Voltage Controlled A(H)R - AD Envelope

Motivation

This is one more voltage controlled envelope generator of a series built around the Atmel AVR 328p and the MCP4921. This one generates a attack hold release envelope when gated and a attack decay envelope when triggered. The envelope starts at the rising edge of the gate or trigger signal. When gated the release begins with the falling edge of the gate. Repeating gates restarts the ENV from the current voltage at attack and release stage. Attack and release (decay) time is manually and voltage controllable. Patching the EOC into trigger makes a looping envelope. Goes up to audio range when looping. Gate is polled every loop. CV input parameters are read with timer0 interrupt ISR (TIMER0_OVF_vect). Attack-, release(decay)- and EOC LED and outputs are switched. Software driven. The software is kept as simple as possible, so you can easily adapt it to your needs. Status signaled with LED. The attack and release(decay) timing is determined with different tables, so you can easily adapt the timing to your needs. The output voltage is adjustable from +5V up to 10V.

The behavior of the envelope generator is mainly determined by the software. So you can adapt this easily to your needs.

The timing is determined by two tables one for attack and one for release/decay. To change the timing just replace the tables

Feel free to experiment with the software. I would like to here from you if you make changes to your liking.

Specs and features

• Attack, release(decay) envelope
• All parameters voltage controlled
• Triggers at +3V
• Triggers at any waveform
• Goes up to audio range when looping
• Software driven
• Buffered outputs
• Overvoltage protected inputs
• Status signaled by LED
• Status outputs
• Adjustable output voltage +5..10V
• Runs on +/-15V and +/-12V
• Power consumption around 35mA positive, 10mA negative rail

Implementation

Schematic

Blue: Envelope; Purple: Attack on; Green: Release on

Yellow: Gate; Blue: Envelope; Purple: Attack on; Green: Release on

Description:

Top

Calibration

• Adjust TR_1 for the output voltage. (+5..10V)

Top

Building hints

• Don't forget to set the correct fuses for the Atmel AVR 328p

Special parts

• None

Download

Voltage Controlled VC_AHR Envelope control board documentation download
Voltage Controlled VC_AHR Envelope control board Gerber files download
Voltage Controlled VC_AHR Envelope main board documentation download
Voltage Controlled VC_AHR Envelope main board Gerber files download
Voltage Controlled VC_AHR Envelope *.fpd file
Voltage Controlled VC_AHR Envelope Software

The software is kept as simple as possible, so you can easily adapt it to your needs. The attack and decay timing is determined with tables, so you can easily adapt the timing to your needs as well.