De-Beeping a KitchenAid Kettle

title-image

Stopping a KitchenAid kettle from beeping, at all.

My wife and I were recently in the market for a new electric kettle and were having trouble finding one of suitable quality and visual appeal. Eventually our attention was drawn to the KitchenAid KEK1722 kettle which, although somewhat expensive, seemed to offer what we wanted. We don’t own any other KitchenAid products, but thought that as it is a respected premium brand, there wouldn’t be be any issues with it right? Wrong. Once again, I didn’t bother to check online reviews. If I had, I would have quickly noticed a very common complaint with this product – it produces a very loud cheap-sounding piezo beep every time a button’s pressed, when the water’s boiled (three beeps!), even when you just put it on the base. And there’s no option to turn the beeps off. To quote Amazon reviewer Charlie2095, who ended up sending his kettle back:

At first the beeping isn’t a big deal. After a while, it becomes annoying. Then grating. This thing beeps for every reason it can think of. It even beeps when you set it back on the base! What the heck for? “Beep! I am back on the base!” “Beep! You just pushed a button! Beep! You pushed another button!”

It astounds me how some of these products get through the design process and out the door with such an annoying and in this case totally unnecessary “feature”. They’ve obviously put some careful consideration into the visual design, but what happened after that? Did they just hand if off to the electronic design guys and say “here you go, we’re done with the visual design, just do what you want and throw it in a box”. Did they not do any customer testing on the final product?

It’s not just the fact that it beeps too much, it’s also the quality of the sound. We have a Samsung dishwasher that beeps, but it is a quieter and more acceptable polyphonic chime, not a cheap loud piezo buzzer screech. At the extreme end of the scale, our Asko washing machine (mentioned in another post) has no beeps at all, and it’s no problem from a functional point of view.

Anyway, like Charlie2095, I put up with it for a couple of days, then couldn’t stand it anymore. But I didn’t send it back, no, I got out my soldering iron and fixed it good! So if you came here because you have an annoying KitchenAid KEK1722 kettle, and you don’t mind voiding your warranty, here’s how to do it. Note that I would not recommend this procedure to anyone without electronics soldering experience and a good temperature controlled soldering iron.

To silence the beeps, you need to locate and remove the piezo buzzer. The circuit board containing the buzzer is located under a cover on the bottom of the kettle itself (not the kettle base that plugs in to the wall). You will need to remove two triangle recess screws (photo below). I didn’t have the correct screwdriver bit, but I managed to use a tri-wing bit. Even a simple flat-bladed jewelery screw driver of the right size will work. Before you start, remove the AA batteries if installed. Remove the triangle screws and carefully lift off the cover.

Start by removing the batteries if installed, then remove the circuit board cover which is held in place by two triangle recess screws (blue arrows)

Start by removing the batteries if installed, then remove the circuit board cover which is held in place by two triangle recess screws (blue arrows)

You should now see the circuit board with the piezo buzzer as shown below. There are three connectors, indicated by yellow arrows, that will need to be unplugged so that you can lift up the board in order to de-solder the buzzer. These connectors were covered with a hot-melt glue in my kettle, so the first task was to very carefully prise away the glue. Once the connectors are un-plugged, remove the three philips screws holding the circuit board (blue arrows). This should allow the board to be lifted from the right hand side as viewed in the photo. You will need to hold the connector wires back out of the way to get the board past them.

The main circuit board exposed, showing the offending piezo buzzer (red arrow), the three screws that need to be removed (blue arrows) and the three connectors that need to be pulled out (yellow arrows)

The main circuit board exposed, showing the offending piezo buzzer (red arrow), the three screws that need to be removed (blue arrows) and the three connectors that need to be pulled out (yellow arrows)

You should be able to lift the board enough (the two wires that pass across the blue capacitor can be pulled out of the base a bit to give some slack) to get in behind with a soldering iron and remove the buzzer (the black component indicated by the red arrow above).

The three connectors removed and the circuit board carefully lifted up.

The three connectors removed and the circuit board carefully lifted up.

I didn’t take photos of the de-soldering because I was on my own, but I just gently pulled on the buzzer with a pair of pliers as I heated each of the two pins in turn on the back side of the board. There are some surface mount components near one of the pins, so be very careful with the iron. Once the buzzer is gone, push the board back down and replace the screws and connectors.

