How many different flavour combinations are possible at Peters’?
Thought I’d share a couple projects from my youth…
First: The CRA-Z-BOY
What happens when you have a chair and pair of skis sitting around? In short, the Cadillac of the hills!
I’ve recently been keen on learning how to use and control stepper motors in a practical application. And it became apparent that the use of a stepper motor in a photographic slider (herein referred to as a PanoSlider) was an excellent challenge to start with. The reason? The PanoSlider had to provide fast, smooth, accurate, and powerful motion while being controlled by an intuitive user interface.
The actual design of the PanoSlider began in a typical fashion: by wandering around my collection of materials and devising a simple, easy, solid structure. I settled on a discarded construction level as a frame. 3/4″ PVC pipes were screwed onto the sides with sheet metal screws, and hot-melt glue (HMG) was added to prevent the pipes from rotating. HMG is a generally underrated material, and its use is often limited to children’s crafts (and results in many finger burns). In reality, it can be used as a fast-setting substrate with good strength, and its poor bond strength is useful in making temporary joints (for instance – I mounted the Arduino board to the PanoSlider assembly with HMG, then simply broke it off when it was no longer needed).
NOTE: The Tracker V2 I described below had a major flaw: the curved threaded rod. It was removed from the design and replaced with a straight section of Acme rod in Tracker V2.1, which works very well. See Tracker V2.1 for more information and be aware that using a curved section of standard threaded rod is a bad idea! Further improvements and a paint job were added for Tracker V2.2.
Having finished a first attempt at building a working Star Tracker, I’ve recently set out to build a second (final) version. The goal was to use scavenged (read: FREE) mechanical components and cheap electronics from eBay China to build an automated tracking mount which could be used to capture high-quality DSO (Deep Space Object) and Planetary images. I’ve also made an attempt to make it look nice.
The main body of the tracker was based around the pivot assembly – a modified treadmill roller. Treadmills contain a large amount of useful mechanical and electrical components, so I try to pick up any old treadmills being given away on the local classifieds. After disassembling the roller, I shortened the shaft and body to a practical and aesthetically pleasing length.
Inspiration for this project came from a MakeZine project: http://makezine.com/projects/high-speed-splash-photography-with-arduino/
Using a lightstand as a base, this Lego build was positioned above a glass bowl filled with water. An Arduino Uno board controlled the camera shutter, a flash, and the Lego ‘Dropper’. The time delay between the drop and the flash trigger was entered into a laptop. The results can be seen at: https://flic.kr/s/aHskhKLsh9. A video of the rig in action is shown below.
The camera and wireless triggers were controlled via a 4N35 Optocoupler circuit (keeping the Arduino and the equipment completely isolated). The shutter speed was quite slow (~1/10s). This was due to the inconsistent shutter lag that plagued the operation at speeds faster than 1/10s. No problem though, the flash stopped the motion better than the shutter could have.
Don’t mind the colour-clashing lego…
NOTE: See the more recent Tracker V2.1 post for a working star-tracking mount.
I’ve recently developed a healthy interest in astrophotography. A very useful tool for photographing the great beyond is an astrotracker. It counters the rotation of the earth (360 degrees per day) and allows for long exposure times without creating star trails. Here’s my POC build- it’s as cheap as borscht and worked great for very light loads. However, it failed to properly support my camera setup- a 5Dc with Tokina 16-28, total mass of over 1.8 kg (without the battery grip). As such, it is to be dismantled and a better version is in the works (waiting on eBay China parts). That said – If you have an SL1 with an EF-S lens (less than 1kg total mass), this may do the trick!
- Screws, 1/4 nuts, 1/4 ready-rod, hot glue
- Linear actuator from DVD-burner
- eBay China L298N dual H-bridge – $4
- eBay China mini breadboard – $1
- Power resistors – $10
- ATTiny85 microcontroller (and programmer)
- Various tidbits here and there
The linear actuator operated on 5v, which meant that our 12v supply needed to be tamed with a couple resistors (biggest cost of the whole project). I used a 11×17 sheet of paper, folded into a tube for the 8xAAA battery holder and a spring to apply pressure to the battery contacts. A cheap battery holder will be a welcome update for the MK2.
As a note for future projects: the linear actuator was excellent for light-duty projects. Do not de-solder the power supply ribbon, instead simply cut it. The ribbon provides support to the feeble leads coming out of the motor (I ruined one motor by treating the leads harshly). The microcontroller was programmed to provide power for a brief duration (500ms) during each step. This greatly reduced heat build-up in the actuator, and likely greatly improved the actuator’s life. Finding a 5v H-bridge would be a nice improvement over the 12v L298N.