Bed cooler, entry 1: the plan, and what the manual gave away

A smart bed that cools you in the first half of the night and warms you before your alarm starts at about A$3,000 in Australia. I have a far simpler product, a Kiva Circadian Sleep Pod, which pumps water through a pad on the mattress and holds it at one temperature.

The difference between the two is mostly a timetable. So the plan is to build the timetable.

Rule one: do not touch the dangerous half

A cooled bed has water, a pump and a mains powered heater, all within reach of a sleeping person. I am not building or opening any of that. The unit stays sealed. My controller will only do what the remote does: press power, up and down.

What the manual gave away

I expected an infrared remote, like a TV. That would have been a five dollar job: record the signals, replay them.

Then I found this in the manual:

Hold down the power button on the control unit until the display flashes “188.” Press the power button on the remote.

That is a pairing step. Infrared remotes never pair, because they just flash light at whatever is in front of them. Pairing means radio. So the cheap infrared plan is dead before I ordered a single part, which is the best time for a plan to die.

Three more things from the manual that change the design:

• It turns itself off after 10 hours. The controller needs to press power as well.
• The display blinks five times after a change. Presses sent too fast may be ignored.
• Condensation forms when the pad is much colder than the room. In a humid Sydney summer the cool phase should not go lower than it needs to.

The up and down problem

The remote cannot say “go to 24 degrees”. It can only say “one warmer” or “one cooler”. If my controller ever miscounts, it is lost for the rest of the night.

The fix is an old trick from machines like 3D printers, called homing. At the start of the night, press down 30 times. The range is only 27 steps, so wherever it started, it is now at the bottom. Count up from there.

A first night profile

These numbers are a guess to start from, not something from a study. I expect to shift them in the first week.

What I still need to find out

1. Which kind of radio. Either the common 433 MHz type used by garage doors, or Bluetooth. I will open the battery cover to look for a printed frequency, and scan for Bluetooth signals while pressing buttons.
2. Whether the first press only wakes the screen.
3. How quickly the bed follows. A temperature sensor under the sheet will tell me.

If the radio turns out to be awkward, there is a fallback that always works: solder wires across the remote’s own buttons and let the controller press them electrically.

Parts so far

Next entry: what is inside the remote.