[Markus] is quite happy with his kitchen scale. It’s one of the tools he uses most frequently when cooking. But recently the button has begun to give him problems. He figures the years of spilling a little bit of this and that has mucked up the contacts. His solution was to bypass the button using a Cherry MX switch.
Really any replacement should do since the switch merely completes an electrical connection. But there’s a subset of hackers who swear by the Cherry MX switches that come in some keyboards. [Markus] had just such a keyboard on hand, which he was already using for parts, so he pulled out the switch and cut a hole in the scale’s case where he could mount it. After temporarily super gluing the switch in place he completed the task by filling the gap on the outside with hot glue, then running another bead of it along the inside. The addition of the ‘T’ key finishes the hack. The plastic key is easy to clean and will help shed flour, oil, or anything else he might spill during his culinary adventures.
This hack was fast and easy and may have convinced [Markus] to roll his own controller board for the device. We’ll keep a lookout for a follow-up post detailing those alterations.
Due to the location of the device, I would have went with something more sealed. The button itself is still exposed, it may take longer to make sticky, but it will end up sticky again at some point. use a rubber cover of some sort, seal it to the case, and then recess the switch inside that to offer a more robust option.
“This results in enormously improved feedback.”
Because feedback is important when zeroing your scale.
“…the MX’s lifespan of up to 50 million actuations should save me from having to do something about sticky buttons for the next couple of years.”
I dont know how a MX’s cycle lifespan has anything to do with how resistant it will be from gumming up the mechanism.
As deathventure pointed out, these switches arent IP rated. Although I havent used Cherry switches before, from my experience keyboard switches do gum up quite easily. And is replacing a switch really worth posting on HaD?
Most simple digital scales are made using a Wheatstone bridge of strain gauges mounted on a short beam anchored at one end, and the other end holding the scale platter. It is relatively straightforward (in that the circuit is a fairly textbook instrumentation amplifier circuit) to get the bridge connected up to a microcontroller, and then after that, it’s another textbook case of reading the signal, applying averaging, calibration, and scaling on a microcontroller.
In short, a perfect hacking project. Highly recommended
This is so funny, because just last week I did replace a button on the very same scale. Though I didn’t have the Cherry MX at hand so I simply had to use a replacement switch instead, but I do use a hack on this, because I push the scale up to 8kg-s, zeroing the scale to -3kg. :D
-_- Remind me why I still check this site everyday?
Because I really don’t know anymore. I mean replacing a switch?
I mean sure, all the more power to ya, I’m glad your scale works again but that is so basic there is absolutely no point to post it on HaD. ugh…. I just don’t know anymore
Maybe spill some isopropyl alcohol or contact cleaner in there next time, chief ;)
I keed because I love. I doubt I could have cut as nice a hole for that key.
After my comment I decided to go look at the scales I have because it seems like the glass platter should just hang over the button to protect it but it turns out I have one that covers and one that doesn’t. go figure.
Keep on tinkerin.
I have the same scale and had the same problem. I just removed the old switch and added a new one of the same type.