A Wooden Based, CD Stepper Scribbler

[Rohit Gupta] is back with a plotter made from scrap CD drives and an old RC servo. [Rohit] is working on hacks to create CNC machines and sharing his activities with the world. His CNC design calls for salvaged stepper motors so he first built a device for testing them. You’ve got to admire his use of the language. He named his plotter project ‘Sketchy’ and his motor tester is called ‘Easy Peasy’.

sketchyAfter finding some CD drives at the scrap pile he tore them down to test with Easy Peasy. The raw materials for the frame came from a wooden crate for an AC unit but he didn’t just start cutting it up. Nope, first he created plans with CAD; now that’s a hack you have to admire.

With the steppers tested working, and the base build under way he moved onto the control system. Originally the hardware was demonstrated using an MSP430. This worked, but a flaw in the hardware design was found. With the pen attached directly to the servo horn, it would draw a long line when being rotated away from the drawing position.

The fix is a replacement servo setup which lifts the pen up instead of rotating it. But that showed that the drawing surface wasn’t smooth. The pen kept missing places or getting caught and destroyed. The use of a spring loaded pen solved this issue. Success!

One further change migrated away from the MSP430 in favor of an Arduino Pro Mini in order to use a GRBL library instead of the g-code generator which was performing questionably. Since he likes Hackaday so much one of his first attempts with the final version of Sketchy was our logo, shown in the video after the break.

When we last saw [Rohit] he had created a fancy PCB ruler to measure components.

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RoomMote, a DIY Remote for Your Room Project

[Rohit] wrote in to tell us about a project he has created. Like most projects, his solves a problem. Sometimes while sleeping, a mosquito will infiltrate his room. He has a mosquito repellent machine but there are 2 problems, he has to get up to turn it on/off and it smells bad when in use. [Rohit] only needed a remote-controlled mosquito repelling machine but decided to make a 6 channel system he calls the RoomMote.

From the beginning, the plan was to use an old Sony TV remote to do the transmitting. The receiver unit was completely made from scratch. [Rohit] designed his own circuit around a surface mount MSP430 chip and made a really nice looking PCB to fit inside a project box he had kicking around. The MSP430 chip was programmed to turn relays on and off based on the signals received from the Sony remote.  These relays are inside an electrical box and control AC outlets. Just plug in your light, radio or mosquito repellent into the appropriate outlet for wireless control. Code for the MSP430 is made available on [Rohit’s] project page for anyone wanting to make something similar.

In addition to the relays, there is an RGB LED strip attached to the custom circuit board. By using more of the Sony remote’s buttons, the LED strip can output 6 pre-programmed colors, some mood lighting for the mosquitoes!

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Chili-Gation With The MSP430

[Dave] used to grow chili peppers, but after moving to Texas he noticed his plants were drying up and dying off. This is understandable; Texas is freaking hot compared to his old home in the UK. These chilis needed a watering system, and with a pump, relay module, and an MSP430 launchpad, it was pretty easy to put together.

The core of the build is an MSP430 launchpad, a Sharp Memory LCD BoosterPack for the user interface, and a few bits and bobs for pumping water from a large soda bottle to the plant.

Before beginning his build, [Dave] took a look at commercial watering systems, but could only find huge irrigation systems for greenhouses or gardens. This was obviously overkill, but with a few parts – a six volt pump and a relay control board – [Dave] was able to make a simple system that keeps chilis watered for seven days between refilling the reservoir.

New Part Day: MSP430 + Cortex M4F

Texas Instruments’ MSP430 series of microcontrollers has been the standard extremely low power microcontroller for several years now. It’s not an ARM, though, so while there are fans of the ‘430, there aren’t a lot of people who would want to port their work in ARM to a completely different architecture. Here is TI’s answer to that. It’s called the MSP432, and it combines the low power tech of the ‘430 with a 32-bit ARM Cortex M4F running at 48MHz.

This is not the first ARM Cortex M4F platform TI has developed; the Tiva C series is based on the Cortex M4F core and was released a few years ago. The MSP432 is a little bit different, leveraging the entire development system of the MSP430 and adding a DSP engine and a FPU. If you’re looking for something that’s low power but still powerful, there you go. You can find the official press release here.

If you’d like to try out the MSP432, there’s a LaunchPad available. $13 to TI gets you in the door. The most capable MSP432 with 256 kB of Flash, 64 kB of SRAM, and 24 ADC channels hasn’t hit distributors yet, but you can sample it here.

Calibrating The MSP430 Digitally Controlled Oscillator

The MSP430 is a popular microcontroller, and on board is a neat little clock source, a digitally controlled oscillator, or DCO. This oscillator can be used for everything from setting baud rates for a UART or for setting the clock for a VGA output.

While the DCO is precise – once you set it, it’ll keep ticking off at the correct rate – it’s not accurate. Without a bit of code, it’s difficult to set the DCO to the rate you want, and the code to set that rate will be different between different chips.

When [Mike] tried to set up a UART between an MSP430 and a Bluetooth module, he ran into a problem. Setting the MSP to the correct baud rate was difficult. Luckily, there’s a way around that.

There’s an easy way to set the DCO on the MSP programatically; just set two timers – one that interrupts every 512 cycles, with its clock source set to the DCO, and another that interrupts every 32768 cycles that gets its clock from a 32.768kHz crystal. The first timer clicks off every second, and by multiplying the first timer by 512, the real speed of the DCO can be deduced.

After playing around with this technique and testing the same code on two different chips, [Mike] found there can be a difference of almost 1MHz between the DCOs from chip to chip. That’s something that would have been helpful to know when he was playing around with VGA on the ‘430. Back then he just used a crystal.

An MSP430-based Automatic Fish Feeder

[Dmitri] wanted to buy an automatic feeding setup for his aquarium, but he found that most off-the-shelf feeders are really inaccurate with portion control. [Dmitri]’s fish is sensitive to overfeeding, so an off-the-shelf feeder wouldn’t get the job done. Since [Dmitri] knows a thing or two about electronics, he set out to build his own microcontroller-based automatic feeding machine.

[Dmitri]’s machine is based around a MSP430 that starts feeding at scheduled times and controls how much food is dispensed. The MSP lives on a custom PCB that [Dmitri] designed, which includes a stepper motor driver and input for an endstop sensor. The board is wired to a stepper motor that advances a small wooden board with a series of holes in it. Each hole is filled with a single serving of food. The board slides along a piece of U-channel, and food drops out of each hole into the aquarium when the hole reaches the end of the channel.

The whole build is very well documented, and [Dmitri] explains each block of his schematic in detail. His firmware is also open-source, so you can build your own fish feeder based off of his design. Check out the video after the break to see the feeder in action.

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Calculator + MSP430 + IR LED = TV Remote?

Eschewing the store-bought solution, [Stefan] managed to build a TV remote out of an old calculator. The brains of the calculator were discarded and replaced with an MSP430, leaving only the button matrix and enclosure. Rather than look it up, he successfully mapped the matrix manually before getting stumped with the infrared code timings. Some research pointed him to a peculiarity with Samsung IR codes and with help from an open source remote control library he got it working.

When the range was too limited to satisfy him he added a booster circuit and an LED driver which he snapped off the top of an old remote; now it works from 30 feet away. Some electrical tape and hot glue later and it all fit back into the original case.

It cannot take photos or play Super Smash Brothers, but it does what a remote needs to do: browses channels in the guide, control volume, and turn the TV on or off. Considering that all this calculator was built to do was boring basic arithmetic, it is a procrastination-enabling upgrade.

See the video after the break for some smiles.

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