Sunday, 29 November 2020

Low Effort Fan Repair for GPU (broken graphics card fan)

A household computer got a few fan blades broken off the graphics card when using compressed air for cleaning. Turns out it still seemed to mostly work okay, but over time more of the blades broke off until the fan couldn't do the job any more.

The usual way to fix this would be to buy a replacement fan but two things made that seem like a not-great idea:

  1. The GPU is old (GTX 750) so parts aren't easy to come by.
  2. The fan looks integrated in to the enclosure and doesn't look like it can be easily replaced.
I instead opted to fix it in a dumb but effective a low-effort way.  I printed a replacement fan, snapped the remaining blades off the hub, and glued the new fan blades on top. Having it hollow helped center it visually so it's not off-balance.

Obviously this isn't optimal, but considering how long the GPU trucked along with a fan whose blades were nearly 50% gone, I think this might be okay.
  • Fan 3D model downloaded from here:
  • I scaled it down a little so it would fit on top of the hub
  • I glued it down, gave it a spin with my fingers and adjusted until it looked centered.
Fan blades nearly 50% gone. It surprisingly trucked along okay for quite a while.

Snap off the old blades. Instead of trimming the little bits off I just opted to glue the new fan right on top.

3D-printed Replacement

A few spins by finger verify that it is centered.

This is obviously not as good as mounting it to hug the hub, but this way I didn't have to 1) clean all the little nubs smooth, and 2) I didn't have to worry about matching the size of the printed part to the fan spindle.  Whenever 3D printing replacement parts that mate to existing pieces, there's always the challenge of getting dimensions just right.  This way I didn't have to.

Tuesday, 19 May 2020

2020 Hackaday Prize: Cold, Hard Cash for Work on Real World Problems

The 2020 Hackaday Prize is now open, and this is the seventh year now of offering cold, hard, cash for people who are willing to work on their engineering ideas addressing real world problems. That means things like conservation, disaster relief, renewable resources, and assistive devices.

All you need to get started is an idea and a willingness to document it. That's it. If your idea needs some seed money to make a prototype, there's money for that as well.

This year there is something new: partnerships with some non-profits working on big ideas. The Hackaday Prize includes microgrants of a $3,000 per month stipend for anyone selected to help work with them for June and July.

There's much more, too. If you have an idea and you've been waiting for an opportunity to turn it into something, this is your chance to get started right now!

Sunday, 23 February 2020

Enclosure for big 100W LED modules

While working on a project that intended to use one of those big LED modules, I looked around to find out that there were no suitable enclosures already designed, so I made my own.

The "thing" with these big 100W LED modules is that they are kind of hard to use. The reason is that they are made of several pieces: the LED, the reflector, the lens, and the lens retainer. None of these parts attaches directly to one another. In other words, they all depend on being secured to something else (with the right spacing, screw holes, etc.)

I designed an enclosure to do exactly that. Everything will screw on to the bottom part, and the top part is made as a cover.  There are multiple screw holes, you can use as many (or as few) as you wish. The design is made to be easily modified to fit into whatever your project needs.

Monday, 6 January 2020

Enclosure (3D Printed) For Ultrasonic Levitator Kit

I recently designed an enclosure for an ultrasonic levitator kit that worked out really well.

The levitator has two ultrasonic transducers that form a standing ultrasonic wave between them. The shape of the waveform (which is really just a sound wave that humans cannot hear) is such that it creates alternating areas of high and low air pressure about 8 mm apart.

Small styrofoam balls or tiny bits of paper can be easily suspended inside one of these pockets. The ball shown in the photo here is about 2 or 3 mm in diameter. This model is not powerful enough to suspend drops of liquid, but small bits of paper or expanded polystyrene (styrofoam) are fine.

The ball is not being suspended because air is blowing upward like a fan; there is no real air movement involved at all. The small ball (or small piece of paper) rests trapped between an area of high and low air pressure, like a little pocket. These stable pockets are roughly 8 mm apart, so the object can be "bumped" up or downwards.

