![](http://engredu.com/wp-content/uploads/2021/11/front.png)
Eurorack EngrEDU VCO 1
Eurorack VCO 1 (Version 1.0)
![](http://engredu.com/wp-content/uploads/2021/11/eurorack-2.png)
Prototype Stage
Electronic Druid website has several CEM3340 VCO (Voltage Controlled Oscillator) designs.
The original CEM3340 VCO was used as a start and modified to include more features.
![](http://engredu.com/wp-content/uploads/2021/11/idea_1_a.png)
The circuit is compatible with eurorack modules (+/- 12V).
![](http://engredu.com/wp-content/uploads/2021/11/idea_1_b-1024x801.png)
After getting an idea on the desired functionalities, input and outputs, the circuit was built on protoboards.
![](http://engredu.com/wp-content/uploads/2021/11/vco_prototype.png)
Reference Designs
Design Stage
3D Model
During design stage, Fusion 360 and KiCad were used to model the board and get an idea on how the board would look like.
![](http://engredu.com/wp-content/uploads/2021/06/final_board-1024x568.png)
This module has 2 PCB boards (PCB A and PCB B) and 1 Panel board.
Panel Board
![](http://engredu.com/wp-content/uploads/2021/06/panel_board.png)
Inputs
- 2 voltage/octave
- Exponential FM
- Linear FM
- PWM
- Sync (Hard and Soft)
- Fine
- Coarse (Frequency)
Outputs
- Sine
- Triangle
- Pulse
- Ramp
- Square
- Mix Out
PCB A
![](http://engredu.com/wp-content/uploads/2021/06/pcb_a.png)
Schematics
Interactive HTML BOM - PCB A
PCB B
![](http://engredu.com/wp-content/uploads/2021/06/pcb_b.png)
Schematics
Interactive HTML BOM - PCB B
Assemble Stage
Testing Stage
Testing setup
- The EngrEDU VCO 3340 is attached to the TipTop audio Eurorack and it is powered by the TipTop audio uZeus
- Oscilloscope: Keysight MSOX3012T - 100MHz @ 5GSa/s
- All waveforms were tested and plotted using the oscilloscope. The graphs will show peak to peak, maximum and minimum voltage.
![](http://engredu.com/wp-content/uploads/2021/11/0_test.png)
Sine Wave
![](http://engredu.com/wp-content/uploads/2021/11/1_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/1_scope.png)
Triangle Wave
![](http://engredu.com/wp-content/uploads/2021/11/2_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/2_scope.png)
Pulse Wave - 0% PWM
![](http://engredu.com/wp-content/uploads/2021/11/3_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/3_scope.png)
Pulse Wave - 50% PWM
![](http://engredu.com/wp-content/uploads/2021/11/4_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/4_scope.png)
Pulse Wave - 100% PWM
![](http://engredu.com/wp-content/uploads/2021/11/5_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/5_scope.png)
Sawtooth Wave
![](http://engredu.com/wp-content/uploads/2021/11/6_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/6_scope.png)
Square Wave
![](http://engredu.com/wp-content/uploads/2021/11/7_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/7_scope.png)
Mix Out - All Waves Off
![](http://engredu.com/wp-content/uploads/2021/11/8_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/8_scope.png)
Mix Out - Square Wave
![](http://engredu.com/wp-content/uploads/2021/11/9_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/9_scope.png)
Mix Out - Triangle Wave
![](http://engredu.com/wp-content/uploads/2021/11/10_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/10_scope.png)
Mix Out - Sine Wave
![](http://engredu.com/wp-content/uploads/2021/11/11_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/11_scope.png)
Mix Out - Pulse Wave - 0% PWM
![](http://engredu.com/wp-content/uploads/2021/11/12_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/12_scope.png)
Mix Out - Pulse Wave - 50% PWM
![](http://engredu.com/wp-content/uploads/2021/11/13_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/13_scope.png)
Mix Out - Pulse Wave - 100% PWM
![](http://engredu.com/wp-content/uploads/2021/11/14_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/14_scope.png)
Mix Out - Sawtooth Wave
![](http://engredu.com/wp-content/uploads/2021/11/15_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/15_scope.png)
Mix Out - Random Wave
![](http://engredu.com/wp-content/uploads/2021/11/16_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/16_scope.png)
Mix Out - "Maximum" Wave
![](http://engredu.com/wp-content/uploads/2021/11/17_test.png)
![](http://engredu.com/wp-content/uploads/2021/11/17_scope.png)
Performance Stage