KitchenYou will see this often
Digital kitchen scale
Also called postal scale, food scale.
One aluminum load cell and almost nothing else. This is the cheapest precision sensor in household trash.
A donor is the dead machine. The parts below are what is still worth removing from it. “Leave it” is a part that is physically in there and should stay in there: too dangerous, too worn, or only useful as part of a repair you are not doing.
Red and black feed the sensor a steady few volts. Green and white are the tiny signal, measured between them, not from either one to ground. Pressing the bar changes that signal by millivolts. A normal meter on DC volts can show that it responds. Turning it into a number on a screen wants a small amplifier board, often an HX711.
Why it is in the trash while the parts are not
The display died, the plate cracked, or the cell was overloaded and now it drifts. A drifting zero may mean the cell is already yielded.
Before you open it
Do this while it is still unplugged, cool, and not leaking. One coin cell or a battery. Nothing exciting.
Where the dead machine usually is
- Kitchen — In the house
- Junk drawer and cable box — In the house
- Thrift store — Retail
Thrift stores sell them for less than a load cell. Buy the dead ones if they are cheap.
How it comes apart
Under the feet. The beam is bolted to the frame and the plate. Note which face is up.
Tools: Phillips, Meter.
What to take
The table is the short version. The notes under it describe that part inside this machine, not only the general description.
| Part | Call | How many | How often | Where to look |
|---|---|---|---|---|
| Load cell | Prize | 1 | always | The center. |
| Tactile switch | Bonus | 2–4 | usually | The buttons. |
| Coin cell | Bonus | 1 | sometimes | The battery. |
| Battery clip and holder | Bonus | 1 | sometimes | AAA versions. |
| LCD panel | Leave it | 1 | always | The display. |
Prize
Four-wire beam, capacity about the scale's range.
The center.
Unbolt. Do not bend it further.
Overload shows up as a zero you cannot calibrate out.
Bonus
Small tact.
The buttons.
Desolder.
Good.
CR2032.
The battery.
Test the voltage.
Often flat.
A holder.
AAA versions.
Clean corrosion.
Corroded is common.
Leave it
Bare glass with an elastomeric connector. Not a module you can talk to.
The display.
Leave it.
Works only in the original zebra-strip arrangement.