Receiving weather satellite pictures in New Zealand – Part 3
July 4th, 2010The other two parts of this are available here: Part1 and here: Part2
Finally some results! But lets start with what I have done so far. Since my initial experiments with my scanner were somewhat successful and I had my new QFH antenna made and ready to go I just needed my Minikits weather satellite receiver to arrive and then I could try getting some decent images.
The kit arrived after just over a week and ended up costing me $NZ125 including shipping. This is far cheaper than any other kit I could find online, all of which you have to pay in Euros or US dollars.
The Minikits kit.
The kit is rather nice. It comes with a tinned double sided plate through hole circuit board. Several little bags of components including all the coils and ICs you need. It also came with an F connector to solder onto the board but I have chosen to use BNC connectors instead. It also comes with the instructions and the description of how the circuit works.
The kit uses an MC13135P receiver chip which is a complete FM receiver on a chip basically. There is also a TL072 op-amp and an MC34119 audio amplifier. All of the components are standard leaded types except for a surface mount NTC thermistor used as part of the automatic frequency control circuit to account for temperature variations.
You do need a few other things so I added the speaker, the signal meter, a AFC switch (the kit comes with a jumper) and the audio out connector. I also used full sized pots for the volume and squelch control since I will mount them off the board. The kit comes with trimmers to use on the board though. The kit runs off a 12 volt supply which is regulated down to 5 volts on the board for most of the circuit to use. I made a small power supply board with a 12 volt regulator on it and powered that from an old power supply from a set of old computer speakers. The used speaker I am recycling came from the same set of old speakers. The signal meter was a nice find. The first place I look for odd electronic stuff, Surplustronics, didn’t have anything so I headed up the road to the top of Queen Street to a real electronics junk shop. I have no idea what it’s called but it’s been there for years now. It’s cram packed with junk. Most of it is useless but the odd interesting thing here and there. Nothing is sorted. It’s all just in piles. I dug about and came up with this nice signal meter with a 0-5 scale on it. He wanted $3 for it. I had $2.20 in change (good thing I hadn’t bought a Mars bar that day) so he said close enough. It was unused and still in the bag!
Assembled kit set. The red thing is a plastic tuning tool.
Building the kit is easy. The instructions say it takes about four hours but I did it in two. All those years of working as an electronics tech to pay for my way through university came in handy! Once you have built it you need to set it up.
The way the receiver works is the incoming signal, which is around 137MHz, first goes though three bandpass filters. These eliminate any extra signals from getting through and just pass the weather satellite transmission frequencies that we want to receive. This is important in some places where there are strong pager frequencies nearby (people still use pagers – probably more reliable that Telecom’s XT network).
We then want to take the incoming signal and convert it down to a much lower frequency. This is called an intermediate frequency. An intermediate frequency, or IF, is used because it is easier to work with and filter on the lower frequency and because if a receiver converts all the frequencies you want to receive down to the same IF then all your circuitry from that point on can be optimised for just that IF frequency. This receiver uses the same IF most FM receivers use, 10.7MHz.
To get to the IF the receiver chip uses a mixer. The mixer takes the received signal and mixes it with another signal that we generate on the board. This signal needs to be 10.7MHz higher than the signal we wish to receiver. The mixer takes our signal and subtracts from it the received signal to get the 10.7MHz IF signal. This process is called Hetrodyning (which is probably what my friend Fing tells his friends he is doing when he comes to visit Auckland and we all go to the pub for lunch). The on board frequency is generated by a thing called a voltage controlled oscillator or VCO.
In this circuit the VCO is controlled by a coil, which gives a rough setting, and the tuning resistors, to fine tune to for each frequency. The kit uses 25 turn trimmers for tuning. Each channel uses one trimmer. The kit only comes with one but you can simply add more and use a multi-pole switch to switch in the appropriate ones. For now I just have the one which I adjust for each different frequency when I need to.
The signal passes though various stages in the chip and eventually gets spat out as audio. There are two audio paths. One is to the audio amplifier chip which is controlled by the squelch circuit. The other is a line output to the PC sound card.
To set the receiver up you need to adjust the VCO to be 10.7MHz above the frequency you want to receive. The receiver needs to receive from 137MHz to 138MHz approximately. The tuning resistor needs to tune across that range. If you set the tuning resistor to half way in it’s travel that would correspond to 137.500MHz. We therefore want the VCO to be oscillating at 148.200MHZ (148.2 – 10.7 = 137.5).
