diy4fun

CMoy for Altoids box

2010-03-10T10:50:00.008+01:00

This is an article about my new PCB design for CMoy headphone amplifier. Main feature is that the new PCB fits exactly to the classic Altoids tin-can. This new CMoy incorporates moreover bass-boost circuit and constant current charger for 9V battery.

Description:
Few weeks ago I decided to modify my first version of PCB for CMoy amplifier. I wanted to implement following improvements:

+ use new nice small stereo potentiometers with On/Off switch
+ increase capacity of input coupling capacitors
+ add possibility for bass-boost circuit
+ add blocking capacitors for opamp
+ add constant current charger for 9V battery
+ add power jack connector for charging
+ use double side PCB with ground plane
+ modify the shape of the PCB

After few hours of thinking new schematic have arrised.

Schematic of the CMoy with battery charger

P1 is the volume potentiometer with On/Off switch. C2 is coupling capacitor. R2 defines the input impedance of opamp. R3 and R4 define the gain of the amplifier (5x in this case). Rb and Cb form bass-boost circuit. These components increase the gain for low frequencies. For the low frequencies the gain is 14. By increasing the Rb resistors you can increase the gain for low frequencies and vice verse. You can decrease the cutting frequency by increasing the Cb capacitors. Bass-boost can be deactivated by shorting out Rb resistors. As a opamp I use OPA2132, but many others can be used as well like OPA2134, OPA2227, NE5532, ... C3+ and C3- are blocking capacitors for power supply for opamp. R5 is optional, but to avoid some bouncing at the output the value should be around 22 ohms.

V1 is a Rail Splitter which creates virtual ground. C1 is high quality blocking capacitor with low ESR. Resistor R1 limits the current through LED. The value should be modify according the type of LED. D2 limits the maximum voltage in the input to 12V. U2 together with resistor R0 create constant current source for charging the 9V battery. In my case the R0 has value 47 ohms and then the current is around 25mA. Cin is tantalum blocking capacitor for U2. D1 is Schottky diode for avoiding any damage when the voltage with opposite polarity is connected.

Realization:
I designed the PCB with two rounded corners. The PCB fits exactly to the Altoids tin (see pictures below). On the PCB are also nice pictures of input jack and headphones. The resistors and diodes must be assembled vertically to reduce occupied space.

Assembly diagram (top side).

Assembly diagram (bottom side)

PCB (top side)

PCB (bottom side)

Assembled PCB (top side)

Assembled PCB (bottom side)

As you can see on my first prototype there are some mistakes and modification:

1) pins 1 and 3 of volume potentiometer P1 must be exchanged, otherwise if the amplifier is switched on the volume is set to maximum

2) polarity signs for battery clip are opposite

3) only one TLE2426 Rail Splitter should be used, I wanted to increase the maximum current by putting two rail splitters in parallel. I have seen in one forum that it is possible. But finally I observed very high current consumption, probably because the voltage splitters are not exactly same. If only one is used everything is OK.

Enclosure:

Last step was to mount the amplifier to the Altoids tin. I made the holes according the position of components on the PCB and than I covered the bottom of the tin with insulation to avoid some short circuit, because the tin is from conductive material.

Mechanical drawing of holes in Altoids tin

Holes in Altoids tin (front view)

Holes in Altoids tin (side view)

Bottom of the Altoids tin is covered with insulation.

And my new CMoy has been done.

Finished CMoy amplifier (front view)

Finished CMoy amplifier (side view)

Finished CMoy amplifier (inside view)

Finished CMoy amplifier

Conclusion:
I'm very satisfied with my new CMoy. It sounds good and is always close to me ready to play.

ATmega16/32 Pinout Sticker

2010-02-27T19:00:00.007+01:00

If you are playing with the ATmega16 or ATmega32 microcontroller in the DIP40 package you can put my sticker on it. The sticker describes function of all pins. Thanks to color printing you will easily recognize each group of pins like different ports, SPI, I2C, UART, JTAG, ADC.

Few days ago I wanted to start investigate one project which incorporate Atmel AVR ATmega16 microcontroller. I put them into my breadboard and wanted to start with wiring. I realized how annoying is to check datasheet and schematic to find out which leg is what and then count the legs. I remembered for my early days when I started with electronics. I used handmade stickers which were put on standard logic IC from 74xx family. So I started OpenOffice Draw and create new modern sticker for ATmega16/32. And here is the result:

I made more copies on one A4 page and printed them on self-adhesive paper. After that I put on them thin cello tape. Thanks to this cover the sticker is resistant for touching and it will stay nice for a long time. After that I cut the sticker from A4 page by using sharp knife and stick it on the chip.

