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Digital Scale Strain Gauge Weight Sensor
We took a digital scale from Target and hooked it up to an amplifier and a microcontroller. This video outlines taking apart the scale, wiring it to the amplifier, and the code, as well as an overview of the concepts behind strain gauges and Wheatstone bridges. There’s a demo of two live scale apps written in Python near the end of the video. For the source code or more information about our microcontroller kits, go to www.nerdkits.com
very usefull information
thank you ~!! ^^
awesome thanx!
thanx man!
You know at 5.30 how you mention that by changing polarities you eliminate some of the noise. Do you change polarities by use an AC current as the excitation voltage?
We use two pins of the microcontroller to drive the bridge. These pins alternate between being +5V/GND and GND/+5V. So effectively, it looks like a 10V peak-to-peak square wave of AC voltage. This technique helps reduce the noise because electronic components tend to have significantly more noise at lower frequencies, which is called 1/f noise, as well as DC offsets. Hope that helps!
If i were to use a filter to filter the noise what filter should I build and whats the cut-off frequency?
Using the bridge approach means that most of the external coupling influences will be common mode and will be canceled by the instrumentation amplifier. If you really get down to it, all you want to look at is the signal at the alternating drive frequency itself, so you could put a narrow bandpass filter around that frequency for the best noise rejection. But a simple low-pass filter set at about 5 to 10x the alternating frequency should be OK while allowing the signal to have time to settle.
Wow! I learned a ton the first two minutes! Thanks! I’m getting a nerdkit soon.
Awesome job guys, you just saved me $1200 dollars in flow meters.
Let me guess, you guys get all the girls…
could you guys do something with peltier plates?that would be really cool……
savin up to buy a nerdkit. already bought a load of 4017 decade counters to test some ideas i had to control dot matrix’s and other LED displays using as few outputs from the micro as possible. i just need the kit now
great! i have a project in class and in it i have to figure out how a scale can tell someone how much food is placed or removed from on top of it. i think i have a better understanding of how a scale works. thanks!
Great video and chip suggestion. Just what I was looking for. I made a homebrew instrumental amplifier, but it is very hard because of all those resistors must match.
Thanks again, friend.
Great video! I really interesting in this project because I’m using a electronic scale to sense the weigth of a baby inside an incubator. My question is about the circuit of the amplifier, I need to know the value of the green capacitor. It’s really important use it? I could amplify my signal without this capacitor?
My other question is, I can use any amplifier differently of the AD620? I can use a LM741? Or a TL081? If I can, I use the same circuit with the same values?
Thanks!
Great , very well explained.
nice project!! can you please send me the schematic? jerome_k89@hotmail.com
nice project!! can you please send me the schematic? jerome_k89@hotmail.com
hey could u send me a schematic.. jerome_k89@hotmail.com
hey dude do you know where can i see how its made an electronico weighing
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