB
  • Supply voltage to the circuit is 9V
  • 3V is required to operate the remote
  • The sensitivity range is maximum 8 meters
read more "Schematics Infrared Burglar Alarm Using Remote control PCB"

Schematics Pin Details of SD, miniSD & micro SD Cards PCB

Secure Digital (SD) Cards are digital removable flash memory cards commonly used in cell phones, digital camera , hand held GPS devices and portable media players an so on. There are three types of SD cards available depending on its size.

  1. SD cards:  32x24 mm^2
  2. miniSD cards :  21.5x20 mm^2
  3. microSD cards:  15x11 mm^2

These memory cards are usually operated either in serial mose (SPI mode) or parallel mode (SD mode). The reading function of SD cards  is accomplished by a memory card reader that can be connected to a USB port in a computer.

A memory card reader  having a USB interface is used for accessing data on the SD card. Most card reader also offer write capability, and together with the memory card, these can function as a pendrive.

Pin Details of SD memory Cards in SD and SPI modes

Pin No.    Pin name         SD mode signal function   SPI mode signal function
1              DAT3/CS           Data line 3                         Chipselect
2              CMD/CI            Command line                     Master in/slave out
3              VSS1                 Ground                               Ground
4              Vdd                    Supply voltage 2.7/3.6V     Supply voltage 2.7/3.6V
5              CLK                  Clock                                 Clock
6              Vss2                   Ground                               Ground   
7              DAT0/D0           Data line 0                          Master in/slave out (MISO)
8              DAT1/IRQ         Data line 1                          Unused or IRQ
9              DAT2/NC          Data line 2                          Unused

Pin Details of miniSD cards in SD and SPI modes

 Pin No.   Pin name        SD mode signal function      SPI mode signal function

1             CD/DAT3        Chip select/Data line 3            Chip select
2             CMD               Command line                         Data in (DI)
3             VSS1               Ground                                   Ground
4             Vdd                  Supply voltage 2.7/3.6V         Supply voltage 2.7/3.6V
5             CLK                 Clock                                     Clock (SCK)
6             Vss2                 Ground                                   Ground
7             DAT0               Data bit 0                                Data Out (DO)
8             DAT1               Data bit 1                                Unused
9             DAT2               Data bit 2                                Unused
10           NC                   Future use                               Future use   
11           NC                   Future use                               Future use   

Pin Details Of microSD cards in SD and SPI modes

 Pin No.  Pin name          SD mode signal function     SPI mode signal function

1             DAT2/NC          Data bit 2                              No connection
2             CD/DAT3          Card detect/Data bit 3           Chip select
3             CMD/DI            Command line                       Master out/Slave in (MOSI)
4             Vdd                    Supply voltage 2.7/3.6V        Supply voltage 2.7/3.6V
5             CLK                  Clock                                    Clock
6             Vss                    Ground                                 Ground
7             DAT/D0             Data bit 0                              Master in/slave out (MISO)
8             DAT1/RSV        Data bit 1                              Reserved
read more "Schematics Pin Details of SD, miniSD & micro SD Cards PCB"

Schematics Remote Control Tester Circuit PCB

Here is an infrared remote control tester circuit that can be made without spenting much money.This IR tester build around an infrared reciever module TSOP1738. We can observe the remote control state by listening to the buzzer sound. The circuit is very sensitive and it support a range of about 5 meters. 

Circuit Diagram of Remote Control Tester  : Click  to enlarge

The infrared receiver module normally remains high and the piezo buzzer is in silent mode. When the IR module receives a signal from the remote control,Its output goes low and the piezo buzzer sounds.


  • Assemble the circuit on a Common PCB and enclose in a small box.
  • Make sure the IR receiver made visible outside.
  • You can directly plug the circuit into mains
read more "Schematics Remote Control Tester Circuit PCB"

Schematics Car Wiper Control Using 555 PCB

In rainy seasons, it is very annoying that wiper of your car wiping instantly all the time. Have you ever think of speed control of the wiper?.There are wiper control modules available on the market but most of them are costly. So here is an automatic wiper control circuit which enables you to control your wiper sweep rates from 1 second to 10 second.