Here are some photos of my ATmega16 with new sticker in my breadboard.

LINK:
Download source file for OpenOffice Draw and one sticker in PDF.

Rotary encoder for ATS - Assembly

2010-02-13T20:40:00.019+01:00

This article describe assembly of the "Rotary encoder for ATS" kit. It is step by step instructions manual, you can find here the photos of the board with description for each particular step.

First of all, put the schematic in front of you and than check and prepare all components. You will need soldering iron with small tip, solder, tweezer, cutter. It is good to have some experience with soldering SMD parts. I recommend following procedure for soldering SMD components: 1. Place small amount of solder on one pad at the PCB. 2. Take a parts into the tweezer and put it in the right position. 3. Head the solder and push the parts little bit. (Arrange the position if necessary) 4. Solder other pads of the parts and then correct the soldering on the first pad. The solder joints should be smooth and shiny.

1. Check visually the PCB.

2. You can clean the PCB with isopropyl or spirit.

3. Solder the four 10k ohms resistors R1, R4, R5, R6. On the resistors is written 1002.

4. Solder the ceramic capacitor C1. The value is 100nF. The tape with capacitors is labeled.

5. Solder the two 680 ohms resistors R2, R3. On the resistors is written 6800.

6. Solder the 470 ohms resistor R7. On the resistors is written 4700 or 471.

7. Solder three transistors T1, T2, T3.

8. Solder voltage regulator U2. The type is 78L05.

9. Turn the PCB and solder the 100nF ceramics capacitors C5 and C7.

10. Solder the ceramic capacitors C2, C3, C4. The value is 1nF. The tape with capacitors is labeled.

11. Solder the microcontroller U1 Attiny 2313. After that check the solder joints for possible solder bridge between legs. The microcontroller is already programmed.

12. Solder electrolytic capacitor C8. The value is 47uF. Take care of the polarity labeled on the PCB and capacitor.

13. Solder electrolytic capacitor C6. The value is 100uF. Take care of the polarity labeled on the PCB and capacitor.

14. Solder the red square LED3. Take care of the polarity. The anode (longer leg) must be on the left side (see picture). Make the length of the legs according to your enclosure. The LED could be also moved to another place with help of wires.

15. Solder the green triangle LED2. The position is given by the direction.

16. Solder the green triangle LED1. The position is given by the direction.

17. Solder the encoder.

18. Bend little bit the mounting legs of the encoder and the solder them.

19. Solder the 5pins single line header for connection to the ATS.

20. Optional, not necessary! Solder 3pins dual lines header for ISP programmer.

21. Install the knob. When you remove cover there is a nut which help to hold the knob on the encoder.

22. Place the cover back on the knob and that's it.

Congratulation! You are done. The rotary encoder should work at the first time. Make the connection with your ATS according to the operational manual. Double check the proper place of connected wires and then test it. Be careful of the polarity when you connect the rotary encoder to the ATS.

Rotary encoder for ATS transceiver series

2010-01-21T22:10:00.024+01:00

This equipment is dedicated for an easier control of the popular mini-transceiver AT Sprint known by ham radio operators as ATS (series ATS-2, ATS-3, A, B, B.1 compatible). Originally the ATS has just four push buttons on the top cover and in combination with the paddle it is possible to send all commands to ATS including the tuning, scanning etc. After connecting the rotary encoder accessory module an easy tune, scan and other functions are available as same as on the big size desktop transceivers. Comfort and operation is much higher even with this mini transceiver.

Description:
Some times ago my friend and colleague Petr (OK1RP) bough and built ATS transceiver. When he showed me how it works I saw that tuning is not very comfortable. I thought that would be nice to be able to control tuning with rotary encoder in the same way as it is possible on large desktop transceivers. Petr was very excited about this idea. We looked at the schematic and the idea of schematic was born in my had. I built first prototype and it worked quite well. And now you can see final version of the rotary encoder module.

The heart of the rotary encoder module is microcontroller Atmel ATtiny2313. The firmware in the microcontroller is watching the turning or pushing of the main tuning knob on the encoder module. According to movement of the tuning knob the microcontroller control three transistors which are connected in parallel with push buttons in ATS.