It's neat and educational. The kit I bought is available from Tindie here and the enclosure I designed is hosted at The enclosure is open on the bottom, so dropped objects just fall right through and don't get caught inside the device.

Wednesday, 11 September 2019

Ironing 3D Prints Can Work, But Have Lots of Top Layers

This spot is the hottest on an iron of this make.
3D printed objects with large flat areas can have their looks improved by ironing the top surface, which is a feature in Cura.  This is done by running the hot end over the top of the print, to help smooth it into a smooth surface.

It is also possible to literally iron a print with a clothes iron, which I tried in a few different ways. It works, but there are some gotchas.  Here is a short list of my observations:
  1. A medium setting on the iron is better than the hottest setting.  My iron was at about 80-90 degrees Celsius.  Too hot, and the plastic softens too quickly and you lose control.
  2. The tip of the iron is where heat is concentrated. The middle and bottom are considerably cooler.
  3. Use a sheet of parchment paper between the iron and the print, otherwise you risk plastic softening and sticking to the iron.
  4. Move quickly, and inspect the results.  Treat it like spray painting, where many thin applications are better than one heavy one that may go overboard.
  5. There is no need to "press down" on the iron. Just let gravity do the work. Concentrate on being even.
  6. Make sure you have plenty of top layers in the print, and a good infill doesn't hurt either. 
The picture below was after ironing with three top layers. The thin top softened and thinned in the ironing process, and you can clearly see the infill pattern below it.  The surface is smoother (and shinier) but it also thinned and weakened, especially near the edges.
This is an example of a surface that was ironed smooth, but the top layers were too thin.  It's smooth all right, but it's also very thin and weak, and the infill pattern is showing through.

Tuesday, 25 June 2019

How to Mark Delrin (Acetal), Even Though Nothing Wants to Stick to it

Nothing sticks to Delrin (acetal), so it's not easy to paint or label.  Or is it?

One easy and reliable way to mark is to use a simple technique common to laser cutting. Shallow cuts or engravings are covered with paint, then the excess wiped away.

What happens is that any paint that got into the shallow cuts stays there, resulting in a mark the same color as the paint.

Acrylic paints tend to work best.  They are water-soluble (as long as it hasn't dried) and is a usually a bit on the goopy side which tends to help the process.

But to be successful, one must be able to cleanly wipe away ALL the excess from the surface.  It's no good if the paint leaves a smudge or a stain.  It needs to come away completely while leaving the filled spots behind.

The good news is that even though acrylic paint won't stick to acetal (also called Delrin), this technique works great for two reasons:

  1. The paint in the marks is being physically held there, inside the shallow cuts.  It doesn't depend on the paint "sticking" to the surface.
  2. Wiping away excess paint completely (the key to success with this method) is super easy to do.  Because paint doesn't want to stick to Delrin, the excess wipes off no problem.

Monday, 10 June 2019

Get Low-Power Mode Payoffs, From a $6 Board

Sparkfun has a new part, one that I almost can't believe didn't get made by someone sooner.  The Nano Power Timer is just under $6 and makes it easy to take just about any microcontroller project (Arduino or anything else) and effortlessly give it a hardware low power mode, all without needing to mess with any low-level microcontroller programming.

Here is how it works: the switches on the board set a time delay. During this time, the Nano Power Timer sips barely 35 nanoamps but the catch is that power to your circuit is completely cut off.

Once the timer is up, power is applied to your circuit and it will turn on to do its job (read a sensor to decide whether or not to do something more, for example.)  Once it is finished doing whatever it needs to do, a GPIO pin signal to the Nano Power Timer's DONE pin is all it takes to go back to sleep and reset the timer to do it all over again. It works on any voltage between 1.8 and 5 volts.

Low power operation is the difference between viable and non-viable for some projects. Not everything can be plugged into the wall all the time and not everyone can easily make low-power modes work.  A board like this is a great companion to a solar charger solution, as well.