No more buzzer! The board is back in place with screws in and connectors reattached

No more buzzer! The board is back in place with screws in and connectors reattached

Put the batteries back in and replace the covers. That’s it! No more beeping, just the gentle sound of heating water.

Moment of truth…yes, it still works!

Moment of truth…yes, it still works!


Solar iDevice Charger in Atomic Punk Style

IMG_2287

For a while I’ve been keen to build a solar powered charger for my phone and iPad, mainly because I wanted to have a play with solar power – something I haven’t done before. It certainly wasn’t to save money. I think I calculated that it would take several lifetimes of daily device charging to pay off the investment in parts. Anyway, I recently completed the project and thought I might showcase it here. The internals aren’t that interesting, being all off-the-shelf parts, but I was particularly satisfied with the way the external design worked out. It’s a style I have dubbed “atomic punk” – a sort of steam punk variant with a 1950-60s technical aesthetic. Let’s go straight to a photo of the finished charger in action.

IMG_2316

The coiled black lightning cable is an essential part of the aesthetic.

The case is made from plywood scraps, and is finished with brushed on “Hammerite” hammered silver finish paint to give it that 50′s technical equipment look (note that before painting with Hammerite I sealed the plywood with a coat of water based varnish). The top panel and sloping instrument panel are removable to allow access to the battery and wiring. The instrument panel has two analog meters, one indicating battery voltage, and one indicating the current being drawn by externally connected loads. It also has a 5A fuse (connected between the battery and the load), a power switch and indicator lamp (filament of course). I really wanted a nice 60′s era coloured glass-bezel panel lamp, but I couldn’t find one. The switch switches the load to the battery, and the lamp indicates when load power is available.

IMG_2299

The power conversion and USB interface circuitry necessary for charging phones and iDevices is provided by two off-the-shelf 10W Belkin USB car chargers. These are plugged in to a twin car accessory socket mounted to the top panel.  I actually started out by building my own USB interface with a small buck converter to provide the step down from 12V to 5V, and circuitry to provide the appropriate voltages on the USB data lines as required when charging Apple devices (2.7V on both data lines lines – as measured on a recent 10W Apple charger). It worked, but I wasn’t sure how to neatly integrate the USB sockets, and my circuitry was large and unweildy compared with the neat and compact off-the-shelf car chargers. So in the end I gave up and went with that solution.

Inside the box. Note the ventilation holes in the base. There is another set of holes on the rear face of the box.

Inside the box. Note the ventilation holes in the base. There is another set of holes on the rear face of the box.

On the inside, the box contains a 9Ah, 12V sealed lead-acid (SLA) battery connected to a Genasun GV-5 MPPT charge controller. Also connected to the controller is a lead running to a 20W monocrystalline solar panel (max. power at 17.2V / 1.17A). The panel is actually mounted flat on a carport roof, but seems to easily provide enough energy to keep up with daily phone and ipad top-ups (at least in summer – we’ll have to see what happens in winter).

IMG_2315

The photo above shows the meter readings when charging an iPad at maximum rate. The ammeter was reading about 50mA high at this time, and the light bulb consumes about 70mA, so we are seeing an energy draw by the USB charger of about 0.88A x 13.5V = 11.9W. I haven’t measured the actual current draw on the 5V side of the charger, but the Belkin units are rated at 2.1A at 5V, or 10.5W, so that’s not a bad conversion efficiency. With an iPhone and iPad plugged in, the maximum 12V side current draw is about 1.5A. If the two devices are topped up daily from say 75% battery, this level of current draw is required for maybe up to an hour, after which it tails off to zero as the device batteries reach full capacity. Looking at the discharge rate data for the SLA battery (see graph below), at a 1.5A discharge rate the battery will be flat in about 5 hours, assuming no input from the solar panel (e.g. charging at night). However, we don’t want to completely drain the battery, ideally we only want to take it down to about 70% capacity. This would happen after about 1.5 hours of discharging at 1.5A, which is just about perfect for its intended duty.

discharge_graph
The amount of energy that you can extract from a lead-acid battery depends on how fast you extract it. Something to keep in mind when you are sizing your battery.

So that’s it, the “Fusionmaster Deluxe” nuclear fusion powered device charger. I hope you enjoyed reading about it.