Block diagram of the rotary encoder

The rotary encoder consisting the main blocks as follows: microcontroller, encoder unit with knob, LED indicators, transistor switching circuit, voltage regulator and connector for connection with ATS.

Schematic of the rotary encoder kit

I designed the double side PCB. The size of the PCB is 38x36mm and it has two mounting holes. Really nice, isn't it.

Assembly diagram (top side)

Assembly diagram (bottom side)

Interconection with ATS:

For correct functionality of the rotary encoder module is necessary to connect five wires as follows:
1) connect the GND of the ATS to the GND of the rotary encoder
2) connect Vcc voltage from ATS board to rotary encoder board
3) connect the push buttons MENU, UP and DOWN on the ATS board to the rotary encoder board

Rotary encoder pins description

The five wires cable should be used for interconnection between ATS and rotary encoder module. Due to this interconnection it is possible to easily disconnect encoder and use ATS alone as originally designed. On the ATS side the wires are soldered to push buttons pins, power supply and GND pins.

Interconnection between encoder and ATS transceiver

Control options:

Rotation 1 step to the left

- simulates pushing the button DOWN (tune down)

Rotation 1 step to the right
- simulates pushing the button UP (tune up)

Pushing the tuning knob once
- simulates pushing the button MENU once (frequency reading)

Pushing the tuning knob long time
- simulates pushing the button MENU long time (go to MENU)

Double click to the tuning knob
- “tuning” mode is activated which is indicated by the both green LED's flashing. Encoder is waiting at this moment for the direction where to go to tune the transceiver. It can be done by simply rotation right/up or left/down of the main tuning knob. After setting the directions as mentioned the encoder simulates holding the push button up/down on the ATS to tune through the band without necessity to hold any button or knobs! We are talking about the automatic scanning through the band. The selected direction is indicated by the flashing of corresponding green LED. To stop the tuning through the band just press or rotate the tuning knob in any direction.

Conclusion:
It took few months from first idea to the final version of the kit, but it was nice work with good result. I would like to thank you to OK1RP and OK1SA for support and testing of this kit. On the following pictures you can see one of the last version of the rotary encoder module on the professionally made PCB. Actually the last version is using 1206 size of resistors and capacitors instead of 0805 size for easier soldering. I will post photos with 1206 part soon in the next post where I will public step-by-step procedure how to assembly this kit (so stay tuned).

Rotary encoder modul (top view)

Rotary encoder modul (left view)

Links:
Operational Manual (PDF)
Rotary encoder module schematic (PDF)
AT Sprint Yahoo Forum

Ordering Information:
Because I thought that this device could interest other ATS radio operators I made a kit with all parts including pre-programmed microcontroller and the PCB. If you would like to buy the kit, please contact me on my mail address diy4fun@gmail.com. The price of the kit is 25USD. The shipping is 5USD worldwide for one kit, 6USD for two kits and 7USD for three kits. I prefer PayPal for the payment and I'm sending the kits by standard postal service.

Make a Sound Card with PCM2704

2010-01-03T14:50:00.011+01:00

This article relates to my previous article Make a sound card with PCM2702. In this time I used newer IC from Texas Instruments PCM2704. Thanks to this circuit with all necessary features inside 28pins SSOP package I was able to built quite small sound card. The result is sound card with size of gumstick.

Description:
This device is fully functional sound card for PC. The main advantage of using PCM2704 against PCM2702 is much easier construction. As you can see on the block diagram it has built-in 5V and 3.3 voltage regulator, HID interface (MUTE, VOL+, VOL-), S/PDIF output. The circuit can be powered directly from USB port. Next advantage is that the outup DAC is able to drive directly 32ohms headphones, but the ouput power is only 12mW. For all details please refer to the PCM2704 datasheet.

Block diagram

The schematic is very simple. It is almost copy of the datasheet circuit diagram. You can see the core IC PCM2704 (U1), crystal with supporting parts (X1, C1, C2, R1), connection to the USB (USB connector, R2, R3,R4, L1), a lot of blocking capacitors for all voltages (C3, C4, C5, C6, C7, C8), S/PDIF output header (J1), HID header (J2), output filter (R5, C11, R6, C12, R7, R8), coupling capacitors (C9, C10) and output 3.5mm Jack connector (J3).