To set the VCO frequency you need to adjust one of the coils on the board. These coils have adjustable ferrite slugs in them that you screw up and down to set the frequency. They are fairly delicate and also metal near them will upset the frequency so you need to use a red plastic tool for adjusting these. This was available as an extra from Minikits cheaply.
The best way to know you have the right frequency is with a frequency counter. Unfortunately I don’t have one. So the next best thing is to use my scanner again. Because the coil is oscillating it is also radiating radio waves. If you hold the scanner close to the circuit board set to 148.200MHz when you adjust the coil and it hits that frequency you’ll hear it on the scanner.
With the VCO set this way you know the receiver should be receiving across the 137 to 138MHz frequencies over the 25 turn range of the trimmer tuning resistors.
Next the instructions say to attach a RF signal generator set to 137.500MHz to the antenna input and adjust the filters and output demodulator for the cleanest signal. Again, I don’t have a signal generator so instead I had to wait until I knew a satellite was overhead. With the antenna sitting out on the front deck railing I used the WXtoImg software to know when to listen and on which frequency. I used my scanner to be able to hear when the signal was there. I then connected the antenna to the receiver and tuned the receiver to the right frequency and quickly adjusted the rest of the circuit while I still had a signal. This can take some time given the low number of passes per day and the short time the passes last. You have about 15 minutes in which to tune things.
To do this tuning I used my ocsilloscope on the audio output to see how clean the signal looked as well as by watching the signal meter and adjust it to give the highest signal as suggested in the instructions. This worked very well.
Initial setup and testing.
One interesting part of the circuit is the automatic frequency control, or AFC. This is quite clever and it will allow the receiver to account for the Doppler shift in the satellite as it passes towards then away from the receiver by adjusting the VCO.
You will see that the EeePC is displaying an image here but I found that it can’t actually decode the pictures properly. I think this is because I was using the mic input instead a a line in (which the EeePC doesn’t have) and so I wasn’t getting a proper signal.
The next thing to do was transfer everything over to my main PC and to put the antenna in a better position (on top of the guttering on the edge of my roof for now). With everything set up like that I finally got my first real picture.
The first image!
And this is what I got. The noise and blank part at the bottom of the image was me trying to tune things in as the satellite passed (from south to north). The horizontal lines were when I was adjusting things. In between though you can see a good image.
With more tweaking and tuning I am now getting nicer images. I am just using the basic settings in the software for now. I think there are a number of different settings to show you different things but I haven’t played with them must so far. These images are using MCIR map colour IR and an Equidistant Cylindrical settings.
First good image.
I still need to manually tune hence the missing bottom to the image but this was a imagine received from NOAA 18 on 137.9125 MHz (that’s why so much of the bottom is missing – I had to turn that 25 turn trimmer a lot) at about 2pm.
The same satellite did another pass about 1 hour 40 minutes later and I got the image below.
Second pass by the same satellite showing Australia.
You can see how the satellite follows different paths on different orbits so you end up receiving differing pictures. Using some (free) software such as WXTrack you can actually see the path the satellite will take overhead. If the satellite is very low on the horizon you will get noisy images. The antenna needs a clear line to the satellite so obstructions in the way will degrade the signal.
So, what’s next? Well, I am still only using the one tuning resistor so for each different satellite frequency I need to re-tune the receiver. This won’t do as a long term solution. Instead of the idea that is given in the kit of using 5 tuning resistors all switched in via a rotary switch I want to try something a bit more automatic.
The kit does provide connection points for adding a phase locked loop or PLL for short. This would allow scanning across the whole frequency range then have it stop once it detects the appropriate signals. You can buy suitable experimenters PLLs that are micro controlled but these are rather expensive and I am trying to do this on the cheap!
I considered using a micro controller to switch between five or so pre-tuned frequencies. Because there are only a few satellites transmitting on fixed frequencies (the status of the satellites and information about them is available on the NOAA POES status site) you don’t actually need to scan the whole range. You can just step through fixed channels looking for a signal. I could use a micro to switch each channel in for a brief period, say 2 or 3 seconds, and if a suitable signal was detected stay on that channel until the signal drops out again.
Switching in a set of preset tuning resistors can be done using a bilateral switching chip. A micro could control the switching. I then though that’s perhaps over complicating things so perhaps I can do it entirely using normal ICs.
