Jumat, 17 Juni 2011

Washing Machine and Mosquito Hitter

I'm feeling like writing today :) but not yet about DIY audio though he he. Recently my wife complaining about our washing machine, the centrifuge just don't work. This machine is less than 1 year old. Here it is.

Opening the front cover reveals this, hmm...another plastic failure case..man....just hire me to do your design :), or pay me to check your design and products...
The broken thing is safety switch housed in plastic casing. When the lid is open the centrifuge stops. Consequently when this switch is broken you can not turn on the centrifuge, since it is a 'normally closed' switch. What went wrong? well, the switch housing is kind of poorly designed, small footprint of attachment and cross sectional area, with lots small and sharp notch. Perfect recipes for failures waiting to happen.

Here is another details of the switch housing. Blue marker indicates cracks that originated from sharp notch.

I reckon only about 2mm X 15 mm square of area that must withstand cantilevered housing of 60mm long. If the force required to close the hard copper leaf switch is 0.1kg then the root suffers 0.1kg X 60mm of bending load plus 0.1kg vertical load reaction, small loadings? maybe..but that small loads repeated over 200 times and with that sharp notch? exactly!...for quick fix I just hardwired  & isolates the leads...at least the centrifuge works now, without the usual 'safety' feature though :)..

Another product  I've observed is the famous mosquito hitter. We have used and throw away many of them, they're cheap and short lived :). The green one here last a month. Most annoying is that the switch of the lamp is on the wrong side, so when you put it on that side, you will unintentionally switch the lamp on, emptying the battery...yes the mosquito's is laughing at  me :)...

Now we got another one, sturdier, better looking and ergonomics, very powerful, until I got that high voltage - low current power right on my leg..I screamed the **** off...yes the mosquito's are laughing even more louder ...sigh...ze power never the same again..absorbed by my leg I think :)

So in one evening with nothing to do, I opened both hitters..1350VDC mylar capacitor?..no wonder :)..
and 2 A3 rechargeable battery...now I know how NOT to buy another hitters...:)...watch out you mosquito's...!!

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