Motor Drivers: Half H-bridge With Brake And More

October 28, 2011 by Mike Szczys 11 Comments

Here’s a nice little circuit that will drive a motor and allow you to stop its rotation, giving your robot a set of brakes. It’s part of [JM’s] post about the in’s and out’s of building microcontroller friendly motor controllers (translated).

This particular setup is a half H-bridge. It allows you to drive the motor in one direction only. The MOSFET used on the ground-side of the motor doesn’t actually need to be there. This is the brake which let you electronically stop the motor from spinning. Without it, the motor will keep turning under its own momentum when the half-bridge is shut off. Depending on the application this can be a big problem. There’s a great demonstration of the circuit braking a fast spinning motor in the video clip below the fold.

It is possible to use this driver with PWM, but [JM] has some warnings about inbuilt functions like FastPWM. Make sure you read his admonition, and if you need a refresher don’t miss this Hackaday video segment.

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The Basics Of Reading Data From Resistive Touchscreens

October 28, 2011 by Mike Szczys 5 Comments

[Chris] just posted his latest tutorial which shows you how to read position data from a resistive touchscreen. These devices are fairly simple, and since they’re used in a lot of consumer electronics you can pick one up for a few bucks. This looks like it is overstock for an old Palm device.

The interface is simple, there’s just four conductors on the tab at the top of the overlay. But connecting to these is a bit of an issue since you can’t really solder directly to them. [Chris] ended up using scotch-tape to hold wires in place, with a paperclip to keep them presses against the conductors. Those conductors are used in pairs, with a positive and negative lead for the X and Y axis. To take a measurement you use I/O pins to connect voltage and ground, then read the voltage that makes it to the gound side using an ADC. This works because the point that’s being pressed on the screen acts as a variable resistor for the circuit. Data for the two axes must be read in separate operations so that the positive voltages don’t interfere with each other.

The nice thing is that once you’ve got it working with a small screen it is easily scaled up. In fact, the 23″ touchscreen used on this Android hack is just another 4-wire resistive device.

You can see a video demonstration of [Chris’] test rig embedded after the break.

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Crawling Zombie Is Shockingly Creepy

October 27, 2011 by Mike Szczys 28 Comments

When [Mark] sent in the tip about this crawling zombie prop he said that it didn’t sound scary but warned us that it is terrifying when you see it. He’s absolutely right, the video after the break shows some remarkably undead movement from the thing.

This crawler is actually radio controlled. Details are brief, but there’s plenty of pictures and the start of a build tutorial for the hardware. A wood frame serves as collar-bone and spine for the zombie. Attached to the spine are two motors which allow independent shoulder operation. We’d wager that the realistic movements are due to a talented operator at the controls, but it can’t be too hard to master if you play around with it for a while. It looks like the initial build was headless, but we think the addition of the zombie head really makes finishes out the project!

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[Vigo’s] Stare Follows You Wherever You Go

October 27, 2011 by Mike Szczys 20 Comments

To decorate the office for Halloween [Eric] decided to make [Vigo the Carpathian] stare at passersby. We hope that readers recognize this image, but for those younger hackers who don’t, this painting of [Vigo] played an important part in the classic film Ghostbusters II.

In the movie, his eyes appeared to be following anyone looking at the painting. [Eric] grabbed a Kinect and used Processing to recreate the effect in real life. The image is displayed on an LCD screen. A bit of work with Photoshop allowed him to cut out the eyes from the image, then create sprites which are moved by the Processing sketch. It’s reading data from the Kinect (so it knows where to ‘look’) which you can see perched on the top of the cubicle wall. The illusion is delightful, see for yourself in the clip after the break. We’ve already watched it a half-dozen times, and it looks like it was a real hit with the guests at the open house.

Can you believe they threw this together in just one day?

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Rooting Sony PRS-T1 Lets You Get At The Android Goodies

October 26, 2011 by Mike Szczys 26 Comments

Cries of “I am root!” abound once again with the rooting of Sony’s PRS-T1 eBook reader. The eBook Reader Blog took the original rooting directions and then looked at some of the things you can do with root access.

This hardware is based around an ePaper display, but we must say that the performance seems to be fantastic. There may be a few missing features from the original user interface (like how pages are turned) that can be fixed with root access, but we think it’s the added Android access that makes this worth it. In the video after the break you’ll see that you can drop through to the Android 2.2 desktop and install any application you’re interested in using. This is a multi-touch display so it’s well suited for navigation although applications don’t work well yet because of excessive screen refreshing. But we’re sure that will improve with time. Of note is the ability to play music through apps like Pandora, and the ability to load content from other providers like Amazon books via the Kindle app.

Every time we write one of these rooted features we can’t help but think back to this I’m a Mac spoof video…. you’ll see why in the last few seconds.

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Macetech Takes On Its Own Ambilight Clone Hack

October 26, 2011 by Mike Szczys 23 Comments

[Garrett Mace] decided to beef up his 58 inches of plasma with 60 Watts of LED lighting. After seeing a ton of Ambilight clones using his LED modules, he’s built his own powerful system. Not surprisingly, it’s nothing short of professional-grade work.

Kudos to [Garrett] for showing the entire process in the video after the break. We’re talking about his planning stages, which are so often left out of build logs. He first measures the back of the television, and does some testing for distance and angle of the Satellite LED modules to establish how many should be used and to estimate the optimal spacing. From there he modelled a framing system before getting down to the actual build.

The wood frame is made up of a box with a horizontal crossbar serving as a place to mount the drivers. Around the edges, tilting rails were added to make the angle of the LED modules adjustable. As with many other Ambilight clones, [Garrett] uses the boblight software to drive his system and we appreciate it that he included his configuration file for reference. Once up and running the effect is breathtaking (and possibly blinding).

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Halloween Time Machine Simulator Built Into An Outhouse

October 26, 2011 by Mike Szczys 24 Comments

[Sam] is an avid Halloween builder and has been hard at work on a time-machine simulator for this year’s festivities (alternate link). He recently assembled the enclosure which is seen above. It’s got room for two riders who will be strapped in place, with plenty of interior items to keep them occupied. There will be three LCD monitors acting as front and side windows for the time machine.

In the video after the break (taken from his vblog on the page linked above) [Sam] walks us through all of the electronics that went into this. He’s got red lights controlled by a servo motor attached to a dimmer switch. There’s a vibrating seat to give the riders a jolt, and a control panel which shows the status of the time machine. The thing is, it’s not just the physical build that’s impressive. We know from his past projects that [Sam] is a showman and he doesn’t disappoint this year. He spent a lot of time filming and generating computer graphics and sound to really make the ride a multimedia odyssey.

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