Testing DRAM, One Byte At A Time

March 18, 2016 by Brian Benchoff 26 Comments

A few weekends ago, [Chris] was in the mood for some retrogaming. That meant digging out the old Apple IIgs equipped with a monstrous RAM card with a whole three megabytes of RAM. This particular Apple IIgs had intermittent issues for a long time, and [Chris] was beginning to suspect the RAM was the culprit. Testing this required testing a few dozen individual RAM chips, so why not build something with an Arduino to make [Chris]’ life easier?

The chips found in [Chris]’ Apple are standard 1 M x 1 DRAM chips, the standard for late-80s computers. To test these chips on an Arduino, he picked up a beautiful ZIF socket, wired up the chip to an Arduino shield, and began the joyous process of figuring out how to interface DRAM to an Arduino.

Unlike static memories, DRAM needs to be refreshed periodically to recharge the capacitors. While this refresh cycle was the bane of designers and engineers throughout time, [Chris] actually doesn’t need to care about refreshing the DRAM. He’s just writing 1024 rows to the memory and reading it straight out – no need to refresh the memory. The trick comes from the multiplexed address bus. For his project, [Chris] needs to write 10 bits of the address, latch it, then write the other half of the address bits.

The DRAM tester was a success, and [Chris] put all the code and schematics up on GitHub. Solving the mystery of the broken Apple IIgs wasn’t as simple, as [Chris] thinks the problem might be in one of the support chips on the gigantic RAM card or the IIgs motherboard. Still, it’s a neat, quick build to test out a few DRAM chips.

Presenting The Internet Of Trash Cans !

March 17, 2016 by Anool Mahidharia 17 Comments

This was gonna happen – sooner or later. [matthewhallberg] built a “Smart” trash can that is connected to the Internet and can be controlled by its own Android App. We’re not sure if the world needs it, but he wanted one and so built it. He started it out on a serious note, but quickly realized the fun part of this build – check out his funny Infomercial style video after the break.

The build itself is uncomplicated and can be replicated with ease. A servo motor helps flip the lid open and close. This is triggered by an ultrasonic ping sensor, which responds when someone waves a hand in front of the trash can. A second ping sensor helps inform the user when it is full and needs to be emptied. A Leonardo with the Idunio Yun shield helps connect the trash can to the internet. An mp3 shield connected to a set of powered computer speakers adds voice capability to the trash can, allowing it to play back pre-recorded sound clips. Finally, a Bluetooth module lets him connect it to an Android phone and the companion app controls the trash can remotely.

For the IoT side of things, [matthewhallberg] uses a Temboo account to send an email to the user when the trash can is full. The Arduino sketch, a header file to configure the Temboo account, and the Android application can all be downloaded from his blog. If this project inspires you, try building this awesome Robotic trash can which catches anything that you throw near it or read the barcodes off the trash being thrown out and update the grocery list.

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Fingerprint Garage Door Won’t Open Every Time A Neighbor Microwaves A Burrito

March 16, 2016 by Gerrit Coetzee 18 Comments

With three kids, including himself, [Dave] faced the very real likelihood of someone absent-mindedly leaving the garage door open and being robbed blind. Rather than installing some plebeian solution, he compiled a feature list. And what a feature list it is!

The garage door needed to notify him of its status with strategically placed LEDs around the house, and give him full control on his devices. He wanted to open and close it using his existing key-code entry system. Lastly, it would be extra-cool if he could add some biometrics to it; in this case, a fingerprint sensor.

The core hardware is the staple Arduino augmented with a fingerprint module, a touch screen, some vitamins, and a WiFi break-out. He also worked up some casings in tinkercad: one for the indoor hardware, another with a flip cover for the outdoor fingerprint scanner.

We think [Dave] has accomplished what he set out to. We can just picture the would-be-thief staring at the finger print scanner and moving their operation one house over where the world is simpler. Video after the break.

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SDRAM Logic Analyzer Uses An AVR And A Dirty Trick

March 15, 2016 by Al Williams 58 Comments

We often see “logic analyzer” projects which are little more than microcontrollers reading data as fast as they can, sending it to a PC, and then plotting the results. Depending on how fast the microcontroller is, these projects range from adequate to not very useful.

