At some point I though about building the smallest PCB for a sensor node that I could. Hence, the ZEN was born. The PCB is small enough to fit on a holder of 2 AA batteries. I have only build a few of these. Here is one reading the soil moisture sensor on basil.
App note from OSRAM on High-power LEDs and their special requirements. Link here (PDF)
In general high power emitters can be driven with DC currents in the range of 1 Ampere whereas most low power products like 5 mm Radials are limited to 100 mA.
As the light output increases with driving current the optical power is raised by a factor of ten compared to standard devices. At the same time much less board space is occupied as fewer devices are needed. On the other hand a careful thermal management is absolutely mandatory because the thermal power dissipation is increasing in the same way as the optical output power. To keep the junction temperature of the chip as low as possible a low thermal resistance is needed and the standard FR4-PCB has to be replaced by a metal core PCB. By this a high optical efficiency of the IRED can be achieved.
The approach I took was a mixed signal one where a capable analog front end would be paired up with a beefy DSP processor to compute the Impedance. Most importantly, in this scheme, the DSP is responsible for discriminating the phase between the sampled voltage and current waveforms; this approach is preferred because it leads to good accuracy and calibration stability.
Alexander Weber has a nice build log on his drawbot called Mechpen, that is available on GitHub:
This is Mechpen, my newest drawbot.
The idea was to have a robot arm that could sketch on a rather large surface.
It is a SCARA (Selective Compliance Assembly Robot Arm) robot arm, meaning the robot has a shoulder and an elbow joint and a hand. Mechpen has a reach of 140 cm which means it could sketch up to A0 format.
NXP’s app note on calculating inductor sizes using MC13783 PWM controller as example. Link here (PDF)
The purpose of this application note is to provide a method of choosing the size of the inductors for the optimized switching regulators versus the current consumption of the application. This will allow to optimize the size and the cost of these components.
Clever way of starting-up relays discussed in this app note from Maxim Integrated. Link here
Relays are often used as electrically controlled switches. Unlike transistors, their switch contacts are electrically isolated from the control input. On the other hand, the power dissipation in a relay coil may be unattractive for battery-operated applications. You can lower this dissipation by adding an analog switch that allows the relay to operate at a lower voltage.
USB Morse Keyer is a microcontroller-based auto keyer project with following features:
*USB / straight key / iambic key inputs
*Support for both standalone and USB operating modes
*64-character USB typeahead buffer and 6-character Morse key typeahead buffer
*Support 5, 10, 15 WPM.
*6-page message memory
*1W Audio output
*Audio and PTT output interfaces
*32 character display
White paper from Integrated Device Technology on the emergence of MEMS thermal mass flow sensors. Link here (PDF)
Flow meters represent the instrumentation of flow sensors and are used to measure the amount of flow that passes through them. There are in principal five different flow meter types: velocity flow, positive displacement flow, differential pressure flow, open channel flow, and mass flow. Mass flow meters are one of the dominant types in the market due to their faster response and better accuracy than other flow meters. They can also be effectively miniaturized and manufactured on silicon wafers. The emergence of MEMS has already revolutionized the consumer electronics market for motion, pressure, and other sensors, and similar micro-machining processes are now being adapted to fabricate flow sensors. Flow sensing applications are typically high-mix and low-to-medium volume compared, for example, to motion sensors that have become ubiquitous in hundreds of millions of smartphones. This paper will focus on the emergence of thermally-based MEMS mass flow sensors and how they match up with existing and more traditional flow sensor technologies.
App note from Analog Devices hinting for proper selection of ferrite bead for you applications. Link here (PDF)
An effective method for filtering high frequency power supply noise and cleanly sharing similar supply rails is the use of ferrite beads. A ferrite bead is a passive device that filters high frequency noise energy over a broad frequency range. It becomes resistive over its intended frequency range and dissipates the noise energy in the form of heat. The ferrite bead is connected in series with the power supply rail and is often combined with capacitors to ground on either side of the bead. This forms a low-pass filter network, further reducing the high frequency power supply noise.
The current Espressif documentation integrating with Eclipse are kind of broken and did not work for me (they are changing from make files to use CMake). The good news is that I have found a way to easily integrate the IDF with Eclipse which is documented below. Because I’m using the ESP32 in combination with the NXP Kinetis and SDK, it makes sense to have everything in the MCUXpresso IDE (I’m using the Version 11.0.0).