Monitor Power Consumption Of Low-Power Devices

February 28, 2018 by Bryan Cockfield 14 Comments

Perhaps the most important consideration to make when designing a battery-operated device of any kind is the power consumption. Keeping it running for longer between battery changes is often a key design point. To that end, if you need to know how small programming changes will impact the power consumption of your device then [Daniel] has a great tool that you might find helpful: an ESP8266-based live power meter.

The power meter itself is battery-powered via a 600 mAh battery and monitors an e-paper module, which also displays information about power consumption. It runs using a NodeMCU and measures voltage and current across a 100-ohm resistor to calculate the power use, although the resolution does start to get noisy when the device is in standby/sleep mode. One presumes this could be solved by changing the value of the resistor in order to get more accurate measurements at the expense of losing accuracy during moments of high power consumption.

While this power monitor was built specifically to monitor power consumption on this particular e-paper display project, it should be easily portable into other battery-based systems that need fine tuning in order to maximize battery life. As a bonus, the display is already included in the project. There are ways of getting even more information about your battery usage, although if power consumption is important than you may want to stick with a more straightforward tool like this one.

Cheap Vacuum Source For Working With Dangerous Chemicals

September 4, 2016 by Gerrit Coetzee 49 Comments

[Nurdrage] puts out a lot of neat videos, mostly about home chemistry. For the home chemist it is occasionally desirable to pull a vacuum. For example, a potentially dangerous chemical can be boiled and distilled at a much lower temperature than at atmospheric pressures.

However, there’s a problem with just going to the local import store and buying the first vacuum pump on the shelf. They are primarily designed for atmospheric gasses and tend to melt when exposed to solvents. If you’re a big university or a commercial lab this is no problem. You just drop three grand on a Teflon diaphragm pump or a liquid nitrogen trap. For the home chemist who’s already having enough trouble just buying the chemicals needed for neat experiments, this is not an option.

[Nurdrage] demonstrates the proper usage of a much cheaper option: an aspirator vacuum pump. You might remember something similar from high school chemistry. School pumps generally use flowing tap water to produce the vacuum. [Nurdrage] is saving water by using a fluid pump and a reservoir to drive his aspirator.

Aspirator pumps use the Venturi effect to create a vacuum. These devices are cheap because there are no moving parts. We looked it up and the one he is using costs ten US dollars on fleabay. It can pull enough vacuum to boil water below room temperature.

The video is really good and provides a lot of useful information. It also seems like a really useful device for other hacking tasks outside of home chemistry. Video after the break.

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Water Use Feedback Changes Behavior

November 7, 2010 by Mike Szczys 26 Comments

How much water do you use when showering, or washing your hands, or washing the dishes? Not how much does the average person use, but how much to you use? That’s what the team over at Teague Labs set out to find with this water usage feedback system. The sensor used is a Koolance flow meter which is intended to measure coolant flow in PC liquid cooling systems. At $20, it makes a nice low-cost sensor which was paired with a WiFi enabled Arduino. In the image above they’re using an iPad as a screen so that you can see how much water you’re using (or wasting) as you wash your hands. This resulted in saving 1/2 gallon of water every time someone washed their hands.

The project code, schematic, and board files are all available for download. Along with the hardware build there’s some nice server-side software that gathers and graphs the data over time. We’ve seen a lot of power-meter hacks, but it’s nice to have the option to track water usage, even if this is tailored to just one tap at a time.