To be honest, my recent simple relay hack wasn’t really all that great. It just used the high power constant current output to drive a SSR. It wasn’t ideal, but it worked. I decided that it was worth the effort to track down some more useful outputs and properly detect the desired state of the bulb.
All it took was a little bit of poking around and probing the pins of the SAM R21 microcontroller with an oscilloscope. It wasn’t actually that hard. On the B22 bayonet fitting version of the bulb I found some.
A teardown of the HP 8620C and HP 86245A by Kerry Wong:
I just picked up an HP 8620C sweep oscillator with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin on eBay. This time around though, the unit does not work. While it was advertised as a working unit I could not get it powered on and there was no sign of life whatsoever. So before I start troubleshooting and repairing the unit, I thought I would do a quick teardown to see what’s inside and if I could spot anything obvious that was out of the ordinary.
I have been working on some games for the ESP32 and needed some decent quality audio with a minimum number of additional components. I was bouncing between using the DAC and using the I2S bus. The DAC requires less external parts, so I went that way. I ended up creating a very simple library for use in he Arduino IDE. (Note: This only works with ESP32)
I got a request, to design and build an electronic metronome. You can find several on the market, but the problem it is ether producing voice or the classical mechanical metronome. The requirement here was a visual effect. To be precise four LEDs for 4/4 beat. It is required for drumming where you have no chance to hear the clicking (or maybe just through headphones).
App note from ON Semiconductor about eFuse or Electronic fuse. Link here (PDF)
The primary function of an Electronic Fuse, or eFuse, is to limit current, the same function provided by any fuse or positive temperature coefficient device (PTC). An eFuse, however, provides this function with much more versatility than either of these devices. An eFuse, unlike a standard fuse, need not be replaced after it functions and eFuses also respond more rapidly than a either a fuse or PTC. eFuses can also limit current in situations in which a traditional fuses and PTCs will not work. This is especially true when voltage is first provided to a circuit, such as during a hot plug operation, when inrush current can be extremely high. This application note will explain the basic operation of an eFuse’s current limit function and explain important eFuse concepts such as Overload and Short Circuit currents, and Kelvin versus Direct connection of the eFuse’s current sense resistor.
App note discussing extended features of NCP12600, NCP12600 is a multi-mode controller for offline power supplies by ON Semiconductor. Link here (PDF)
Beside the novel multi−mode structure it embarks, the NCP12600 packs a lot of features such as an efficient short−circuit protection architecture, a start−up sequence with a slow switching frequency ramp−up, a fast reset when latched and an auto−recovery scheme when line cycle dropout occurs in latched versions. Let’s discover these novelties in the present application note.
So I posted a while back about how I had used these 22mm pcb’s I’d made in prototyping an ematch ignitor system for use in rocketry. Although I made these stackable boards so they would fit inside a popular size of Estes rocket body tube I’m aware that they are quite useful for lots of things. So i’ve open sourced them so anyone can get some made, or add improve or change them.
There are three boards,an Attiny85 board with some power LED and indicator LED, a SOT89 power supply board which could be built up with either a 3.3v or a 5v supply. Finally there is a “kludge” board which is useful for adding in some thru hole components into the system. Some quick pics here but in the files on Git each board is well documented in a pdf. All the dust components are 0805 so super accessible for hand SMD soldering. :)
I recently helped repair the card reader for the Computer History Museum’s vintage IBM 1401 mainframe. In the process, I learned a lot about the archaic but interesting electromechanical systems used in the card reader. Most of the card reader is mechanical, with belts, gears, and clutches controlling the movement of cards through the mechanism. The reader has a small amount of logic, but instead of transistorized circuits, the logic is implemented with electromechanical relays.1 Timing signals are generated by spinning electromechanical cams that generate pulses at the proper rotation angles. This post explains how these different pieces work together, and how a subtle timing problem caused the card reader to fail.