DIY engineering

portfolio of my projects - electronics and traditional

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Anonymous asked: Hi...I am thinking of a DIY TDA7293 amp project myself. How is the sound quality of the 7293 module? Any particular sensitivities? What is your RMS rating/channel?thanks AK

The sound quality of the TDA7293 is very good, even hi-fi grade, and you need very few components to build it. I don’t have a resistive dummy load so I haven’t been able to measure the RMS personally.
If you want to build it I recommend Elliott Sound Products: 
There you’ll also find lots of other projects and articles. 
Good luck! 

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Portable active mixer!


Yet another dumpster Frankensteins monster!

It’s a basic active mixer built for home use, needed some audio control for my portable gear so I cut the transformer and run it off yet another laptop battery that fits inside the casing. Equipped it with a treble and bass control ripped from a car stereo (also junk I found), and a VU-meter ripped from an old stereo someone dumped in a shrubbery.
I also rewired it so the fader fades between AUX1 and AUX2 instead of PHONO (not planning a portable turntable at the moment).


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Parksys 2.0


Modular portable soundsystem with a punch built from junk, powered by laptop batteries!

Bad sound makes my ears hurt, so I looked into 2.1-systems for computers and it turns out most of them use chipamps designed for car audio, which means you can drive them directly with a battery. Although you need a powerful battery, but I’m no fan of lead accs because of their weight.
Now, car audio chips amps work from ~10 - 18 Volts so I use laptop batteries instead, they hardly take any place and wieghs practically nothing yet runs the systems for many many hours (depending on how hard you drive them). They’re allways charged and ready to go as well.

The system is modular where the subwoofer works as the receiver and can either be hooked up with satellite speakers for a smaller system, or work with the speaker above through a wireless audio link (extracted from a pair of wireless headphones).


Both speakers are rescuees from recycled electronics. For the subwoofer I just cut out the transformer and plugged in the laptop battery, and built in the remote in the back. The other speaker is built together from two speakers and driven by a TDA8563Q chip amp that delivers 2 x 25 W RMS into an 4 Ohm load.
Most car audio chip amps also has a diagnose pin which is to easy interface to a clipping indicator.



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Rebuilt vintage power amplifier

I found this beautiful set of preamp and amp from 1977/1978 in the recycled electronics, it’s a 2 x 43 W @ 4 Ohm, slightly defect because of old electrolytes.
I had some TDA7293 IC power amps that I bought sometime earlier and set out to refurbish it and replace the old amp in it since transformer voltage was just right for the TDA7293.

I cleaned them thoroughly and replaced the broken lamps in the power meter with white LEDs.

Rebuilding the power meter drivers on a separate card.

Reinforcing the tracks on the rectifying card and replacing the rectifying bridge to handle more power, also making the transient filtering of the rectifier bridge a bit better and fresher.

The dual TDA7293 on heatsink fitted inside with the drivers for the power meters.

Added a power LED on the amp to make the look more symetrical and also a clipping indicator on levels (built in feature of the TDA7293).
Now it’s 2 x 100 W continuos power @ 8 Ohm, hi-fi grade sound! 

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DIY laser show from discarded electronics

This laser is built purely from electronics junk I’ve found, and my Basic Stamp 2 I had laying around for quite some time, so it has costed me nothing!
The laser diode is from a recordable DVD player, not sure how strong it is but since it can handle 3 Volts at 240 mA it must be atleast x16, don’t have the means to determine the power of the laser but can safely asume it’s a Class IIIb and should not be taken lightly, the direct beam into your eye can damage your retina!
The collimator is from an old laser printer that I stripped long ago, it has great cooling in it’s housing which is needed.
The casing is made from the scrap metal of the DVD and wellplast from an IKEA box, the motors are from the DVD as well.

I’ve designed the circuitry myself (not the LD driver), I studied the motor and mirror setup in a cheap laser crab I had. It’s quite simple: the motors are aligned 45 degrees in accordance to the beam, and the first motors mirror is angled 4 degrees and second motors’ about 6 degrees. This is tuned depending on how big a flower you want, mine is about 2 m in diameter from a distance of 4 m.
The BS2 simply runs the motors at random speeds (through an LM358 and small signal PNP), for random seconds. I probably will burn a PIC and put in there later since I need the BS2 for other projects.

RPM VAR Byte ‘random seed for rotation
Idle VAR Word ‘random seed for seconds
RPM = 213
Idle = 11000
RANDOM RPM ‘randomize value in variable for motor 1
PWM 0, RPM, 50 ‘PWM out on pin 0, with random duty (voltage) and cycles (adjusted to the RC in my circuit, 10kOhm + 1uF)
RANDOM RPM ‘randomize value in variable for motor 2
PWM 1, RPM, 50 ‘put it out on pin 1
RANDOM Idle ‘randomize time before changing pattern
PAUSE Idle / 10 ‘pause ms, divide Idle time with 10 to avoid too long periods
GOTO Main ‘and repeat!

The whole build and designing took me about 3 weeks on and off.

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Falling down from a tree, climbing with my older brother!

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I wanted to design and build my own LED matrix from scratch using my knowledge of electronics and logic. It works on the same principle as an CRT-screen, running one LED at the time from upper left to right, then down one line and repeat.
It takes a signal in so you can control every LED’s intensity.

The sync is built around a 555 timer and the downside is that it slides in frequency so I’ll probably switch it for a crystal oscillator later. Now I just have to build something that generates a signal for it so it shows graphics! probably something PIC-isch.

Filed under LED matrix

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Framed color throbbing heart

So, I bought this strip with SMD RGB LEDs to play with because I always liked LEDs. 
I soon wanted a controller for the colors and built a color cycler around a 555 and 4017 that cycles the colors in spectrum order when holding down a button.

Next I customized the housing of an old IR guard to fit the circuit inside (added a voltage stab since the guard wants 12 Volts) and put the LEDs in a box where I mounted a plastic heart, and put an antique frame around it.

When you walk past it, it will cycle colors for approx. 2 seconds and stop at current color.