Schematic of sound card with PCM2704

Realization:
I designed my own PCB. The dimensions of the PCB are 55x18mm, including USB and Jack connector it is 73x18mm. To keep the size as small as possible 0805 size of capacitors and resistors were used. The L1 is ferrite bead which reduce high frequency hum. With good soldering iron and litle experience it is possible to assembly the PCB by hand.

Assembly diagram (top side)

Assembly diagram (bottom side)

PCB (top side)

PCB (bottom side)

Assembled PCB (top side)

Assembled PCB (bottom side)

Conclusion:
I built two pieces of this sound card. I have tested the sound card under Windows XP and Windows Vista and it works without any problem. I wanted to use this device for my Internet radio receiver, which I'm building according to the project published on mightyOhm.com. The receiver is based on Asus WiFi router WL-520GU with OpenWrt Linux distribution. The sound card works under the Linux as well, but it stop and start playing the sound periodically (the period varied from few minutes to one hour). I guess it is driver problem (if somebody has any idea how to fix it I will be very grateful).

You can ask me why to build this sound card when you can buy similar device for few bucks. I have also one sound card from China which cost around 5$ but the quality of the sound is very bad, so the main difference is sound quality.

Links:

PMC2704 (TI)
PCM2704 Evaluation Board (TI)

Coreduino

2009-04-29T15:20:00.012+02:00

Coreduino is another clon of amazing Arduino board. Main advantage of Coreduino is compact size, minimized price and easy connection to a breadboard. If somebody don't know what Arduino is please visit website www.arduino.cc for more information, because Coreduino is based on the Arduino concept. In this post you can find information about Coreduino module, USB and Serial programmers for Coreduino.

Coreduino:
When I first met the Arduino I was really impressed by this great idea. Arduino is very powerful and extremely easy to use. Big Arduino community share projects, components, libraries and codes, which save time to all people who wants to do similar projects. Programing of the Arduino is very simple. Thanks to bootloader, which is programmed inside the ATmega by clicking on one icon in Arduino IDE, the code is loaded and executed in the microcontroller.

I wanted to have my own Arduino but I also wanted something more universal. I took only core components from Arduino and put them to as small PCB as I was able to manufacture practically at home and Coreduino came to light. It consists only from few components: microcontroller ATmega168, crystal 16MHz, reset button, some resistors and capacitors and header for ISP, USB or Serial programmer and also headers for connecting to breadboard.

I put the programmer to stand alone PCB because you can built only one and use it for as many Coreduino boards as you want. This save your money against Arduino board, where each board has his own programmer.

Coreduino is compatible with Arduino Decimalia. It also supports RESET from RTS or DTR line.

Coreduino has three solder bridges (W1, W2, W3), which allow you to make following settings:
W1: allows to supply Coreduino from ISP programmer
W2: connects Vcc to Aref pin
W3: allows to supply Coreduino from USB programmer (see bellow)

Schematic of the Coreduino

Assembly diagram (top side)

Assembly diagram (bottom side)

3D model made in Google SketchUp

Assembled Coreduino (top side)

Assembled Coreduino (bottom side)

Description of pins

USB Programmer:
USB Programmer is actually USB-to-Serial interface. It consists from USB-to-Serial converter chip FT232RL. It is more or less connected as in datasheet schematic. RTS line is also connected to the programming header to allow reset function of Coreduino.

USB Programmer has three solder bridges (W1, W2, W3), which allow you to make following settings:
W1: logic levels will be set to +5V
W2: logic levels will be set to +3.3V
W3: connects supply voltage to programming header. It allows supply Coreduino from this programmer. Supply voltage depends on logic levels voltage set by W1 or W2.

Schematic of the USB programmer

Assembly diagram (top side)

Assembly diagram (bottom side)

Assembled USB Programmer (top side)

Assembled USB Programmer (bottom side)

Serial Programmer:
The serial programmer is easier and cheaper solution for programming of Coreduino. It consists of two level shifters. LEDs on the board indicate sending or receiving data. Serial programmer is not able to supply power for Coreduino.

USB Programmer has two solder bridges (W1, W2), which allow you to make following settings:
W1: use RTS line to reset Coreduino
W2: use DTR line to reset Coreduino

Schematic of the serial programmer

Assembly diagram (top side)

Assembly diagram (bottom side)

Assembled Serial Programmer (top side)

Assembled Serial Programmer (bottom side)

Bridge:
Serial or USB programmer can be connected to the Coreduino with help of small bridge.

