In case you are using multiple Raspberry Pies and have little space to store them, you may need cluster case for computers. It should have multiple vertically located shelves for these computers, so it will not take too much place on desk, shelf or somewhere else. As an example I will describe my own computers and for what purposes they are used.
I have 3 Raspberry Pies working 24/7 for different purposes:
- Kodi media center - it is connected to TV and can be used for watching movies and photos. It is controlled by remote or using smartphone. Can be used the same TV remote controller for media center on Raspberry Pi. It is possible because new TVs support Consumer Electronics Control technology that allows through HDMI cable to control multimedia devices. On smartphone I have Yatse application that functions as remote controller plus can stream Youtube or local smartphone videos to TV. Raspberry Pi has hard disk connected for storing movies and photos. Earlier I have wrote about installing media center on Raspberry Pi, Installing OSMC with KODI - free and open source media center.
- Web server - this Raspberry Pi has docker and hosts this blog, NextCloud, provides proxy for torrent client that is located on Kodi media center. This computer is not connected to any screen and is controlled only using SSH. Raspberry Pi has hard disk connected to one of USB ports for storing cloud files. There are several posts how to install all these things: 1) Install Docker and Docker Compose on Raspberry Pi, 2) Install NextCloud on Raspberry Pi, 3) Let's encrypt proxy, 4) Installing Ghost blog on Raspbery Pi
- Music center Volumio - is used for listening to music. It is connected to speakers and also has no connection to any monitor or TV. It is controlled by smartphone using Volumio application. Also it has Raspotify application installed and it allows to play music using Spotify applicaion on smartphone. Instructions how to setup it can be found on the Internet, for example here. This Raspberry Pi has no own hard disk but has access to Kodi Raspberry Pi using local network.
Items required to create such cluster:
- Cluster Case Shelf Stack For Raspberry Pi 4/3/2 B and B+. It can be purchased on Aliexpress, Gearbest or Bangood
2. Power supply BlitzWolf BW-S7. It has 4 regular USB ports and 1 Quick Charge port. After testing I have found that regular port can supply up to 4.8 ampers. Power is divided between all USB ports. Raspberry Pi 3 can take up to 1.5 - 2A, Raspberry Pi 4 - up to 2.5A when it is fully loaded and uses USB ports, monitor, etc., so it is possible to connect 2-3 Raspberry Pi 3 or maximum 2 Raspberry Pi4 boards. Additional Raspberry Pi can be connected to Quick Charge port. This power supply will be connected to 220V plug.
3. Ethernet switch for 1Gbit network. I use not very expensive switch TP-LINK TL-SG108. It has 8 ports and it is more than enough. It use used to connect all three Raspberry Pi to local network, so they will have connection to the Internet. It is better to use wired connection because Wifi can be unstable, especially 2.4G that is used in Raspberry Pi 3 model B. Unfortunately can not plug switch to power supply usb port because it uses 12V instead of 5V. So it's own power supply will be also connected to 220V.
4. Hard disks. One for web-server and one for Kodi media center. For media center I use WD 4TB disk, for web-server Toshiba 750 GB. Actually you can use any external hard disks that can be plugged to USB port. Even can use SSD, but it will not run in full speed, because Raspberry Pi supports only USB 2.0 version, so maximum speed can be 20-30 Mb/s. I think this is enough for third version of Raspberry Pi, because it has only 100 Mbit Ethernet and you will not able to download and write data to HDD faster.
5. USB cables to connect power supply and Raspberry Pies. There is big problem with powering Raspberry Pi, often you can see undervolting sign - yellow lightning. This can be power supply issue, but more often is because of cable. Cables have resistance that can be measured. Power supply can give for example 5.1V, but due to cable and it's resistance, Raspberry Pi can get only 4.7V that is not enough. Quality cables drops less voltage. I have tested many cables to find cable with less resistance and I have found the best cable for me: BlitzWolf Micro USB Cable 2A Charging USB Data Cable. I use 30 cm long cables, because shorter cables have less resistance. I need 3 items - one for each Raspberry Pi.
6. Ethernet cables. They are used to connect each Raspberry Pi to switch. I use short cables - 0.25 m.
That's all components for cluster of Raspberry Pies constructing. I will not describe components that are required to run Raspberry Pi. You will need micro SD card and optionally case and heat sink for each computer. I use case that is also used as big heat sink. There are versions for Raspberry Pi 3 and Raspberry Pi 4.
If you use these cases, then Raspberry Pies can be attached to cluster case using cable bindings. Also they are used to attach switch, hard disks and power supply.
When all components are attached together can place cluster in safe place and plug power supply and switch to 220V plug. Also have to plug Internet cable to switch. For Raspberry Pies that uses monitor also should connect HDMI cables.
Using cluster case you can easy make maintenance of it: for example to switch off one of computers or replace micro SD card. Because of very little space between computers and hard disks, they can be little hotter than usual. Raspberry Pi temperature is about 8 degrees more than without storing it in cluster case. I have tried to use USB fan to cool computers, but I think it is not worth of it unless you are using Raspberry Pies for heavy work.