[Fran] has been researching the Saturn V Launch Vehicle Digital Computer – the computer that flew all the Apollo flights into orbit and onwards towards the moon – for a while now. Even though she’s prodded parts of the LVDC with x-rays and multimeters, this is the first time she’s committed to a little destructive testing.
After [Fran] took a flight-ready LVDC spare to the dentist’s office for x-raying and did an amazing amount of research on this artifact from the digital past, there was only so much she could learn without prying apart a few of these small, strange chip packages. Not wanting to destroy her vintage LVDC board, she somehow found another LVDC board for destructive reverse engineering.
This new circuit board was a bit different from the piece in her collection. Instead of the chip leads being soldered, these were welded on, much to the chagrin of [Fran] and her desoldering attempts. After removing one of these chips from the board, she discovered they were potted making any visual inspection a little difficult.
While [Fran]’s attempts at reverse engineering the computer for a Saturn V were a bit unsuccessful, we’ve got to hand it to her for getting this far; it’s very, very likely the tech behind the LVDC was descended from ICBMs and would thus be classified. Documenting the other computer used in every Apollo launch is an impressive feat on its own, and reverse engineering it from actual hardware, well, we can’t think of anything cooler.
[Ben Krasnow] is back, and this time he’s tearing down a kilowatt hour meter (kWh). While not as exciting as making aerogel at home, or a DIY scanning electron microscope, [Ben’s] usual understated style of explaining things makes a complex topic simple to digest.
These old mechanical meters have been a staple on the sides of houses and businesses since the dawn of commercial power. We always thought the meters were a basic electric motor. Based upon [Ben’s] explanation though, these meters are a complex dance of electromagnetic fields. Three coils create magnetic fields near an aluminum disk. This creates eddy currents in the disk resulting in a net torque. The disk spins, turning a clockwork and advancing the dials.
Why three coils? One is a high turn high gauge voltage coil, and the other two are low turn low gauge current coils. The voltage coil has to be phase shifted 90 degrees to create the proper torque on the disk. Confused yet? Watch the video! [Ben] does a much better job explaining the field interactions than we could ever do in text.
Continue reading “[Ben Krasnow] Explains Kilowatt Hour Meters”
There are loads of Internet content depicting the usefulness of salvaged innards found in defunct microwave ovens. [Mads Nielsen] is an emerging new vblogger with promising filming skills and intriguing beginner electronics content. He doesn’t bring anything new from the microwave oven to the dinner table, yet this video should be considered a primer for anybody looking to salvage components for their hobby bench. To save some time you can link in at the 5 minute mark when the feast of parts is laid out on the table. The multitude of good usable parts in these microwave ovens rolling out on curbsides, in dumpsters, and cheap at yard sales all over the country is staggering and mostly free for the picking.
The harvest here was: micro switches, X and Y rated mains capacitors, 8 amp fuse, timer control with bell and switches, slow turn geared synchronous 4 watt motor 5 rpm, high voltage capacitor marked 2100 W VAC 0.95 uF, special diodes which aren’t so useful in hobby electronics, light bulb, common mode choke, 20 watt 68 Ohm ceramic wire-wound resistor, AC fan motor with fan and thermostat cutout switches NT101 (normally closed).
All this can be salvaged and more if you find newer discarded units. Our summary continues after the break where you can also watch the video where [Mads] flashes each treasure. His trinkets are rated at 220 V but if you live in a 110 V country such components will be rated for 110 V.
Continue reading “One man’s microwave oven is another man’s hobby electronics store”
This project definitely was a patience tester. As the control system of the Helsinki metro was (and still is) under big renovation, [Konsta] could buy three old information displays for a very cheap price (5€ each). However, these displays came with no information whatsoever about the way to drive them, thus starting a long reverse-engineering journey.
[Konsta] started by taking one apart, discovering that each side of the display was composed of 10 daisy-chained LCD screens and some kind of control box. As you may have guessed, the key to reverse engineering the display was studying the contents of this box. It turned out that the control electronics were composed of an 8085 CPU, some RAM, a peripheral I/O chip, an UV-erasable EPROM chip (containing 32KB of program memory) and an EEPROM.
[Konsta] used an AVR to dump the memory contents of the two latter chips and it was at this part of the project that the Helsinki Hacklab joined in. Together, they reverse engineered the control PCB, studied the assembler code, sniffed the different on-board buses to fully understand how the display could be controlled.
We strongly recommend reading [Konsta]’s writeup, especially knowing that he made this english page just for us!
We don’t know how [Ben Krasnow] gets his hands on so much cool hardware. This time around is a bit of vintage tech: a thermocouple vacuum gauge.
The part seen above, and represented in the schematic, is the sensor side of things. This is interesting enough by itself. It has an air chamber with an electric heater element in it. When air is present it dissipates the heat, when under vacuum the heat builds and causes the thermocouple to generate some voltage on its connections.
Keep watching his presentation and things get a lot more interesting. The original unit used to measure the sensor is a throwback to the days when everything had sharp corners and if you were running with scissors you’d eventually teach yourself why that’s not such a good idea. The designers were rather cavalier with the presence of mains voltage, as it is barely separated from connections grounding the case itself.
Want to see some of the other cool equipment he’s got on hand? How about a CT scanner he built.
Continue reading “Thermocouple vacuum gauge teardown”
[Angus Gratton] recently cracked open a pair of USB to Ethernet converters to see what’s inside. One was an Apple branded device, the other a no-name from eBay. The former rings in at $30, with the latter just $4. This type of comparison is one of our favorites. It’s especially interesting with Apple products as they are known for solid hardware choices and the knock-offs are equally infamous for shoddy imitations.
From the outside both devices look about the same. The internal differences start right away with a whole-board metal shield on the Apple dongle and none on the off-brand. But the hardware inside is actually quite similar. There’s an RJ-45 jack on the left, followed by the Ethernet isolation chip next to it. From there we start to see differences. The off-brand had a blank chip where Apple’s ASIX AX88772ALF USB to Ethernet bridge controller is located. There is also a difference with the clock; Apple is using two crystals with the other using just one.
This component is a one-shot thermal fuse. When the body rises above the specified temperature the two leads stop conducting. They’re useful in applications like motors, where you want to make sure power is cut to an overheating piece of hardware before permanent damage happens. They’re pretty simple, but we still enjoyed taking a look inside thanks to [Fatkuh’s] video.
The metal housing is lined with a ceramic insulator, which you can see sticking out one end in the shape of a cone. It surrounds a spring which connects to both leads and is under a bit of tension. The alloy making the connections has a low melting point — in this case it’s about 70 C — which will melt, allowing the spring to pull away and break the connection. In the clip after the break [Fatkuh] uses his soldering iron to heat the housing past the melting point, tripping the fuse. He then cracks the ceramic cone to show what’s inside.
The only problem with using a fuse like this one is you’ll need to solder in a new component if it’s ever tripped. For applications where you need a fuse that protects against over current (rather than heat) a resettable polyfuse is the way to go.
Continue reading “Non-resettable thermal fuse teardown”