Nevermore Stealthmax PCB 2
Nevermore Stealthmax filters had a somewhat recent update, they moved the electronics mounting location from the fan hub to a new location in the rear chamber, similar to the old Nevermore Max 2 and Nevermore Stealthmax S (250mm version) filters. This new electronics mounting location was not ideal for the Nevermore Steatlthmax PCB (1), so I decided to make a new one. This new PCB also has a bunch of new features based on demand from its users and new features leaked by Nevermore devs, which will be detailed later in this post. But I want to start with the earlier PCBs in this series to more cover the evolution of these PCBs and past/current/future use cases.
Nevermore Max 2 PCB
This was my first PCB for Nevermore filters, and my third open source PCB project with actual electronics (so, excluding breakouts). I've come a long way since the design of this project, but a lot of its features and components are still used for the newer Nevermore PCBs, since they work perfectly.
The development of this project started in October 2022. Back then, Nevermore Max 2 filters were new, Nevermore Stealthmax filters or Sanaa's Nevermore Controller firmware (more about this later) didn't exist. It took me 5 prototypes to get to a version I was happy with, but the final version that I ended up using on my Nevermore Max 2 filter and released on GitHub featured:
- STM32G0B1 MCU
- 2x I2C Sensor Connectors (for SGP40 & BME280)
- 1x 4-Pin Fan Connector for PWM Fans
- 1x 3-Pin Fan Connector (for Negative Pressure Fans)
- 1x Neopixel Connector
- USB C Connector, No CAN or BT
- Ran Klipper Firmware
- JST-XH Connectors
This PCB was released on GitHub and also shared on YouTube last summer. By then, the Nevermore Stealthmax filters were released, so there was a lot of demand for a PCB for these filters, so I worked on that next.
Nevermore Stealthmax & Mini PCB
(Originally: Nevermore Stealthmax PCB)
This is very similar to the Nevermore Max 2 PCB, but with these changes:
- Size and Mounting Holes Designed for Nevermore Stealthmax
- Removed the 3-Pin Fan
- Added a CAN Transceiver
- USB C Swapped with Micro-B
- Added On-PCB Sensor Option
- JST-PH Connectors
This PCB ended up being a little bigger than a Raspberry Pi Pico, which it replaced, but it fit well in the fan-hub electronics chamber of the Nevermore Stealthmax. This electronics also allowed for the on-PCB sensors, since the PCB was in the path of the airflow. One set of sensors could be soldered on the PCB, and you only had to wire the other pair.
This new electronics mounting location had some other limitations though, mainly about the USB cable routing. The USB connector had to be vertical because it wasn't possible to plug in a cable on the PCB's side. Vertical USB had to be USB micro-B, because USB C was too tall. Even with micro-B, routing a relatively thick and bulky USB cable was a challenge, so CAN bus support was added too, with a TI CAN transceiver.
I also had to use JST-PH connectors because of the size limit of the PCB. 3-pin fan support was removed because Stealthmax didn't need them, but I kept the Neopixel connector just in case they decided to add Neopixels to the Stealthmax filters.
Most of these are fairly minor changes, which meant that I didn't need more than 1 prototype, so it was released quickly, in October of the same year.
This is still compatible with the newer Stealthmax filters, but vertical connectors are not ideal in the new electronics location. However, this ended up being the perfect Nevermore Mini PCB (hence the renaming of this PCB), because it fits really well in its electronics chamber, and adds Klipper support for its optional air sensors and fan control. I will make a dedicated video about this soon™.
Nevermore Stealthmax PCB 2
And finally, time to talk about the new PCB.
The development of this PCB began when I heard of these changes to the Stealthmax filters, in March 2024. With the new chamber, the filter had very limited height available, not ideal for the straight connectors on the Stealthmax PCB. Also, the on-PCB sensor option is not useful in this location, as there's no filter airflow in here. I wanted to do a bit more than just adapt the size/connectors though. The original Stealthmax PCB ended up being quite popular, which meant that I received tons of ideas for improving the design. I also had input from 0ndesk4, Nevermore creator, about what features to add. I also posted a poll on my vendor channel on the Nevermore Discord server.
Based on all the input, I ended up doing these changes:
- Adapted the Size/Shape for the New Mounting Location
- Added 12V & 5V Buck Converters, Users No Longer Need to Supply These Externally
- Added 1x UV LED (12V) Connector, with a Big MOSFET for Control
- Added 1x UV LED AUX Connector, with 12V, GND and a Spare PWM
- Added 1x Peltier (24V) Connector, with a Big MOSFET for Control
- Added 1x Thermistor Connector
- Added 1x Thermistor on the PCB for Monitoring its Temperature
- Removed Neopixel Control
- Swapped USB Micro-B with C, Used XT30(2+2) as CAN & VIN Connector. Still JST-PH
The buck converters were a highly requested feature, it seems a lot of people aren't comfortable with the wiring for external 12V and 5V, and/or they don't have a good source for them. This was the biggest contributor to the significantly increased (3X) BOM cost though.
The UV LED control, and peltier control are not fully implemented into Stealthmax filters yet. For UV, the PCO add-on is an option, but their plan is to implement this into the now electronics-free fan hub of Stealthmax filters. Below is a picture 0desk4 (Nevermore creator) shared in a public channel about the the LEDs that he plans to add into the fan hub. I know this design evolved further since he shared this, but I'm not sure how much of it is public, so I won't risk sharing it. There should be more info about it soon though.
The thermistor connector was also added because of the UV LEDs, for monitoring the LED temperatures to ensure their longevity. The AUX connector is a backup connector, unlikely to be used, but it is also for potential UV suff.
The peltier connector is also a feature 0desk4 (Nevermore creator) requested, it is for cooling the active carbon down, which increases their filtering efficiency without needing to use something like Nevermore Scorch. It's also not implemented yet.
The on-PCB thermistor is to keep an eye on the buck converter temperatures. It should not overheat during normal operation, but an extra data point never hurts. The Neopixel connector was removed to make room for the UV AUX connector. Stealthmax doesn't have any Neopixels, so it was unused anyway.
MX3.0 connector was chosen for the peltier due to its high current draw (JST-PH wasn't sufficient), XT30(2+2) was chosen for CAN/VIN because fitting a 2x2 MX3.0 connector in the new electronics chamber was not possible due to the limited height available.
This project is now released!
PCB: https://store.isiks.tech/products/nevermore-stealthmax-2-pcb
Bundle: https://store.isiks.tech/products/nevermore-stealthmax-2-bundle