Hi everyone,

Months ago I've posted some doubts about my master thesis related to piezo sensor.

I've solved the issues and tried experimenting with weight on the piezo and hardware and software part works good.

Now as next step I have to integrate an ADC which I found to be good the ads1220 (for sampling frequency and to have good discretization 24bit); I'm implementing it but I wan't some help from you to know if what I'm doing is good or not, because right now I don't have the ads yet in my storage.

This is the circuit I've designed but Idk if it works. the part That I've tested has only the charge to voltage directly read by arduino.

Another question that I have is: my final load will be high (10 tons or more) and as my charge to voltage is right now, the voltage generated will be very high. I read that to get a lower V I need to use an higher capacitor

Here is my calculation: d33=21pC/N; Fmax around12000kg*9,81m/s^2; Vout max that I can manage is 5V.
Qmax=d33*Fmax=2575micro C
C2=Qmax/Vout(max=5V)=515nF
R2=tau/C2= around 120kOhm (tau has been calculated knowing that L of my piezo is 5cm; Velocity is 30km/h-> around 6ms; multiplied by 10 to have some delays)

 

Quick question: are you trying to measure static loads or dynamic loads? If the former, a piezo sensor is not going to work.

 

First question: Is the piezo device adequate for that amount of force?? Next question: Is it linear to that force level??
And a consideration is about the maximum input voltage that the LT1366 amplifier can accept.

 

Quick question: are you trying to measure static loads or dynamic loads? If the former, a piezo sensor is not going to work.

Dynamic loads

 

First question: Is the piezo device adequate for that amount of force?? Next question: Is it linear to that force level??
And a consideration is about the maximum input voltage that the LT1366 amplifier can accept.

for that question i haven't actually an answer; how may I know the input voltage? I mean, from mine piezo (PVDF TrFE, 5cmx5cmx300um) I got my q, the LT is used as a charge to voltage; how may i know if it will work correctly under this load? thanks.

Anyway, the pcb scheme is ok? I mean, all the connector are in the right place as they should be? thanks

 

I do not see any capacitors between the regulated power circuit and the power circuit "ground. Nor do I see any connections between either IC and the actual power ground connection. I do see rather confusing "ground" connections relative to DC supply bypass capacitors. And if I see it as confusing, certainly the PCB autorouter will be confused. Thus I am suggestion reconsideration of the digital portion of the negative return circuit, both bypass capacitor connections and actual power return connections.

 

I do not see any capacitors between the regulated power circuit and the power circuit "ground. Nor do I see any connections between either IC and the actual power ground connection. I do see rather confusing "ground" connections relative to DC supply bypass capacitors. And if I see it as confusing, certainly the PCB autorouter will be confused. Thus I am suggestion reconsideration of the digital portion of the negative return circuit, both bypass capacitor connections and actual power return connections.

In my calculus I should use C2= 600nF to have something lower than 5V for the LT1366 (calculus posted in the first thread), so for this the OpAmp should work well, right?
I'm not really into electronics, can you tell me where should i put capacitor and saying if that's for stability or what else?
Thanks