At first glance, [esot.eric’s] logic analyzer project has an AVR in it, so it ought to be on the low end of the scale. Then you look at the specs: 32 channels at 30 megasamples per second. How does that work with an AVR in it?

The answer lies in the selection of components. The analyzer uses a 128MB SDRAM DIMM (like an older PC might use for main memory). That makes sense; the Arduino can’t store much data internally. However, it isn’t the storage capacity that makes this choice critical. It seems [esot.eric] has a way to make the RAM “free run”.

The idea is to use the Arduino (or other host microcontroller) to set up the memory. Some of the memory’s output bits feedback to the address and data lines. Then the microcontroller steps aside and the SDRAM clocks samples into its memory by itself at the prevailing clock rate for the memory.

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Laser PCB Exposer Built From CD-ROM Drives

March 14, 2016 by Gerrit Coetzee 45 Comments

[Neumi] has built a CNC Laser using CD-ROM drives as the X and Y motion platforms. The small 405nm laser can engrave light materials like wood and foam. The coolest use demonstrated in the video is exposing pre-coated photo-resist PCBs.

With $61 US Dollars (55 Euro) for the Arduino, stepper drivers, and a laser in the project, [Nuemi] got a pretty capable machine after adding a few parts from the junk bin. He wanted to avoid using existing software in order to learn the concepts behind a laser engraver. In the end, he has a working software package which can send raster scans to an Arduino mega. The mega then controls the sync between the stepper and laser firings. The code is available on GitHub.

The machine can do a 30x30mm PCB in 10 minutes. It’s not about to set a record, but it’s cool and not at all bad for the price. You can see the failed PCBs lined up in the video from the initial tuning, but the final one produced a board very equivalent to the toner transfer method. Video after the break.

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Petite Package Provides Powerful Robot

March 13, 2016 by Rud Merriam 5 Comments

The Robot Operating System (ROS) is typically associated with big robots but [Grassjelly] decided to prove differently by creating Linorobot. This small, differential drive robot is similar in appearance to many small Arduino based robots often used for line following. Linorobot packs a lot more computing power with a Teensy 3.1 connected to a Radxa Rock Pro. The Teensy handles the motors, reading their encoders, and acquisition of IMU data.

The Radxa, new to us here at Hackaday, is a single board computer based on the quad-core ARM Cortex-A9 1.6 GHz CPU. It may not have been seen on our pages but if you’re at Hackaday Belgrade you can attend a session on building a cluster using it. The ability to run Linux is key to using ROS, which is an open source system for controlling robots. With the Radxa running ROS it interfaces directly to the Neato XV-11 Lidar’s dedicated controller board.

Avoiding the hand.

Mapping with lidar.

The Linorobot packs into a small robot the capabilities usually seen in much larger and expensive robots such as the Turtlebot 2. With this diminutive robot hackers can learn about doing SLAM (Simultaneous Localization and Mapping) and autonomous navigation, plus the other capabilities of ROS.

[Grassjelly] has a tutorial on building the robot which is also a good introduce to ROS. He provides the software as open source. It’s an impressive project which provides a small, comparatively affordable robot for learning and working with ROS. A video of Linorobot SLAMing and navigating [Grassjelly’s] lab is after the break.

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Blinky LED Bike Bag

March 13, 2016 by Richard Baguley 20 Comments

Bicycle riders can never be too visible: the more visible you are, the less chance there is someone will hit you. That’s the idea behind the Arduibag, a neat open-source project from [Michaël D’Auria] and [Stéphane De Graeve]. The project combines a joystick that mounts on the handlebars with a dot matrix LED display in a backpack. By moving the joystick, the user can indicate things such as that they are turning, stopping, say thank you or show a hazard triangle to warn of an accident.

The whole project is built from simple components, such as an Adafruit LED matrix and a Bluno (an Arduino-compatible board with built-in Bluetooth 4.0) combined with a big battery that drives the LED matrix. This connects to the joystick, which is in a 3D printed case that clips onto the handlebars for easy use. It looks like a fairly simple build, with the larger components being mounted on a board that fits into the backpack and holds everything in place. You then add a clear plastic cover to part of the backpack over the LED matrix, and you are ready to hit the road, hopefully without actually hitting the road.

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