Tuesday, August 30, 2011

Camper Trailer LED Conversion

My parents recently got a camper, which was a huge step up from a tent and considerably better than the cramped tent trailer from my childhood. One issue for myself was the lighting, almost all campers still use 12 volt incandescent bulbs, they bathe everything in a terrible orange glow and either are too dim or have a pathetic lamp life of less than 200 hours.

This simply would not do, my parents did not use the campers lights simply because the damn lights got too hot and melted the polycarbonate dome causing it to sag. They used too high a wattage bulbs but the ones that were rated for the fixture you could not even read by.

A quick bit of searching and i found appropriately sized cool white 108 lumen 12 volt led panels, they took forever to arrive but a a price of 2 dollars apiece on a bulk order in november i would not expect them to arrive any time soon anyways.

Considering the life expectancy of leds drops quite a bit at higher temperatures and that the panel would be enclosed i decided to add a heatsink. Mounting the lights ended up being easier, i simply broke the the glass and soldered the panel directly onto the wire that held the filament. The result was alot sturdier than i thought it would be and required no modification to the fixture. The heatsink was attached using some silicone thermal glue.

The result was impressive, the light given off was much better than the original bulbs. A much better brighter white light. The leds get around 35c after being left on for an hour... considering that they will not be under continuous use and will only be used seasonally i would expect them to last the life of the camper.

A few of the led panels exhibit problems when they heat up

Saturday, August 13, 2011

Crazy Analog Memory

Sadly i recently had to dismember my ancient Tektronics Analog scope, it happened to be manufactured in 1967 and was the first analog storage scope commercially available from Tektronics

Channel one was toast and the tube was quite slow but it did its job for a year after i pulled it from a dumpster along with a few hundred pounds of industrial equipment.

It will be missed, although it has been replaced with a much faster and considerably smaller analog scope and a function generator. I stripped it for parts and scrap aluminum simply because i am moving in a few weeks and could not find a home for it. Lots of dials, switches, tubes, germanium diodes and whatnot inside but there was something that made absolutely no sense, a heavily shielded cable about 2 meters long stuffed inside of a shielded box labeled danger high voltage. It has 2 enameled wires inside tightly wound around a plastic core, i worked out that each wire had to be several kilometers long.

After some pondering i concluded that this had to be what was used for the storage component of the scope. It simply used the length of the cable to provide sufficient delay followed by amplifying the signal and feeding it back into the other end, an analog version of delay line memory.

Friday, August 12, 2011

POV Clock

I found an interesting persistence of vision clock for a few dollars at a local thrift shop

Its a simple 8 led array on a thin piece of pcb held up by a spring with a magnet, a large coil pulls the array forward and the spring does the rest of the work, the base is a nice polished piece of aluminum... when running there is a surprising amount of rocking force so a heavy base makes sense


Other than showing the time there are a number of annoying messages, looks to be an easy thing to hack

It is controlled by an old Atmel AT87F52 microcontroller, an LM339 comparator for the break beam sensor (i think), 74hct244 to drive the leds and a 2k eeprom to store custom messages. A ksp2907 transistor drives the coil. I would like to replace the mcu with something more modern, with a proper RTC and communication, adding RSS feed capabilities and maybe changing the led color

Wednesday, August 10, 2011

Solder Pot

I recently acquired a cheap 200 watt solder pot to speed up disassembling old electronics, it took 600 grams of solder to fill... its quite deep, i might consider stretching the amount of solder using steel ball bearings if if have to refill it.

The element is regulated by a simple triac circuit, there is nothing to stop it from overheating and no real way to precisely control the temperature, also the base is small and the entire thing is top heavy when filled. After the solder is completely filled i turn it down almost as it can get, anything higher causes the solder to rapidly oxidize.

After an hour of messing around with it im pretty happy with the results, and i have a good future project of building a digital temperature control and a larger sturdier base, the electronics are currently right beside the element and will most definitely fail rather quickly if i let the thing overheat.