I've got a project that's using 4 x 50kg load cells that have three veryyyy thin wires coming from each them linked to a HX711 board. At the moment I have that all wired up via jumper cables for my testing. I need to now extend those over a much larger distance so need some "general wire" to solder to the existing wires between the cells and the HX711.
What AWG wire is generally used for smaller electrical projects like this? Don't want to accidentally order some really thick wire online first and looking online it seems to be based on AWG ratings. Looking online I'm finding a mix of AWG ratings and just mm (at least here in the UK).
Would I be fine with something like this at 1.5mm?
You need to ensure the resistance of the leads is smallish compared to the load cell resistance, so that variation
in the cable resistance doesn't affect the reading - temperature variations affect resistance of copper wire
somewhat.
I'd suggest trying to keep the lead resistance below 10% of the load cell resistance. For 10m that's likely to
be easy, CAT5 cable will do. 1.5mm^2 cable has about 0.1 ohm per 10m, which is overkill as temperature
effects are very small compared to that. 10 ohms per 10m is probably fine. CAT5 is cheap and reliable.
Shielded cable might be a good idea though.
Each wire to the load cell should be the same type and length, note, to keep the bridge symmetrical.
MarkT:
CAT5 is cheap and reliable.
Shielded cable might be a good idea though.
Thanks MarkT!
I'm hoping to find a 3-core wire so that I can link each sensor to that and then run those cables into a central box to handle the linking between them and the HX711 module there rather than connecting each cell directly to another. If that makes sense. I think I'll struggle to get the distances exactly the same as the control box they're linking to isn't going to be right in the middle of the H bridge and it's not an exact square, do you recommend keeping the cable lengths all the same as the longest one then and just tie the excess up?
Seemingly difficult to find a 3-core wire in the UK much thinner than the 1.5mm one I linked there but I didn't even consider CAT5 cable! I've only ever considered that for networking but is it as obvious as just buying a standard longer shielded network cable, strip the ends and then twist the pairs into single cables before connecting to the cells/boards? (with one left over)
You may want to do a Google of Strain Gauge Bonding Pads which can come in very handy. I also like flat flex cabling. I also like it because it can come color coded Red, Black, Green and White. I solder my leads to the pads then clean a surface I use super glue to mount the pads. Matter of fact likely all of this sort of stuff can likely be found with a Google of "strain gauge accessories".