My current plan is to use a 555 timer providing a slow clock pulse. These I feed into a 4017 decade counter (one of the first ICs I ever experimented with so a favourite). The outputs of the counter feed into a 4066 bilateral switch to switch in each tuning resistor in turn. They also turn on various LEDs to show what channel is currently selected. When a signal is detected the counter stops on that signal until the whole signal is received. This part I haven’t worked out yet. I was thinking of using the squelch signal but I don’t think this will work too well. Instead I might make a tone detector to listen for the tone you hear when the signal is coming in. The APT system used to transmit the images used a 2400Hz sub-carrier it should be possible to detect easily.
Progress so far.
So far I have got the clock, counter and switching working. You can see those on the breadboard in the picture above. I need to start on the tone detector. Perhaps using a LM567. My backup plan if I can’t get that working is to use an Arduino perhaps. Everyone loves Arduino!
Also I need a more permanent antenna installation. Perhaps a small mast mounted on the roof of my garage so I can put it there and get a nice, clear view of the sky.
And of course once done everything needs to be put into some nice housing.
Will update this with progress soon.
Receiving weather satellite pictures in New Zealand – Part 2
June 28th, 2010You may want to read part 1 of this story about receiving weather satellite pictures if you haven’t already.
Now I will describe how I made a much neater QFH antenna to receive the satellite signals. My wooden one worked fine but it was not waterproof or particularly pretty or accurately made. So I decided to make a waterproof, prettier and more accurate one.
Again I followed the directions given here: http://www.g4ilo.com/qfh.html
I started off with the raw materials which I got from one of my most frequented places – Bunnings Warehouse. There are probably cheaper places to buy this stuff but Bunnings is convenient. I bought a 1m length of 32mm diamater PVC pipe and three lengths of black 15mm diameter Enduroflex pipe. I have no idea what that stuff is used for. Water piping I think. The PVC pipe cost NZ$15.51 and the black pipe was $11.16 for the three lengths although I only ended up using two of them. That black pipe incidentally is the perfect size for the barrel for a home made Nerf gun firing suction darts (a project for another day)!
I also bought some RG-58 (50 ohm) co-axial cable from Jaycar rather than the RG-6U I used on the wooden antenna. The The problem I had with the RG-6U is that the braiding isn’t copper but rather aluminium so it was impossible for me to solder the connection easily. The RG-58 is somewhat thinner diameter than the RG-6U which does mean the antenna is more easily bent out of shape but as my antenna will only be used occasionally it should be fine for now. The 15 metres of co-ax was $28.50.I cut the PVC down to about 800mm long and marked it up ready to drill the holes for the cross arms. I was very careful with the dimensions on this antenna. An easy way to mark around the pipe is to wrap a piece of printer paper around it ensuring the paper is square to the pipe by making it overlap itself perfectly as it wraps over itself. You can then mark off the place the sheet overlaps. You unroll the paper and the distance form the edge of the paper to the mark you a made is exactly the circumference of the pipe. It is then easy to mark off the quarter and half way points on the flat paper. Then you wrap the paper around the pipe once more to transfer those marks to it.
I then put the pipe on a nice flat surface and use the ended of a long, straight piece of wood to transfer the lines down the entire length of the pipe.
After carefully marking the pipe and measuring it several times I drilled the holes to hold the cross members. I first drilled a pilot hole with a 3mm bit then I used the spade bit to drill out a larger hole (sorry for the badly focused photo).
To make the holes a nice, tight fit I drilled slightly undersized then used a tapered reamer to enlarge the holes to the exact right diameter.
Once done you end up with mast finished. The positioning of the middle set of holes holes isn’t very critical as those arms just hold the ends of the cables in the correct place. Obviously you want them close to the mid point though.
I next carefully cut the six cross arms from the black pipe. Note the two different sizes for the two different sized loops in the antenna. I trimmed the ends square in the lathe (because I could, not for any technical reason) then carefully marked and drilled the holes in the ends. Looking at the plans you can see these holes need to be a fixed width apart to ensure the loops of the antenna are the correct size. They also need to be drilled at 45 degree angles to the mast so the cable has the correct spiral to it.
To drill the holes so they are at 45 degrees to the mast when installed you actually need to drill the holes in each cross member 90 degrees apart, one at either end of the support. Since the drill press drills down vertically all I did was drill one hole then push a piece of aluminium tube through it temporarily. Then, turning the tube around I simply adjusted it in the vice until the aluminium tube was parallel to my drill table. With it parallel when I drilled the vertical hole I could be sure the two were 90 degrees apart. When you push the crossmember through the mast you simply twist it so that one of the holes is at 45 degrees to the mast and the other will be aligned at 45 degrees too. You do have to twist it the right way though so that the cable is spiraling down anti-clockwise when viewed from above.
