Miele Induction Hob Problems 2.0

 Miele Induction Hob Problems 2.0

The Miele hob has gone wrong again. The previous fix was a relatively simple capacitor replacement. This time things are not so straightforward. The initial fault was that the hob tripped the RCB in our fuse box when an attempt was made to turn on either of the front two rings. This happened several times. 

The hob was removed to the workshop to see what could be done. Once wired up there the controls report an FE60 error whenever the hob is turned on.

I managed to find some documents online that said that FE60 was a communication error. After a few hours of going round in circles I decided to buy some replacement PCBs. After swapping all of them into the hob I continued getting the FE60 error. So still no working hob. A cheap-ish hob came up on ebay so I bought that and tried that out. Absolutely amazingly that hob came up with the exact same FE60 error. After ruling out an airborne electrical virus of some sort I finally found out what the problem was when I tried operating the hob with the lights out in the workshop. The lights I was using were interfering with the touch sensors used to control the hob. I suspect the code saw that as a communication error with the push button PCB and reported the FE60 error. 

How do you fix FE60?

Operate the hob with the dark glass cover in place. 

So, hob was replaced in the kitchen with a completely new set of PCBs. As I now have two hobs and about three sets of PCBs I have enough spares to last for a while and can completely swap electronics.

A few days later the RCB trips again. This is with completely different PCBs, so I now think that there's a dodgy piece of equipment somewhere in the house and that caused the leakage current to go up. Induction hobs are known to have high leakage and that pushed the RCB over it's trip limit.

At least I now have spares for the hob for about three decades...

Trust Your Tools (Well, Sometimes)

Trust Your Tools (Well, Sometimes)

One of my rules of thumb is 'Trust Your Tools'. If your multimeter says it's 4V then it probably is. If your debugger says that a variable is a certain value, then assume it is. Don't assume your tool is faulty. Most of the time it isn't.

So, when I needed to program a PIC16F84A for my Microtan, I immediately went for my newest programmer, a PICKit4 from Microchip. After installing MPLAB, which I didn't have on my laptop for some reason, I built a small circuit on perfboard which has the required bits and bobs needed to program a PIC.

I popped a 16F84A into the adapter, attached the PICKit4 and, oh dear, the bank check has failed. OK, try another chip. Same thing. OK, check wiring, all OK.

OK, get the PICKIT3 out as well. I tried programming the two initial chips and had no luck. Not good.

I had bought three chips from China, so decided to try the third chip with the PICKit3 and no luck. I decided that the chips had to be bad, so after trying them with the PICKit4 again, just to make sure, I bought some more chips from a reputable supplier and waited for them to arrive.

When they turned up I had another go with one and the PICKit4. No luck, exactly the same as the Chinese chips. Maybe they weren't bad after all. I checked the programming circuit for the PIC16F54 and found that I'd left out the capacitor from MCLR to ground and the Schottky diode from the RC circuit to the MCLR line. I added these and tried again with the PICKit4 and still no luck.

I then decided to go back to the PICKit3 with the new circuit and a fresh chip. It worked. Finally I had a programmed chip. A quick test in the Microtan keyboard PCB confirmed that it was working fine.

So, what happened? Looking on the internet it seems that the PICKit4 destroys PIC16F54A chips (unless, maybe you have a series resistor in line with the MCLR line, I haven't tried that). It is also reported that you may destroy the PICKit4 as well.

I'm not happy about that. The PICKit4 has the device in it's list of supported chips and lets you program it. Destroying them is not an acceptable outcome. I'd prefer it if they dropped the device from the supported device list.

Here's a picture of the 5 destroyed chips I ended up with, they seem to be permanently damaged as I can't program them even with the full circuit and the PICKit3.

In the 'olden days' the PICs were excellent little things and they worked. As well as the PICKit4 problem, I've had trouble with a PIC16F707 that simply seemed to not work, and a problem with MPLAB a couple of years ago where it just did not work on my Linux laptop, that appears to have been fixed now, but that's quite a lot of problems, especially as I don't use the PICs that much.

Oh well. I'll have to check on the interweb before I use the PICKit4 in future...

Tumble Dryer Alarm Clock

It looks like my tumble dryer has an alarm built in to it that wakes me up about once a year. Last year it was a clacking clanking scraping sound (see here).

This year it's a thump thump-thump sound. (Sort of D in Morse code). OK, it's 1:30am so I don't get up, but try to sleep through it. After a couple of hours the dryer finishes its program and I get some sleep. Five o'clock comes round and I get up and investigate.

I've forgotten how to get the top off properly (just undo the side screws and the top comes off to the front. Don't undo the rear screws like I did. Again). To get the sides off I need to take the front panel off and to do that I need to take the bottom vent off. I forgot that it slides on these clips:

I finally have the top and two sides off and can now look for the D-thump. Turning the drum manually I can just feel a bump now and again. The rear bearings look fine, so I have a look at the rollers. They are fine too. Then I notice the drum has some black marks where something has stuck to the track the rollers run in.

I find that there's a big blob and several smaller blobs, which probably accounts for the D pattern of thumping. I scrape the blobs off with a wooden stick and re-assemble the dryer.

A quick test and the D-thump is gone. I have no idea what the black blobs were. At first I thought it might be material from the rollers, but they look fine, with no obvious missing material. Maybe something fell onto a roller and ended up smeared around the drum?  I have no idea, but the dryer seems well again, which is good.

