Actuator Opens The Door To Drier Dishes

Dishwashers are great at washing dishes and even rinsing them, most of the time. Where they tend to fail is in the drying part. Somehow these things dry hot enough to warp stoneware dishes, but not so well that things are actually dry when you open the door. Blame it on the lack of air movement.

Ideally, the dishwasher cycle is started soon after dinner time so it can be finished and opened up before it’s time for bed. But if you do that, then you miss all the dishes from late-night snacking and the occasional wine glass. Wait until bedtime to start it, and it has to sit several hours with moisture inside. Obviously, the answer is to listen for the victory beeps at the end of the cycle, and use a slow but forceful actuator to push the door open.

[Ivan Stepaniuk] is listening for the dishwasher’s frequencies with a microphone, amplifying them with a trusty LM386, and using an STM32 blue pill to crunch the audio. [Ivan] has plans to incorporate an ESP8266 board for IoT, presumably to get a notification when the door has been opened successfully. Check out the demo after the break.

Yes, dishwashers are great until they aren’t, and some little part breaks. But why pay for a new detergent compartment cover when you can just print one?

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The Swiss Army Knife Of Bench Tools

[splat238] had a ton of spare sensors laying around that he had either bought for a separate project or on an impulse buy, so he knew he had to do something with them. He decided to build his own digital multi-tool focusing on sensors that would be particularly useful in a workshop setting. Coincidentally, he was inspired by a previous hack that we covered a while back.

He’s equipped his device with a bubble level, tachometer, IR thermometer, protractor, laser pointer, and many, many more features that would make great additions to any hacker’s workspace. There’s a good summary of each sensor, making his Instructable somewhat of a quick guide to common sensing modalities for hardware designers. The tachometer, thermometer, laser pointer, and a few other capabilities are notable upgrades from the project we highlighted previously. We also appreciate the bigger display, allowing for more detailed user feedback particularly in using the compass and bullseye digital level among other features.

The number of components in [splat238’s] build is too extensive to detail one-by-one in this article, so please see his Instructable linked above for all the details. [splat238] made his own PCB for mounting each sensor and did a good job making the design modular so you wouldn’t need to add certain components if you don’t need them. Most of the components take some through-hole soldering with only a handful of 0805 resistors required otherwise. The housing was designed such that the user can handle the tool with one hand and can switch between each function with a push of a button.

Finally, the device is powered using a rechargeable lithium-polymer battery making it very reusable. And, if there weren’t enough features already, the battery can be charged via USB or through two solar panels mounted into the housing unit. Okay, solar charging might be a case of featuritis, but still a cool build either way.

Check out some other handy DIY tools on Hackaday.

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A Simple Yet Feature-Packed Programmable DC Load

If you’ve got the hankering to own a lab full of high-end gear but your budget is groaning in protest, rolling your own test equipment can be a great option. Not everything the complete shop needs is appropriate for a DIY version, of course, but a programmable DC load like this one is certainly within reach of most hackers.

This build comes to us courtesy of [Scott M. Baker], who does his usual top-notch job of documenting everything. There’s a longish video below that covers everything from design to testing, while the link above is a more succinct version of events. Either way, you’ll get treated to a good description of the design basics, which is essentially an op-amp controlling the gate of a MOSFET in proportion to the voltage across a current sense resistor. The final circuit adds bells and whistles, primarily in the form of triple MOSFETS and a small DAC to control the set-point. The DAC is driven by a Raspberry Pi, which also supports either an LCD or VFD display, an ADC for reading the voltage across the sense resistor, and a web interface for controlling the load remotely. [Scott]’s testing revealed a few problems, like a small discrepancy in the actual amperage reading caused by the offset voltage of the op-amp. The MOSFETs also got a bit toasty under a full load of 100 W; a larger heatsink allows him to push the load to 200 W without releasing the smoke.

We always enjoy [Dr. Baker]’s projects, particularly for the insight they provide on design decisions. Whether you want to upgrade the controller for a 40-year-old game console or giving a voice to an RC2014, you should check out his stuff.

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Fail Of The Week: The Arduino Walkie That Won’t Talkie

There’s something seriously wrong with the Arduino walkie-talkie that [GreatScott!] built.

The idea is simple: build a wireless intercom so a group of motor scooter riders can talk in real-time. Yes, such products exist commercially, but that’s no fun at all. With a little ingenuity and a well-stocked parts bin, such a device should be easy to build on the cheap, right?

Apparently not. [GreatScott!] went with an Arduino-based design, partly due to familiarity with the microcontroller but also because it made the RF part of the project seemingly easier due to cheap and easily available nRF24 2.4 GHz audio streaming modules. Everything seems straightforward enough on the breadboard – an op-amp to boost the signal from the condenser mic, a somewhat low but presumably usable 16 kHz sampling rate for the ADC. The radio modules linked up, but the audio quality was heavily distorted.

[GreatScott!] assumed that the rat’s nest of jumpers on the breadboard was to blame, so he jumped right to a PCB build. It’s a logical step, but it seems like it might be where he went wrong, because the PCB version was even worse. We’d perhaps have isolated the issue with the breadboard circuit first; did the distortion come from the audio stage? Or perhaps did the digitization inject some distortion? Or could the distortion be coming from the RF stage? We’d want to answer a few questions like that before jumping to a final design.

We love that [GreatScott!] has no issue with posting his failures – we’ve covered his suboptimal CPU handwarmer, and his 3D-printed BLDC motor stator was a flop too. It’s always nice to post mortem these things to avoid a similar fate.

