Wednesday, March 27, 2013

Our normally great tasting water tastes bad.

We have a very shallow well with rather slow delivery. In about 1976 we added a underground 1000 gallon water reservoir. I have only inspected this reservoir a couple of times in the ensuing 35 years.  The last time I remember was in 1999 when I was preparing to build a garage and the county, bless their little hearts, insisted I upgrade the septic system and since I was doing that, to upgrade the well system also. Whew, no small task to get the old systems to pass new standards.

Well in the last month the water which normally taste superior was now tasting yucky. I opened the shallow well and visual inspection seemed just fine. So I dumped in some chlorine and washed the walls that I could reach. Then let this rather high concentration on chlorine water reach the reservoir and sit some. The chlorine passed through in a couple weeks but the bad taste remained. Meanwhile we carried our drinking water from our neighbors.

I then uncovered the reservoir lid which is about a foot underground. A visual inspection looked rather good. The water was clear and I could see the bottom easily. There was no water leaking into the tank that I could see. But I did see some contamination, about 0.5 inches round, in the bottom which appeared to maybe be a bug or something. I got a hose working as a siphon and was able to suck this contamination out first thing. Then I went further and let the hose siphon run for 4 hours emptying 2/3 of the tank. I climbed in the tank and used a broom to scrub the reservoir walls and also stir up the maybe 1/8 inch of sand/soil on the bottom making the water very muddy. I then used the house pump along with the siphon to remove most of the rest of the reservoir water. With 1/2 inch of water remaining I used a shop vacuum to remove the remaining water along with any remaining sand/soil.

I then turned on the well pump and started the fill process. Do to the design of the system it is best to let the reservoir fill almost half way before turning on the house pump after the prime is lost. I let the reservoir fill overnight and the following noon was able to turn on the house pump which primed first time. Before I buried the reservoir again I covered the lid with some tarp material which may stop any critter from entering the tank again.

So we lost all water for well 16 hours. Linda did several loads in the washing machine the same day and also we ran the dishwasher. We expect the water to be slightly cloudy for a couple of days and hopefully when all settles out should be back to perfect soft, clear and great tasting water, again.

 The two floats tell the well pump when the reservoir is low and needs water and also when it is full and don't send more water.
The cleaned reservoir.
The lid is under this section of walkway. So this is after all the digging.

Tuesday, March 5, 2013

ABS Brake Sensors Analysis

I saved 3 used ABS brake sensor assemblies cables. One from a BMW which had indicated it was bad. One from Andre’s vehicle as a new ABS sensor was provided when he replaced the left front wheel bearing assembly. The third when Paul replaced his front wheel bearing assembly.

To test these brake sensor assemblies I used a 9 volt power supply and connected the minus lead to a 1,000 ohm resistor then to one of the two leads to the sensor.
The other lead of the sensor I connected to the plus side of the 9 volt supply.

I then placed an oscilloscope across the resistor. By running a screwdriver past the sensor I would get a nice negative pulse on the oscilloscope when connected to the sensor one way and no pulse when connected in the other polarity.

The pulses I observed are shown below.

This all makes good sense as the bad sensor was known by the BMW’s computer fault code to be bad. The two sensors that I could get a pulse from were replaced only because a wheel bearing went bad. (The sensors I suspect are just hall effect sensors.)

The Antilock Brake System (ABS) works something like this, I suppose. For some interesting physics phenomenon, a tire that is sliding has less traction than a tire that is not quite sliding. So if we keep a wheel turning slightly in an emergency brake we can stop sooner than if the wheel is completely stopped. Also one can continue to steer the car. If you are in a complete slide the car will not turn. So enter ABS. Using a thin light cogged disk which is attached to the wheel they place a sensor near the cogs at the outside edge of the disk which senses when each cog rotates past the sensor. At each sense a little pulse is created by the sensor. Now if the wheel is turning the sensor will send out a series of pulses which relates to how fast the wheel is turning.

This string of pulses goes to the computer which does nothing if there are pulses. However if the vehicle is moving and the one wheel’s pulses stop the computer (ABS) interrupts the hydraulic pressure going to the brake caliper at that wheel in a pulsing motion which ensures that wheel continues some spinning which increases traction for faster stopping and also providing some steering control.