Circuit Diagram of Automatic Wiper Control circuit Using 555 : Click  to enlarge

The heart of this circuit is an astable multivibrator using 555 Ic. We actually change the duty cycle of the square wave to obtain different sweep rates to control the wiper. The output pin 3 of the IC remains high for a time period set by R2. During this time the wiper motor will sweep at rates.

The power supply to this wiper control circuit should be 12V. fit the potentiometer R2 anywhere on the dashboard of your vehicle and control the sweep rates according to the intensity of the rain.
read more "Schematics Car Wiper Control Using 555 PCB"

Schematics USB Power Booster Circuit PCB

Most of the peripherals that interface with PC uses USB port . The computers power supply circuit of SMPS will be designed to maintain constant power to all computer parts only. however we connect external peripherals to PC that requires significantly large power, USB power shortage will occur  result in a instability of PC.when too many devices are connected simultaneously, there is a possibility of power shortage. Therefore an external  usb power amplifier or source has to be added to power the external devices.

Circuit Diagram of USB Power Booster : Click to enlarge

This circuit is of USB power booster designed to feed power to USB type A socket. To increase power to usb, we use an MOC3021 which is an opto-diac which triggers, BT 136 which is a triac which result in a available power boosting through transformer. We know that IC 7805 is a 5v voltage regulator which regulates the output to give constant voltage to usb peripherals.

Assemble the circuit on a common PCB and place inside a cabinet and enclose within the CPU cabinet

read more "Schematics USB Power Booster Circuit PCB"

Schematics TOP PCB Design Rules For Beginners PCB

A printed circuit board popularly known as PCB is the first thing you would require when you decide to build an electronic circuit. A proper PCB design ensure that various circuit components are interconnected as per the circuit diagrams once they have been placed on the PCB in their proper positions  and subsequently soldered. Simple circuits can sometimes assembles without PCB. However your collage project work may a little bit complicated and you will surely need to design and etch the pcb of your own circuit. This post will share some basic pcb layout design rules that you need to know before proceeding.


Layout design is the first step of the PCB design and it is a rough design of the artwork which contains some proper information for preparing pcb artwork. For the preparation of layout, the pcb designer should have the following information.

  1. Physical size of each component
  2. Pin configuration details of components (Transistor, IC etc)
  3. Design rule for particular application (Analog or Digital)
  4. Preferable size of PCB
  5. Termination of connection


Depending upon the accuracy of the designed circuit board required, layout should be produced at 1:1, 2:1 or 4:1 scale. The 4:1 scale is used only when high precision is required. 2:1 scale is commonly used. After completing the layout, it should be reduced to 1:1 scale photographically.


  1. Prepare component layout first as viewing from the component side.
  2. Layout should be prepared in the direction of signal flow as far as possible
  3. Among the electronic components, larger ones are placed first and the space in between them is filled with smaller components like resistors, small transistors, diodes.
  4. Components that require input-output connection are placed near the connectors or pcb edge.
  5. All components are placed in the printed circuit board in such a manner that desoldering of the other components is necessary if they have to be replaced.
  6. The electronic circuit can be sub-divided into functional subunits and each subunit is realized on a defenite position of the board.
  7. While preparing the layout, it is a common practice to draw conductor lines only on graph sheet.
  8. Spacing between the components must be uniform and it must be checked when the conductor passes between pcb pads.
  9. For critical signal parts, optimum precaution have to be taken such as minimum conductor length guard lines and clear separation of input and output lines etc.
  10. Components producing considerable heat have to be identified on the circuit diagram so as to avoid concentrated heat on the circuit board.
  11. To identify the conductor lines on layout for double sided PCB's, pencils of different colour's can be used. Another possibility is to draw all of them with an ordinary pencil, but to draw interrupted lines for conductors on one of the side.

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Schematics Water Activated Sensor Alarm Using 555 PCB

Here is a circuit diagram of water activated sensor alarm using 555 IC.We may use this circuit for the following applications:
  •  Water leakage detection from water tank and can be used as a water leak alarm
  •  To detect presence of rain outside the room
  •  Do detect the presence of moisture or water molecules on a substance
  •  Used as detector of water in water overflow alarm
 Also we can fix this circuit anywhere in the basements and roof parts to detect any type of water leakage.

