My plan is to make an improved stair lift remote since the official Meditek remote only has 2 buttons (Up/Down) so to send the stair lift to the top/bottom you need to hold the button down for around 40 seconds.
First up I wanted to take a look at the existing remote to see what the Up/Down signals looked like so out came the oscilloscope and I probed directly over the IR LED pins. It was late so I just grabbed the camera rather than saving the images to a USB stick.
Looking at the traces it was easy to spot the timing differences between the Up/Down signals.
The repeat time commands whilst holding the button down was around 118ms.
Looking at the software side I found 32.6 kHz Infrared Remote test code from “jaysee” on the Arduino.cc forum which looked like it could be easily modified to send the commands I needed. To the breadboard…
The breadboard version comprises of an Arduino Nano (clone), 3 IR diodes (one temporarily replaced with a red LED so I can see it’s sending the signal), a MOSFET for the increased current capability to drive the LEDs on/off a Relay and a few diodes.
The switch (of which there will be four in the completed project for Up/Down/Top/Bottom) connects via a diode to the + side of the relay, as does pin D7 of the Arduino via another diode to OR the signals. This allows the Arduino to keep the relay coil energize whilst it’s sending the IR signal to take the stair lift to the top or bottom. The relay coil is low power (firstname.lastname@example.orgV / 50mW) so the current draw from the Arduino pins is safely within it’s capabilities for driving directly.
Work in progress – sending the stair lift up.