[electronicsNmore] has uploaded a great teardown and tutorial video (YouTube link) about wax motors. Electric wax motors aren’t common in hobby electronics, but they are common in the appliance industry, which means the motors can be often be obtained cheaply or for free from discarded appliances. Non-electric wax motors have been used as automotive coolant thermostats for years. Who knows, this may be just what the doctor ordered for your next project.
As [electronicsNmore] explains, wax motors are rather simple devices. A small block of wax is sealed in a metal container with a movable piston. When heated, the wax expands and pushes the piston out. Once the wax cools, a spring helps to pull the piston back in.
The real trick is creating a motor which will heat up without cooking itself. This is done with a Positive Temperature Coefficient (PTC) thermistor. As the name implies, a PTC thermistor’s resistance increases as it heats up. This is the exact opposite of the Negative Temperature Coefficient (NTC) thermistors we often use as temperature sensors. PTC’s are often found in places like power supplies to limit in rush current, or small heating systems, as we have in our wax motor.
As the PTC heats up, its resistance increases until it stops heating. At the same time, the wax is being warmed, which drives out the piston. As you might expect, wax motors aren’t exactly efficient devices. The motor in [electronicsNmore's] video runs on 120 volts AC. They do have some advantages over solenoid, though. Wax motors provide smooth, slow operation. Since they are resistive devices, they also don’t require flyback diodes, or create the RF noise that a solenoid would.
Continue reading “Wax Motors Add Motion to Your Projects”
A story surfaced a few days before Halloween on Russian news site Rosbalt (yep, that’s in Russian), claiming Russian authorities intercepted Chinese-made electric irons and kettles: each equipped with microphones and WiFi. You can read a summary in English on the BBC’s website. The “threat” imposed by these “spy appliances” is likely the result of gross exaggeration if not downright fear mongering against Chinese-made products. It’s not worth our (or your) effort to speculate on what’s really happening here, but the situation does present a fun exercise.
Say you wanted to spice up your pen testing by altering a small home appliance: how easily could you build it? Let us know in the comments which appliance would serve as the best “host” for the modifications and what features you would include. Could you manage all the components listed in the article–a microphone, WiFi (any chance of cracking unsecured networks?), plus some vague indication that it “spreads viruses?” There’s a video below with a few glimpses of the electronics in question, but unless you speak Russian it probably won’t offer much insight.
Continue reading “Ask Hackaday: Can you Hack an Appliance into a Spy Device?”
[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.
Continue reading “Electric clothes drier repair heats things up”
I think we can all agree that sometimes projects are a bit of a stretch. We rack our brains for something interesting and unique to bring to the table and end up stretching for that special strange twist trick or technique that will garner that special kind of admiration from our peers. In that sense it is easy to loose sight of some of the best projects, the simple ones that prove you can fix anything anytime anywhere and improve it while you are at it.
This is just such that kind of project, [UnaClocker] had a washer fall victim to its own condensation. Instead of shelling out a ton of money for the repair man he took on the job himself, fitting the washer with an Arduino, relays and a breadboard. A little reverse engineering revealed the (notably well labeled) control board, evidently the control signals involved are extremely easy to interpret. [UnaClocker] also found a temperature sensor to control dish sanitation. At this point he had FULL CONTROL over the dishwasher and was able to design the ideal prewash/wash cycle timings.
Now that a wash cycle is all set [UnaClocker] can now go ahead and embarrass the hell out of the OEM. He plans on adding a real time clock module to time washings and a clean dish indicator, after which we think he should get rolling on some wireless/tweet/ethernet/capacitive touch/voice communication. After that he is going to work on buttoning up the design and making it pretty.
Check out the setup in action after the jump!
Continue reading “Hey OEMs, Arduino controlled dishwasher has much potential”