Sunday, 11 March 2018

Kenwood BM250 repair.... and Doz' wholemeal pizza dough recipe

Friday night. Pizza night.

I like to make my own pizzas. I don't particularly like white bread bases, so a few years ago I took to making my own wholemeal pizza base. I use a Kenwood BM250 bread maker I bought about 10 years ago, on it's dough setting to make the dough, roll it out and bake the pizza. Excellent.

Well I'd set the machine going, and it was whirring away in the kitchen whilst I was working in the workshop. *CLUNK* and the house power tripped. The mains monitor text me! I went to investigate. The RCD had tripped, indicating an earth fault somewhere, and refused to reset. I unplugged the bread maker, and it reset... and I was stuck with some half mixed dough...

After ordering domino's... I decided to take a look...

First thing of note was the damaged mains cable ...

Tsk tsk! I should have noticed this before...

Much unscrewing followed, and the mains cable was replaced. Although requiring replacement, the cable's inner insulation was intact, and not the source of the problem...

Here you can see the motor drive for the stirrer thing, and the control PCB. I performed an insulation test on the motor at 1KV, and all was well....

The heater element inside the oven compartment, however, showed very poor insulation of just 10 Kilohms when cold. No good at all.

The element is removed. There's a small screw and a nut holding one end in....

... and a screw and nut holding this ceramic saddle clamp arrangement on the other.

A replacement element was found inexpensively on eBay (£6.39 delivered) and put the problem right. Another saved from landfill, and £70 cheaper than a new machine.

and if you want to try a healthier wholemeal pizza dough ... here's my recipe!

230ml Water
380g of wholemeal bread flour
~30ml Olive Oil ( a good glug! )
1 packet of bread machine yeast.
Some Italian herbs and spices!


Saturday, 3 March 2018

Arduino programming tool. ISP and IDE.

The big hifi pre-amp is on hold for a bit, as I await some parts to arrive.

In the interim, I've wanted to make a programming tool for ATMEGA328 chips, that will ease programming changes when using them in stand alone units. I've looked about on the net, and there's some solutions which are nearly what I want... but nothing quite hits the mark.

The idea is to have a ZIF (zero insertion force) socket into which the blank chip to be programmed is inserted. I want it to be able to program chips with the bootloader, as well as straight from the IDE.

The fitted micro is loaded with the "Arduino as ISP" sketch. The switch, S1 & S2 (actually 1 four-gang switch, I just didn't have a library for it!) is used to switch between ISP programming for bootloader, and IDE Programmer. LEDs indicate various functions. D1 is ISP heartbeat, to show it's OK, D2 is Error in ISP programming, D3 is ISP programming activity, D4 indicates ISP mode, D5 indicates IDE mode (also lights when in ISP mode, as I forgot about the steering diode D5), and D6 indicates slave activity during bootloading (ICP1).

...a simple board is designed and etched....

The keen-eyed amongst you will notice the steering diode, D5 is missing from the layout. I mounted it underneath the board, as I'd missed it...

... and it works a treat !

Oh yeah, a quick note on R2 and R7... both 1 megohm across the crystal. I've picked up this bad habit from the original Arduino design. It doesn't need to be there. It was originally to provide some bias for gate-based oscillators. The ATMEGA328 has bias provided internally. It's a waste of 1 meg resistors! Don't bother to fit it, and I promise never to include it again!!