Because I might want to experiment with this antenna a little I didn’t want to glue the crossmembers fully in place yet so I am temporarily using some pieces of split ribbed tubing to stop the crossmembers moving in the mast.
In the top and bottom sets of holes I needed to file slots so that the cable could pass through into the mast. The holes for the arms at the ends of the mast I drilled so that the centre of the co-ax cable would be sitting at the exact right measurement given in the plans with the cable running along the outside of the crossmember , not inside it. Running the cable inside the crossmembers would of course be neater. But there is then no way to make sure the cable lies flat in the correct place. Does this make much difference? I have no idea! But the dimensions are given down to fractions of a mm accuracy so I decided to get things as close as possible.
I started putting the crossmembers in place and also soldering the connections. Shown here is the bottom most connection. That is the feed wire soldered to the shield of the bottom of one of the loops. I insulated the connection with waterproof tape then carefully pushed it into the mast and then pushed the crossmember fully home.
Similarly at the top I carefully soldered the connection inside the top of the mast once the loops and the crossmembers were all in place. Notice the anti-clockwise direction of the spirals. I used lots of cable ties to hold the co-ax down flat across the crossmembers. Eventually I will remove the split tube and just glue the crossmembers in place once I know everything is correctly positioned.
To finish off the antenna I put a PVC cap over the top of the mast and I also made a quick and dirty stand from a scrap piece of wood and another off-cut of pipe that the mast happens to slide into perfectly. Eventually my plan is to hang it from a line suspended above my garage roof where it will have a clear view of the sky. The antenna might be connected to a line going around a pulley so I can hook the antenna onto the line and pull it up into position but still bring it inside if the weather is too bad. Either that or I will make a third, more robust version to permanently mount on my house roof.
With the antenna on it’s temporary stand I was able to move it about outside to see how well it would work. It works well when it has a clear line to the satellite down to very low on the horizon. The signal is very easily blocked though so building and even trees will cause you to lose the signal.
Now I just need my receiver kit to arrive so I can build that and really see how this works!
Update: The kit arrived! Read about it in Part 3.
Receiving weather satellite pictures in New Zealand – Part 1
June 27th, 2010This project came about after I started playing about a little more with my Uniden UBC93XLT scanner. This is a toy I got a wee while ago from Dick Smith Electronics. I hadn’t really done too much with it apart from the usual listening to various coastguard, airport and Police transmissions (the number of people doing stupid things in cars who get stopped by the police who have no vehicle license, no WOF and suspended drivers licenses is amazing – you’d think they drive in a way that means they wouldn’t get stopped). That all gets boring pretty quickly so I wondered what else this little scanner could do.
I should point out that I am not a radio amateur, or HAM, as they are known. I am just an electronics tinkerer. Anyone with good, general electronics skills can do this.
Bender showing off my scanner.
One thing you can do is pick up pager frequencies. I pick up 157.950MHz easily at home which is a Telecom pager frequency. It sounds like a random collection of bleeps and bloops – R2D2 with his knickers in a twist. Apparently with a simple mod you can break out the unfiltered audio (called the discriminator output) in the scanner and then, using some software called PDW, decode the pager signals.
Even though the mod is easy to do (if you are electronically inclined) looking at other peoples pager messages strikes me as being terribly uninteresting, kind of like having to overhear other peoples one sided phone calls on the bus, so I haven’t tried this modification myself.
One other thing I could try (after doing the discriminator mod above) is receiving AIS signals. These are the identification signals used by ships. Since I work in the city and it’s not too far down to the port I should really try seeing if I can receive them. Perhaps the Northern Steamship Company pub might be a good place to try!
The frequencies used are 161.9750 for AIS1 and 162.0250 for AIS2. Apparently you can then feed the signals into a sound card on a PC and using some software like Shipplotter you can track the movements of shipping in your area. Something to try another day.
One thing I did want to try, being interested in all things to do with space and space technology, is receiving weather satellite transmissions. Now, before I start I should say that you cannot actually decode the weather satellite transmission using this particular scanner. You can HEAR the signals but you cannot generate any kind of useful pictures with them. Well, I have been unable to. But given that you can hear them was enough to start me off on this project.
