- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Intefacing Piezo sensor with PSoc4, I successfully tested a simple charge mode amplifier for it.
My Problem is that my project maybe need to use number of sensors, maybe up to 16.
If I keep use the charge mode amplifier, that means I need 16 op-amps, but PSoc4 provide just 2 op-amps,
How can I resolve this problem.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
You could multiplex your input-signals to one OpAmp. this would take a reasonable time to stabilize, but you did not tell yet how much the frequency of the signals is. Wouldn't be too bad, when you tell us a bit more about what you want to perform.
Bob
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
If you mux a charge mode amp, since its corner frequency usually quite
low, there are very long settling times. Google "charge mode amplifier",
there are quite a few hits, TI, LTC, AD all have ap notes.
So take this into consideration.
Regards, Dana.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
thanks all.
If I mux multiple piezo sensors to single op-amp, I think I should wait the state of the charge amp discharged.
Can I use a swich ( instead of feedback resistor ) to instantly discharge feedback capacitor to reduce discharge time ?
Does PSoC provide the switch function? or Can I implement it with a discrete device outside of PSoC.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
You can program io-pins on the fly to be Hi-Z or connected to gnd, so this is like a switch as you need it. Beware of the restricted pin-routing capabilities of a PSoC4, so have all your IO's ready and working before you start to manufacure your pcb.
Bob
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Yes by using an open drain output to ground cap or
use an internal mux terminated in Vss. The former
approach has a much lower switch R than a mux.
So tradeoff is
open drain mux
lower Rdson higher Rdson
higher discharge spike lower discharge spike
shorter discharge time longer discharge time
Regards, Dana.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hi!
I am trying to interface piezo sensors too.
Can you please shate with me the ampifier circuit? and the code?
Did the "muxing" worked?
Thanks!!!
Anna
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
If you google something like "single supply opamp microphone circuits" you get
quite a few hits.
One collection of circuits - www.circuitlab.com/browse/by-tag/microphone/
Regards, Dana.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hi Piona.
Unfortunately, I stopped my project for interfacing multi-piezo sensors.
but if you have any question, I would like to be your help.
thanks.
kkadin.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hi kkadin!
Thanks for your want to help:)
I am trying to interface piezo disk to psoc 3 . I built an amplifier that works great but when I am inputing a piezo it behaves strange. I am aware to the specs of the piezo and had learn ( a lot of google) that the best interface is charge amp with big resistanse load. I saw you made one:)
Just want to see 🙂
If you can please attache the schematics or tel me how you bias the "big resistance load"
Thanks!
Piona
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Piona, on the other thread I did another config, using a Piezo, got ~ 1 V pk-pk
out if it.
Regards, Dana.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hi Piona
unfortunately again, I cannot upload the files because my company is monitoring network..
but I think following information would be helpfull.
* for charge mode amp
Rf (Feedback R) : 10 MOhm
Cf (Feedback C) : 0.05 uF
opamp reference voltage : Vcc/2
vout = -Q/Cf + Vcc/2
Q : charge generated from sensor, I tested a pvdf film so your piezo disk needs another Cf
Time constant : Rf*Cf, so you need to change Rf again
* reference link ( chapter 3.2 )
Signal Conditioning Piezoelectric Sensors from TI