Sunday, December 6, 2020

A Really Simple "Dishwasher Clean" Signal


The dishes are clean!

We have a bit of a strange problem in my house when it comes to the dishwasher. The rule here is the one person loads and turns on the dishwasher while someone else is tasked with the job of unloading it. 

A bit of an ongoing issue has started to happen with the recent installation of the new dishwasher.  With the old dishwasher, everyone knew when the dishes were being washed based on all the racket that was coming from it.  Since the new dishwasher is so quiet, you really don't have any way to know when the dishes are clean, which causes a bit of tension when it's discovered that the dishwasher is still full of clean dishes several hours after being washed. 

I suspect that this is a fairly common problem in a lot of households since I have noticed that you can quite easily get magnets that you can stick on your dishwasher that say "Clean Dishes". 

While I suppose I could easily get such a magnet to stick on our dishwasher, but since we tend to be a bit pre-occupied with other things, I have my doubts that a plain old magnet is just not going to get much attention around here. 

We needed something that would be a bit more eye-catching.

The other day I ordered a box of 5mm LEDs, with the idea that I could make a bunch of mood lights based on the one that I made in my last post that I would give away as gifts. 

The LEDs were a very nice assortment of colors, including some colors that I hadn't seen before, so I was a bit interested in trying out one of these strange colors in a project. 

The LEDs are also quite bright, so they definitely were very hard to miss when they were on. 

Perfect for signaling that the dishwasher needed to be emptied. 

The project I had in mind was simplicity itself, basically, a battery, a switch to turn the LED on or off, and of course the LED itself.

In my parts box, I had on hand an enclosed battery box that had a built-in on-off switch.  The battery box held 2 AA batteries that would put out 3 volts of power to the LED.  These battery boxes are pretty easy to get a hold of and are pretty cheap to buy (I got this one at my local surplus store for about 50 cents) 

The battery box also had two wire leads coming out of the box through a hole in the top of the box. 

Looking at the LEDs in my box I picked out one that was labeled as Pink. I don't think I ever have seen a pink LED before, so I was pretty interested in seeing how it looked.  Doing some searching online indicated to me that pink LEDs had an operating voltage of 3.2 to 3.8 volts - meaning that I could just simply hook the LED directly to the terminals on the battery box with no need to add any resistors to reduce the voltage - Really Simple! 

Battery box, LED and batteries

To start the build I opened the battery box and took a look at how things were in relation to the switch. 

Looking at the connections, I noted that the negative wire was the one that was connected to the switch while the positive wire was directly soldered to one of the battery terminals in the box. 

Focussing on the positive wire first, I started by removing the battery tab that the wire was connected to by gently lifting the terminal out of the box along with the red wire.

battery terminal with positive wire
Removing the terminal and wire

While I was at it, I also pulled the negative wire through the hole in the box so that it was effectively inside of the battery box.  

Removing the negative wire

This left me with a really nice hole in the battery compartment that was conveniently located beside the on-off switch. The hole looked like it would just be about the right size for the LED

Hole into the battery compartment
Test fit the LED

After confirming that my LED would work, I proceeded to remove the positive wire from the battery terminal that I had just removed from the box. This was done by heating up the solder on the tab with a soldering iron until the wire fell off. 

Removing the wire

I then reinstalled the battery terminal back into the box and inserted the LED through the hole in the box, making sure that the anode (the longer wire) of the LED was in contact with the terminal that once held the positive wire. 

Connecting one lead to the terminal

I then soldered the LEDs anode to the positive terminal  

Soldering the lead to the terminal
Soldering the lead to the terminal

Next, I took the negative wire that I had pulled through the hole in the battery box and I shortened it so that it was only a couple of inches long coming out from the switch. I then stripped a half-inch of insulation from the end of the wire 

Shortening the negative wire

As a final step, I connected the wire to the other lead to the LED and soldered the two together.

Connecting the negative wire to the LED
Connecting the negative wire to the LED

If everything worked as it should, when I inserted batteries into the box and flipped the switch on, the LED should light right up. 

It works!
It actually works!

To finish up the project, I buttoned up the battery box and put a piece of two-sided tape on the back of the battery box, and stuck the box on the door of my dishwasher. 

Applying double sided tape
Attaching to the dishwasher

When turned on, the LED is very bright, even when the room itself is brightly lit. 

It definitely makes it obvious that the dishwasher needs attention.  

Works well

Granted this is a very easy project to build, but certainly is a lot more elegant solution than sticking a magnet on the door!

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