Assembly diagram (top side)

Assembled bridge (top view)

Coreduino <-> Bridge <-> USB Programmer

LINKS:
Download schematic, assembly diagram and PCB.

Note:

I think that somebody of you could be interested in Coreduino and because the board is on the edge of home manufacturing, I'm willing to arrange ordering of PCBs in professional PCB manufacturing company (PCB would be with vias, solder mask and silk screen). The more people will append the better price will be. In case of interest please write an email to diy4fun@gmail.com.

Simple Serial Programmer for AVR

2009-01-04T22:00:00.013+01:00

This is a very simple and easy to build programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming. This programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer.

Description of the serial programmer:
The programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. The Zener diodes D2, D3 with the resistors R2, R3 reduce the voltage from the ouput pins DTR, RTS on the serial port to around 5V which is suitable for microcontroller (MOSI, SCK). MISO signal is connected directly to the input CTS pin. The Zener diode D1 with the resistor R1 drive the NPN transistor T1, which controls RESET signal. The AVR microcontrollers are in reset when the signal has low level. The resistor R5 works as a pull-up for reset signal. The resistor R4 helps to close the transistor T1. The programmer has standard 10 pins header.

Schematic of the serial programmer

Assembly diagram

PCB (top side)

PCB (bottom side)

Panelization (When you need more pieces.)

Assembled PCB (top side)

Attention:
The transistor T1 should be in opposite position then is depicted in the assembly diagram.
Please check the position of Base-Colector-Emitor on your transistor.

I use this programmer for programming Attiny13, Attiny26, Attiny2313, Atmega48, Atmega88, Atmega168, Atmega16 and it works very well. I also use the programmer with desktop computer, laptop, with and wihout USB-to-RS232 adapter and it works in all cases.

Using PonnyProg2000:

When you want to program your microcontroller with the PonnyProg2000 you have to setup the program as you can see on the following picture. You have to select chosen COM port, where is connected your programmer.

Ponyprog I/O port setting

Using Avrdude:
When you want to program your microcontroller with Avrdude you have to select the keyword "ponyser" as a programmer type and appropriate COM port. I'm using this method to program my microcontroller directly from the Atmel AVRstudio when I'm debuging my application. I create a batch file with the command for the avrdude and I call the batch file directly from the tool bar. It is very fast and easy. Avrdude is also part of the WinAVR package.

Microcontroler programming by avrdude

Programming header reduction:
Sometimes you have to program microcontroller in a aplication where is only 6 pins header instead of 10 pins. I created small adapter for this purpose. The adapter has 10 pins header, 6 pins header and 6 pins header in one line. 6 pins header in line is useful when you want to bring the signals to the breadboard.

Schematic of the programming header reduction

Assembly diagram

PCB (bottom side)

Assembled PCB (top side)

With this equipment you should be able easily program your AVR microcontrollers. Good luck.

LINKS:
PonyProg2000

Download project including schematic, assembly diagram and PCB.

Make a Sound Card with PCM2702

2008-04-22T15:14:00.024+02:00

Make a sound card is no more a complex issue. If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don’t need to install any driver for Windows XP and Vista, because they are already inside. This is really plug and play.

Few months ago I have seen USB sound card called Alien DAC. The construction on the project web page inspired me to build this thing also.

Description:
The core of this construction is 16-Bit Stereo Digital-To-Analog Convertor with USB interface PCM2702.

PCM2702

Schematic of sound card with PCM2702

PCM2702 needs only few additional parts to work. The schematic is not complex. Sound card can be powered directly from USB port (jumper W1) or from external power supply (jumper W3). PCM2702 needs two power supply 3.3V (3V-3.6V) and 5V (4.5V-5.5V). I used fixed output voltage LDO TPS76733Q for 3.3V (IO2) and adjustable output voltage LDO TPS76701Q for 5V (IO3). Both LDO are produced by TI, I used this because I had it in my drawer. Any similar LDO can be used. Output voltage of IO3 should be set to little bit lower than input voltage to allow LDO good stabilization, in my case output voltage is set to 4.8V. Output voltage can be set by adjustable resistor R33. In case of low power supply, IO3 can be shorted by jumper W3. LED D3 signalizes power on.