Fixed: One Squeeky Asko W6884 Eco Washing Machine

Asko W6884

A couple of months ago my washing machine, a long serving top loader, finally died. I wasn’t particularly sad, as I’d been thinking about replacing it with a nice new water efficient front loader for a while. And so it was that I ended up buying a Swedish made Asko model W6884 Eco wasing machine. I hadn’t looked at reviews of the Asko machines, but the salesman sold me on the Asko. In particular I liked the door seal arrangement, which does not feature the big rubber boot that needs to be wiped out after each use. I got the machine home, installed it, and eagerly fired it up with a load of washing. I noticed a few squeaks as the drum rotated, but when it got to the spin cycle, particularly with a heavy load, the machine sounded like someone bouncing up and down on an old inner-sprung matress. Surely that can’t be right, I thought, but I left it for a while to see if it would wear in and settle down. It didn’t. I noticed that the squeaking occured if I rocked the drum backwards and forwards. Since it was an expensive, brand new machine I was reluctant to start pulling things apart myself,  so I called the Asko serviceman. On taking the top off the machine, he found that the spring attached between top rear the drum and the back of the case was rubbing against a lug on a bracket which provides an attachment point for one of the transport bolts. He called the Asko agents and discovered that there was a new type of spring, which he ordered. In the mean time he tried to bend the spring to make it clear the lug. It helped, but the rubbing still occured. About a week later the new spring arrived and was fitted by the serviceman. Dissapointingly, the squeak persisted. This time I took the lid off myself (three torx screws along the back edge of the lid) and examined the spring (which looked exactly the same as the old one, so no wonder the problem remained). The solution was obvious. I went and got my drill and drilled a 3mm hole above the two existing slots into which the spring hooked, then moved the spring up to use the new hole (see photo below). The spring is now well clear of the lug, and the squeak fixed. I’m just left wondering if all examples of this model have this flaw, or if mine was unusual? If they do all squeak, how did such a design flaw slip past quality control at Asko? Anyway, if you have this problem with your Asko, at least you now know how to fix it.

The problem and solution to the squeeky spring.

The problem and solution to the squeaky spring (click to enlarge).


Pimp My Rocket (Espresso Machine)

Combining Coffee and Electronics – An Idea for a Project

Having played around with fixed function logic ICs, such as the Johnson counter used in the Spindicator project, I was keen to move on and experiment with programmable microcontrollers. I decided to obtain and play with some PICAXE chips, as they looked like they would provide an easy introduction to using microcontrollers. Soon enough I was flashing LEDs and building touch-activated computer power switches. But what I really wanted to try was using the chip to control the colour of an RGB LED. For a suitable project I came up with the idea of using a strip of RGB LEDs to provide accent lighting for my Rocket Espresso coffee machine, where the colour of the LED would depend on the temperature of the machine (specifically the inlet water to the brew head). I thought this had the potential to not only look pretty, but actually provide useful visual feedback on the all important brew water temperature. If you are reading this because you’re a coffee geek interested in E61 HX type espresso machines, you may want to skip the electronics part and read the last section to see how it turned out.

PICAXE is a low-cost, easy to use microcontroller system which uses a simple BASIC like programming language. I’m not going to provide a tutorial on how to use and program PICAXE chips in this post. If you are interested in that, the PICAXE website has excellent documentation, free programming software, and lots of circuit and code examples. There are several different PICAXE chips you can buy, with different numbers of inputs/outputs and different inbuilt functionality. The inbuilt PICAXE function that is central to this project is PWM (pulse-width modulation).

Controlling RGB LED Colour with PWM

An RGB LED is actually made of three LEDs under one lens, a red, blue and green LED (I’ll call these sub-LEDs). Each sub-LED can be switched on separately, so you can switch on blue and red to get purple for example. By switching each sub-LED completely on or off  you can make six colours (red, blue, green, purple, cyan and yellow). In order to gain access to a complete spectrum of colours, you need to be able to precisely control the brightness of each sub-LED, and the way to easily do that is via pulse-width modulation. PWM controls the brightness of an LED by switching it on and off very fast (20,ooo  times per second in my program), and controlling the amount of time it is on during each on-off cycle. The time for an on-off cycle is called the period (50µs in this case), and the time of the on pulse as a percentage of the period is called the duty cycle. So a for duty cycle of 50% at 20kHz, the LED will be switched on for 25µs, then off for 25µs. The switching is too fast for the eye to see, and so the overall result is that the LED will just look half as bright. Thus the LED brightness is directly proportional to the duty cycle. Most PICAXE microcontrollers have a PWM control function built in and accessible on one or more of the chip’s pins (see pinout diagrams in the PICAXE manual). Some PICAXE chips also have separate PWM control circuitry referred to as “HPWM”, or hardware PWM. The circuit and program described below uses the software PWM function. To control an RGB LED you need a chip with three (or more) independent PWM outputs such as the 14M2 or the 20M2. For this project I used the 20M2.