Lets start with some background first. Up there, in space (well, low earth orbit 850km up), there are some weather satellites. Both the Americans and the Russians have them up there, the NOAA and the METEOR satellites respectively. There are others of course but the NOAA are the ones you can easily receive signals from so they are the ones I am listening to. These satellites are continuously transmitting signals down to earth using a system called APT. The Wikipedia Automatic Picture Transmission article gives you all the background you need but here are the basics.
The NOAA satellites are in a polar orbit around the earth and as they orbit they are continuously scanning a line beneath them 3000km wide and transmitting this line back to earth. Being in a polar orbit means each satellite will pass over the entire planet as the earth rotates beneath them. As a satellite comes up over the horizon and passes overhead a receiver on the ground can start receiving these lines, decode them in sequence and build up a picture. Due to their low altitude these satellites orbit rapidly and each satellite will make several passes over your location each day.
The signals are transmitted on a group of frequencies around 137MHz. The actual picture received contains two views of the earth below the satellite – one in visible wavelengths and another in infrared. A line is scanned twice every second and each line contains the image data as well as non image data. This system has been used since the 1960s so it is quite remarkable it is still in use today. You can get up to date information about the NOAA weather satellites from this status page.
To receive the pictures you need three things: a receiver, an antenna and a PC (with a sound card and some software to do the decoding).
First, the receiver. As I mentioned above my particular scanner (or indeed most scanners) isn’t suited for doing more than hearing the signals but it is enough to let me work on the second piece, the antenna.
The antenna obviously needs to pick up the 137MHz signal the satellites transmit on. It also needs a wide receiving pattern as it has to be able to pick up the signal from horizon to horizon. The signal from the satellites is circularly polarised so the antenna must be designed in a particular way to receive the signal. Two suitable antenna designs are the turnstile antenna or the quadrifilar helix antenna (QFH).
Looking around online I came across several references to the QFH antennas with very good instructions on how to make them specifically for receiving weather satellite pictures. The design I decided to use was from here: http://www.g4ilo.com/qfh.html
Because I didn’t know if I was going to be able to receive anything I made my first QFH using materials I had on hand, namely wooden dowels. I made an antenna using the instructions and dimensions given above. I used RG-6U coaxial cable as that was easy for me to get quickly in order to try things out. I first tried using the antenna indoors until a friend pointed out that the metal roof would block the signal (a duh moment) so instead I simply took the antenna outside and hand held it in order to try it out. To my amazement it worked! I could hear, albeit with a lot of noise and static, the satellites transmitting their signals.
It’s worth mentioning that because the satellites are constantly orbiting you need to know exactly when a satellite will be passing over. This brings us neatly to the third thing you require, a PC with a sound card and some software running on it.
The software I am using is called WXtoImg and it is available to download and use for free (you can also pay to register it for additional features). Interestingly it seems to be written here in New Zealand. This software does two things. It decodes the received audio signal and formats that into usable images and it also tells you when (and where) the next satellite will appear.
Another useful piece of free software is WXTrack by David Taylor. This software lets you see exactly where satellites are over the earth at any given time.
Both of these programs require you to download up to date satellite tracking information called Keplers but this is well explained and easy to set up.
Since I could now hear the signal and I had downloaded and installed the appropriate software I rigged up a temporary support to hold the antenna up outside my window were it would have a (reasonably) clear view of the sky and attempted to feed the signals into my PC.
My quick and dirty wooden QFH antenna and dodgy mounting method.
The results were not good (it wooden work)! This I expected and the problem isn’t the antenna itself but the limitations of my scanner.
There are various problems with using scanners for receiving weather satellites. Other weather satellite sites explain the problems better than me but to summarise the main problem is due to bandwidth. Now bandwidth, as I understand it (and I could be wrong!), when talking about receiving weather satellite transmissions is the difference between the lowest frequency and the highest frequency that you need to be receiving signals over to get the full signal. A scanner like mine is designed for receiving voice signals. Voice signals don’t need a very wide frequency range so we say the scanner has a narrow bandwidth. The bandwidth of a scanner like mine is about 15kHz so the scanner will filter out any signal outside that range around the main frequency.
The satellites transmit their signal over a much wider range spread around the main frequency, i.e. is has a wider bandwidth. To accurately receive the entire weather satellite signal you need a receiver with a 30kHz to 50 kHz bandwidth. So in effect my scanner is blocking out part of the signal. We basically lose information from that lost signal so the software can’t build a good picture from it.
