Maytag Top Load Washer (LAT8826AAM) Lid Switch + Fuse Module

Today’s distraction came courtesy of aging appliance. Specifically, the 20+ years-old Maytag top-loading clothes washer stopped working this morning. It has just started doing a load of heavy laundry that was out of balance and shut down when the tub started shaking. This itself has occurred before, we just had to redistribute the load and restart. Except this time pulling the knob failed to restart the machine. There was no sign of life, not even the power “ON” light.

Given that the machine acted as if it had no power, I first checked the house circuit breaker, verified the machine was plugged in, the easy things. After the simple checks were out-of-the-way, I started looking for a circuit breaker or a fuse built into the machine. A web search turned up several mentions of the lid switch which I initially ignored. During normal operation, an open lid would prevent the wash cycle from starting, but the power “ON” light would still be on. Since that light was dark, I had decided the lid switch couldn’t have been the problem.

That was the wrong decision.

The lid switch is actually a module that included the switch and a fuse. This fact didn’t sink in until I found this page, which described how to test continuity with a multimeter and cautioning that improper switch module installation may blow the fuse inside the module.

I removed the lid switch module from my washing machine, tested with my multimeter, and confirmed it was not behaving as it should. I am annoyed that Maytag did not design the fuse to be easily replaced. The whole module had to be replaced as a single unit: it was held together by fasteners that were clearly not intended to be removed. While I had the tools to remove them, it is a permanent removal.

Maytag Lid Switch

Once opened, the fuse was quickly found. The red arrow in the picture below points to a black piece (now broken in two pieces) that looks and feels like plastic but is electrically conductive.

When intact, this piece of fuse material holds the “LINE” terminal always in contact with the “MACHINE” terminal. When the washer lid is open, there is continuity between “NEUT”(RAL) to “MOTOR”. When the washer lid is closed, “NEUT” loses its connection to all other terminals, but “MOTOR” is put in contact with “LINE” and “MACHINE”.

The narrow neck of the fuse material is now broken, which also broke the usually always-on contact between “LINE” and “MACHINE”. When the washer lid is open, none of the terminals have continuity with any other terminal. When the lid is closed, “MACHINE” is in contact with “MOTOR” but that doesn’t do any good as “LINE” is disconnected.

Maytag Lid Switch Fuse

Now that I know how the module incorporates a fuse in addition to the lid switch, it was easy to rig up a quick test to see if the rest of the machine works. A successful test gives me the confidence a replacement module will bring the washing machine back up and running safely.

The next question is why the black piece broke. Was it from old age (innocent) or because there was a problem causing excessive amperage flow (worrisome)? The multimeter found no obvious short on the washing machine. And since the machine has been working for more than two decades, age is a plausible explanation. I’ll try the replacement module first. If the fuse blows again, I’ll have to dig deeper.

 

Simple Circuit Board On 3D-Printed Plastic

CircuitBoardHere’s a behind-the-scenes follow-up to the LED test fixtures of the previous few posts: when we only need a simple circuit for a 3D-printed project, we can meld the two instead of using a formal circuit board. In this context “meld” is meant literally: the parts of the circuit can be heated up with the soldering iron so they melt into the 3D printer plastic.

When I built the dual-LED acrylic illumination test rig, I wanted the simplest circuit possible. It’s not something I need to be durable long-term and I wanted to be up and running with my tests as quickly as possible. The full length of a resistor and its wires are almost long enough to bridge the gap between the two sides of the fixture, so I tried to make that work.

When I started soldering all the wires together, I had planned to just leave everything dangling. But the close proximity of the soldering gun to the 3D printed PLA plastic started softening the plastic and I realized I can use this to my advantage. A few seconds with the soldering iron was all it took to heat up a wire so it can be melted into and embedded into the plastic. The resistors themselves took a little more effort, but I sunk them into the plastic as well. The LEDs had been held in place by their bent legs, which was sufficiently stable but had a tiny bit of wobble. Melting the plastic around LED legs gave us a much more secure placement.

Components melted into the plastic are no longer subject to flexing and eventually breaking from metal fatigue. Add a strip of electrical tape to guard against short circuiting to complete the quick and simple circuit to light up the test rig LEDs.

Illuminate Acrylic Edge: Test Fixture 2

After running through a few acrylic test pieces looking for the best edge illumination, I decided I need a dual fixture to allow side-by-side comparison as I swap through test pieces.

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Another change I made in the text fixture is to remove the aluminum foil at the bottom. While the foil may be useful to direct light, it distracts from the testing. If a particular test piece is losing light to the fixture, I don’t want that light reflected back in. I want to be able to see the failure in the form of illuminated white plastic. When there are no acrylic test pieces in the fixture, the cone of illumination is clearly visible.

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Test fixture #2 illuminated without acrylic test pieces.

The two sides aren’t exactly identical. One of the LED is slightly brighter than the other, and the two sides ended up with slightly different textures. But it should be good enough for our comparison purposes.

The first fixture implied that the cavity surround the LED is where we should focus our attention, so let’s try a few shapes. A square and a circle seems to differ only slightly in the brightness of the center top hot spot.

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Square LED cavity (left) and circular LED cavity (right)

A triangular cavity was much more interesting – all the light has been diverted from the top center, sending them off to the side. And I tried a teardrop shape just to see what would happen. The important detail to note on the teardrop is that a lot of light was lost to the fixture instead of being sent to the edges. This tells us the cavity edges should be as small as possible to push its surface right up against the LED to reduce light loss.