Small ferrite beads are placed before all power pins of PCM2702 and in Vbus and GND of USB. These small beads reduce high frequency hum. I had a problem find this small SMD ferrite beads in local stores but finally I acquire few of them from old hard drive. They are not absolutely necessary, you can use zero ohm resistors instead of them.

Low-pass filter is placed in output signal path to reduce sampling frequency. An OPA2353UA dual op amp is configured as a stereo 2nd-order low-pass filter.

Led diode D1 is illuminated when PCM2702 plays audio data received from the USB bus. Led diode D2 is illuminated when USB bus suspends audio data transmission to the PCM2702.

Realization:

PCB Assembly diagram

Bottom side (single side PCB, made by standard etching method)

Assembled top side

Assembled bottom side

Conclusion:
This circuit works very well. I only shorted crystal during soldering so the circuit didn’t work, but after removing the short the sound card started to work. I have tested in Windows 2000, XP and Vista. It works in all mentioned systems. Drivers are present in operation system so the sound card is ready in few seconds after you connect it.

During writing this article I have found that PCM2702 is now not recommended for new design, but TI offer even better solution. PCM2704, PCM2705 have same functionality as PCM2702, but they include output filter. They are able to drive directly headphones. Volume and Mute can be controlled through SPI bus in PCM2705 or with pushbuttons in case of PCM2704. PCM2704 and PCM2705 are in TSSOP28 package. PCM2706 is similar to PCM2704 and PCM2707 to PCM2705 but in addition they have I2S bus. PCM2706 and PCM2707 are in TQFP32 package. I recommend using these new chips for new design (look at the TI web page).

LINKS:
PCM2702 Texas Instrument

PCM2702 Evaluation Board

Alien DAC

Download project including schematic, assembly diagram and PCB.

ATmega48/88/168 Development Board

2008-04-01T13:10:00.050+02:00

This is versatile development board for AVR microcontrollers ATmega48/88/168. It is good for testing and debugging embedded programs. It has many built-in peripheries connected to microcontroller so you can use them without soldering. ATmega microcontrollers are produced by ATMEL and they include a lot of features: I/O, Timers, PWM generators, ADC, RS232, TWI, SPI, Analog Comparator, Oscillator, EEPROM… These microcontrollers are very versatile, easy to program and easy to use. This is the reason why I like these microcontrollers and why I decided to make development board for them.

The development board consists of:

1. ATmega AVR microcontroller in DIP28 package
The development board is designed to use ATmega48 with 4kB flash memory or ATmega88 (8kB), ATmega168 (16kB). New version of these microcontrollers ATmega48P/88P/168P and ATmega328P (with 32kB) are pin compatible with old version, so they can be used also.

External crystal X1 is placed in socket, so it is easy to change it or remove it. If internal oscillator is used then two PB6 and PB7 pins dedicated for crystal can be connected to the Port B connector.

Microcontroller can be reset by pressing reset button S1.

2. AVR Ports B, C, D headers
If built in peripheries are not used another device can be connected to the PORT B, C and D. Each port is connected to the 10-pin header. You could connect LCD display, Rotary Encoder, SD Card Reader, etc. with microcontroller. See my future posts.

3. 5V Power supply
Both AC and DC voltage can be plugged in, because of using rectifier bridge. Input voltage can be connected to 2.5mm power jack connector or screw terminal. Power can be switch on / off by SW1. Power supply voltage is stabilized by common IO 7805. When the power is switch on red LED6 is lighted.

4. 4x LEDs
Four green LEDs can be connected to the Port D shorting jumpers JMP6-9.

5. 4x Buttons
Four buttons are connected to the Port B.

6. Piezo
Piezo speaker can be connected to pin PB1 through JMP5.

7. ADC accessories
The microcontroller has built-in 10bits AD converter. On the board is LC filter for power supply of this ADC. You can use internal or external reference. The rotary trimming resistor R2 is connected to Aref input for playing with the external reference.

8. Potentiometer
For simulation of varying ADC input voltage the rotary trimming resistor R1 can be connected to PC1 (ADC1) through JMP12.

10. Temperature sensors
If you want to play with temperature sensor, you can connect temperature sensor with either analog or PWM output. Temperature sensor with analog output can be connected to the PC0 (ADC0) through JMP10. Temperature sensor with PWM output can be connected to the PB0 through JMP11.

