Author: Michael

Posted on

Raspberry Pi 3B+ Enclosure 3D Model

The 3D model of the Raspberry Pi 3B is hosted on Thingiverse. This page contains the bill of material, in case you want to build a similar setup.

Thingiverse

Cloud Server

The above setup is used for a Nextcloud setup. Nextcloud is a self-hosted productivity platform and allows you to host your cloud data such as pictures of your phone yourself.

It is a full replacement for DropBox and Google Drive for me, with the benefit of protecting my privacy. Additional features enable video chat and many other fun things.

The installation script can be found on Github.

Backup Server

The above setup is used for a backup server which regularly backs up all Raspberry Pis in a rolling backup on a daily and monthly basis. The installation script can be found on Github.

I have several PIs installed in my home. One of them acts for example as Nextcloud server and resides in a DMZ.

In such a setup, servers pushing into the private zone pose a security threat. To overcome this, another server/PI resides in the private zone and cyclically pulls the data such as pictures and logs in.

The backup PI uses CRON jobs and scripts to do a backup every day and month. It hereby keeps data for 12 months in a rolling backup.

Bill of Material

AmountDescription
1 1TB 5400RPM SATA3/SATA 6.0 GB/s 8MB
1 USB 3.0 to 2.5″ SATA HDD Adapter
1 Raspberry Pi 3 B+
1 64GB Ultra microSDXC UHS-I
1 Quick Charge 3.0 60W 6-Port USB Wall Charger
1 USB 2.0 a Power Enhancer Y 1 Female to 2 Male
1 #4×1/2 Pan Head Phillips Zinc Screws
1 #4×3/8 Pan Head Phillips Zinc Screws

Not used by me but recommended in setups with a fan: Nocturna Fan or WINSINN  Fan.

If you don’t need a hard drive, you might find this Raspberry Pi 3 B+ Case with Fan attractive as it includes a fan already.

Posted on

Designing a Parabolic Trough made easy

This tool will help you to design a parabolic trough and give you the information you will need to build a simple one on your own. Download ParabolaTool_v190

Reflector Width

You can enter the width of the reflector here. This is the real/planar width of the mirror.

Supporting Beams

To stabilize the parabolic shape, it is useful to place supporting beams along the curve. The middle is always fixed to x=0 and the outer one to the highest point of the reflector.

Focal Point Height

Parabola Tool calculates the curve by selecting the damping of the parabola.

The height of the focal point is the most important variable you have to select to get good results. The higher this value is, the lower are the shadowing effects.

Keep in mind that this will also increase the vulnerability to inaccuracy. A good starting point should be 30cm-1m for 1m x 2m base frames and 3/4 ” absorbers.

Parabola Width

Parabola width is the shortest distance between both ends of the reflector. You can use this as a starting point for the width of the base frame.

Revision History

ParabolaTool v1.9: Compiled without source code guarding. Exe will start correctly on machines without additional DLLs

ParabolaTool v1.8: Export functions are available now.

ParabolaTool v1.7: Using the ” Print 1:1 ” functionality you are now able to plot the parabola at its real size and to use it as a template for cutting the beams or to cut a solid beam.

Posted on

How to build a Parabolic Trough

It’s easy to build a low-cost parabolic trough, similar to the ones used for example at Desertec, for experimental purposes.

I suggest designing the base to be split into several segments to be used with 1000mm x 500mm polished stainless steel reflector material.

The tool used to calculate the support structure can be found here.

A technical drawing (1:10) is available here: parabolic trough_technical_drawing

A series of tests showed the capabilities of the new mirror mounting.

To get 700ml water to boiling temperature, one of the four modules (500mm x 918mm) took 7min. If the absorber is preheated, the water already starts boiling in less than 5min.

In the following tests, the absorber was filled with cooking oil to determine the maximum temperature of the module.

The highest temperature was 138°C after 4-5min with the poor, quickly black lacquered aluminum tube.

That’s not that bad for a first test and optimizing the absorber will most likely increase efficiency

Further steps are:

  • Try to get a ” cheap ” vacuum absorber tube.
  • Try different materials for the tube.
  • Aluminum has good thermal conductivity (235W/(m·K)) but it is cooled down too fast by the fluid inside the tube and shadowing effects.
  • In my opinion, it would be better if the tube acts as a capacity and could store the heat, which could then be transmitted more steadily.

See also the Parabola Tool if you want to build your own.