Hello all.
I'm building the electronics for a Torsion bar dyno for a mate. It's a device that tests the load at various amounts of twist on a race car torsion bar.
It is a Teensy 3.2, a load cell, and an encoder.
I've used a cheap hx711 breakout board for a similar project successfully. (but using an arduino nano).
A week ago while testing I found the load cell readings were very erratic, giving random readings posotive & negative and occasionally correct.
It appeared to be a power supply or noise issue:
-Running the HX711 board and the teensy off USB power and the readings would be fine. With HX711 at 10SPS or 80SPS
-Running the board off 7805 power would work well at 10SPS but give random readings at 80SPS
Testing my supplys on my scope, the usb looked terrible compared to my 7805... or even pololu regulator, which looks even better. (something else I don't understand).
USB voltage is however sligtly lower than 5VDC.
I have now got the teensy and HX711 board setup for testing running at 10SPS.
With pics to follow, you will see that:
-@ 5000mV max supply I get good looking serial data out of the hx711, load cell readings are stable. Logic 0 at 630mV?
-@ 5040mV max supply I get slightly dodgy serial data out and load cell readings are starting to look noisy. Logic 0 is still offset.
-@ 5120mV max supply the serial data (DOUT) is pretty much no good.
I've reached the point where I don't want to spend allot of time solving the problem.. That is, I just have a feeling I'm going to go down the track of trying to fix this with my limited abilites..resistor deviders and zennor diodes or level shifters.. or separating hx711 analog and digital supplys, but I'm not confident I will succeed in a reasonable time.
This project has exhausted me for various other issues.. Looks like one of my nextion displays may have a hardware fault, had to custom build a linear encoder from a rotary encoder/linear bearing/rail, after switching away from a straight rotary encoder setup.. to a potentiometer... back to an encoder..
Anyay. I'm pretty sure I need a nice flat logic zero a bit closer to gnd than it currently is when the supply voltage approaches 5VDC. I would like to run my nice stable pololu reg that flat lines at 5.1VDC.
Please help me understand what is going on here and how I would fix it.
I'm building the electronics for a Torsion bar dyno for a mate. It's a device that tests the load at various amounts of twist on a race car torsion bar.
It is a Teensy 3.2, a load cell, and an encoder.
I've used a cheap hx711 breakout board for a similar project successfully. (but using an arduino nano).
A week ago while testing I found the load cell readings were very erratic, giving random readings posotive & negative and occasionally correct.
It appeared to be a power supply or noise issue:
-Running the HX711 board and the teensy off USB power and the readings would be fine. With HX711 at 10SPS or 80SPS
-Running the board off 7805 power would work well at 10SPS but give random readings at 80SPS
Testing my supplys on my scope, the usb looked terrible compared to my 7805... or even pololu regulator, which looks even better. (something else I don't understand).
USB voltage is however sligtly lower than 5VDC.
I have now got the teensy and HX711 board setup for testing running at 10SPS.
With pics to follow, you will see that:
-@ 5000mV max supply I get good looking serial data out of the hx711, load cell readings are stable. Logic 0 at 630mV?
-@ 5040mV max supply I get slightly dodgy serial data out and load cell readings are starting to look noisy. Logic 0 is still offset.
-@ 5120mV max supply the serial data (DOUT) is pretty much no good.
I've reached the point where I don't want to spend allot of time solving the problem.. That is, I just have a feeling I'm going to go down the track of trying to fix this with my limited abilites..resistor deviders and zennor diodes or level shifters.. or separating hx711 analog and digital supplys, but I'm not confident I will succeed in a reasonable time.
This project has exhausted me for various other issues.. Looks like one of my nextion displays may have a hardware fault, had to custom build a linear encoder from a rotary encoder/linear bearing/rail, after switching away from a straight rotary encoder setup.. to a potentiometer... back to an encoder..
Anyay. I'm pretty sure I need a nice flat logic zero a bit closer to gnd than it currently is when the supply voltage approaches 5VDC. I would like to run my nice stable pololu reg that flat lines at 5.1VDC.
Please help me understand what is going on here and how I would fix it.