20 Jun


Just a short notice:
This website was unreachable from many browsers for some time, but now it’s back again.

I had forgotten to renew my letsencrypt HTTPS certificate, and many browsers would refuse the connection on this reason.

22 Feb

New slide holder revision 80!

Revision 80 of the Guerilla projector slide holder is here and fixes some minor flaws.


  • The slide slot is now designed to be exactly 2mm (thus narrower by 0.2mm). I made this change because after some use (or very thorough removal of support material artifacts) CS slide mounts would sit very loose and could eventually fall out. In theory, this should also improve the alignment of the image plane and therefore the image quality.
  • The ridges on the side are gone. They were intended to give some additional grip to accessories, but did not turn out to be of much use.
  • Fixed the end of the slide slot. While this did not affect Agfa CS slides, some other 2mm slides could not be pushed all the way inside the slide slot.
  • Redesigned the bottom fresnel lens slot. Inserting a lens (or color gel) is now much easier.
  • The markings are now embossed only 0.25mm (was 0.4mm).
    The intention was to improve print quality and make painting the markings easier. However, i’ll probably change this back soon. The contours are now (at least with my Ultimaker 0.4mm nozzle) less sharp, leading to increased bleed when painting the markings. Also, the paint is now less scratch resistant.

Rev. 80 also carries the (previsously undocumented) additional Fresnel lens slot of revision 79. This second slot is 6mm away from the image plane. Using this slot reduces artifacts on the projected image which result from imperfections on the fresnel lens.

The slide holder is available to buy here, and (new!) also on Thingiverse.

photo of gBeam slide holder rev.80

gBeam revision 80 slide holder

08 Feb

Simple LED flashlight tuning with thermal grease

Here’s a simple tip that can significantly improve your LED flashlight. I use it wherever I can.
The trick is really simple: Use thermal grease to bridge air gaps, thereby increasing thermal conductivity and decreasing the LEDs operating temperature.

As you can see in these charts (taken from the Cree XM-L datasheet, © Cree, Inc), temperature has a significant impact on the LED performance.

Improved cooling will result in lower temperature of the LED, thereby improving:

  • brightness
  • energy efficiency
  • lifetime

In the example of the TrustFire (or UltraFire) X8, this can easily achieved by applying thermal grease to the screw threads of the flashlights head.

You can use the same thermal compounds used for CPUs (like Arctic Silver), but even simple (zinc oxide based) thermal grease will yield significant improvements.


27 Dec

Slide-Print-O-Matic updated

I’m happy to announce that the little webpage I use make homemade slides is revamped and ready to use.

Producing slides is now as easy as:

  1. Dragging & Dropping any number of images from your computer (or a browser window) on the page
  2. Printing on transparencies, using desktop printers (inkjet or laser)
  3. Cutting and inserting into slide mounts

The page also provides you with the following helpful functions:

  • Resizing pictures to print size (36x24mm)
  • Cutting marks (39x35mm)
  • Rotating and mirroring pictures
  • Providing black backdrops

It works 100% locally on your computer (that’s why there is no upload button, just drag & drop) using just CSS and (very little) Javascript. It’s still work in progress and doesn’t work in many browsers, but it works.

Go ahead and try it here! Your feedback is appreciated!

Update: Testing on additional machines showed that

  • some browsers seem to rely on browser-specific attributes like -webkit-transform and don’t accept a simple transform
  • Low resolution printers like copy machines won’t reproduce the cutting marks.

I’ll be working on that soon. In the meantime please be aware of it.