Close-up of the RGB LED strip used in this project. Note that the strip has current limiting resistors built in, and uses a common anode configuration.

The Circuit

The circuit for this project is fairly simple as the PICAXE microcontroller does most of the work. For the LEDs I used a strip of six RGB LEDs. These  are pre-wired to a strip of adhesive backed flexible circuit board as shown in the photo above. They come on a long roll which can be cut to any multiple of three LEDs. Initially I was going to use two sets of six, one mounted under the Rocket on each side. Consequently, this circuit is designed to drive 12 LEDs, and can drive up to 15 using the transistors and resistors specified. When I tried it though, I didn’t like the look of the reflections of the individual LEDs off the stainless steel bench on which my machine sits. In the end I decided to use one strip of six mounted behind the machine and reflecting a nice diffused colour off the wall behind. The first circuit diagram below shows the power supply for the PICAXE and LEDs. The 12 volt DC input is supplied from a small 500 mA 12V plug-in power adaptor. This 12V input is used directly as the power supply for the LEDs, and also as the input to a 7805 voltage regulator with 5V output. The 5V rail powers the PICAXE chip and peripheral circuitry. I added a small LED to the 5V output as visual confirmation of PICAXE power on. The switch on the 12V input is to assist with programming the PICAXE (the best way to program the chip is to initiate transfer from the computer with the power off, then quickly switch the power on). To save space I implemented this switch with a simple two pin header and jumper, which is actually a bit fiddly. If I were to build it again I would use a proper PCB-mounted mini toggle switch.

Power supply circuit

The rest of the circuit is shown in the diagram below. It can be divided into four parts; the 20M2 PICAXE chip itself, the serial programming interface circuit, the thermistor voltage divider and the LED switching transistors.

Click for larger image

The serial interface part of the circuit consists of two resistors and a 3.5mm stereo phono jack,  and is the standard minimum serial communication circuit as specified in the PICAXE literature. This can be used with either a simple serial cable (for connecting to a computer serial port, if your computer still has one), or the PICAXE USB  cable. For a temperature sensor I used a standard 10KOhm NTC thermistor (a component whose resistance changes in response to temperature). The thermistor forms half of a voltage divider with a 2.4K resistor, the divided voltage being read by the PICAXE analog to digital conversion function (ADC). The value of 2.4K was chosen to give a reasonably linear relationship between the divider voltage and thermistor temperature over the range of interest (25 to 120°C), as well as the greatest change in voltage over this range. This relationship can be calculated, and is shown in the plot below for my thermistor, which has a specified calibration constant (beta) of 4,100K.

The PICAXE ADC function converts the voltage at the input pin to a number between 0 and 255  in direct proportion to the voltage. This number is then used by the program to calculate and adjust the duty cycle of each sub-LED (red, blue and green). Because the LED strip requires a supply voltage of 12V, and because a PICAXE output can only sink or source up to 20mA, the LEDs are switched via three BC337 transistors (for my final 6-LED configuration, I could have also used BC548 transistors with say a 2KOhm base resistor). For the particular RGB LED strip I used, I measured the 100% duty cycle current per sub-LED at 6.2mA (red), 5.5mA (green) and 5.7mA (blue). Thus for a strip of six LEDs, the maximum current that any transistor will switch is 37mA. In the circuit shown above, the BC337′s can switch 100mA and remain saturated (probably more, but that’s a safe figure), which means that the circuit will safely switch a strip of 15 LEDs (they come in multiples of 3 remember). By reducing the base resistor value you could switch a lot more LEDs, as BC337′s have a maximum collector current of 800mA (you may need a gruntier 12V supply than I’ve specified though, and don’t forget the PICAXE per-output 20mA maximum current, with 90mA maximum per chip).

After going to some trouble to design a PCB layout in Illustrator, I decided that I couldn’t be bothered trying to etch a circuit board, so I made up the circuit using a prototype board and jumper wires, with screw terminals to connect the power supply, thermistor and LED strip. The board is illustrated below.

The circuit board

The prototype board. Not very elegant, but it does the job.

