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 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.
Schematic
PCB
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
source by : ELECTRONIC LAB
USB Sound Card with PCM2702
Schematic of sound card with PCM2702
High Power LED mood Lamp
In this page we will introduce a great project designed by Toon Beerten. His project named "DIY Led Mood Lamp" can become a very interesting add-on for your room that's absolutely sure it will impress everyone. As you can see on the photos, we talk about a color fading lamp, that looks amazing!
The purpose of this page is to try to give some hints building it successful. This high power led mood light is based on PIC16F628 and the ability of this mcu to produce PWM pulses. Varying pulse width we can produce millions of color combinations using only the three basic colors. So only one RGB (Red-Green-Blue) led is capable producing a rainbow of fading colors.
With the help of four switches we can handle all functions of the lamp. We can choose fading or jumping between colors, we can select a rainbow style or a random color changing behavior, we can choose slow or fast changing of colors and we can pause on a desired color.Finally we will make some power dissipation measurements to help us select an appropriate power supply unit.
Housing for best color diffuse
You can use your imagination to find a housing that will be able to diffuse colors uniformly. Color difussion is necessary to achieve best results. In original design the author used the 45cm IKEA Mylonit lamp. That's a great housing for your lamp. Instead you can use the smaller 31cm IKEA Mylonit lamp with the same amazing results. That's the lamp we used in our construction.
In our research we found other lamps (ex. sphere shape) that are ideal for housing your big led.High Power LED
The led used is a high power 3W RGB LED. It can be found on ebay at LEDSEE-electronics. You can also check ebay for other high power RGB leds. It will do the jod the same way. Details of this brilliant led shown below.
3W high power RGB LED
 Note: Minus on the bottom right pin is common anode (positive voltage) |
Light Angle of the LED 140 degree°
Nominal current B,G,R 350mA
Forward voltage:
Red Typ 2,2V
Green Typ 3,55V
Blue Typ 3,55V
Wavelength of the LEDs:
Red Typ 625nm
Green Typ 530nm
Blue Typ 470nm
Luminous Intensity:
RED Typ 32lm
Green Typ 35lm
Blue Typ 10lm
LED type: Common Anode
Schematic
The schematic used is shown in the next image. It's as simple as it shows. Take care on the correct transistor mount and correct polarity of power source.
Schematic (click image for higher resolution)
BC337 Pin out
Parts List
Here is a list of the components i used for making the led mood lamp.
- - 3 x NPN transistors capable of driving 500 mA, for example the BC337
- - one PIC 16F628(A) and a programmer
- - a small perforated circuit board
- - 7 x 10K resistors (1/4W)
- - some 1 watt resistors (4,7, 10 and 15 Ohm) and a DIP switch
- - a power supply (5 volts, 500 mA)
- - Ikea Mylonit lamp or other housing
- - silicon paste from your local DIY shop (if you want to use a heatsink)
- - one z-power 3 watt rgb led
- - a little heatsink and some cooling paste (if you want to use a heatsink)
Circuit board
On the next image you can see the circuit arranged on a perforated board.
Programming The PIC 16F628 MicroprocessorProgramming the PIC16F628 can be achieved using this very simple pic programmer and a program called ic-prog. Just use your programmer and upload the .hex file on your PIC. For successful results you should pay attention on the fuse bits. You should enter the correct fuses as noted on the following table.
Fuses
IntRC I/O = Enabled
PWRT = Enabled
BODEN = Enabled
MCLR = Disabled
Rest of fuses = Disabled
DIP Switches functions
SW1 - makes you choose between G->GB->B->BR->R->RG-->>G effect and random color change effect
SW2 - makes you choose between fading and jumping from one color to another
SW3 - makes you choose between slow or fast
SW4 - pauses at the current color displayed
Mounting
A good way to mount the circuit board is to use a hot glue gun to "mold" the circuit underneath the lamp housing. There is plenty of space there for your board. At the next photos you can see the circuit board mounted on the small 31cm IKEA Mylonit Lamp.
The glue is still hot. Temperature of glue didn't damage the PIC or other parts.
The glue is now cold and you can easily access the dip switches. Lamp is working!
A view from top of the lamp.Power dissipation
Finally we have done some current measurements to measure power dissipation. It's clear that current changes as colors are changing. As you can see the max current needed is 232mA. You should keep in mind that this depends on the led you have and the power resistors you choose.
As a conclusion a power supply rated at 5V/500mA will be sufficient.
Touch Switch ON-OFF
The modern mechanic switches are improved concerning of old technology. We need however many times to replacement some old switch or to check currents bigger than the durability of certain switches or simple we need something with modern appearance. For he and different reasons is essential the up circuit. He is simple in the manufacture and the materials that use they exist everywhere. This based in the known 555, which drives a relay of which the contacts play the role of switch. The metal surfaces can have what form we want, but it should they are clean and near in the circuit. In order to it changes situation it suffices touch soft somebody from the two plates. Plate JF1 in order to the contacts of RL1 close [ON] or plate JF2 in order to the contacts of RL1 open [OFF]. The current that RL1 will check depended from his contacts. The Led D2 turns on when the switch they are in place ON and the contacts of RL1 closed.
| Part List |
| R1-2=3.3M 1/4W 5% | D1=1N4148 | RL1=12V Relay [Your choise ] |
| R3=10K 1/4W 5% | D2= Red LED 3 or 5mm. | JF1-2=Metal Plate |
| R4=1K 1/4W 5% | Q1=BC547 | |
| C1=10nF 63V MKT 5% | IC1=555 |
electronic smoke detector circuit that can be used as a fire alarm
This circuit uses a very simple approach to detecting smoke in the air. Quite simply, it uses a bulb as a light source, and an LDR (Light Dependent Resistor) as a light detector. As fire smoke comes between the bulb and LDR, the resistance of the LDR changes, which in turn trigger an alarm.
This probably isn't an ideal approach given that ambient light levels are likely to cause false alarms, however it is an interesting experiment. Just please don't set any fires while experimenting. And please don't rely on it as a replacement for a real fire alarm device.
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