I'm building a kite flying robot, in which I've already got some sensors built in. I now also want to measure the pulling force on the rope which is attached to the kite. So I thought of attaching a hanging digital scale to the rope which can then measure the pulling force in kilograms. I of course need to read out the data from the scale using GPIO pins or USB.

Furthermore, I also have a raspberry pi installed within the kite and I want to measure some pull on ropes in the air. So if possible, I also need very small/light scales from which I can read out the data. It would be great if the scales can measure up to about 50kg, but with some pulleys about 20kg would be fine as well.

Unfortunately I can't find any digital hanging scale with a possibility to read out the data and which is reasonably light. There are some simple USB powered hanging scales, but I think they just use USB for charging, not for reading out data. And I also found this one, but that's a bit overkill (too heavy and too expensive).

So question #1: Does anybody know where I can get a simple existing hanging scale from which I can read out data?

If needed I can also build something, but I just wouldn't know where to start. I did find this page on Alibaba, where they show the contents of the scale they offer:

enter image description here

So as far as I understand I need the component which I highlighted. But I have no idea how that component is called (what do I search for?) and whether it is actually doable to read it out from a Raspberry Pi.

Question #2: does anybody know what the highlighted component is called, where I could possibly get it and if I can read it out from a Raspberry Pi?

In conclusion; can anybody point me in the right direction?


The component you highlighted is called a tensile load cell. You could buy one from a supplier, but it probably would be cheaper to buy a cheap digital hanging scale and taking the sensor out of it - at least I couldn't find one less than $100, ten times the price of a 50kg digital hanging scale.

You will need to do some analog conversion and amplification of the signal and then convert to digital with an ADC; I haven't done so myself but Sparkfun's load cell tutorial seems a good start.

The other means is to create your own scale, with a stiff spring and some sensor detecting its movement, such as a digital depth gauge - which costs $3 and has a serial output.

  • $\begingroup$ Awesome, thanks. Using the magic word "load cell" I found quite a few affordable load cells (±€30) and through your link to Sparkfun I also found the OpenScale board, which apparently makes converting the raw signal to a usb port really easy: learn.sparkfun.com/tutorials/… Thanks a million! $\endgroup$
    – kramer65
    Mar 8 '17 at 9:09

What about a flex sensor? Here's one for less than $10 at Sparkfun.

Wherever there is tension there must also be flexsion in a crossmember of the kite or in the membrane. A little bit of experimentation might get you the data you seek.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.