 Circuit Diagram of  Water Activated Sensor Alarm : Click  to enlarge

The circuit comprises a 555 IC as the core. This is designed to work as an astable multivibrator. When we connect a positive 9 volt to pin no. 8, the circuit will produce a sound through speaker.  But here the connection to pin 8 goes through the transistor BC 109c or BC 548. In this condition, the base of the NPN transistor haven't any positive voltage. But when the resistance between the "contacts" is lower due to water, the transistor get it base voltage and the circuit will produce a sound.


We can connect the the 555 output pin no. 3 to loudspeaker through a 100uF electrolytic capacitor. The resistors, R1 and R2 are used for IC biasing. We can change the tone of the sound coming from the speaker by changing the value of capacitor C1.
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Schematics Simple Transistor Tester Circuit PCB

Most of us needs to test electronic components while in work bench. What should you do if your multimeter s battery become weak? Here is a simple circuit to test transistors, diodes and other components. The circuit is very simple and you only need to connect the two leads of the testing components.

Circuit Diagram of Simple Transistor Tester : Click  to enlarge

For example if you need to test a diode, connect the two leads to test probes in two polarities. If the LED glows while in one direction, we may conclude that the diode is good. Also we can check the transistors in a similar manner. The circuit is also useful when there is a need to check the continuity between two points.
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Schematics How to Increase TDA2030 Amplifier Gain PCB

TDA 2030 is a widely used 14W audio power amplifier monolithic integrated circuit in Pentawatt [ package, intended for use as a low frequency class AB amplifier. However some home theater prototype came with
TDA2030 design has a problem of low volume. There are two ways to increase the speaker volume that uses TDA 2030A design. 

1. Simply use a pre amplifier

For low frequency subwoofer amplifier using 2030, you can increase the volume level using a pre amplifier. The best method is use a subwoofer filter board using DUAL LOW-NOISE OPERATIONAL AMPLIFIER - NE 5532. The power supply required for this NE5532 board is asame as that of TDA 2030 requires (12 - 0 - 12) The advantage of using this type of pre-amp is that we get high frequency cut-off as well as necessary gain for the input signal from DVD player or computer.

2. Circuit Change -  Closed loop gain control resistor.

Some circuit board designs usually soldered  a 10K or less value resistor in place of default 22K recommended by the 2030 designers. USe 22K or more instead of 10K to increase the gain thereby reducing the bypass of input to ground. (input should be noise free) However the increasing gain over the reccomended value may result in overheating the IC unless you have  best heat control methods.
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Schematics Door Bell Circuit Using BEL 188 PCB

Circuit Here is a low cost one touch door bell circuit using Bel 188 transistor. I think this may be the most cheap bell circuit that can be made. The core of this circuit is a output transformer of push-pull amplifier that often used in transistor radios and a Bel 188 PNP transistor.

Circuit Diagram of Door Bell Using BEL 188 : Click  to enlarge

The sound produced from the circuit of calling bell is a machine gun like and it produces when ever we press the switch. It starts from loud and then fade out to silence.

The circuit can be assembled on a common PCB. This door bell circuit is designed to work on a 9 Volt supply but it may works even low voltages at the cost of slightly reduced volume.

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Schematics Sound Level Meter Circuit Using LM3915 PCB

How ever nowadays trend is using digital audio equilisers, here is an audio level meter circuit using LM3915 sound level IC. This IC works great on even low voltages up to 3V to as high as 20 volts. This Audio indicator circuit is designed to give an input of 1v (p-p) and a maximum input voltage of 1.4 V.

Circuit Diagram of  Sound Level Meter Using LM3915 : Click  to enlarge

The circuit shown in figure uses 10 standard LEDs to display a mono channel sound level. If you need to display two channels, you need two identical circuits. Unlike other circuits, this circuit can be configure to show moving bar or dot display by connecting or disconnecting the pin no.9 from +V

Component Details

       Parts                                                                Description

  • U1                                                                    LM3915 Audio Level IC
  • LED1-10                                                          Standard LED
  • R1, R3                                                             1K 1/4W Resistor
  • R2                                                                   10K 1/4W Resistor
  • R4                                                                   100K 1/4W Resistor
  • R5                                                                   1M 1/4W Resistor
  • C1                                                                   2.2uF 25V Electrolytic Capacitor
  • C2, C3                                                            0.1uF Ceramic  Capacitor
  • D1                                                                   1N914 Diode
  • Q1                                                                   2N3906 PNP Transistor
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