The Program

Of course the circuit above doesn’t do anything interesting until you load a program into the PICAXE. Programs are written in a simple language modelled on BASIC, but with many commands specific to the PICAXE functions. These include ‘readadc’ which measures the voltage on a pin and converts it to an 8 bit number (used for reading the thermistor), and ‘pwmout’ which sets the pwm duty cycle of an output pin. Again, there’s excellent documentation on these commands available on the PICAXE website. If you click on the link below, you can download my program in open document format, which you should be able to open in your word processor of choice (WordPress does not seem to allow uploading plain text files). You can simply copy and paste the text from this document into the PICAXE Programming Editor.

PICAXE BASIC Program for Rocket LED Controller

Here’s a brief description of how the program works. The objective of the program is to ramp the LED colour from blue through green to red in response to increasing brew water temperature as monitored by a thermistor attached to brew head water inlet pipe. The two important parameters that need to be set in the program are the thermistor readings that will correspond to 100% blue and 100% red. The half way value for 100% green is calculated from these by the program. I obtained the red and blue values by measuring the thermistor resistance when the machine was cold and fully hot (which happens about 45 minutes after switch on out of interest). I converted the resistance values to PICAXE ADC readings using a spreadsheet (the same one that produced the graph above). You could also directly observe the ADC readings by writing a simple program that reads the thermistor and reports the value back to an attached computer using the PICAXE debug function. The program uses the range of ADC values corresponding to 0-100% duty cycle for an LED and calculates a scale factor for converting the ADC value into a duty cycle output for the LED. Note that the PICAXE duty cycle output value is not a number between 0 and 100 as you might expect, but is calculated from the PWM frequency and the clock frequency of the chip itself. It’s all a bit confusing, but there is a ‘PWM wizard’ function in the programming software that helps you calculate the values to use. In this program, the PWM output values range from 0 to 400 (corresponding to 0 and 100% duty cycle). Anyway, having initialised these values, the program then enters the main loop where it reads the thermistor value and determines if it falls the blue-green ramp or the green-red ramp. It then calculates the appropriate duty cycle output for the two ramp colours (the third colour being off) and issues the pwmout command for all three colour channels. It then returns to the beginning of the loop, reads the thermistor again, and checks to see if the value has changed. If not, it just keeps re-reading the thermistor until it does.

Installing the Thermistor

So having built and tested the circuit, the next step in this project was to install the thermistor into the Rocket. In this case, I attached it to the copper pipe that supplies water from the heat exchanger to the brew head (I’ll talk a bit more about this below). The top panel of the Rocket can be removed for easy access to the brew head plumbing. Here’s the thermistor installation in pictures.

Thermal compound is applied to the water inlet pipe

Teflon tape holds the thermistor against the pipe. A short length of adhesive foam is then wrapped around it for insulation.

A final layer of foil tape completes the installation.

Installing the LEDs

As I mentioned in the above, I eventually opted for a strip of six LEDs installed at the back of the machine so that they reflect diffuse light off the wall behind. The LED strip adhesive stuck well to the polished stainless steel case. Importantly, it also seemed to be removable without damage to LEDs or case. However to test the set-up I just exposed a little adhesive at each end of the strip, and that’s how it has remained attached so far.

The LED strip attached behind the machine.

The End Result

Most of the measured temperature rise occurs in about the first 15 minutes after switching the machine on, so that’s about how long it takes the LEDs to change from blue through green to red. Over the next half hour or so the temperature does increase a few degrees more as the whole machine warms up to a steady equilibrium temperature. I decided that the best way to show what the heat-up looks like was to make an animated gif image from a series of stills. The quality’s not great, but you’ll get the idea.

An animated sequence showing the LED colour change as the machine heats up from cold.

Out of interest, the circuit draws 49mA from the 12V supply when operating, which gives a power consumption of 590mW. Of this, the LEDs consume about 330mW

More Than Just Pretty Lights?

