random thoughts of an engineer

 As promised this is update to last post about our PCB holders. Technical difficulties It turns out that if I want tapped hole every 10mm that's a lot of tapping. Additionally tapping steel is quite hard, especially with such small tap. Most companies decided that they don't want to do such job, one that agreed is research institution so I guess they're used to nontrivial requirements. After some negotiations we got price of almost 5k euro for 300x300mm sheet. That's a bit too much for this project. Required changes My changing steel to aluminum and moving holes onto 15x15 grid we considerably reduced required engineering time. After initial testing it turned out that 15x15 hole spacing is more than sufficient, but swapping to aluminum means magnetic mounts are no longer an option. I guess it's low price to pay to reduce manufacturing cost to 740 euros. plates when they first arrived in our lab   Designed mounts We designed few mounts for plates to mount things on t...

 Today's post will be quick one. I got too irritated by all PCB clamps that don't all work all too wall so I decided to make my own! Inspiration came mostly from optical tables we use all around our labs. I decided to make thin, heavy base plate with M3 holes every 10mm and adapters to be able to mount support wherever I want. The design looks like this: quick render of design Before commiting to expensive and long process of getting them milled from steel plate I decided to make sure that it's as useful as I think. For that I 3d printed prototype out of PLA. I wanted to make it out of black PLA but part way through filament ended and I had to quickly switch to orange. This is how it looks assembled: PCB mounted for soldering everything prepared for mounting PCB It make look more complex than usual clamps to use but keep in mind that if board has screws on 10mm raster then spacers can be screwed directly into base plate. Additionally thanks to modular design boards can be m...

 So what this story is about? Qpass is a method of measuring weight of small mass by depositing it on quartz resonator and measuring changes in electrical properties. Most common are frequency and Q factor changes. Of course because it's sensitive method and requires disposable quartz resonators it's used mostly for very sensitive measurements, hence detected deviation values are very small too, often at the order of sub ppm. Typical solutions Most modern commercial solutions use frequency scanning, building frequency or frequency and phase response and searching for peaks and 3dB width. There're few problems with that solution. For once it requires very dense scanning to make sure you find basic mode and not spurious ones. Phase measurements help in finding "missed" resonances but requires more complex analog frontend. Big upside of this method is that one finds interesting mode they can just scan very small range to track Q and resonant frequency. Another someti...

 What now? I know that dye dies proportionally to pumping power levels, I also know that chlorophyll, like all dyes, has triplet level that "steals" possible molecules. First one rules out high pumping power densities, second rules out continuous wave pumping. Knowing that I can't really make it work in my workshop due to lack of any pulsed laser for pumping. Consequently  I decided to again contact universities for help.  Act one - Warsaw University of Technology I started by contacting my professor at Warsaw University of technology. He was very eager to try it out, he even found some old master's degree work of his student that was coumarin laser. Basic plan was to try aligning it first using well established laser dye and when system will be up and running then swap dye for chlorophyll.  laser resonator On the picture you can see laser, as left by master's student 10 years ago, just after cleaning. For pumping we used OPO pumped with 3rd harmonic of pulsed Nd:...

THR power supply board   Time travel Let's jump into a timeline a little bit. Before I finish writing about all of my adventures while designing this system I'd like to write about its final form, the one, that is hitting the market right now. Quick start guide Many people probably landed here just to use their board or to judge how hard it is to use them, So here is a simple a guide on how to set up your new THR: Mount the board either on a test bench or in a case. If the mounting is to be permanent consider the thermal requirements first. Connect your power supply to the two-pin connector. Don't search for polarity markings, there aren't any, but the board is reverse polarity protected so if it doesn't work just try to reverse the  connection (just in case - is closer to the edge, + is closer to the capacitor). Make sure that all 3 LEDs are lit up. If neither is lit probably there's a problem with the input power. If some are working and some are not or only b...