An awesome open source, 3D-printed vase stand with addressable RGB LEDs that fade between selectable colors to light up your life.
Project tutorial by vorpalrobotics
A 3D-printed, open source, Arduino-based, Bluetooth-controlled, Scratch-programmable, six-legged robot built for games, education, and fun!
Project showcase by Vorpal Robotics, LLC
Build your own Arduino-powered light switch that can be controlled using Amazon Alexa.
Project tutorial by Tinker Project
The servo size the project expects is MG90 size. Tower Pro MG90S work very well, as do Turnigy MG90S from Hobby King.
Don't use SG90, the plastic gears can't take the stress of walking. (also the shaft spacing is different so you'd have to adjust the 3d models a bit).
Clone/counterfeit Tower Pro MG90S are all over the cheap electronics places (and even amazon/ebay etc). If you see any price under about $6 for something claiming to be a tower pro mg90, then it's very likely to be counterfeit. If you see a price under $3 it is absolutely counterfeit, because even in large quantities real TP MG90S servos cost nearly $4 wholesale.
We used to use clone MG90S in our projects, but we would test every one and reject the 10% that were bad. However, recently the factories in china have been churning out batches of clones with sometimes 50% bad servos so we stopped using them and switched to real tower pro servos. If you want to buy those clone/counterfeit servos for $2 or $3, buy a bunch of extras because you're likely to have a good percentage of bad ones. A lot of them have bad gearboxes that will fail within minutes of using. Many of them recently will lose their home position after heating up, the shaft will drift 30 to 90 degrees from proper position.
You could have little "cars" (lights that are off) zoom down the stairs in a speed proportional to the traffic conditions (slow = jam, fast = clear sailing). You could then modify the color of the LEDs to indicate weather forecast (yellow=sunny, off-white = cloudy, off-white with some yellow here and there = partly sunny, off-white with little sparkles fading on and off = rain or snow).
Make sure you use a low-self-discharge battery or all bets are off. Some NIMH for example will eat up 1% of their charge every day even if sitting in a drawer.
So, basement stairs is a different use-case than I analyzed before! The basement might always be dark even in the daytime. So using a light sensor to power down in daylight to save power will not work, it will always be dark there. This means a different strategy is needed: rig up the arduino so it is in "power down sleep mode" most of the time, and only wakes up when the PIR sensor triggers.
Here is an nice instructable showing you how to use a PIR sensor in exactly this way:
That article claims the PIR sensor only consumes 0.06 milliAmps when not detecting.
Here is an excellent article about how to modify an Arduino Pro Mini to have an ultra-low consumption power-down-sleep mode (by disabling the power LED!):
That article claims that by disabling the power LED, the pro mini only consumes 0.03 milliAmps in power down sleep mode.
Assuming these articles are accurate, by combining these two techniques we're looking at the project consuming only about 0.1 milliAmp when the sensors don't detect anyone and therefore the LEDs are turned off and the Arduino is in deep sleep.
Assuming low self-discharge batteries rated 3000 mAh, the project would take 30,000 hours or over 3 years to eat up the batteries from quiescent current usage. Of course, that's if the lights were never used ;) Now throw in 3 minutes per day (several trips up and down the stairs) of lights consuming 400 mA, and you get a rough battery life of "several months". The more you use the stairs, the shorter the battery life of course.
The back of my envelope is on fire today!!!
Hope this helps,
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