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Triangular (left) and teardrop (right)

The cavity sizes were then minimized for the next set, again testing for different shapes. A flat top to the cavity didn’t work as well as the cavity shape conforming to the LED shape.

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Flat top cavity (left) and conforming curve cavity (right)

But the best results came from putting a small curve in front of the point of the LED. This appears to break up the central beam and sends it to the edges like we want.

LED scatter curve

From an cost/benefit ratio perspective, this small curve is a winner. It is a very minor change to the geometry and yet it delivers significant improvement to the resulting light. When put into a larger sheet of acrylic, with greater number of internal reflections, it should do quite well. And for a little extra smoothness in illumination, we can take a piece of sandpaper and lightly roughen up the surface. Adding a frosted edge reduces the reflections somewhat, but it does help even out the overall illumination.

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Best illumination to date with the small curve (left) which can be further enhanced by a frosted edge (right)

These experiments have been quite informative. I look forward to applying what was learned here to future acrylic projects.

Illuminate Acrylic Edge: Goals and Test Fixture

After the surprising success of LED illumination in FreeNAS v2 enclosure, I wanted to spend some time experimenting with the concept. When searching for “acrylic edge illumination” on Google, everybody seems to be talking about positioning the LED at the edge of the acrylic sheet and lighting up the pattern of something engraved on the acrylic. My goal is the opposite: I want to place the LED in the middle of the acrylic, and I want the light to shine out to the edge of the acrylic sheet.

We start with the assumption that by default, a LED shining inside a piece of acrylic will only illuminate in the direction it is pointed.

Hotspot

Our ideal goal is to determine how to direct this light so it illuminates all the edges of the acrylic sheet, not just the direction of the LED face.

Ideal

I 3D printed a small test fixture for these experiments. It has space for a 75mm x 75mm test piece of acrylic and a LED that pokes up in the middle of that space. There’s a 10mm wide border around the test piece so I can observe the pattern of illumination beyond the edge. At the outside edge of the border, a wall to observe the intensity of illumination beyond the edge. A piece of black tape covers the direction of the viewer so the LED doesn’t overwhelm the rest of the observation. A piece of aluminum foil lines the bottom of the test fixture to reflect any light back into the acrylic.

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The fixture lights up as expected in the absence of any acrylic.

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These two experiments tested cutting grooves in the acrylic. One set had straight grooves, a second set curved. They were successful in breaking up the center top hot spot, sending some of that light elsewhere. But the light seems too concentrated on the bottom third.

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Instead of cutting grooves, this piece tested cutting entirely through the acrylic. The circular shape does seem to disperse the light fairly well.

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These were interesting, but the most surprising result came from a test piece of acrylic with nothing cut in the middle. I had expected the light pattern to resemble the triangular hot spot of the LED by itself without any acrylic, but we got this:

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It has the same basic trend of the other light patterns in this set of experiments, which tells us the majority of the light scattering is not done by the curved/straight grooves or the circle. The feature with the largest impact is actually the small cavity surrounding the LED itself.

The fixture has been informative, but it has one problem: it is difficult to make comparisons between different test acrylic pieces. Before proceeding with investigation, the test fixture will be expanded so there are two test pieces side by side for comparison.

Acrylic Lights: Infinity Mirror

I’ve played with putting lights in my 3D-printed creations for glowing illumination effects. There were limits to what I could do with 3D printing, though, because printing with a clear filament does not result in a clear object. In contrast, acrylic is clear and works as a light guide with a lot of possibilities.

I’ve noticed a few attention-getting light effects in my acrylic projects to date, most of them created by happy accident. The acrylic box with external fixture made good use of external light. The Portable External Monitor version 2.0 was built from stacks of acrylic sheets: its fluorescent back light reflected between the layers like an infinity mirror.

PEMv2_InfLights

This effect was on my exploration to-do list for the future, but I moved it to the top of the list after seeing surprisingly good results on the FreeNAS Box v2 enclosure.

I had planned for it to have the standard PC status LEDs: one for power, and one for disk activity. The acrylic plate for motherboard mounting spacer also had two cutouts for 3mm LEDs along the center line. The red hard drive activity light is to be mounted high, and the blue power light mounted down low. The idea was for the blue light to illuminate the top edge of the plate. When there is hard drive activity, red LED will light up the center of that edge, and it should blend to purple with the power light. Both LEDs were blocked from direct view by the motherboard, so all we should see is a nice soft glow emitting from behind the motherboard.

FreeNASv2LightPlan

That was the plan, the reality was different. The red activity light worked as expected: when there is disk activity, the center of the top edge had a little red glow.

The blue LED decided to ignore my “nice soft glow” plan and put on an extravagant light show. It didn’t just light the top edge, it lit every edge of that acrylic sheet and had plenty of extra light energy to throw on the surrounding shelving.

FreeNASv2_LightsAbove

Here’s a close-up of the sideways illumination.

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The many rays visible in the side illumination, as well as the lines making up the top illumination, indicate infinity mirror action going on inside that sheet. It wasn’t directly visible, and probably very difficult to photograph even if so. Without internal reflections, the blue light would have just gone straight up. But with the smooth surfaces and edges of the acrylic reflecting inside the sheet, the light of a single LED bounced around, found different angles, and was emitted in many more directions.

This LED illumination effect warrants further investigation. It is a happy accident that I fully intend to learn from, and put into future acrylic projects.

I want every acrylic project to look this awesome!