Slew Limiter
A slew limiter is a simple circuit that makes changes in voltage more gradual. This build has independent rise and fall settings. Rise controls how fast a voltage ramps up, while fall controls fast a voltage can drop down.
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/slew-scope-both-max.png)
I use it with a sequencer to make my oscillators slide up or down to notes. You can also use it with a gate source as a simple AR envelope generator. The circuit will even work as a low pass filter!
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/slew-p2p-front.jpg)
This build is based on HAGIWO’s Slew Limiter.
He has a more in-depth discussion about this build on his website (Tip: Google Translate works great!). He also has a nice demo of it on his Youtube channel.
Build
I built this circuit as a deadbug module. Due to the minimal parts count, I think this is a good point-to-point building exercise.
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/slew-p2p-back.jpg)
The front panel I use is 3D-printed. I designed it using my EuroPanelMaker library for OpenSCAD. You can find my STL and OpenSCAD files on Github.
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/slew-openscad.png)
I power it using a 3-pin JST XH2.54 connector with +12V, GND, and -12V. It is supplied by a custom-made bus board that I use for most of my Eurorack stuff.
Schematics
I got my initial schematics for this from HAGIWO’s design.
I flipped the pins of the potentiometers such that clockwise = more rise and fall times.
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/SlewLimiter%20-%20Schematics.png)
Testing
Here are some test outputs from my oscilloscope.
I have the input signal hooked up on channel 1 (yellow) and the output at channel 2 (blue). These tests were done with a 1uF capacitor at C1. The input signal I’m testing it with is from my Baby-8 sequencer clocked at 120BPM.
C1 can be swapped with higher/lower capacitors for longer or shorter rise and fall times.
![](https://benjiaomodular.com/post/2024-06-06-slew-limiter/images/slew-p2p-controls.jpg)
Conclusion
I’ve really enjoyed having this as an option on my modular rig. I’m thinking of doing a 2HP PCB for it – I really should be releasing more PCBs!
Huge thanks again to HAGIWO for making your designs open-source.
Follow me on Instagram @benjiaomodular for more updates.