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.
I’ve been playing with a Scientifica Patchstar. The Patchstar is a patchclamp manipulator. It has a claimed electronic resolution of 20nm which is pretty impressive but I think that’s just the step size.
Unfortunately I don’t have the driver, and a new one would cost about 1500USD. However it appears to just use bipolar steppers and operates with an Arduino and a Easydriver quite easily. From the travel I get from the EasyDriver it looks like it would need to use 256 microstepping. I’ve purchased some drivers to try this out at some point.
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]
RSS