Donation meter raises alarm when not plugged with coins

This is something of a mandatory donation meter. If you don’t feed it with coins it sounds a very loud alarm continuously.

[Piet De Vaere] built the device for a free festival in Ghent, Belgium. The intent is to help raise awareness that although free of an admission price, the success of the event depends on donations. It works much like a parking meter. When you feed it coins time is added to the meter. When it runs all the way down that large loudspeaker on the right side of the case sounds the alarm.

In the video after the break [Piet] walks us through a demonstration, followed by a tour of the hardware. The pointer on the meter is a piece of cardboard connected to a servo. An Arduino board controls the servo, adding time in two-minute intervals whenever a coin enters the chute and passes by an optical sensor. There is no distinction between types of coins.

The use of a pizza box as a prototyping board shows that you don’t have to be fancy to build something neat.

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Visual rain sensor — so you never have to look outside

Now you can find out how hard it is raining outside without leaving the confines of your mancave/womancave. Pictured above is the sensor portion of what [Frapedia] calls his visual rain sensor.

Most rain gauges just use a graduated cylinder to capture water as it falls from the sky. That will give you a reasonably accurate measure of how much it rained, but it tells you nothing about how hard it rained. The measurement made here is based on sound. The harder it rains, the lounder the sound will be from water hitting an up-turned metal bowl. The unit above turns the system on when water bridges the traces, then a microphone is used to monitor the sound from the bowl. This is visualized by a VU-meter chip on a column of LEDs mounted inside the house.

After the break you can see the project box that houses the status display. We say it’s too small an needs to be replaced with a much larger LED meter.

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Wristwatch measures your perception of time; also tells time

This wristwatch is hiding a lot of features in its hardware and its software. It’s called the TicTocTrac and it’s a Senior project for a pair of students at Cornell University. Judging from the sheer volume and quality of the project documentation we wonder if someone has a science writing career ahead of them? Be we digress… It’s a clock and we love it!

First off, this does more than just tell the time. In fact, that’s almost an ancillary function in this case. The wristwatch is more of a metering device to record your own time-based behaviors. Find yourself checking your watch frequently as the lunch break approaches? This watch records that activity and you can later graph the data. This allows you to analyze how you percieve the passage of time. The more often you check the time, the slower you feel time progressing. The documentation does a much better job of describing this than we have time for, so check it out.

On the hardware side of things we’re quite impressed. The housing is 3D printed. It hides two half-circle PCBs below the full-circle PCB face plate. The half-boards leave space for a tiny rechargeable battery, and host a vibrating motor and RTC chip. Instead of using buttons, there’s a piezo sensor which detects when you tap on the top of the watch.

Harvesting and graphing wireless household utility meter info

Both our electrical meter and our gas meter are located in the basement of our house (we recently had the gas meter moved outside though). When people see this they always ask if the meter readers have to come inside once a month. The answer is no, these meters broadcast usage data which is picked up once a month when a utility company vehicle drives down the street. If you have wireless meters in your house, here’s a way to harvest and graph the wireless data so that you can analyze your usage patterns.

The hardware used here is a special USB dongle. This has a 900 MHz radio which picks out the packets from a reasonably large list of meter types, and pushes them through the USB interface. In the image above you can see that an Arduino with a USB host shield is used, but there are also drivers if you want to connect this directly to your computer.

We looked around and didn’t find any specifics on the hardware used on that board. But it can’t be all that hard to make one of these at home… the populated board seems to have just two ICs and a few passive components. Anyone up to the challenge of hacking together their own packet sniffer? We wonder if the Next HOPE badge could pull down the data?

[Thanks Chris]

Polish your understanding of capacitors by building this meter

Building a capacitance meter is a great exercise. If you’re feeling quite safe in your digital-circuit-only life, this will push just far enough out of the comfort zone for you to see there’s nothing to fear in adding analog circuits to your designs. Here, [Raj] compares a voltage divider and RC timer to calculate the value of a capacitor. The project is aimed at teaching the concepts, and will be easy to follow for anyone who has at least a bit of experience working with a programmable microcontroller.

The meter is based on an established equation that uses are starting and ending voltage, as well as the time it took to transition between the two, to calculate capacitance. The capacitor will be charged from 0 volts to 0.5 volts. Using the built-in analog comparator is the easiest way to do this. [Raj] breadboarded a voltage divider to establish a 0.5V reference on one of the comparator’s pins. The other input comes from a circuit that places a resistor in line with the capacitor being tested. When that reading rises above the 0.5 volt reference the comparator match will be tripped, stopping a timer that had been running during the charge cycle. From there it’s just a matter of using the timer value in the calculation.

Simple hardware and Python drive this Splunk LED meter

Want to monitor the company system without continually loading up the Splunk dashboard? It turns out that they’ve got their own Python package which makes pulling down data a snap. All [Rick] needed to do was hook up an LED meter as an external display.

It used to be that this would take a lot of wire and bit of soldering (or some special Christmas lights), but the advent of affordable LED strips has really taken the guess-work out of it. He’s using an RGB version acquired from Adafruit Industries. These strips are driven using SPI and multiple-colors mean you can display multi-dimensional data using one column. He chose to use a Teensy microcontroller, grabbing some plastic packaging for welding rods as the enclosure. These strips are extremely bright and to help soften the impact he added wax paper to the inside of the enclosure to act as a diffuser.

Looking for more projects that use strips like this one? They make fantastic addressable accent lighting for your home.

Quick project: Hard drive system meter

[Ginge] sent in this fun little project. He gave himself 3 hours to complete a hack (not including research time) and managed to come up with this cool activity meter. He handles the entire project like it is some kind of contest. Ground rules are laid out, requiring practicality of the final product, minimum investment, and almost complete use of junk pile pieces.

Using an old hard drive for the frame of the project as well as the “dial” part of the meter, he hacked together a system load/ hdd and proc activity meter. The brains of the project are an AVR and he even implemented some PWM to smoothing things out. He goes into some fair detail on the construction of the thing (was the writeup included in your build time? -50 points!). Even though he’s using a piece that he manufactures and sells (OSIF), you could probably figure out how to do it without.

You can see a video of it in action after the break

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