Hand soldering BGA wafer chips

hand-soldering-bga-chips

And here we’ve been complaining about Flat Pack No-Lead chips when this guy is prototyping with Ball Grid Array in a Wafer-Level Chip Scale Package (WLCSP). Haven’t heard that acronym before? Neither had we. It means you get the silicon wafer without a plastic housing in order to save space in your design. Want to use that on a breadboard. You’re crazy!

Eh, that’s just a knee jerk reaction. The wafer-level isn’t that unorthodox as far as manufacturing goes. It’s something like chip on board electronics which have that black blob of epoxy sealing them after the connections are made. This image shows those connections which use magnet wire on a DIP breakout board. [Jason] used epoxy to glue the wafer down before grabbing his iron. It took 90 minutes to solder the nine connections, but his second attempt cut that process down to just 20. After a round of testing he used more epoxy to completely encase the chip and wires.

It works for parts with low pin-counts. But add one row/column and you’re talking about making sixteen perfect connections instead of just nine.

Salvaging Lithium cells and circuits

salvaging-lithium-cells-and-circuits

Lithium cells outperform Nickel Cadmium and Nickel Metal Hydride in almost every way. But they also need a little bit more babysitting to get the most out of them. That comes in the form of control circuitry that charges them correctly and won’t let them get below a certain voltage threshold during discharge. We enjoyed reading about [Carlos'] Lithium cell salvage efforts as it discusses these concerns.

He wanted to salvage a Lithium power source for his projects. He had the three cell pack from a dead Macbook Pro seen in the upper left, as well as the single blown cell from a digital picture frame shown on the right. The three-pack didn’t monitor each cell individually, so the death of one borked the entire battery. He desoldered them and probed their voltage level to find one that was still usable. To prevent his project from draining the source below the 2.7V mark he scavenged that circuit board from the digital picture frame. A bit of testing and the system is up and running in a different piece of hardware.

Don’t be afraid of this stuff. If you learn the basics it’ll be easy to use these powerful batteries in your projects. For more background check out this charging tutorial.

Replace your project power supplies with recycled Li-Ion cells and a switching regulator

buck-regulator

[Dr. Iguana's] experience moving from projects powered by disposable Alkaline cells and linear regulators to recycled Lithium Ion cells using the buck regulators seen above might serve as an inspiration to make the transition in your own projects.

The recycled cells he’s talking about are pulled out of larger battery packs. As we’ve seen in the past, dead battery packs for rechargeable tools, laptops, etc., are often plagued by a few bad apples. A small number of dead cells can bork the entire battery even though many perfectly usable cells remain. Once he decided to make the switch it was time to consider power regulation. He first looked at whether to use the cells in parallel or series. Parallel are easier to charge, but boosting the voltage to the desired level ends up costing more. He decided to go with cells in series, which can be regulated with the a less expensive buck converter. In this case he made a board for the RT8289 chip. The drawback of this method requires that you monitor each cell individually during charging to ensure you don’t have the same problem that killed the battery from which you pulled these good cells.

Hall effect limit switches for a 3D printer

hall-effect-limit-switches

We’re used to thinking of limit switches as a mechanical device that cuts the motor connection before physical damage can occur. [Anthony] decided to try a different route with this project. He built this set of no-contact limit switches using a hall effect sensor. The small black package sticking out past the end of the protoboard is the sensor. It is used to detect a magnetic field.

[Anthony] chose to use an Allegro A3144 sensor. Apparently it is no longer in production but was easy to find for a song and dance on eBay. When thinking about the design he decided to add two LED indicators, one lights when the switch is open and the other when it has been tripped. This would have been easy to do with just one LED, but he needed to add more parts to get both working. In the lower left corner of the protoboard you can see the configurable gate device (74LVC1G58) he added to monitor the hall effect sensor and switch the output and LEDs accordingly.

DIY $6 serial cable for vintage Apple QuickTake cameras

diy-serial-cable-for-vintage-apple-cameras

Knowing he was a guy who liked electronics and taking things apart, one of [Erik]‘s friends sent him a vintage Apple QuickTake 100/150 digital camera as a bit of a joke. [Erik] enjoyed the gift, but since his friend hadn’t sent the necessary serial cable he really couldn’t do that much with it. He searched online only to discover the cable is very difficult to find these days, and thus very expensive. So, being the handy guy he is, he built his own.

Starting with an Apple MiniDin8 Male cable, he cut off one end and attached the wiring to a RJ45 connector. That got plugged into a modular adapter with a DB9 Female Plug end and wired up. The procedure required no soldering, and cost less than $6. Awesome.

Unfortunately the lack of serial cable isn’t the only problem he faced. QuickTake isn’t compatible with newer Apple computers that use Intel. You have to either have a much older Mac, or use a Windows XP emulator. If that wasn’t bad enough, the cameras only want to save photos in QuickTake file format. Luckily, [Erik] documents how he overcome all these issues in his post.

[Thanks Erik]

Non-resettable thermal fuse teardown

non-resettable-thermal-fuse

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.

[Read more...]

Tracking a car like it were a computer mouse

optical-mouse-sensor-tracks-vehicle-motion

This is [Paul Mandel's] Ground-truth velocity sensor. That’s a fancy name for a device which tracks the movement of a vehicle by actually monitoring the ground its travelling over. This differs from simply measuring wheel rotation (which is how traditional odometers work) in that those systems are an indirect measurement of motion. For us the interesting part is the use of an ADNS-3080 single-chip optical mouse sensor on the left. It’s cheap, accurate, and only needs to be ruggedized before being strapped to the bottom of a car.

[Paul] designed a case that would protect the electronics and allow the sensor to mount on the uneven underbelly of a vehicle. The optical chip needs to be paired with a lens, and he went with one that cost about ten times as much as the sensor. Data is fed from the sensor to the main system controller using the PIC 18F2221. One little nugget that we learned from this project is to poll a register that always returns a default value as a sanity check. If you don’t get the expected value back it signals a communications problem, an important test for hardware going into the vibration-hell that is automotive technology.

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