Hello!
I have a project where I propose an alternative pavement that each time someone steps on generates electricity. I have almost achieved that prototype, but now want to measure and show the voltage and current produced each time on a website. I also have an ethernet shield and will figure out how to put the information I get on the site (with help from ChatGPT). Now, what I need is to measure the voltage and the current, where I'm having difficulties. From my research, I understand that current can be measure with a hall sensor - the magnetic field around the cable...? Correct me if I'm wrong. With voltage... I have measured my prototype and it could produce up to 30V each time, if it is pressed fast. I also read that for voltage you'd have to bring it down using a resistor and the mutiply the result with the reversed ratio of the resistor, then measure it using one of Arduino's analog pins (max. 5V). Is there any other easier method? I am not sure if this would precisely measure. I was looking for an external meter to buy, but it seems there aren't such things. Why couldn't some device just measure it, and then send it to Arduino? I found this on AliExpress, but am not sure what's the difference between closed and open CT. Any idea is welcome!
Thanks for helping!
In order to have "current" you must have a load and a completed circuit. IF you know the load resistance and you measure the voltage across the load, you compute the current. That is how almost ALL currents are measured!
So much depends on the length of time the voltage is produced, which you have not told about.
Is that AC or DC voltage. Meaning is it always positive or can it go positive and negative.
Why do you need to measure current?
If the resistance is constant, current is proportional to voltage. Ohm's Law says:
Current = Voltage/Resistance.
(Resistance is "the resistance to current flow".)
If you are using a voltage divider into an Arduino (or multimeter) the load resistance is the sum of the resistors.
An Arduino or multimeter by itself (with no other load resistance) has megohm resistance and almost no current flows.
I am also concerned about the duration if you have something like a piezo sensor that doesn't put-out continuous voltage. The Arduino takes an instantaneous sample or "snapshot" every time you read, so in a loop you might miss a short-term peak. A multimeter is "smoothed" or averaged so you won't get the not get the true peak voltage.
There is a circuit called a Peak Detector (AKA voltage follower) that charges-up a capacitor and holds the peak for some time duration. That's a good way to measure peaks.
I am going to venture a guess here that your sensor is a Piezo Disc Transducer likely similar to these. Yes they can produce a pk to pk waveform of 30 volts or greater. They also produce a waveform going above and below a 0 volt reference. Most micro-controllers like an Arduino ADC will not measure the negative going portion of the waveform and more on target a negative going spike can destroy your ADC. I am sure you have that worked out if in fact you are using a piezo transducer similar to those I linked to. Next the issue of current. Measuring current you will, as mentioned, need a load. Now again the sensors I linked to provide a current in the nano amp region. You can forget about current transformers or hall effect sensors to measure micro amps let alone nano amps.
What sensor were you planning to use and a link to the data sheet(s) would be nice. Same for what ADC you plan to use?
Ron
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