Creating a Scanning Monochromator

If you need a specific wavelength of light for research purposes, the naïve way of obtaining that is a white source light, a prism, and a small slit that will move across your own personal Dark Side of the Moon album cover. This is actually a terrible idea; not only won’t you have a reference of exactly what wavelength of light you’re letting through the optical slit, the prism itself will absorb more of one wavelength of light than others.

The solution is a monochromator, a device that performs the same feat of research without all the drawbacks. [Shahriar] got his hands on an old manual monochromator and decided to turn it into a device that performs automatic scans.

The key of a monochromator is a diffraction grating, a mirrored surface with many fine parallel grooves arranged in a step pattern. Because of the surface of the diffraction grating, it’s possible to separate light according to its spectrum much like a prism. Unlike a prism, it’s effectively a first surface mirror meaning all wavelengths of light are reflected more or less equally.

By adding a stepper motor to the dial of his monochromator, [Shahriar] was able to automatically scan across the entire range of the device. Inside the monochromator is a photomultiplier tube that samples the incoming light and turns it into a voltage. By sampling this voltage and plotting it with MATLAB, [Shahriar] was able to plot the intensity of every wavelength of light within the range of the device. It’s all expertly explained in the video below.

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Miter Saw Stop Saves Time and Aggravation

V Wheel Adjustable Miter Saw Stop

Miter saws are great tools for cutting pieces of wood at a variety of angles. If you have ever cut a really long piece on a miter saw there is no doubt you’ve either propped up the extended end on a pile of scrap wood or asked someone to hold the dangling piece so you could get an accurate cut. Doing either is a little hokey and is a general pain in the butt.

[Kram242] started a project that could eliminate these problems and also provides a solution to consistent length cuts of multiple pieces. It’s an adjustable stop that is sure to make miter saw cuts much less annoying.

The rig is extremely simple and consists of a piece of aluminum extrusion, v-wheel carriage and lever-actuated clamp. The movable carriage lets the operator quickly position the stop to ensure the wood is cut at the appropriate location. This stop also makes it easy to cut several pieces of wood to the exact same length.

If we had to make any suggestions for improvements it would be to add supports to the carriage that emulate the saw bed and backstop as well as an adhesive measuring tape guide.

V Wheel Adjustable Miter Saw Stop

Attiny PWM Generator and Servo Tester

PWM-Servo-Tester

Having the right tool for the job makes all the difference, especially for the types of projects we feature here at Hackaday. [Jan_Henrik's] must agree with this sentiment, one of his latest projects involves building a tool to generate a PWM signal and test servos using an Attiny25/45/85.

Tools come in all kinds of different shapes and sizes. Even if it might not be as widely used as [Jan_Henrik's] earlier work that combines an oscilloscope and signal generator, having a tool that you can rely upon to test servos and generate a PWM can be very useful. This well written Instructable provides all the details you need to build your own, including the schematic and the necessary code (available on GitHub). The final PWM generator looks great. For simple projects, sometimes a protoboard is all you need. It would be very cool to see a custom PCB made for this project in the future.

What tools have you build recently? Indeed, there is a tool for every problem. Think outside the (tool) box and let us know what you have made!

Helix Turning Tool Born From Necessity

helix turning tool

Sometimes while working on a project there comes a point where a specialized tool is needed. That necessary tool may or may not even exist. While [Fabien] was working on his DNA Lamp project he needed to bend a copper wire into a helical shape. Every one of us has wrapped a wire around a pencil and made a little springy thing at some point. While the diameter may have been constant, the turn spacing certainly was not. [Fabien] came up with a simple gizmo to solve that problem.

The tool utilizes an 8mm rod that will ensure the ID of the helix is indeed 8mm. We’ve already discussed that was the easy part. To make certain the turn spacing is not only consistent but also of the correct amount, a wooden frame is used. The frame has holes in it to allow the 8mm rod to pass through. Adjacent to those rod holes are much smaller holes just a bit larger than the copper wire that will become the helix. These holes are drilled at an angle to produce the correct turn spacing. [Fabien] figured out the correct angle by taking the desired turn spacing distance, helix diameter and wire diameter and plopping it in this formula:

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DIY Router Base For Your Dremel

dremel-attachment-main

Dremel rotary tools are handy. Some of the attachments are convenient.  [vreinkymov] felt the convenience wasn’t worth the cost, so he decided to make a Router Base for his Dremel. These types of attachments are used to hold the Dremel perpendicular to the work surface.

Underneath the little nut/cover near the spindle of the Dremel, there is a 3/4″-12 threaded feature used to attach accessories. A quick trip down the hardware store’s plumbing aisle resulted in finding a PVC reducer with the correct female thread to fit the Dremel. Once on the rotary tool, the reducer threads into a PVC nipple that is glued to a piece of acrylic. The acrylic acts as the base of the router attachment.

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Build Your Own Desoldering Station on the Cheap

Desoldering Station on the Cheap

[Sable Wolf] tipped us off to his DYI desoldering station for under $70. We know we have seen this conversion before, but it hasn’t been featured on Hack a Day. [Sable Wolf’s] hack is unique and has added features that make building, cleaning and the overall longevity sounder. However, some kind of sound deadening housing would have to be built around the pump as it seemed uncomfortably loud in the video.

Some Chinese made desoldering stations are getting quite cheap so maybe it’s not worth the effort unless you can salvage more components for the build. Thanks to [Sable Wolf’s] detailed blog you can browse through his BOM and scrounge up the majority of these items from your salvage bins. A cheap but reliable desoldering station would be an extremely handy tool to have on your bench.

This is much safer than desoldering with a candle or using fire as featured in the past, and is kind of a flip around on the SMD hot air pencil hack.

Follow long after the break to watch the video of the desoldering station in action.

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Connecting an old scope to a computer

Scope

A friend of [Michael]‘s said his company was getting rid of some old lab equipment and asked him if he wanted a very large and very old digital storage oscilloscope. A ‘hell yes’ and we’re sure a few beers later, [Michael] found an old Gould 200 MHz four-channel scope on his bench. Even 20 years after its production it’s still a capable tool, but the serial ports on the back got [Michael] wondering – would it be possible to plot the screen of the scope on his computer?

The scope has three ports on the back – GPIB, miscellaneous I/O, and RS423. The latter of those ports is similar enough to RS232 that a USB to Serial converter just might work, and with the help of a null modem cable and a terminal, [Michael] was able to connect to this ancient scope.

In the manual, [Michael] found a the serial commands for this scope. The most useful of these is a command that prints out the contents of the scope’s trace memory as a series of 1-byte integers. With a short bit of PERL programming, [Michael] can create a PDF plot of whatever is on the scope’s screen. It’s formatted perfectly for Gnuplot, MATLAB, or even Excel.

Awesome work, and especially useful given these old scopes are slowly making their way to a technological boneyard somewhere.