Other issues with a normal scanner are sensitivity, how strongly it picks up the weak satellite signal, and selectivity, how well it picks up only the frequency you want. Another, more subtle problem, is the doppler shift caused by the movement of the satellite as it passes overhead. This causes the frequency to shift as the satellite passes overhead.
All these issues mean my little scanner isn’t up to the job. To really demonstrate this here is what a properly recorded signal of a weather satellite should sound like: http://n8imo.com/APT/images/N14.WAV (from http://n8imo.com/wefax4.html).
What I get is this: http://www.asciimation.co.nz/misc/06250521.wav\
Image produced by the scanner.
My friend Dave wanted to see a picture of what the scanner produced. This is the best that I ever managed to get. Mainly noise. With some vague picture in the middle as the satellite passed right overhead.
So when people say a normal scanner won’t work, they are right!
The next thing to do is sort out a proper receiver. There are a number of options here. You can buy a scanner that does have the correct bandwidth but these are very expensive. Or you can buy a ready made receiver just for receiving weather satellites. These are also expensive. Finally you have kit receivers you buy and assemble yourself. Being an electronics tinkerer this is what I was after. There are various kits on offer but I chose the Minikits weather satellite receiver.
This receiver is very reasonably priced, should do everything I want and the company is more or less local (well, Australia) so I was able to pay in Australian dollars rather than US dollars or Euros which tend to work against someone earning NZ dollars. Shipping was also cheaper and faster.
I ordered the kit last week and it should arrive any day now so I will be building that as soon as possible.
In the mean time, having proved that a QFH antenna would indeed work I set about making a more accurate, more weather proof version.
Will describe that in part 2 here.
Tearing apart my Miele S5210 vacuum cleaner
December 29th, 2009This is my vacuum cleaner.
Miele S5210.
It’s a Miele S5210. It’s a very, very good vacuum cleaner. Well, it was until the point that it broke! Actually I was somewhat responsible for that. For a little while now I have been restoring a car (OK, almost 6 years but I am nearly done – www.asciimaton.co.nz/pics). After weeks of filling and sanding of filler I finally sent it off to the panel beaters to be painted. This left me with a garage full of sanding dust. I swept up what I could the used the vacuum to clean up the rest. Unfortunately your average house vacuum isn’t really designed to handle lots of very, very fine filler dust. I ended up clogging it up and the motor stopped running smoothly and instead started stuttering. I needed to take the vacuum cleaner apart to clean it and remove all the dust so it would run properly again. What follows is the procedure I used to take the vacuum cleaner apart. I imagine the process is probably similar to other Miele vacuum cleaner models.
I was inspired to do this page after I found the following page online for a different Miele model (a Miele s300): http://www.sannerud.com/house/miele.html
You don’t need many tools to take the vacuum cleaner apart. Just a Torx T20 driver and a small flat screwdriver to push on the plastic clips that holds the parts together. All the screws used to hold it together are the same. The Torx bit shown here is actually a tamper proof Torx bit with a hole in the middle but it works fine on the screws. Click on any of the pictures for a larger view.
Torx screw and T20 Torx driver bit.
First unplug the vacuum cleaner and remove the bag and all the filters. The small silver honeycomb filter just clips in place. Remove this so you can then remove the lid.
The clips holding the lid on.
The lid just slides onto the hinges and two small square clips hold it in place as shown above. Depress the small squares and then slide the lid off the hinges.
Large honeycomb filter.
The large honeycomb filter is also just clipped in place. Carefully push back the two clips shown circled above and the filter should come out.
Rear plastic piece.
The plastic piece at the rear between the two buttons is also just held in place by clips. Brute force will remove this. Just yank it upwards and it will pop loose.
Removing the speed selector.
With the rear cover removed you should see two screws holding the speed selector part in place. Remove these.
Clips holding speed selector in place.
With the two screws removed the speed selector can be removed by pushing in the small clips that hold the front of it in place and lifting it off. This piece just contains the knob that controls the speed. The knob has a stalk that sticks down underneath it that fits into a selector switch on the electronics board.
Top cover screws.
The top cover is held in place with four screws shown, two at the front and two down deep holes in front of each button. Undo these then the top cover should lift off.
Electronics board plug.
With the top cover removed you can see the electronics board. It’s pretty simple really and doesn’t have much on it. The board should be free to pull off now. The only thing holding it in place is the connector shown above. Simply unplug this connector and the board will lift off.