The objective of this project was not just to make pretty accent lighting for the Rocket, but to also see if it could provide useful visual feedback on the temperature of the water entering the brew head. It is essential that this temperature is right if you want to make good coffee on a heat exchanger E61 type espresso machine like the Rocket. Actually it is essential on any machine: the brew water temperature needs to be in a certain range in order to make good espresso (85-95°C). Different machines have different ways of achieving this temperature. In heat exchanger machines there is a water boiler which is maintained at a certain temperature, usually around 120-125°C. This boiler provides steam for milk frothing, and is also the heat source for heating the brew water. The pipe taking cold water to the brew head passes through the boiler so that the brew water is heated and will be in the correct temperature range when it hits the coffee, hopefully. Unfortunately there is more to achieving the correct brew temperature than just the  boiler temperature and design of the heat exchanger. Firstly, the machine needs to be properly heated up (at least 45 mins for the Rocket, especially if you want to do more than one shot) as getting the correct temperature requires the pipe-work and brew head to be warm. To keep the the E61 brew head warm, which is a large chunk of brass, the pipework forms a loop between the heat exchanger(HX) and the E61 head. This creates a convective flow as water in the head cools and flows back to the HX and water in the HX heats and flows up to the head. This also helps keeps the water in this ‘thermosyphon’ loop cooler than the boiler temperature, but in the rocket (and I suspect most machines of this type) it still quickly becomes too hot for making coffee. Reading my thermistor, I observed the head inlet pipe stabilise at 113°C when the machine was properly warmed up. So before you make your coffee you need to flush the over-heated water from the inlet pipe. However the machine design relies on some heating of the loop between shots, and on the heat stored in the brew head, to achieve the correct water temperature. If you keep running water through the HX and out the brew head, the water will quickly become too cold to brew coffee! It all sounds a bit tricky, but remember that these machines are based on a commercial design, and you can see how it might work in that environment: you pull a shot and while you clean and refill the portafilter the loop water reheats just the right amount, then you pull another shot. At home the machine is more likely to be sitting idle for a long time between shots, which makes controlling the temperature more of a challenge.

So do the LEDs help? Well sort of. I found I use the LED colour as an indication that I’ve got my flushing about right.  So, if the machine has been warming up for an hour, or sitting idle for a time, the LEDs will be red and I know from experience that the loop will be too hot, probably in the order of 113°C at the head inlet. The first step is to grind and tamp some coffee. The next step is to flush the over-heated water to drain. When I start the pump I can observe the super-heated water boil and splutter as it comes out of the head. After some seconds, the boiling will stop as the water temperature drops below 100°C. At this point I leave the flush running for maybe 5 seconds, which brings the temperature at the head down below brew range (around 80°C). There is a lag in the thermistor response, so a few seconds after stopping the flush I observe the LED colour stabilise to greenish-yellow. During this time I lock in the portafilter and get a cup ready. Now I wait for usually 30-50 seconds so that the cool water in the HX can heat, and the water at the inlet warm back up, but not above the acceptable brew range. This is indicated by the LED colour changing to a yellow- orange. Then I pull the shot. The LED’s certainly aren’t essential, but they’re fun and I think I’ll keep them.

Here’s a short video I made to illustrate the process:

Hmm, I don’t know why the captions are dropping off the bottom. I’m not very good at this video making business.  Anyway that’s about it. I hope you enjoyed reading about this project as much as I enjoyed doing it.

 

UPDATE July 2013

I thought I’d just add a note here to say that my Rocket LED lights are still going and have now become an essential part of my coffee brewing process. The technique I’ve settled on is to run a 10 second flush of the grouphead after it stops spluttering (see paragraph above). While this flush is running, I grind and tamp the coffee. After some seconds the lights will change to green and then slowly back through yellow to light orange. It is at this point that I pull the shot. Currently, with low ambient air temperature in the morning, this happens anout 1 minute and 20 seconds from the beginning of the flush.


A Warm Antique Brown Finish for Pine

IMG_1498-2

I make a lot of things from pine as hard woods like oak are crazy expensive where I live. It’s fine for things like the set of small drawers pictured above. The problem I used to have with pine was achieving the Arts and Crafts style warm reddish-brown finish that I like. Dyes give patchy results on soft wood like pine, so I have been experimenting a lot with pigment stains. A particular favourite of mine is a reddish-brown colour called “traditional cedar” (a Wattyl Colourwood stain). I usually combine it with a small amount of another very dark brown (almost black) stain (Wattyl Colourwood “terra”) in order to achieve a rich dark brown. For durability I usually finish with a couple of coats of polyurethane. That gives an OK finish, but pine is a very white wood and the stained colour lacks the depth and amber warmth of an antique Arts and Crafts finish. Also, polyurethane can be very difficult to apply without getting dust nibs or runs or missed patches, and tends to give a bit of a plastic look to the finish. It’s great where you need durability though, such a the towel cupboard I made where people are likely to touch the wood with wet hands.

