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Adventures with Arduino (pt 2)

by on Mar.25, 2020, under General, Hardware

In part 1 I outlined the general – if crazy – idea I intend to attempt. In this part, I’m getting down to actual hardware – starting with the switch and illumination LED I left off at in part 1.

Picture of RJS-K16-291-GE-65J
RJS-K16-291-GE-65J

The switch I ended up buying was a RJS-K16-291-GE-65J , a momentary push-button switch with a green illuminated button that is lit up using a LED set up for use with a 12V supply. This is, as previously noted, less than ideal for use with the 5V supply used by the Arduino Nano – so the first thing to do is take the switch apart to see how easy it might be to replace the resistor or the LED assembly with something more suitable.

Switch with the button removed

The datasheet for the switch isn’t entirely helpful about how the switch goes together, so I approached the problem by the tried and true method of pulling on bits until something gives. Thankfully, the green button actuator pulls off to reveal the LED module behind it.

Disassembled switch

Less helpfully, the LED module has the resistor built-in, and it is a pretty-much sealed unit – this is the little green module at the bottom of the picture to the left. I couldn’t work out a way to get inside without irreparably damaging it, so I decided it’d be best to just replace the whole thing, and solder the current limiting resistor to the contact on the back of the switch rather than inside it.

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And now for something completely different (pt 1)

by on Mar.19, 2020, under General, Hardware

And by “different”, I obviously mean “anything at all”. Normally I wouldn’t write up something like this – which part of  the reason this site gets updated so infrequently – but right now I’m not burning a chunk of the day commuting, so what the heck…

Back in the ancient and near-forgotten times of the last days of 2019, our venerable washer-dryer stopped working. This was honestly not overly surprising for a device nearly nine and a half years old, but it was… inconvenient, at the very least. Better yet, it wasn’t showing any error codes! It would simply refuse to run any programs with an “Err” message. In order to find out what was really happening I had to put it into a maintenance diagnostic mode, where it finally gave an error code… except it was an error code that doesn’t appear in the manual! After much consultation with the great Internet Oracle I determined that the error was trying to tell me that either the heater element was out, the heater relay was broken, or that the deep state had infiltrated our lives in a subtle plan to use our washer-dryer as a portal for alien overlords.

Upon opening it up and applying lots of cursing I discovered the real culprit: the relay was fine, as was the heater, but a SMD diode was blown, and a corroded track on the main board had broken. And no trace of aliens, either. I was able to replace the diode with an equivalent scavenged from another old board I had in my pile of it-might-come-in-handy-some-day parts, and solder in a wire to bridge the damaged track, but the machine was obviously not much longer for this world. After much intensive research by my better three-quarters, we bought a new machine and awaited its delivery with baited breath.

And it works great, does a good job, except for one issue: it turns itself off a few minutes after it has finished a program. When the old machine finished a program, it would leave the display on and you could tell there was stuff in there that needed to be taken out… the new one, in the name of power efficiency, doesn’t do that and that has lead to things being forgotten in the machine for hours. Normal timers aren’t useful, because they go off and might be ignored at the time, and then forgotten about.

So, I’ve decided to build something a bit more in line with our needs.

(continue reading…)

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