Eagle CAD PCB footprints for audio processors TDA7313 and TDA7315

TDA7313 and TDA7315 are digital controlled audio processors that can be used in applications where digital control of audio is needed. TDA7313 and TDA7315 are are pretty same just TDA7313 is more complex by hawing 3 stereo input channels and two outputs (front and rare). Both chips have volume control (step=1.25dB), tone (bass and treble) balance, independent faders for each output processors. Also there are loudness functionality. TDA7313 and TDA7315 have low distortion, low noise, that makes them ideal for quality audio applications for car audio and Hi-FI systems.   Both chips can be controlled by MCU via I2C(TWI) protocol. This makes easy to interface microcontrollers with additional features like LCD, buttons. Or simply control directly from PC using RS232 or other interface. Both chips can be found in DIP or SO packages. Here are Eagle libraries of both digital audio processors that I have made. tda7315.zip(2kB) tda7313.zip(2kB) I have intent to make control board with TDA7315 with LCD and button control using Atmega8 microcontroller.  

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PCB Exposure using UV light LED box

I came across this interesting project. The guy decided to make UV PCB exposure box made of UV light LED’s. The main reason why he used LED was the power dissipation and compactness. Assuming that one UV tube would take about 6W while one UV LED would take about (20mAx3.2V=64mW). Most of that energy UV tubes dissipate as heat energy. So he took: 54 x UV LEDs of 400nm (6000 – 7000 mcd) – 100 units in Ebay costed 12€; 18 x 68ohms resistors 1/4W – 0,36 €; 1 connector – 0.50€; 1 electrolytic condenser of 2200uF – 30v; 1 Eurocard Plate 100×160 about 5 € ;  

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Place electronics parts correctly on PCB

Lets go through few examples how to place electronic parts correctly on PCB board. SMD electronic parts especially if lead pitch is above 1 mm, then placement of leads has to be symmetrical on copper planes: If IC has smaller lead pitch like 0.5 – 0.8mm positioning by hand become harder. Sometimes it is recommended to use special glue to fix SMD part before soldering. DIP electronic parts has to be soldered as close to PCB board as possible to make them stand stabile and to avoid heat resistance. Electronic parts with axial leads are placed vertically for better air ventilation. Because of this diodes and Zener diodes has to mounted with cathodes up with gap of 1-2 mm between electronic part and PCB board. If there is enough place – they can be mounted horizontally. This way between electronic part and PCB has to be a gap of about 1 – 2 mm. Single side pin electronic components like ceramic, electrolytic capacitors, crystals, semiconductor fuses have to be placed with minimal gap (about 1 mm) between PCB. H49U crystals have to be placed with minimal gap between PCB. It under resonator there is no via holes or tracks, then…

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Generic PCB design guidelines

How repeatedly make good PCB? Many hobbyists faces this issue every time they are prototyping their ideas. Designing the PCB layout (doesn’t matter is it a through hole or surface mount) may be tricky task especially when dealing with dimensions like 0.2mm tracks or 0.5mm surface mount pitches. Laser printer, plotting or other similar transfer technologies can’t deal with such dimensions. After I have tried photographic method of PCB artwork transfer, I don’t even want to touch Iron and laser printer. Using photosensitive laminate and single transparent media I can repeatedly make any number of PCBs. Benefits of using photographic methods are as follows: Transferred artwork is very clear, edges are smooth; Track thickness may be up to 0.2mm or even less with good mask quality, which can be made with good laser printer (usually new one). After printer cartridge refill – printing quality drops down; With one artwork mask I can clone many PCBs; Pay the biggest attention to artwork fabrication. Without good artwork you won’t be able to make good PCB. From My experience I can say, that I always do small mistakes with PCB artworks and I spot them usually after PCB is etched. Devote more time…

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PCB Etcher

After UV-80 vas built there was a thought about automatic PCB Etcher with autonomous Heater and bubble machine. This project is hanging in prefinished phase but it does a job. It was used to etch several PCB’s. As this etcher supposed to be used for making PCB’s using photoresitive technology, the controller supposed to control both = the heater of etching tank and heater of developer. As Sensors there are used AD7416 digital temperature sensors. I decided to publish this small project as this is not clear when it will be finished. When it will be, I will update this article. There is a little dirty drawing with dimensions: The dimensions are as follows 215x275x30 exterior. Inner volume is smaller as glass is 4mm thick. So overall volume is less than 1,2 liter. It is ideal volume to use one bag of ammonium persulphate or 250 grams of FeCl3. The glass plates are glued with aqua silicone. Sides are strengthened with aluminum profiles (not necessary if you have skills of gluing aquariums). As you can see it is only manual control 🙂 Thermometer, heater and tank with etchant. Thermometer has scale with more than 50°C as solution shouldn’t exceed this…

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Ultraviolet light source UV-80 for PCB exposure

One of more advanced PCB manufacturing methods is exposing laminate copper boards covered by photo resistive layer through mask. Using UV light in manufacturing PCB’s has many benefits according to other methods: you can get thin tracks like 0.2mm. You couldn’t do this by using other home techniques like laser printers or hand artwork; other advantage is that this method gives clean image – smooth edges of PCB tracks. Little bit effort and you can compare results to commercial products. And pf course third benefit is speed and multiple replications of your boards by using the same mask. In this article is described the manufacturing of an automatic ultraviolet light source exposure box.   Parts for UV box Case with organic glass Panel UV lamps ballasts and starters Controller     Case Case is made of 5mm wood board wired with screws.   Making a control panel Control panel consists of two parts:”Power control” and “Automatic control” POWER switch is used to turn on/off power of the UV box. Green LED indicates the ON. MANUAL/AUTOMATIC switch is used to power l the UV lamps manually or automatically. Switches UPSIDE and UNDERSIDE are used to enable upper and lower lamps separately…

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