My contribution to the increasing entropy, and eventual heat death of the universe
The previous revision of the AD5791 board worked well, however after reading this analog whitepaper on the ad5791 I decided to change the routing. I split out the ground planes so the board is more clearly divided into analogue and digital sections now. I really need to figure out how to correctly measure the noise on the output, but at some point it would be useful to benchmark the designs for noise. As always Kicad files and gerbers are linked below:
Files: ad5791rev4.tar
It’s 3am what better time to fiddle around with photodiodes! I received the photodiode array boards today and decided to have a quick play around. With a 10M feedback resistor they’re only outputting about a volt, this will work but the OpAmps have 12v rails so I might change the feedback resistor at some point. Too quickly test the board I soldered 4 of the Opamps in and wired the output directly to some LEDs, later I’ll look at acquisition options, including the 8 channel ADC board I’ve made. For a demo and some rambling see the video below:
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…
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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