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Modeling The Classic 555 Timer On A Breadboard

Over the years, readers have often commented that microcontrollers (or more specifically, the Arduino) are overkill for many of the projects they get used in. The admonition that the creator “Should have used a 555” has become something of a rallying cry for those who think modern electronic hobbyists are taking the easy way out.

But what if you think even the lowly 555 timer is overkill? In that case, perhaps you’ll be interested in a recent blog post by [TheMagicSmoke], where the reader is walked through the process of creating an analog of the classic integrated circuit on a somewhat larger scale. Finally, we can replace that cheap and handy IC with a mass of wires and components.

Alright, so you’ve probably guessed that there’s no practical reason to do this. Outside of some theoretical MacGyver situation in which you needed to create a square wave using parts salvaged from devices laying around, anyway. Rather, the project is presented as a good way to become more confident with the low-level operation of electronic circuits, which is something we think everyone can agree is a good thing.

The components used include a 74S00 quad NAND gate, a LM358 dual operational amplifier, a 2N2222A transistor, and a handful of passive components. [TheMagicSmoke] not only explains how the circuit is constructed, but shows the math behind how it all works. Finally, an oscilloscope is used to verify it’s operating as expected.

We respect a hacker on a mission, just last month [TheMagicSmoke] put together a similar “back to basics” post on how to interface with an I2C EEPROM.

Building An ESP8266 Doorbell On Hard Mode

It certainly seems as though it should be an easy enough project; all [Miguel De Andrade] wanted was to receive a notification when somebody was pressing his doorbell, and thought it would be a good project to get his feet wet in the wonderful world of ESP8266 hacking. But as fate would have it, not everything went according to plan. In the end he got it sorted out, but it’s an interesting look at how even the “easy” projects can call the gremlins out of hiding.

Arguably, the problems started when [Miguel] picked up an ESP-01 module from a local electronics retailer. While the convenience of buying the hardware in a brick and mortar store can’t be overstated, it did mean he was stuck with a slightly more spartan experience compared to the more common ESP “development boards”. Programming it externally with a Teensy ended up not being much of an obstacle, but it did mean he was stuck with only two GPIO pins.

At any rate, with ESP in hand, the next step was figuring out how the existing bell and intercom system even worked. Unfortunately, after some experimentation [Miguel] found there was a bit more going on there than he’d hoped. According to his multimeter, the one line from the intercom sits at approximately 5 VDC when it’s open, and drops down to 2.5 VDC when pressed. If that wasn’t bad enough, picking up the handset to answer the intercom sent the voltage up to a microcontroller-killing 12 VDC. To complicate maters further, the supply line for the intercom was 23 VAC, so he’d need to rectify that somehow if he wanted to avoid a separate power supply for the ESP.

To turn this jumble of voltages into a nice clean 0 – 3.3 V signal for the ESP8266, he came up with a circuit based around the LM358 comparator that utilizes an LM117 regulator to power itself and the ESP at the same time. A couple of diodes are there to block the AC component from causing trouble, and an A2N2222A transistor is used as a buffer amplifier to boost the output of the comparator so it registers as a digital HIGH on the ESP. The circuit took a bit of fiddling to get sorted out, but in the end [Miguel] says it seems to get the job done.

You might think the problems were solved, but this is where it gets really annoying. The system would work fine for awhile, and then inexplicably go silent. In diagnosing the problem he realized that his circuit connected to GPIO_0 was inadvertently putting the ESP8266 into programming mode, since it was holding the pin LOW unless the intercom button was pressed. He assumed he could just move the circuit to the other GPIO pin, but as that one has the board’s LED on it, that caused its own problems. For now, [Miguel] hasn’t come up with a solution to this issue, and has learned to live with the fact that the system won’t come back up cleanly should it lose power for any reason.

If you’re looking for a slightly classier look than a scrap of perfboard stuck on the wall with what appears to be chewing gum, we’ve also seen the ESP8266 used in some more ornate doorbell setups. Of course if you still haven’t gotten your head wrapped around the whole Internet-connected button thing, you can always start with something a little easier.

DIY Arduino Soldering Iron Hits Version 2.0

A few months ago we brought word that [Electronoobs] was working on his own open source alternative to pocket-sized temperature controlled soldering irons like the TS100. Powered by the ATMega328p microcontroller and utilizing a 3D printed enclosure, his version could be built for as little as $15 USD depending on where you sourced your parts from. But by his own admission, the design was held back by the quality of the $5 replacement soldering iron tips he designed it around. As the saying goes, you get what you pay for.

But [Electronoobs] is back with the second version of his DIY portable soldering iron, and this time it’s using the vastly superior HAKKO T12 style tip. As this tip has the thermocouple and heating element in series it involved a fairly extensive redesign of the entire project, but in the end it’s worth it. After all, a soldering iron is really only as good as its tip to begin with.

This version of the iron deletes the MAX6675 used in V1, and replaces it with a LM358 operational amplifier to read the thermocouple in the T12 tip. [Electronoobs] then used an external thermocouple to compare the LM358’s output to the actual temperature at the tip. With this data he created a function which will return tip temperature from the analog voltage.

While the physical and electrical elements of the tip changed substantially, a lot of the design is still the same from the first version. In addition to the ATMega328p microcontroller, version 2.0 of the iron still uses the same 128×32 I2C OLED display, MOSFET, and 5V buck converter from the original iron. That said, [Electronoobs] is already considering a third revision that will make the iron even smaller by replacing the MOSFET and buck converter. It might be best to consider this an intermediate step before the DIY iron takes on its final form, which we’re very interested in seeing.

The first version of the DIY Arduino soldering iron garnered quite a bit of attention, so it seems there’s a decent number of you out there who aren’t content with just plunking down the cash for the TS100.

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