3 ms·

> A small microcontroller with a relay tends to be more reliable. Until some bug surfaces that requires a reboot to -fix- work around, but since the device is

> A small microcontroller with a relay tends to be more reliable. Until some bug surfaces that requires a reboot to -fix- work around, but since the device is powered by a battery (EDIT: still puzzling through what might happen when this battery runs out..) which isn't user serviceable and has no reset switch... The device I tore down this morning fits that description. I'll take my chances with a bit of calibration and some yearly maintenance. My vehicles all have grease points and maintenance schedules, I can handle also greasing my thermostat contacts ;) That said, the regulators taking away the mercury switch isn't an excuse for the user hostility. They could have made a device that is less sketchy. Even if they actually did a great job and it's in fact much safer and more reliable than the analog device (in which case they should show data), I know I can open up the analog one and make it work. I can figure out how to keep it working. I can look at it and evaluate whether I trust it. I cannot do that with some proprietary blob on an MCU.

cyberax 8mo ago
They are typically not powered by batteries. These thermostats either use the common wire or utilize the fan circuit to periodically charge a capacitor powering the MCU. > I can look at it and evaluate whether I trust it. I cannot do that with some proprietary blob on an MCU. Your air conditioner/heater likely has a controller. Probably several, at least for thermal protection and overcurrent.
- jcgrillo 8mo ago
  You make a good point about the furnace. It remains to be seen how long it'll last. My only hope is that it was designed to be serviceable. I was very surprised to find the battery. This thermostat is designed to be compatible with older 3-wire systems, so I suspect they slapped a "10 year" battery in it and hope for the best. It's also marketed fairly deceptively. Or at least enough have fooled me--I thought I was buying an analog device. EDIT: now I'm looking at the data sheets for an LM57 and getting some ideas

cyberax 8mo ago

They are typically not powered by batteries. These thermostats either use the common wire or utilize the fan circuit to periodically charge a capacitor powering the MCU. > I can look at it and evaluate whether I trust it. I cannot do that with some proprietary blob on an MCU. Your air conditioner/heater likely has a controller. Probably several, at least for thermal protection and overcurrent.

jcgrillo 8mo ago
You make a good point about the furnace. It remains to be seen how long it'll last. My only hope is that it was designed to be serviceable. I was very surprised to find the battery. This thermostat is designed to be compatible with older 3-wire systems, so I suspect they slapped a "10 year" battery in it and hope for the best. It's also marketed fairly deceptively. Or at least enough have fooled me--I thought I was buying an analog device. EDIT: now I'm looking at the data sheets for an LM57 and getting some ideas