Build fun circuits! Impress your friends! (Or at least the ones who aren’t in-the-know 😉 )
With some inspiration from The Fifth Element and Iron Man, here’s a voice-activated light switch that provides the illusion of a more advanced artificial intelligence, with the simplicity of “the clapper”.
I’ve gotten a lot of questions on the blog about the new version of the MHS5200A function generators available on eBay. Viewer Tolga was kind enough to send one in to me to review and tear down. Although some improvements have been made over the older models, there are some concerning issues with these new models too!
Ever tried searching through your datasheets for the motional parameters of that quartz crystal you just bought? Good luck! Vendors simply don’t specify these parameters to general end users, and for most applications that’s OK. But for high Q oscillator and filter design, measuring and matching crystals can be important.
This video discusses crystal motional parameters, how to measure them with a crystal impedance meter, and finally examines the measured values of 150+ real world crystals.
Below are some interesting correlations/statistics gathered from the measured data; raw measurement data is available here.
Average C0 capacitance for each crystal holder type
Average motional resistance vs frequency
Average motional inductance vs frequency
Average unloaded Q vs frequency
Average unloaded Q for each crystal holder type
Unloaded Q of glass-sealed crystals vs average unloaded Q
Overall statistical analysis of unloaded crystal Qs
References and additional reading:
Crystal motional parameters and relevant equations
The LCD in my beloved HP 5385A frequency counter (with the OCXO option, naturally) has been gradually deteriorating, and it was high time I replaced it:
The HP5385A’s failing LCD
Of course it’s not a standard HD44780 LCD, but a custom branded HP part (#5061-5212, revision A).
Luckily, I was able to salvage a replacement from an HP 6622A power supply front panel off ebay. The front panel cost about 1/3 of what I paid for the HP 5385A in the first place, but it’s a great frequency counter, so it was well worth the investment.
My main bench multimeter is an HP3466A that I found at a hamfest a couple years ago. Mind you it’s older than I am, but it looked to be in good functional order, and $30 seemed like a fair price for a 4.5 digit bench meter, so I picked it up.
After a while though, I noticed that its DC voltage readings seemed to be low when probing circuits containing larger resistances; anything around 100K ohms caused a noticeable discrepancy in the expected voltage reading, and it worsened with larger resistances.