Rainwater Madeira Candle

Posted in Candle Making on January 13, 2011 by themidnightengineer

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Winter Persimmon Wine Candles

Posted in Candle Making on January 13, 2011 by themidnightengineer

Photographic artwork courtesy of “R Elgin” of The Marmot’s Hole.

San Pellegrino Candles

Posted in Candle Making on November 18, 2010 by themidnightengineer

Mysterious Car Battery Drainage Problem Solved

Posted in Auto Maintenance, Electronics on November 10, 2010 by themidnightengineer

As mentioned here, I had a problem where something was draining the juice from the battery in my car. I was able to find out, by troubleshooting the fuse boxes, that it had to do with the stereo system.

Removing the radio unit, however, did not make the problem go away. There was something else that was causing the drain.

After consulting the schematic from my Haynes repair manual and much searching, it turned out to be the stereo component amplifier, a separate unit that was located below the front passenger seat.

The green outline boxes in the photo above shows signs of water stains on the unit.

Opening the unit and inspecting the circuit board inside reveals water damage causing short circuits.

AC/Heater Control Unit LCD Backlight Repair

Posted in Auto Maintenance, Electronics on September 18, 2010 by themidnightengineer

Recently the backlight for the liquid crystal display for my dash-mounted AC/Heater Control Unit stopped working. I disassembled the unit to inspect the innards and discovered that the backlight had been provided by three incandescent lamps soldered on a PCB whose filaments had expired.

These tiny light bulbs were sheathed by translucent green rubber “condoms”. Before I disconnected the PCB from the unit, I measured the open-circuit voltage (~9.7 VDC) across the leads of the bulbs.

I also noted the polarity of the leads using a marker on the PCB. This is because I was planning to replace the bulbs with LEDs. LED is a polarized device, with cathode and anode leads, unlike an incandescent bulb. The polarity of the supply voltage across an LED matters, just like with any diode. I do not know why Toyota never designed this backlight using LED lights in the first place, but being that it is a solid-state device, it is much more reliable and efficient than a filament bulb.

I purchased four 5mm white LEDs from Radio Shack that were selling for $1.99 for a pack of two. These LEDs were rated for a luminosity of 7000mcd. I also bought 270 Ω resistors to be connected in series with the LEDs as current limiters to provide a forward current of 25 mA and a forward voltage of 3.3 VDC.   This link has a useful current limiting resistor calculator for simple LED applications.

The following photo shows one of the bulbs (bottom) extracted from the PCB next to the LED (top).

I soldered the LEDs and the resistors onto the PCB. One lead of the resistor was soldered into the via marked positive. The anode of the LED was soldered into the via marked negative. The cathode lead was fed through the lamp base mount hole and soldered onto the other lead of the resistor for a series connection. I covered the  LED/resistor pair on the right with heat shrink tube to prevent possible short circuiting with an adjacent IC.

This view shows the LEDs on the other side of the PCB after the soldering was completed.

I took the PCB to the car to connect it back to the AC/Heater Control Unit. I turned the ignition half-way to provide power. The LEDs turned on. I could tell they were much brighter than the previous bulbs.

I reassembled the unit and covered the LEDs with the green condoms. This is how the display appears now.

Total cost of this repair job: $5.32

Wine Candle

Posted in Candle Making on September 10, 2010 by themidnightengineer

 

The glass container is a cut wine bottle. The wax was colored with magenta liquid dye at 4 drops per pound. The idea was to make the melted wax look like red wine.

A 15 Year Old Car is like a Woman

Posted in Auto Maintenance, Troubleshooting on August 30, 2010 by themidnightengineer

Two words: high maintenance.

There’s been a vexing problem with my 95 Lexus ES300 ever since I purchased it for $700 in cold hard cash from my friend Taek back in February. The car constantly needed a jump-start. Taek had the battery and alternator replaced but the issue didn’t go away. When the most obvious solution fails, the problem becomes bigger and more mystifying. The battery was replaced two more times, poor quality being the suspect. No dice. The rear trunk latch was faulty and so I fixed that. I also unplugged the lights for the glove compartment and trunk for good measure. I also discovered and repaired a damaged electrical cable harness under the hood. Each of these issues could have had a bearing on the starting problem and each time I thought I had hit upon the root cause. Yet the problem stubbornly remained. Something was draining the charge on the battery. Leaving the car parked for more than 24 hours resulted in a dead battery and ignition failure, requiring a call to AAA to request a jump-start. However, disconnecting the cable from the positive terminal on the battery prevented the drain and served as a temporary fix.

I took the car to the Lexus dealer and explained the situation. They did some tests and told me that I needed to replace the battery. That was singularly unhelpful since I had gone down this route already. I suppose it is possible that three different batteries in a row could all be bad but its highly doubtful.

This weekend I measured the current drain on the battery using my multimeter.

This current draw is equivalent to leaving the car door open (which results in several lights being turned on).

My car has three fuse boxes (two under the hood and one below the steering wheel). To pinpoint which electrical sub-system was causing the drain, I pulled each fuse one by one until I saw the current draw drop to a nominal level.

This is one of the fuse boxes located under the hood. I pulled out the RADIO fuse.

The reading on the multimeter dropped from ~ 0.59 A to ~0.03 A.

So now I know exactly what’s been causing the drain. For now, I will leave that fuse unconnected.

Troubleshooting this car is like playing Whack-A-Mole. You take care of one problem and two or three other problems emerge. Next, I need to figure out why the windshield wiper fluid refuses to spray.