Projects

Introduction Sometimes, it is useful to have a circuit implementing a piecewise linear function. For example, I was recently involved in the development of some power cycling instrumentation for automotive MOSFETs, where we needed to measure swings in the VDS of our DUTs from about -5V to +60V. The negative portion of the voltage requires a much higher degree of accuracy than the positive portion. I decided that a nice way to do this would be to split my measurement ADC’s range in 2: positive voltages are divided by 20, and negative voltages are passed through undivided....

Introduction The world of digitally controlled switchmode power supplies has always held a certain allure for me: the idea that you could sample things like output voltage and current, apply some DSP techniques, and then based on that output a gate drive signal in real time, giving you whatever response you want out of your buck/boost converter just seems so… insanely cool. That being said, a lot of times these require a good understanding of the control loop architecture and parameters of switchmode power supplies to be able to properly stabilize, which has proven to be quite the barrier to entry....

Introduction I started off this project when I realised that the official Discovery BNC adapter board has too high an input capacitance to be used with generic scope probes, which usually have a compensation range of 5-35pF ish. Using scope probes is really necessary in some cases where low loading is desireable, since the quoted 1MΩ || 24pF input impedance of the Analog Discovery 3 loads down sensitive analog circuits quite significantly....

Before reading on, please refer to the previous part/MK1 of this project, otherwise some of the stuff here might seem a little odd. Schematic <?xml version="1.0" encoding="UTF-8" standalone="no"?> SVG Image created as AD3 Front End Amplifier-CH1.svg date 2023/12/18 09:48:42 Image generated by Eeschema-SVG C207 C207 1u 1u -2V5 -2V5 1 1 2 2 SW201 SW201 AC/DC AC/DC C203 C203 1u 1u V- V- 2 2 V+ V+ 5 5 1 1 + + 3 3 - - 4 4 U202 U202 C201 C201 10n 10n -2V5 -2V5 +2V5 +2V5 C208 C208 1u 1u R207 R207 402 402 R201 R201 1k 1k R208 R208 22 22 V- V- 2 2 V+ V+ 5 5 1 1 + + 3 3 - - 4 4 U201 U201 D201 D201 R202 R202 1M 1M C205 C205 1u 1u C204 C204 1u 1u R203 R203 100 100 R204 R204 402 402 R206 R206 402 402 +2V5 +2V5 C206 C206 1u 1u R205 R205 22 22 C202 C202 10n 10n 1 1 2 2 J201 J201 CH1 CH1 COM COM 1 1 NO NO 2 2 V- V- 3 3 IN IN 4 4 V+ V+ 5 5 IC201 IC201 TS12A4516DBVR TS12A4516DBVR OUT+ OUT+ OUT- OUT- V+ V+ V+ V+ V- V- U202 U202 V- V- 2 2 V+ V+ 5 5 1 1 + + 3 3 - - 4 4 -2V5 -2V5 SW201 SW201 AC/DC AC/DC 1 1 2 2 -2V5 -2V5 U201 U201 V- V- 2 2 V+ V+ 5 5 1 1 + + 3 3 - - 4 4 C206 C206 1u 1u IC201 IC201 TS12A4516DBVR TS12A4516DBVR COM COM 1 1 NO NO 2 2 V- V- 3 3 IN IN 4 4 V+ V+ 5 5 D201 D201 Check out the design files here Compared to the MK1 design, the gain stage is essentially identical....

The Analog Discovery 3 is a great debugging tool, but as I discovered here in a note on using it with 10x scope probes, the input capacitance was too high for the probes to be compensated correctly. Custom LNA design To combat this, I decided to design an amplifier that would have a low input capacitance so that we fall within the 5-35pF compensation which is typical of these 10x scope probes....

One of the (many) weird quirks of studying in the University of Cambridge is that our terms only last 8 weeks. Yes, the number of days we are officially “studying” is less than the number of days we are ostensibly on “holiday”. Of course, it never works that way, and Cambridge is probably one of the only places where going to uni feels exactly like going to secondary school. Over these long break, we are told that our rooms are going to be used for conference purposes, and that we would have to move all our stuff out to a tiny, cramped storage container....

As part of the Winter Logger project, I got myself some DIP EEPROMs from eBay which were ostensibly AT24C256’s, mostly because I didn’t feel like buying yet more stuff that I probably would never use just to pad out Mouser’s £33 for free shipping minimum order. This is what I got: Suspicious… With all the counterfeit semiconductors floating out there, I wanted to verify if I at least had functional EEPROM that wasn’t literally just plastic with some legs tacked onto it - I wanted to test if all the memory cells actually worked....

This is an attempt to try to get more signal out of dynamic microphones, as I literally have to max out the gain on my Presonus AudioBox iTwo to barely get a usable signal level, and that is with me speaking right on top of the microphone. This design is based on Project 66 by Eliott Sound Products , with some minor modifications, mostly me just playing around to see what are the effects of changing stuff around....

This is not really a “project” in and of itself. Rather it’s a small experiment that me and my buddy Chris ran to investigate two things: Just how well do the figures coming out of the Patch Antenna Calculator that I botched together translate into the real world. How does bending the patch antenna (such as conforming it around a rocket tube) affect its parameters. The antenna itself This antenna was born on a chilly Friday night, in a generic teaching room in Lucy Cavendish College here in Cambridge....

The good, and perhaps bad, thing about passions and hobbies is that the energy to zealously pursue them ebbs and flows as the days, weeks, months or even years go past. Just recently, I experienced a strangely strong desire to just go out there and design something again out of frusration over what we’re “learning” at university, so here we are. Preface: Why LCSC Because DigiKey/Farnell/RS wouldn’t give me free shipping until I spent tonnes of cash, and even then, the VAT here in the UK is just crazy… It’s times like this when I really, really miss being in Malaysia....