A Smart Clothes Dryer

dryer6 Here’s a question that will rack your brain: does your clothes dryer stop when the clothes are dry? It seems if you have a machine that guzzles power for one single purpose, you’d like it to stop when its job is done, or for the sake of convenience, keep going until the clothes are dry. Temperature and humidity sensors are cheap, and if you don’t have an auto sensing clothes dryer, a DIY smart clothes dryer seems both efficient and convenient.

[Andy] figured when clothes are dry, they stop emitting moisture. Based on that premise, he could monitor the operation of a clothes dryer and either shut off the machine or send a message that it’s time to take the clothes out. It’s a simple enough idea, and with an Arduino and a DHT11 temperature and humidity sensor, it was pretty easy to put together.

The clothes dryer used for this experiment was a self-ventilating model that doesn’t vent to the outside. Instead, it condenses the water in your towels and jeans into a tub to be emptied by hand later. This might introduce a little error into tests, but [Andy] did come up with a way to mount the temperature sensor without modifying his dryer in any way. From the initial data, the ventless dryer might be introducing a little experimental error, but it’s still too good of an idea to not try out with a traditional dryer that vents to the outside. Here’s the code should you want to try this yourself.

Electric clothes drier repair heats things up

clothes-dryer-fix

[How To Lou] sure has shown us how to do quite a few things. This time he’s dealing with an electric clothes dryer that won’t heat. We’ve been elbow deep in our own appliances and we think [Lou's] matter-of-fact demonstration will help you gain the confidence to investigate problems before deciding if it’s a job to be relegated to the repair man.

This picture shows the back side of a clothes dryer after having a protective panel removed. Just out of frame is a functional schematic which lists each part and it’s resistance measurement. Lou has labelled those parts in this image to help us understand what we’re looking at. In the video after the break he begins doing the same troubleshooting that a repair would use. He grabbed his multimeter and used it to test the resistance of each component after removing the wires from it. All of them should read zero Ohms except for the heater coil which the schematic rates at 7.8-11.8 Ohms. The high limit thermostat is loose and measures an infinite resistance. This, coupled with the charred wire on one side is the culprit. As with that ice maker repair from yesterday, [Lou] searches for the numbers on the part to find the replacement he needs.

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Reclaiming waste heat from appliances

Here we see [Christopher Suprock] hanging out in his basement laundry area in order to show off his intelligent heat exchanger. The reason for the device is simple, when you use your clothes dryer , hot water heater, other other utilities that generate heat, energy is often wasted in the form of hot exhaust gases. Why not get the most for you clothes drying dollar by sourcing that hot air to warm your house.

The block you see on top of the dryer is a heat exchanger. The exhaust from the dryer passes through a radiator assembly before being vented outside the house. Some control hardware monitors the temperature of the input side and switches on the fan when it detects a higher temperature than the ambient air. Air then flows through the radiator, picking up heat energy from the exhaust gas. See [Christopher's] explaination, and some thermal readings while the dryer is running, in the video after the break.

This makes us wonder, if the heat exchanger drops the exhaust gas fifty degrees before being vented, will this cause any issues with condensation?

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