Harnett Lab

This semester we have four students working for independent study credit.

There are two GE Edison students working on low-power Internet of Things applications:

Juan Espinosa is using Estimote Bluetooth Low Energy beacons (a) to develop a location-based iOS app, with the goal of setting an alarm when an item (or person) wanders off.

Laura Artunduaga is investigating MQTT for sending sensor data to a database over Wi-Fi, using a Raspberry Pi (b). She attended the recent Wi-Fi workshop at LVL1 and is looking at Adafruit as a place to store sensor data for her experiments. She is also evaluating how the low-power MQTT method applies to secure health sensor data.

Troy Kremer, the ECE 412 (Embedded Systems) TA, continues his work on serial interfacing for the A3BU microcontroller (c) that we use in class.

And Amer Beharic is investigating 3D printing on soft materials, and is also putting together a delta 3D printer (d). The most appealing feature of the delta printer for our group is that the printed object does not have to move during printing. This means you could potentially print on a giant roll of material, one section at a time.

Often in electronics you hear about parasitic capacitance, an unintended side effect.

But the purple-and-gold circuit above is a deliberately parasitic circuit board that can tap into another circuit and extract power for itself. The most important thing is that the parasite not kill the host by shorting out its wires. The parasite board has a lot of small contacts (1mm brass beads), and each has components to prevent current flowing in the wrong direction. As a result, you can power the circuit if there is a sufficient voltage difference on any two contacts, and you need not know which ones ahead of time. In the picture below, the parasite is tapping into a powered electronic textile circuit.

The board picks up enough power from the underlying live circuit to run its LED. (The green cable is measuring the voltage, and the orange one just plugs the LED into the circuit). No special effort was made to align things. This basic version is kind of like a stethoscope for the textile circuit. With power acquired, and with an onboard microcontroller, the parasite could start scanning all its contacts for interesting signals, maybe eavesdrop on the textile circuit or configure itself to talk with another parasite. If the parasite could patch a hole in the underlying circuit by carrying signals across, it could even give some payback instead of just being a vampire.

However, for this 7×7 design, there are 200 parts (including those contacts). Diodes and resistors are hidden between two small boards. More construction photos below!

Continue reading “Parasitic circuit taps into power”

We are integrating fibers with 3D prints, laser-cut materials and other mechanical parts that aren’t traditionally mixed with soft materials. Here are some 1×1 cm laser-cut tiles sewn together with an embroidery machine to make flexible hinges. Shrinking thread locks the final design in a 3D shape. This consumer embroidery machine required some custom alignment software to line up the needle with the 0.7 mm laser-cut holes so it could stitch at top speed without hitting the plastic part.