Monday, February 22, 2016

Mullard 3-3 Amplifier Project (Part 2)

This is a second article related to Mullard 3-3 Amplifier Project and in this article we introduce HT transformer and HT power supply related to this amplifier. As mentioned in previous post, power supply unit of this tube amplifier is constructed using 400V 5A bridge rectifier, 220µF (400V) and 82µF (400V) electrolytic capacitors.

Homebrew HT transformer and PSU

The most vital component of this power supply is HT transformer and due to limited availability we construct this transformer by ourselves. We construct this transformer to obtain following voltages and primary winding is design for 230V AC mains lines.

Monday, February 15, 2016

Simple door bell for access control systems

This is very simple electronic doorbell circuit which is specifically design to interface with commonly available access control systems. This circuit is designed around NE555 timer IC and LM386 audio power amplifier IC. Because most of the access control systems use 12V power supplies this doorbell is also design to work with 9V to 15V DC power source.

Final view of our doorbell project prototype.

We test this doorbell with several YOUHE access control systems and it works well with all the tested models.

In this design NE555 is setup to obtain 840Hz - 860Hz output with above 80% duty cycle. To get more effective output we use small 3.5 inch, 8Ω tweeter with our prototype design.

The PCB design and schematic of this design is available to download at google drive.

Sunday, February 7, 2016

Musical trees

"Musical trees" is a part of creative arts installation and this project is capable to produce different audio tones by detecting human touch to its attached plants. Existing version of this driver is capable to monitor 8 plants and produce different sounds for each plant.

Prototype version of "Magic Tree" project with 2 plant samples.

This project is build around PIC16F628A 8-bit microcontroller and PT2399 echo processor IC. To drive the sensor electrodes we use pair of CD4011 quad 2-input NAND gate ICs. This prototype use TDA7052 1W audio amplifier IC to drive the speaker(s).

The existing firmware of PIC16F628A is designed to produce tones in between 155Hz to 1244Hz and this range can be change by modifying the supplied firmware source code. In this design PT2399 echo processor IC is used to get more natural (/ deep) sound effect by adding some reverberation to the output.

Schematic and firmware of this project is available to download at google drive.