Inner cover.
With the electronics board removed you should be able to see the screws holding the inner cover in place. There are three at the back and one in the centre as shown above. Remove all these screws.
Clips holding inner cover.
As well as the four screws there is a clip either side of the cover on the sides of the vacuum. You can simply pop these apart by hand then the inner cover should lift off. There is a small rubber hose that goes between the cover and the cord retractor mechanism which you also need to disconnect from the cover (it will probably just fall off anyway).
Inner cover removed.
With the inner cover removed you can now remove the motor (which has a foam pad over it) and the cord retracting mechanism. The only trick here is to unplug the connector that joins the two together.
Motor connector.
The motor and cord retractor will simply lift out. I gave everything a good cleaning to get all the dust out. I used my air compressor to blow it all clean. With all the dust removed from the motor I sprayed it’s brushes with electrical contact cleaner. I didn’t go as far as dismantling the motor itself (March 2010 – OK, I did eventually See below!).
Contact cleaner for the brushes.
The brushes are either side of the motor and I simply sprayed cleaner into the hole at back of them.
After letting the contact cleaner dry I put the motor, cord retractor and electronics boards temporarily back in place the tested the vacuum. You need to be VERY careful doing this as nothing is properly attached and there are exposed mains connections that will bit you it you touch them (don’t ask how I know). Also the vacuum motor is extremely loud when not encased in plastic!
Once everything was cleaned and working again reassembling the vacuum cleaner is basically the revers of taking it apart. Make sure you reattach the small rubber hose and also make sure the cord and plug are free and don’t get caught when screwing all the pieces of the case back together.
After my cleaning and spraying the motor with contact cleaner the vacuum is working nicely again. I know now I should really get a nice shop vac for cleaning the garage and leave the Miele for purely domestic duties!
I can really recommend these vacuums. They are good value for money and very powerful. And now, having seen how they look inside, I can say they are very nice quality too.
Update March 2010.
I have had a few people comment that this page was useful so I decided to post the second part of my vacuum cleaning story in case people find this further detail helpful.
My cleaned up vacuum worked well for a little while but then the motor started stuttering again until eventually it stopped running altogether. Another tear down was in order. This time right down to the motor itself. Again the nice design of the Miele made this an easy job to tackle.
First you need to remove the motor from the vacuum as described above. Then carefully tap off the metal shield on the end of the motor exposing the blower fan. Next remove the nut holding the blower fan in place. Now it was a few months ago that I did this but from memory the nut is a reverse threaded one, i.e. turn it clockwise to undo it. This allows you to pull off the aluminium blower and the flat spacer washer.
Nut and blower removed.
Next you can lift out the two carbon motor brushes. These are simply held in with spade connectors so you can just pull them straight out. In the picture below you can see the female spade socket on the face of the stator housing.
One brush already removed. The other still in place.
The brushes are nice and long so should last a very long time.You can see the long male spade connector on the bottom of the brass housing. You can also see how despite my previous cleaning this brush is still covered in sanding dust. If I didn’t mention it above I should say don’t sand filler off a car (http://asciimation.co.nz/pics/page18.html) then use this vacuum to collect the dust!
Nice brush. Boom! Boom!
With the brushes removed (and cleaned up with electrical cleaner) you can remove the stator. There is a metal spring clip that holds it in place. If you press this down the stator should then slide out.
Spring clip holding stator down.
The electronic controller is attached to the stator and will come put with it. You can see the top of a TO220 type device sticking out of the top of the plastic housing. We get to that in a minute. The inside of the stator and housing were both covered in the sanding dust so I cleaned these up as well.
Stator removed. Note the electronics are still attached.
Next you can carefully pull out the rotor. This has bearings on each end and the lower bearing is a press fit into the housing. You need to carefully pull this out. The rotor will come out in one piece. Be careful not to lose the little flat spring washer though.
Rotor removed.
The observant of you will probably have noticed one of the problems with the motor. The commutator on the end of the rotor, that ring of copper strips the brushes rub against, are filthy and scored. To fix this I carefully mounted the rotor in my mini-lathe. You only need to grip it very lightly in the three jaw chuck. I made sure it was running true and turned it on. I then used some fine wet and dry sandpaper folded into a long strip to carefully sand down the commutator.
Rotor mounted in lathe.