Recently, however, I discovered shellac. Of course I knew about shellac, but had never used it. Suddenly I was able to achieve the finish I wanted on pine. The key to the finish is amber shellac. It affords a lovely amber warmth to the finish, complimenting the red-brown stain. Now I know heaps of woodworkers will already be familiar with shellac and probably have their own preferred way of using it, but for those that are new to it here’s how I achieved the finish on the drawers in the photo above.

IMG_1468

The first step is to sand the wood down to 180 grit with sand paper.

IMG_1482

These are the pigment stains I use. “Traditional cedar” on the left, and “Terra” on the right. For the drawers I used a mixture of about 4 parts trad cedar and 1 part terra.

IMG_1474

The stain mix is wiped on with a rag to give a nice dark reddish-brown (I think I’ve used too much terra in this test piece, more like 3:1).

IMG_1480

Once the stain is dry, I apply a coat of amber shellac with a brush. You can see the instant warmth it adds.

IMG_1478

I buy pre-made shellac. It comes in both amber and clear. Being dissolved in ethanol, it dries very fast and can be tricky to apply with a brush over large areas, especially if the air is warm. You have to work quickly, but build-ups from overlaps can be sanded back later.

IMG_1481

When the first coat of shellac is dry (after one or two hours), I rub the surface with #0000 steel wool. You have to be careful at this stage or you’ll rub through the shellac and remove the stain. Difficult to fix.

I don’t have a good picture of the next step, but after the steel wool I rub on and wipe off a “glaze” of the dark Terra stain. Not much actually sticks, but it does make a difference and helps to give it a more aged look.

IMG_1491

Once the glaze is dry, I apply two coats of the clear shellac with a brush to build up some depth. You only have to wait about an hour between coats, but after the second coat I leave the shellac overnight to dry and harden properly.

IMG_1492

With the shellac properly dry I use some #000 or #0000 steel wool to sand the surface smooth (if it’s really rough I might even start with some 600-800 grit paper). I have done this step dry, but in this photo I’m using Danish Oil to lubricate the job (wipe it all off before it starts to dry). Here I am rubbing in circles to help reduce the fine ridges created by brushing the shellac. After this I rub the steel wool with the grain to remove the circular scratches (it doesn’t take much work). Finally, I finish the sanding with #0000 steel wool to give a smooth dull finish (like the third photo above).

The last part of the finish is to apply three coats of Danish Oil. This fills the surface and creates a beautiful shine which is not too glossy. I like Danish oil as it dries quite fast so you can build up the finish quickly.

IMG_1515

And here it is with the Danish oil applied.


More Photos of iPad Stand Construction

After the success of my original iPad stand I decided to use the left-over length of oak board to make four more stands. I slightly modified the design this time to include an angled front face on the base. I am calling this design “iPad stand No. 3″, as it is the third modification to my basic stand design (there was an original prototype with a shorter upright, as well as the design described in my earlier post). I decided to photograph the construction of these stands and write another post as I felt my previous post was lacking in photos and might have been hard to follow. So here again is a description of how to make my stand for the iPad 2.

Note: measurements below for the iPad 2 only.

As before I started with a board that was 110mm wide by 22mm thick after squaring and milling (the same board in fact). From this I cut four base blocks, this time 110mm long to match the width of the board (the length should exactly match the width of the board). Making them 110mm long meant I could use the full width of the board for the upright parts.

IMG_1336

The four 110x110mm base blocks.

The next job was to cut a slot 14mm wide by 5mm deep in each block. The slot is cut 20mm in from the front edge of the base as indicated in the diagram below.

vanishing pt test

IMG_1350

This is my simple home made router table. An acrylic plate screws onto the base of the router and sits in a recess in the table.

IMG_1339

The slot is cut in one of the bases. I made the slot in two passes as my biggest router bit was 12mm diameter.

After cutting the slot, mark a line along the bottom of the slot, 9.5mm (can be a small as 9.1mm) in from the front edge of the slot.

IMG_1341

I found a stick that was 9mm wide and used that to measure out the cutting line in the slot.

Next, mark a cutting line for the front face of the base. This should be located 8mm from the slot front as shown in the diagram below. Ultimately you’ll make four angled cuts in the base as indicated by the blue dashed lines.

vanishing pt test 2

IMG_1343

Set your saw blade angle to 14°. The rest of the cuts will be made at this angle. Start by cutting the angled front face of the base. Keep the off-cut as you’ll need it for the glue-up.

