$4 volt meter from a dollar store pedometer

[Paulo]‘s got a few solar panels on his shed, and while he does have a fairly nice setup with a battery charge controller, he found himself looking around for a panel voltmeter. Of course you can buy a panel voltmeter for under $20, but [Paulo] wanted something that fit his 4-4-4 plan; his voltmeter should cost under $4, draw less than 4mA, and last for 4 years. The jury is still out on the 4 year qualifier, but he did manage to meet his other goals by repurposing a dollar store pedometer as a voltmeter.

The pedometer in question is a very simple device. After inspecting the PCB, [Paulo] found it operates by looking at a trigger pin and incrementing the number on the display each time the circuit closed. [Paul] designed a very small PIC12F-powered circuit that reads the voltage of his batteries and triggers the pedometer’s LCD for every 10th of a volt. To display 12.6 Volts, [Paulo]‘s code triggers the LCD 126 times, for example.

After wiring up the reset button so the display will go back down to zero for each new reading, [Paulo] encased his new volt meter in a plastic box. It’s not exactly a fast way of measuring voltage, but seeing as how that won’t change very fast, it’s the perfect solution for [Paulo]‘s solar charger setup.

Steam-powered pickup winder

[Valve Child] has been building a few three-string cigar box guitars. Of course he’ll need a few pickups, but three-string guitar pickups aren’t exactly easy to come by. To solve this problem, he’s built a guitar pickup winder powered by a steam engine.

The pickup winder is powered by a Wilesco D20 model steam engine, connected to the actual winding mechanism via a rubber belt. To the right of the bobbin bracket is a mechanism built out of Meccano – Erector sets for us americans – that provides a mechanical counter for the number of wire turns and a wire traverse to keep each layer of wire somewhat even across the width of the bobbin.

Previously, we’ve seen [Valve Child]‘s really sweet sounding lap steel build from a log using a hand-wound pickup and a preamp tube as the bridge. It’s questionable if the guitar signal came from this lap steel via the pickup or the microphonic tube, but now [Valve Child] has a really, really good method of improving his pickup production abilities.

Video after the break.

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Linux on a Nspire CAS CX Calculator

It’s great to see Linux running on a device in a way that was never intended. [tangrs] has successfully run a Linux kernel on the ARM based Nspire CAS CX graphing calculator. He’s developed an in-place bootloader that allows a kernel to be loaded from within the stock Nspire OS. It also allows for peeking and poking at memory for debugging.

[tangrs] also managed to get USB host mode working on the calculator. This allows for a USB keyboard and Wifi dongle to be connected. At this point, the calculator can connect to the internet and browse using a text-based browser: Links. The calculator runs a SSH server for remote access, and graphical browsing is in the works.

It looks like this calculator is on the way to being a handheld Linux device. All of the source for the kernel and bootloader are available on [tangrs]‘s Github and updates on his blog. After the break, check out a video of text-based browsing using a full keyboard.

[Read more...]

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