Fisher Problem and Fix

The friend's problem with his Fisher printer has probably been fixed. The problem was a snag of the filament when the angle of the Bowden tube was anything other than vertical. The filament enter the heatsink in the hot end through a pneumatic fitting on his printer. neither of mine have that arrangement, so I haven't seen that problem. I made an aluminium tube that helped to hold the Bowden tube vertical, but it didn't quite fix the problem. Some support from the RepRap people and a design for a bracket was sent and printed. This does seem to have fixed the problem, except maybe when the effector is at the top of its travel.

The final arrangement is here:

It's difficult to see how the tube can be anything other than vertical, with all this encouragement...

Fisher 3D Printer Widget

This isn't for either of my Fishers, rather it is for a friend who has a Fisher that only prints when the Bowden tube is held in a particular orientation. This is odd and hopefully a proper solution will come forth. Until it does, I knocked up a widget that hopefully will perform the 'holding in a particular position' job. The position is vertical, so it was easy to make this widget on the lathe:

The pneumatic fitting is the latest way that the Fisher attaches the Bowden tube to the effector. Both of my printers have the tube screwed directly into he heatsink. The tube comes out at quite an angle and I see no problems.

The widget has a hole each end, one for the tube:

and one for the pneumatic fitting:

The fitting is a (very) snug fit into the end:

The flat is to provide some clearance for the fan which is close to the tube entry point. This could maybe have been 3D printed, but I didn't have any dimensions for the part, other than a 4mm hole for the tube. I machined the fitting hole by performing many test fits as I bored the hole out. To 3D print this would have taken many prints to get the correct fit. Hopefully Aluminium is a bit more rigid and durable than PLA.

Miele induction Hob FE32 Problem Update

The post a while back that detailed my fix to our Miele induction hob has been quite popular and, I hope, useful to people. I thought I'd have a dig around to see if I had any more information about the fix process.

I found some more photos, which may be of use. I'll put them all here, just in case.
This is the mains input connection area, we're in a 240V area, this will probably change for different voltages.

 This is the PCB that had the problem, I removed it to do the replacement of the capacitors. The problem capacitors are bottom left, either side of the coil.

 

Here's a couple of close-ups of the capacitors with the problem:

I found this video on YouTube, which has details of a fix that looks very similar to mine:

German Fix Video

Rainwater Harvesting Pump Controller Problem

Our rainwater harvesting system uses a pump and that pump is controlled by a, well, controller. This has worked fine for years, but about six months ago it gave a fault and I had to press the reset button to get it going again. It then ran for several months, but about four weeks ago it tripped again, and then it tripped many times.

The controller is a controlmatic E, I believe and it has a PCB inside which performs all the functions. From the symptoms I thought it might be an electrolytic capacitor problem as the frequency of occurrance is increasing. I took the PCB out and tested the electrolytic capacitors and found that they were fine. I then took the power supply dropper capacitor out and tested that and it did not look fine. I replaced it with a parts bin capacitor and the controller ran for a few days with no faults. I bought some new capacitors as I didn't want to leave a parts bin component across he mains, even though it seemed to solve the problem. It was also slightly wrong in value. I put a new capacitor in the PCB when they arrived and the controller has run ever since with no faults.

I have a couple of videos about it here:

https://uk.rs-online.com/web/p/polypropylene-film-capacitors/1447774/

https://uk.rs-online.com/web/p/polypropylene-film-capacitors/8712613/

Mendel

The replacement for the cartridge heater arrived yesterday and I fitted it this morning. Unbelievably it also failed in the same way. I cut the heater open and it seems to be a problem where the heater element joins the connecting wire. The element is 3R, the join is open circuit. So maybe it isn't anything I'm doing...

Mendel 3D Printer Problems

My Mendel 3D printer has been working fine for a while, apart from an over temperature moment when a thermistor went open circuit. Recently, though, I've wondered if the platform stepper belt was a bit loose. As things were still being printed I didn't worry too much. The printer is in a box that has filament reel holders and so didn't flex too much when I moved it about. Now I have a new workshop and a dedicated place for the printer to live, I moved it to it's new home. I haven't had time to start it up recently, but yesterday I decided to run it up and install the software on a new control PC. After powering on I popped to the other workshop room for something and when I came back noticed that there was a 'hot PLA' smell. Not good. Here we go again I thought, thermistor problem. Power off, multimeter out to check the thermistor resistance. The problem was obvious when I started to probe the thermistor screw contacts: the wires to the thermistor had fallen out. Not good. The second wire down in this picture was hanging out:

This meant that the thermistor was open circuit and the control electronics seem to always be performing the PID (even when hot end is off) and with the open circuit it drives to max temperature. Which is quite hot.

I reconnected the thermistor wires and started again. No smell this time.
All started off quite well and I tried printing a badge holder. No luck. Twice I got a mis-alignment of later layers, like this:

Platform stepper belt I thought. Turns out I was right, and I have now found out where the M3 nut I found came from. The stepper belt connection blocks are under the bed and I hadn't noticed that one had fallen off. As the connector block has a tooth that engages with the belt teeth, it looks like it had only jumped a tooth or two. 

After removing the bed and re-tightening the connector blocks it looks like the printing is much better, no misaligned layers yet, and a much tidier print. It's working more like I remember from just after I built it.