10. RS232 line
Standard serial interface is placed on the board. Level shifter MAX232 is used. MAX232 has two receiver and two transmitter lines. You can connect RXD and TXD of RS232 with RXD and TXD of microcontroller with help of config header. RTS and CTS of RS232 can be connected with PD6 and PD7 through JMP3 and JMP4. See config header part.

11. Config Header
Config header allows interconnect different I/O microcontroller pins with RS232 line or with screw terminal.

12. Srew terminals
Screw terminals allow easily connect wires to microcontroller. Through this terminal you compose for example frequency counter of voltmeter, etc. Ground and 5 Volts are also presented on screw terminal.

13. ISP
Development board includes serial port interface to allow direct in-system programming (ISP). Microcontroller can be programmed trough RS232 serial port by using program Pony Prog or Avrdude (ponyser). To avoid interference with RS232 signals, programmer can be disconnected using analog switches 4066. These switches can be closed manually by SW2 or automatically when the reset is active (using JMP13).

14. Mounting Holes
In each corner of PCB is placed one ø3.2mm mounting hole.

And the result ...

Assembly diagram

Top Side

Bottom Side

LINKS:

Following web side inspired me to build the development board.
AVR Development and Application Boards

You can download this project including whole schematic, assembly diagram and PCB.
ATmegaa48 Development Board

CMoy

2007-11-11T11:00:00.005+01:00

CMoy is very simple portable headphone amplifier. The amplifier was originally posted by Chu Moy on headwize.com. The best source of information about this amplifier is article How to Build the CMoy Pocket Amplifier. If you use Google, you will find many pages and pictures about CMoy. Few months ago I decided built this amplifier also. In my post you can find my experience with creating this simple but very good amplifier.

First of all I prepared the schematic. It is standard CMoy schematic, non-inverting amplifier with gain 11. The power supply is making virtual ground (half of supply voltage). My power supply unit has two possibility. Firts possibility is use passive voltage divider, consist of two resistors R1a and R1b. In this case it is necessary use also two electrolytic capacitors C1a and C1b. The second possibility is used active divider TLE2426 from TI. In this case it is necessary connect only one capacitor between Vcc+ and Vcc-.

1. Schematic

After I had schematic I designed the PCB. My PCB is prepared for both variants of power supply. I can connect also one or two 9V batteries. In first case it is necessary shortcut one supply connector P1a or P1b. Power switch can be connected to P2.

2. Design of PCB

I let make the film in Prague's design studio Winter.

3. Film

The PCBs were made in Prague's company PLspoj.

4. PCB

I assembled CMoy during one hour. Instead of R5 and R25 is used only wires. These resistors are assembled only in case of oscillation. The value should be few ohms. Now I have to find some good box, and put my CMoy inside. It will be maybe most difficult part of building CMoy amplifier :-).

5. Finished CMoy

The sound is very good for so easy and small device. It can improve the sound of MP3 players, mobile phones and other portable devices. I would like to make some measurement of frequency characteristics, THD and also try to use different OpAmps, but unfortunately I don't have enough time to make it now.

LINKS:

A lot of information about CMoy : http://tangentsoft.net/audio/cmoy-tutorial/

Step by step tutorial how to make CMoy: http://williamneo.blogspot.com/

Let's start :)

2007-11-11T09:00:00.004+01:00

Hello Everybody,
welcome on my blog DIY4FUN. After long time thinking about making my own web site, I decided to create blog site, because I don't want waste my time fighting with HTML, CCS, ... even if I have some experience with this. On this blog I would like to share with you my experience with building electronic devices and my new ideas, advice, opinions about electronics.

For those who don't know what means DIY, it means Do It Yourself. Even If we can buy almost everything, there is still good reason why build small electronic devices yourself. You can learn new thinks, obtain new experience, save some money and the most important think you can taste great feeling when your devices is working.

Let me shortly introduce myself. I'm now 27 years old. I live in Prague in Czech Republic. I graduate Czech Technical University and I was focused on measurement, technical diagnostic and aircraft electronics. I'm working as a product engineer in ST Microelectronics. Company which produce semiconductor parts. Even if electronics is my job, I like it and electronics is also my hobby.

I'm looking forward for your comments.
You can contact me trough email diy4fun@gmail.com

Best regards
Miroslav (Mirek) Batek

PS: English is not my mother tongue. I would like to apologize for mistake which I will make. I will be glad if you will correct me, because I can improve my English.