IMG_1344

The front face cuts have been made.

Next make the cut in the slot to create the front piece of the base.

IMG_1346

Lining up the saw for the slot cut.

IMG_1338

The photo above shows a narrow piece I used for testing the cuts. Here the slot cut has been made and you can see that small bit of the slot remains on the back bit of the base. The next task is to trim that face to remove the residual slot.

Now mark another cutting line on the top face of the bask part of the base, 60mm from the sloping face as shown in the cutting diagram above. Cut along this line to create the rear sloping face (at the opposite slope to the front face). Keep the off-cut.

IMG_1348

The parts of your base block should now look like this.

Next, I took a length of my 110x22mm board and cut it through the middle of the 22mm side on a table saw to create two thinner 110mm wide boards for the upright parts. These I milled to about 7.5mm thick. These were then cut into 160mm lengths with the saw blade still at the 14° angle (same slope direction at both ends).

IMG_1351

Cutting a 160mm upright piece from the thin board.

Before gluing the parts together, sand the upright board to 180 grit, and also sand the slot in the base, and the top face of the rear part of the base. These surfaces are difficult to sand properly once glued.

The final construction job is to glue the upright board to the base parts. To do this, make a sandwich of the base parts, including the off-cuts (front and back, don’t glue these of course, just glue the faces that butt against the upright) and the upright and clamp it tight between two lengths of timber as shown in the photo below. For glue I use cross-linking PVA.

IMG_1353

When set, remove the clamps and discard the off-cuts. The stand is ready for final sanding and finishing.

IMG_1355


Spindicator Mk 2–Now With Fade Effect.

IMG_1229

I’ve had a couple of questions asking about using capacitors to fade out the  LEDs of the spindicator to give a sort of trail effect, and I thought I’d like to try it myself. So let’s get straight to the circuit.

Spindicator with Fade

The first thing to note is that in this version I have used the computers 12V supply, not the 5V supply as in the original spindicator. This is necessary to obtain a good fade effect from the capacitor.

The motherboard interface and low pass filter are the same as in the original circuit. The difference is that the counter’s outputs now switch  general purpose NPN transistors (a BC 547 in this case). When a transistor switches on, its associated LED is lit via the 1k Ohm resistor, and the 47uF electrolytic capacitor charges. When the transistor switches off, the capacitor discharges via the 1k Ohm resistor and LED, fading the LED as the charge dissipates. The fade time is a function of the values of the resistor and capacitor; the larger the values the slower the fade. The resistor is also the current limiting resistor for the LED, so that sets a limit to its value (between 470-1000 Ohms for most LEDs). What I found with breadboard testing is that if the fade time is too long, the whole spindicator ring lights when there is lots of disk activity, and you lose the spinning effect. I found that a 47uF capacitor gave a noticeable but suitably quick fade to each LED.

A challenge I faced with this circuit is that it has many more components than the original spindicator, with an extra 10 capacitors, 10 transistors and 20 resistors. The prototype board and patch wires approach would be too big and messy, so I decided to make my own PCB. With some trial and error I managed to get a reasonable result by laser printing (Brother HL-2170W) a design onto some Canon glossy photo paper (GP-401) and using an iron on its hottest setting to transfer the toner to a blank copper circuit board. It required some hard pressing to stick the print to the board, and then more working over the areas where the traces were with the tip of the iron. What I found though is that the paper then pulled away cleanly, leaving the traces stuck to the board. There was no mucking around soaking off the paper in water as others have reported when using this technique. If some of the traces pull off with the paper, you can just clean the board with some xylene based brush cleaner and try again with a fresh printout.

IMG_1217

The above photo shows my copper board with its toner transfer sitting in the ammonium persulphate etching solution. You’ll notice some rough edges on the left hand ground trace, but there was enough cover left so I didn’t bother to print it again.

The end result, with components all soldered in is shown in the photo at the beginning of this post. I’ve connected all the LED cathodes together (not shown) so that there is only one common cathode wire and 10 anode wires running to the LEDs. I have not yet installed this spindicator – I’m waiting for the next time I’m doing some work inside the server (probably when I upgrade to WHS 2011).

Here’s a quick video of the spindicator mk.2 working at a constant clock frequency of about 25 Hz. The background sound in the video is rain on my workshop roof.


Follow

Get every new post delivered to your Inbox.