Design Story
During the summer of 2021, my brother purchased a new home and was very excited to add some smart technology. He asked me to wire up a smart thermostat to control the swamp cooler. To our surprise, those are not compatible since most smart thermostats work off of 24 VAC and evaporative coolers (swamp coolers) run on 120/240 VAC. Currently, most evaporative coolers do not have step down electronics to work with smart thermostats. Thus the idea for this project was born!
The Prototype
Fast forward half a year or so, I've designed the first version of the printed circuit board (PCB) and tested it! It is a pretty simple design. I've used relays to switch the higher voltage circuits with lower voltage outputs from the thermostat and added analog circuitry for the timer. The timer circuit allows for presoaking of the evaporative pads. You can adjust it from the absolute minimum of 3 seconds to the maximum of about 90 seconds.
The timer circuit was designed around capacitor charging. The delay produced by the time needed to charge the capacitor when the blower motor is on. The capacitor slowly discharges when the blower motor turns off, which allows for the analog memory of some sort. The delay will slowly increase toward the initial one, so if your smart thermostat frequently shuts on and off, the board will have a shorter presoak cycles. If you or the thermostat decide to turn off the blower motor for a long time, it will return to the initial duration.
Latest revision of the board
Anatomy of the Swamp Cooler
The swamp cooler is made up of two parts:
evaporative pad
blower motor
Here is a visual to give you a better understanding of the principles behind an evaporative cooler operation.
Swamp Cooler Design (Source: Premier Industries, Inc)
Obviously the Smart Swamp Cooler product was designed and targeted towards whole house evaporative coolers and limited set of window coolers. The portable and smaller swamp coolers might work as well but are not targeted under this product.
Swamp Cooler Core Benefits
I know some people might say that the Evaporative coolers are the relics of the past and we should move on with the traditional ACs. But before we move on, lets consider the bullet point section below. And yes, I should add small print stating that the evaporative cooler technology only works in certain climates (dry ones).
Core benefits of using swamp/evaporative cooler over traditional AC:
Fresh Air. The air is coming from the outside instead of recirculating the air
Filtered Air. The pads (towels) on your evaporative cooler not just cool but act as a filter as well
Moist Air. Chances are if you are using evaporative cooler – you are living in a dry climate. Your evaporative cooler acts as a free of charge dehumidifier which is good for your skin and wellbeing.
Airflow. Since swamp coolers are using the air from outside you have to open windows/doors to create airflow. It is a simple way to control the cooling areas and it feels good!
Low Operating Cost. Evaporative cooling is simple, cheap and effective. Running traditional AC can be 5x to 10x more expensive.
The Smart Thermostat
The smarts of the smart thermostat are the abilities to control your HVAC system remotely, perform smart scheduling and control your heating/cooling while you are out of town automatically. Smart or not, the thermostat has a set of universal signals that control the flow of hot or cold air.
Smart Thermostat (Source: Google Nest)
As long as we can translate those signals to higher voltage, we will empower thermostat to control anything.
The Final Product
Let’s be honest the enclosure and the printed circuit board isn’t very sexy. It is far more important to have a durable design. Most likely, it will live in an attic or a crawl space. So being slick is not necessary for this product!
