I have a set of scales for my car that wire to a central head unit. Right now it is all hardwired and the head unit is failing. Its over 10 years old. I am looking to make a fun project out of it. Basically I want to take the existing load cells, Add a load cell amplifier. Some sort of wireless module and run each scale independently off battery.
For my new head unit. I was looking at a raspberry PI but it seems it might be beneficial to have an Arduino inbetween. So basically the Arduino would need to pickup the wireless signals then have a program that would interface with the PI for a display where I could display the weights. Also a method of calibration and zeroing.
What do you guys think of this? Any advice for components?
I have an electronics background (what I went to school for). For a living I am a PLC/Robot Programmer. So software programming I have very little experience with. However I am willing to spend the time learning but I want to make sure I have all the right components selected. Hopefully someone can help me understand what is possible and if it is a good method. It is very important that I am taking into account the full accuracy of the load cell. It would need to read in 1700 lbs with a minimum of 0.1% accuracy.
Sounds like a fun project. I would suggest getting the technical information on the load cells proper so you can design a proper interface and be sure there accurate enough for what you are trying to do. Since it is 10 years old do you have a way of calibrating it and or checking its calibration? If the load cells are bad it is an exercise in futility. Once you know the output interface you can design the hardware to match your computer. You need to determine how many bits you will need on your A/D, is ten enough??
I am pretty familiar with load cells so I am not worried about that side of things. Most of the amps I was looking at are around 17 bit. 10 bit would be really close. 12 bit would definitely be more comfortable. Anything more then that I don't believe the load cell would be accurate enough for it to matter. Im looking to maintain 0.1% accuracy over 1500 lbs. I am trying to figure the hardware interface. If im using a traditional load cell amp I have lots of options. But then how to can I get that signal wirelessly to a arduino or PI.
Oh this looks really cool. This would definitely do it. Looking at this. I wonder if I could go right into the PI with and skip using the arduino. Maybe the wrong forums for that lol!
I think I will start with this tho. I will need to pickup the radio modules but I already have the arduino.
If you guys have some other ideas please let me know!! Im much strong in python on the PI then I am in C in arduino
I will need to pickup the radio modules but I already have the arduino.
You will need an Arduino for each load cell, too. The Arduino would read the load cell (using a load cell amplifier like the HX711) and control the radio to send the data.
With your background it must be possible to do what you want to do.
You can use 2 Arduino UNO-WiFi boards, connect the first to a HX711 transducer and use UDP messages to send results to the second one. On the second one you can connect an LDC 20x4 display using I2C. The only thing you would need is WiFI but I assume this is available at the location. HX711 is 24 bit DAC (Wheatstone measurement), so 0.1% must be possible, the example below measures 0..5000 g with an accuracy better than 0.5g. The demo is really detailed and could get you on your way.