My contribution to the increasing entropy, and eventual heat death of the universe
Archive for the ‘Uncategorized’ Category.
These notes are for use in the Cracklebox building workshop.
Soldering isn’t very hard but there are a few things to keep in mind:
The main components are shown below to help you identify them:
Forrest Mims is somewhat famous for using LEDs as light sensors. I wanted to try this myself:
It seems to work reasonably well with a transimpedance amplifier and a 100M feedback resistor. I was using the LED from a torch (as it was the only clear LED I had to hand). The response time was surprisingly slow. I kind of wonder if the torch LED module has a decoupling cap in it (and also a current limiting resistor) so I’ll try this experiment again when I have some proper LEDs…
Today I was playing with an Electret mic, salvaged from a bluetooth handsfree kit. I’ve not used a Electret mic before so it’s operation/preamp was of interest to me. It seems that most of these mics now include a single JFET common source amplifer in the mic can itself. As such they just need a single resistor and some biasing and they’re ready to go. The pic above shows the Mic internals.
In the video below I play with the Mic a bit and run a tone generator against the mic and show an FFT on my scope. A fun 5 minute project if nothing else…
Today I’ve been playing with Photodiodes and transimpedance amplifiers. The video below describes the circuit I’ve been playing with:
It’s a very straight forward TIA circuit using an LM741. The 741 is almost certainly not a good opamp for this application, but it seems to work reasonably well here. I also laid out 9 photodiodes on a board using a similar circuit. When I come to build them up I may not use the 741, but another opamp with a similar pinout (possibly FET input). The basic TIA circuit and the build is shown below.
Kicad files/Gerbers: photodiode.tar
My name is Nava Whiteford. I’ve worked for a few sequencing companies. I have equity in a few sequencing companies based on my previous employment (I try to be unbiased in my posts). You can contact me at: [email protected]
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