Ciro Matheus Costa

 In this post I'll document the making of my DIY MIDI controller CONCEPT The controller is based on a STM32f1 microcontroller that polls a daisy chain of SN74HC165 shift registers. Each register bit is connected to a keyboard key (taken from a broken keyboard) to a total of 24 keys or two octaves. At the panel there are controls for inhibiting the transmission of the MIDI signal, inhibiting the transmission of the analog signal, selecting the note range of the keyboard, start/stop the sequence, setting the speed of the sequence and recording notes to the sequencer. The panel also contains the connector for 12V DC. The case for the controller was made with a one centimeter thick plywood sheet, cut and glued into place. The keyboard was fixed with screws from underneath that thread through a plywood block before reaching the keyboard. This raises the keyboard up and prevents the keys from hitting against the base. CONSTRUCTION Glueing the plywood parts for the case The panel and boar...

 In this post I'll document the proccess of making my digital synthesizer based on a STM32 microcontroller. The synth is capable of producing a square wave, a triangle wave and drum sounds and it's aimmed at chiptune music. CONCEPT The board contains the microcontroller, the digital to analog converter (DAC) and the pin header connectors for the components mounted on the panel. Eagle schematic for the whole board. The choice for the opamp was not correct. The best choice for the job would be a TL071.                                                                                      The board layout CONSTRUCTION The board was made in a CNC machine. The copper traces where coated in silver nitrate to prevent oxidation. Full assembl...

 In this post I'll document the making of a 4 channel mixer for audio purposes. CONCEPT The mixer is a simple build. It has a volume control and a kill switch per channel and offers two standards for audio input (P2 and P10). The only difference from the circuit shown above to the one in the mixer is the operational amplifier. The one used was a LM741 which is still not ideal. The best choice would have been a TL071 due to it's low noise feature. As for the theory behind it, the overwall circuit is an opamp adder. The potentiometers are for volume control and the capacitors offer DC blocking.  Adding another DC blocking cap at the end creates a high pass filter which is not desirable. CONSTRUCTION The components were assembled in a perf. board. The 'X'ed components were removed from the final circuit. The opamp was mounted in an IC socket for maitenance reasons. The connection to components meant for the pannel are through the pin headers. The panel was made from a salv...

 In this post I'll document the process of creation of the power supply for my DIY synthesizer. CONCEPT The PSU itself is a very simple design. We got a ~110V to ~12V transformer and a subsequent rectifying circuit.  The rectifying circuit is composed by a rectifying diode, filtering 4700 micro Farads capacitors, LM7812 12 volts regulator and another diode across the regulator for protection. The same circuit is repeated for the negative voltage side with it's due changes. CONSTRUCTION The assembly of the components was done on a perf. board.  The leads of the components were used to form the connections along with solder. The front panel was cut from a salvaged steel sheet, and painted with common black spray paint. A common power switch was added in the mains side of the transformer along with a DC connector for later applications. 

 Hello, welcome to my blog! Here I'll document the my personal projects in the area of analog electronics, digital electronics and firmware.