Hacking Cheap Chinese PID Temperature Controllers

[Harvs] hacked a cheap PID controller he found on eBay to improve its performance. The controller originally used a K-type thermocouple but lacked cold junction compensation. As thermocouples only provide a differential measurement between the measurement junction and cold junction, this meant the controller was assuming the cold junction was at room temperature, and would in many cases be significantly inaccurate. The system also used a no-name brand Chinese microcontroller making firmware hacks impractical.

[Harvs] decided that even with cold junction compensation a K-type thermocouple wasn’t ideal for his application anyway, and designed a replacement PCB to interface to the display and power supply. The new PCB is based around a Cypress PsoC (a popular choice for its great analog functionality) with a DS18B20 temperature sensor. At the lower temperature ranges [Harvs] is interested in the DS18B20 is far more accurate and easy to use than the thermocouple.

Though the project hasn’t been updated recently, [Harvs] was planning on adding an ESP8266 for remote monitoring and control. Great work [Harvs]!

Thanks to Peter for the tip.

Get Biohacking with a DIY CO2 Incubator

The [Pelling Lab] have been iterating over their DIY CO2 incubator for a while now, and it looks like there’s a new version in the works.


We’ve covered open source Biolab equipment before including incubators but not a CO2 incubator. Incubators allow you to control the temperature and atmosphere in a chamber. The incubator built by the [Pelling Lab] regulates the chambers temperature and CO2 levels allowing them to culture cells under optimal conditions.

While commercial incubators can cost thousands of dollars the [Pelling Lab] used a Styrofoam box, space blanket, and SodaStream tank among other low cost parts. The most expensive component was a CO2 sensor which cost $230. The rig uses an Arduino for feedback and control. With a total BOM cost of $350 their solution is cost effective, and provides an open platform for further development.

The original write up is full of useful information, but recent tweets suggest a new and improved version is on the way and we look forward to hearing more about this exciting DIYBio project!

It Keeps on Going and… Arduino Edition

How long can you keep an Arduino circuit running on three AA batteries? With careful design, [educ8s] built a temperature sensor that lasts well over a year on a single charge of three 2250 mAH rechargeable cells (or, at least, should last that long).

Like most long-life designs, this temperature sensor spends most of its time sleeping. The design uses a DS18B20 temperature sensor and a Nokia 5110 LCD display. It also uses a photoresistor to shut off the LCD display in the dark for further power savings.

During sleep, the device only draws 260 microamps with the display on and 70 microamps with the display off. Every two minutes, the processor wakes up and reads the temperature, drawing about 12 milliamps for a very short time.

Along with the code, [educ8s] has a spreadsheet that computes the battery life based on the different measured parameters and the battery vendor’s claimed self discharge rate.

Of course, with a bigger battery pack, you could get even more service from a charge. If you need a refresher on battery selection, we covered that not long ago. Or you can check out a ridiculously complete battery comparison site if you want to improve your battery selection.

Continue reading “It Keeps on Going and… Arduino Edition”

Keep an Eye on Your Fermenting Beer with BrewMonitor

The art of brewing beer is as old as civilization itself. Many people enjoy brewing their own beer at home. Numerous steps must be taken before you can take a swig, but fermentation is one of the most critical. [Martin Kennedy] took up the hobby with his friends, and wanted a convenient way to monitor the fermentation temperature remotely. He started working on the BrewMonitor, a cloud-based homebrewing controller powered by an Arduino clone.

His goal was to create something cheap, convenient, and easy to set up. Traditional fermentation monitoring equipment is very expensive. The typical open-source alternative will set you back 80 euros (roughly $101), using the Arduino-sensor with a Raspberry Pi gateway via the BrewPi webserver. [Martin] did not want to go through the hassle of viewing BrewPi remotely, since it requires a home network and all of the configuration that would entail. Instead, he coupled an Arduino clone with a DS18B20 temperature sensor while using an ESP8266 module for wireless communication, all for less than 18 euros ($23). This connects to a simple webpage based on Scotch.io with a PHP backend (Laravel with RESTful API), a MySQL database, and an AngularJS frontend to display the graph. Once the sensor is placed into the fermenter bucket’s thermowell, the temperature is transmitted once a minute to the REST API. You can see the temperature over time (in Celsius). The design files are available on GitHub.

[Martin] would like to expand the functionality of BrewMonitor, such as adding the ability to adjust the temperature remotely by controlling a heater or fridge, and lowering its cost by single boarding it. Since the information is stored on the cloud, upgrading the system is much easier than using a separate gateway device. He doesn’t rule out crowdfunding campaigns for the future. We would like to see this developed further, since different yeast species and beer styles require very stringent conditions, especially during the weeks-long fermentation process; a 5-degree Celsius difference can ruin an entire brew! Cloud-based temperature adjustment seems like the next big goal for BrewMonitor. DIY brewers salute you, [Martin]!

[via Dangerous Prototypes]


Automated Bathtub Prepares Your Bath Just The Way You Like It

Automated Bathtub Controlled by Arduino

We live in the future don’t we? Is there a reason why only rich people have touchscreen controlled showers and temperature regulated bathtubs? [Raptor_Demon] shows us how to make our very own automated bathtub for cheap, using our favorite microprocessor — the Arduino.

The system controls the filling of the tub, monitors the temperature based on a user profile — and it even adds bubbles. Why do you need this? You probably don’t — but why not, wouldn’t it be nice to press a button and have a bath drawn for you? It uses an Arduino compatible board that controls 3 relays for the water system, a DS18b20 temperature sensor on the inlet and a second wireless (434mhz) Arduino compatible board for monitoring the tub temperature and adding bubble bath using a hacked automated soap dispenser.

[Raptor_Demon] showcased his prototype at the Maker Faire NC 2013 and 2014 where it was a huge hit. He even had a full size tub going, in which he would sit in during his explanation — check it out!

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DIY thermostat keeps the harsh winter cold at bay


[Phil’s] parents grow their own organic food, but the harsh Ukraine winters make storing it a difficult proposition. Since it can drop to -30°C on occasion, they asked him to find a way to keep their storeroom at around 5-7°C above zero. He decided to construct his own programmable thermostat to keep things in check, and has been documenting the process as he goes along.

The thermostat uses a DS18B20 temperature sensor to monitor the room, and the logic is handled by an ATtiny2313. When the temperature dips low enough, the ATtiny triggers the room’s heater via a standard 240v relay. He can check the current temperature via a small 7-segment display mounted on the control board, which also contains three microswitches for controlling the heater.

It looks like a pretty solid build so far, and while he hasn’t finished coding the thermostat just yet, [Phil] says that those details are forthcoming. He has published a schematic however, so you can get a jump start on building your own if you’re looking to warm things up this winter.

Continue reading to see a video overview of the thermostat’s design.

Continue reading “DIY thermostat keeps the harsh winter cold at bay”

Bluetooth temperature module

Wanting to know the outside temperature, [Jamie Maloway] built his own temperature sensor that can be read with a Bluetooth device. Let’s take a tour of the hardware above from right to left. There’s a linear voltage regulator with two filtering caps and a terminal block to attach a 9V battery or other power source. Next there’s an 8 MHz crystal and it’s capacitors, followed by a programming header on top and a 1-wire temperature IC, the DS18B20 we’re all familiar with hanging off the bottom. These both connect to the 8-pin PIC 12F675 that drives the system, and transmits using a Bluetooth module from Sure Electronics. Since this is using a serial protocol and transmitting ASCII data, it can be read using an automated script, or simply by using a terminal program.

Now, who’s going to be the first to get rid of the battery and leech off of the mains through inductance?