I didn’t try to get the commutator perfectly smooth as I didn’t want to sand too much away. It still has a few small scores around it but it doesn’t need to be perfect. The deep scoring is actually where the edges of the brushes are in contact with the commutator so the brush is in contact with smooth copper on most of it’s face.
Commutator after sanding.
Next I cleaned up the aluminium blower which was quite clogged with dust. A bit of electrical cleaner and a poke around the fins with a long cable tie did the trick.
After doing all this and cleaning everything to remove all the dust I reassembled the motor. Since I had given it a good clean with electrical cleaner I left the motor on top of my dark coloured garage roof to make sure it was fully dry before trying to run it again. I wanted to make sure all the cleaner had evaporated out of the motor and windings.
Unfortunately after putting it back in the vacuum cleaner and reassembling everything (with a little Loctite around the rotor bearing where it pressed into the housing) the motor was still dead! I had to take it apart again. This time I removed the motor, opened that up and removed the motor electronics. Again thanks to nice design this module just unclips since it is held in place with spade connectors.
Motor electronics.
The electronics on the motor are incredible simple. Basically it’s just a TRIAC and what I think is a thermal cutout device.
TRIAC and thermal cutout thingy?
About now the problem was pretty obvious. This TRIAC was burned out! A close inspection and a little prodding showed that TRIAC was burned out. Two of the legs were not even connected to the body anymore.
Well there’s your problem!
I am not sure why this happened. I am guessing a combination of a badly connecting and arcing commutator and a motor clogged with sanding dust ended up cooking things. The TRIAC itself is a T2550h 600T which is a 25 amp TRIAC. These are available in NZ but not from the easy places like Jaycar or Dick Head Smith (who don’t really do electronics anymore despite their name). You can probably get them from the bigger suppliers like Farnell or RS but they would cost a bomb and you might not be able to buy just one. So I looked on eBay and found someone in the UK sells them for just a couple of quid. I ordered one of them.
This is the data sheet for this particular part: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/6697.pdf
Once that arrived a week or so later it was a simple matter to unsolder the dead part and solder in the new TRIAC. I reassbmbled everything again (after this many time apart you get good at this bit) and finally everything was working again!
All that was actually done several months ago and the vacuum cleaner is still working happily now. I know these things aren’t supposed to be customer serviceable but it is nice to see that they are engineered in a way that means a customer with the right skills can successfully get in there and fix things.
A door alarm for my house and garage.
December 26th, 2009If you’ve looked about my sites you’ll know I make things. Lots of things. This means spending lots of time in the garage. Often I am dashing about between house and garage as I am busy making stuff. My house actually has two garages, an old on on one side of the house and my new, double garage on the other. It is in the new garage I have all my tools work on most projects.
My house and separate garage.
One thing that always worries me about being in the garage is making sure no one goes into the house (and vice-versa). Locking the doors each time I go from one to the other quickly becomes annoying so instead I decided to make a little door alarm. Basically, when I am in the garage, an alarm sounds if someone opens the front door of the house and, when I am in the house, an alarm sounds when someone opens the door to the garage.
To build this I used two small boxes, some magnetic reed switches, some switches and LEDs (with current limiting resistors), a six volt power supply and four wires of the data cable I had run between the house and garage when I had it built.
Circuit diagram.
The circuit is really simple. Everything on the left is in the house, everything on the right in the garage. Basically each little box contains a toggle switch, an LED to indicate the alarm is on, a buzzer and a magnetic reed switch attached to the door.
The alarm works by sounding a buzzer when the opposite door is open. So if you are in the house and have the alarm switched on the buzzer in the house sounds if someone opens the garage door. If you are in the garage and the alarm is on the buzzer in there sounds if the house door is opened. The toggle switch on each box turns off it’s buzzer (say you are in the house and you know the garage door is open and don’t want it buzzing). The LED just shows the alarm is on and will buzz when the opposite door is open. The reed switches are wired so that the switch is open when the magnet is in place. The reed switch itself is attached to the door frame and the magnets are on the door. When the door opens the switch closes and the alarm sounds.
The power supply is an old 6 volt wall plug I had lying about. To completely turn off the the alarm I simply pull out the power supply lead.
Garage alarm box showing wiring and reed switch.
Garage alarm box (the power was off so the LED isn’t glowing).
House alarm box next to normal home alarm.
Now I can work in either the garage or house and leave the doors unlocked (but closed) and know that if anyone opens a door I will hear it where ever I am.