Hello everybody, I need help. I’m a total beginner in electronics and arduino and I working on a project aimed to get de strain of multiple part of a rocket structure.
I was thinking to mesure the strain of the différents with multiple strains gauges and to connect each strain gauge to an Hx711 amplifier. But after that I’m lost… if I use an multiplexer, how do I know that the amplifiers i’m using are compatible with the multiplexer ? Moreover, I want to read the output of each strain gauge separately in my computer how do I perform that, like the multiplexer is a good way to do that ? And finally, which Arduino would be the best ?
Thank you !
I am lost long before that. How about getting strain gauges and figure out how to attach them to your rocket. The worry about the rest.
Who told you to use an multiplexer?
You could ask this forum, mentioning what model of multiplexer you propose to use. If it is not compatible, the forum can help you understand why, and suggest some models that would be compatible.
It depends what application/software on the computer will be receiving and using the readings, and what format it expects the data to be in. Communications between the PC and an Arduino is typically done using a serial port, normally using a USB cable. The type of multiplexer used, if a multiplexer is used, is not relevant to this question. The multiplexer, if used, would be part of the interface between the HX711 and the Arduino, not the interface between the Arduino and the PC.
Almost any model of Arduino would be suitable. As this is your first project, chose a basic and inexpensive model because there is a risk you will damage it and need to replace it.
Since you need to build a prototype circuit involving an Arduino and multiple HX711, I suggest the first step would be to build the prototype on a breadboard, so choose a breadboard compatible Arduino such as a Nano 3. Models like Uno and Mega are not convenient for building prototypes on breadboards.
you're right, I will begin with one strain gauge. Do you think one strain gauge(like BF350-3AA) with an amplifier like this https://www.makerfabs.com/strain-gauge-module-with-bf350.html could be enough ? Or do you think I would need to do a weastone bridge mount like this https://europe1.discourse-cdn.com/arduino/original/4X/d/9/b/d9bc3e2e54477501d62b094d1f366f564fb19743.png. If yes do you know where I could find some tutorial to make one. And finally, I need to have a memory to stock the data. Would you have an idee of what could be used ? Thank you so much !!
You initially wrote that you would send it to your PC, That still seems like a good idea.
for a first step to the computer, but in the finally design, it won't have a computer in the rocket..
Then you have a problem. Storing data on a SD card will mean you cannot read the strain gauge while the writing to the SD card is happening. It blocks the code from doing anything until the SD card process is done.
You could use FRAM
If "...could be enough?" means, "if I use that module, I do not need the HX711, right?" then the answer is yes: you will not need, and in fact can't use, the HX711.
If you really want to use an HX711, then you need to create a Wheatstone bridge using one to four strain gauges and zero to three resistors. The site linked below describes the various methods and their advantages and disadvantages. (The HBK website is a great place to do some quality self-education. Spend some time browsing their technical articles.)
By enough I was meaning « accurate enough »
And I found everywhere how to theoretically make a Wheatstone bridge but nothing concrete like can I just weld the strain gauge together and pute my cables on it ?
How could anyone possible answer that question with the information you have provided? Edit to add: and even if you were somehow able to quantify your requirements, I doubt anyone here would be able to give you a definitive answer. If that is true, you will have to do your own tests and draw your own conclusions.
Take a close look at the HKB website resources. You'll find virtually everything you need to know there.
PS: one does not usually "weld" strain gauges...
You are right I am absolutely not clear.
Finally I found the answer of all my question. But I have a last. I’m to be not clear but this is very hard to understand for me. My question is only : on the hx711 amplifier there is 4 wire that come into the amplifier but there is only 2 wire welded to the strain gauge, how do I manage do connect the strain gauge to the amplifier ?
These wires go to the Wheatstone bridge you build from 3 resistors and the strain gauge.
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