Is there a particular reason you used copper to make the capacitor? For liquid sensing purposes, is this the best choice, and why? Thanks so much, your videos have been very helpful.
I used copper because I had a roll of thin copper sheet at hand. In this application the material, as long as it is a reasonably good conductor, really doesn't matter. You could use a carbon/graphite film if you wanted.
If you just need a relative capacitance change: A simple Schmidt trigger RC relaxation oscillator with HC14, AC14, or cmos 555 timer have input C's about 5pf (short leads at sensor). Period is directly proportional to C; choose R for whatever is convenient for noise or frequency. 555 timer has fixed hysteresis - HC14, AC14 are slightly dependent on voltage or temperature and manufacturer. { ~ 1-1.4v @ 5 Vs }
I show the 74HCT14 circuit in the next installment (published yesterday). That was the chip I had ordered but hadn't arrived. I also mention the LMC555 (CMOS) timer and the use of analog comparators in that video. Hope I've covered all the bases 😅
@@robertssmorgasbord You can use a diode across the relaxation R to make a duty cycle modulated output. Fix the charge or discharge time - simple AD convertor. You might want to look at TLV3501 5v comparators; adjust the hysteresis for best signal with a couple resistors.
@@jim9930 Thanks for the tips! Depending on the application I would definitely go for such optimization. But in this video series I really just want to demonstrate the principles. Besides, considering my "broomstick" sensor with hook-up wire leads that would be putting lipstick on a pig (broomstick) 😅
@@robertssmorgasbord ~35 years ago, I had to put the lipstick on the pig. Liquid tank for dialysis - copper ribbon on the circumference. 25 years ago, I did another capacitive sensor with two patches on the outside of a dielectric (variable) and used an overlapping patch on the interior to couple the outside plates. We made that one work at about 10pf using charge pumping into a 2N5210 high gain lo noise x-istor. {I = VCF} My boss at the time had built the mic preamps at Bell labs in the 60's under the Atlantic for the sub detection. Just some ideas, have fun!
@@jim9930 Nice challenging project you did there! And I will have fun 😀 However, I guess within the context of this video series I will restrain myself to the basics and what works in principle and what doesn't (equally important). Maybe, some time in the future I'll showcase some real nice chips from TI and AD (capacity range +/-4pF, accuracy 4fF). No need to roll your own nowadays 😅
You can use my Google Drive folder RJM 😅: drive.google.com/drive/folders/18Z8rZJd16rKonHA62jzMaQELdCEdChun?usp=sharing Note that you have to be logged on to Google in your browser (just use the same browser you're watching RUclips in). Regards Robert
@@rene-jeanmercier6517 Hello René-Jean, that board just looks fabulous! Makes we want to by a little CNC router and throw my chemicals away 😅 No, seriously, I do have at least have to look into UV sensitive solder masks. I really need that for an upcoming project. Anyway, I thank you for the files (especially the CPP) and as always, you're very welcome! Best Regards Robert
You're absolutely right! My fault! But please, try yourself to talk consistently over the course of half an hour or so about the capacitance change of a capacitive sensors that is basically just a capacitor 😅
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Is there a particular reason you used copper to make the capacitor? For liquid sensing purposes, is this the best choice, and why? Thanks so much, your videos have been very helpful.
I used copper because I had a roll of thin copper sheet at hand. In this application the material, as long as it is a reasonably good conductor, really doesn't matter. You could use a carbon/graphite film if you wanted.
If you just need a relative capacitance change: A simple Schmidt trigger RC relaxation oscillator with HC14, AC14, or cmos 555 timer have input C's about 5pf (short leads at sensor). Period is directly proportional to C; choose R for whatever is convenient for noise or frequency.
555 timer has fixed hysteresis - HC14, AC14 are slightly dependent on voltage or temperature and manufacturer. { ~ 1-1.4v @ 5 Vs }
I show the 74HCT14 circuit in the next installment (published yesterday). That was the chip I had ordered but hadn't arrived. I also mention the LMC555 (CMOS) timer and the use of analog comparators in that video. Hope I've covered all the bases 😅
@@robertssmorgasbord You can use a diode across the relaxation R to make a duty cycle modulated output. Fix the charge or discharge time - simple AD convertor. You might want to look at TLV3501 5v comparators; adjust the hysteresis for best signal with a couple resistors.
@@jim9930 Thanks for the tips! Depending on the application I would definitely go for such optimization. But in this video series I really just want to demonstrate the principles. Besides, considering my "broomstick" sensor with hook-up wire leads that would be putting lipstick on a pig (broomstick) 😅
@@robertssmorgasbord ~35 years ago, I had to put the lipstick on the pig. Liquid tank for dialysis - copper ribbon on the circumference. 25 years ago, I did another capacitive sensor with two patches on the outside of a dielectric (variable) and used an overlapping patch on the interior to couple the outside plates. We made that one work at about 10pf using charge pumping into a 2N5210 high gain lo noise x-istor. {I = VCF} My boss at the time had built the mic preamps at Bell labs in the 60's under the Atlantic for the sub detection. Just some ideas, have fun!
@@jim9930 Nice challenging project you did there! And I will have fun 😀 However, I guess within the context of this video series I will restrain myself to the basics and what works in principle and what doesn't (equally important). Maybe, some time in the future I'll showcase some real nice chips from TI and AD (capacity range +/-4pF, accuracy 4fF). No need to roll your own nowadays 😅
Hi Robert. I have a file to transmit to you. Do you still have the Dropbox (or an equivalent) that I can used ? Thank you. Regards, RJM
You can use my Google Drive folder RJM 😅: drive.google.com/drive/folders/18Z8rZJd16rKonHA62jzMaQELdCEdChun?usp=sharing
Note that you have to be logged on to Google in your browser (just use the same browser you're watching RUclips in).
Regards Robert
@@robertssmorgasbord Done ! You can pick-up the zip file. Thank you for all. RJM
@@rene-jeanmercier6517 Hello René-Jean, that board just looks fabulous! Makes we want to by a little CNC router and throw my chemicals away 😅 No, seriously, I do have at least have to look into UV sensitive solder masks. I really need that for an upcoming project. Anyway, I thank you for the files (especially the CPP) and as always, you're very welcome! Best Regards Robert
Smørgos :))
😆
Capacitance change not capacity change
Good job Ray, because I was worried we created a new capacitance fluid changer!
You're absolutely right! My fault! But please, try yourself to talk consistently over the course of half an hour or so about the capacitance change of a capacitive sensors that is basically just a capacitor 😅