Driving A 16×2 LCD With Voltage Modulation

The basic 16×2 LCD is an extremely popular component that we’ve seen used in more projects than we could possibly count. Part of that is because modern microcontrollers make it so easy to work with; if you’ve got an I2C variant of the display, it only takes four wires to drive it. That puts printing a line of text on one of these LCDs a step or two above blinking an LED on a digital pin on the hierarchy of beginner’s electronics projects.

What’s that? Even four wires is too many? In that case, you might be interested in this hack from [Vinod] which shows how you can drive the classic 16×2 with data and power on the same pair of wires. You’ll still need a microcontroller “backpack” for the LCD to interpret the modulated voltage, but if you’ve got an application for a simple remote display, this is definitely worth checking out.

The basic idea is to “blink” the 5 V line so quick that a capacitor on the LCD side can float the electronics over the dips in voltage. As long as one of the pins of the microcontroller is connected to the 5 V line before the capacitor, it will be able to pick up when the line goes low. With a high enough data rate and a large enough capacitor as a buffer, you’re well on the way to encoding your data to be displayed.

For the transmitting side, [Vinod] is using a Python script on his computer that’s sending out the text for the LCD over a standard USB to UART converter. That’s fed into a small circuit put together on a scrap of perfboard that triggers a MOSFET off of the UART TX line.

We actually covered the theory behind this technique years ago, but it’s always interesting to see somebody put together a real-world example. There might not be too many practical uses for this trick in the era of dirt-cheap microcontrollers bristling with I/O, but it might make a fun gag at your hackerspace.

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Robots Invade Your Personal Space

If you have ever had to complete a task such as building a LEGO model over a remote connection, you will know that the challenges are like an absurd grade school group project. The person giving directions often has trouble describing what they are thinking, and the person doing the work has trouble interpreting what the instructor wants. “Turn the blue block over. No, only half way. Go back. Now turn it. No, the other way. NO! Not clockwise, downward. That’s Upward! Geez. Are you even listening‽” Good times.

While you may not be in this situation every day, the Keio University of Japan has an intuitive way to give instructors a way to physically interact with an instructee through a Moore/Swayze experience. The instructor has a camera in typical pirate parrot placement over the shoulder. Two arms are controlled by the instructor who can see through stereoscopic cameras to have a first-person view from across the globe. This natural way to interact with the user’s environment allows muscle memory to pass from the instructor to the wearer.

For some of the other styles of telepresence, see this deep-sea bot and a cylindrical screen that looks like someone is beaming up directly from the holodeck.

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Bouncing Pack Eases Those Tired Shoulders

If you are a hillwalker, wherever your preferred stomping ground may be you’ll know the importance of a pack with a good strap system. A comfortable pack will make the difference between tiredness and agony, and can easily add a considerable difference to your daily range.

At Arizona State University’s Human Integration Laboratory, they were approached by the US Army to investigate means by which the effect of carrying a heavy backpack could be mitigated. A soldier’s full kit is extremely heavy, and while the best available webbing systems will make a contribution to the comfort of carrying it, they can only go so far. There is still the jarring effect of the impulse force of such a significant load bearing down on the soldier’s shoulders as it comes down after every step, and this when taken over a lengthy march makes a significant difference to overall endurance.

The ASU lab’s solution was to mount the load on a spring-loaded vertical actuator attached to the pack harness and frame. The on-board microcontroller judges the moment of maximum downward impulse force as the wearer comes down from a step, and applies a corresponding upward force to the actuator. Power comes from a lithium-ion battery pack. The effect is to make the load oscillate up and down, and to lessen the wear and tear on the shoulders. It does not reduce the weight you are carrying, but it does lift it off your shoulders for an instant just when you need it.

There is a video of it being tested in the sun-drenched Arizona mountains, that we’ve placed below the break.

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Two-wire Serial Backpack For GLCD Screens

[Debraj] wrote in about his 2-wire serial backpack he developed for a Graphic LCD screen. It’s build on a hunk of protoboard and uses a pair of 595 shift registers to translate incoming serial data to the parallel interface which is used by the LCD screen. It takes more time to push commands this way, but the interface is still quite snappy as you can see in the clip after the jump.

The real trick here is how the hardware has been configured to get away without a third wire for latching the shift registers (if you need a primer on 595 chips check out this feature). The idea of using a latch is that all of the data can be shifted in over the serial pin before it appears on the output pins. Otherwise, the GLCD would see each bit as it shifts into the register, wreaking havoc on its communication protocol. [Debraj] gets around this by using a diode AND gate trick he learned from this other serial LCD project.

One good thing about this method is the 595 chips have a wide range of control voltage that will allow you to drive this with 3.3V or 5V microcontrollers. But you do need to implement the communication protocol and push those commands via serial. For nearly the same cost in chips something like an ATtiny2313 could be substituted to make an even simpler addressing scheme — or even switch to 1-wire protocol. But you’d then lose the wide input voltage tolerance.

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Brake Light Backpack Overpowered With LED Pixels

led-motorcycle-backpack

Here’s another Flora Arduino based project from [Becky Stern]. It’s a backpack with brake lights and turn signals for use when motorcycling, but it should work just as well for bicyclists. From this view the project looks pretty normal, but things get downright crazy when she decided to use the WS2801 pixels for the LEDs. Sure they take all the work out of driving an array of LEDs, and they offer full color and dimming levels. But when you see the bulk of cabling and PCBs this adds to the project (shown in the video after the break) we think you’ll agree that this was an interesting choice.

That issue aside the project is a lot of fun. The system doesn’t patch into the motorcycle’s electronics. Instead, it uses an accelerometer to detect when the brakes are applied and light the LEDs according. The turn signals are switched with an RF remote control that can be mounted on the handlebars.

Anyone looking to hack outerwear with electronics can learn form the fabrication techniques used here. [Becky] details how to make holes in the bag and sew parts to them, as well as using Sugru to waterproof vulnerable components.

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Fabricating Your Own Backpack Straps For Unorthodox Uses

Back in the 1980’s there was a movie cliché that the person with the largest boombox on their shoulder was always the coolest. It’s obvious to us that [Tim Gremalm] thinks that’s silly. Why be uncomfortable carrying something like that on your shoulder when you can strap a much larger object to your back? He’s working on a mammoth speaker enclosure which can be carried around, but he needed a set of backpack straps to make it happen.

This thing is going to be adding some serious weight to his body, so he also whipped up the padded waist belt seen above. For fabric he reused an Ikea couch cover. The material is made to survive a lot of pulling and stretching. For padding he used what he calls ‘floor mop’. It looks like it might be microfiber mop cloth be we can’t really be sure. With ten layers of the mop encased in the couch cover he finish off each strap by sewing it to some nylon webbing.

After the break you can see a picture of [Tim] modelling the huge polycarbonate speaker enclosure for which these backpack and waist straps were made. This project has many posts associated with it so if you’re interested in seeing more you can use this project tag link.

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‘Tis The Season To Decorate Bags With EL Wire

We hope you’ve already got parts on hand for your holiday projects because shipping might be a little slow at this time of year. But if you’ve got a bag and some unused EL wire here’s a one-day project you should try. Make yourself a Tron-inspired shoulder bag, or backpack.

On the right, [PT] is doing fantastic job of modeling with his electroluminescent offering. This is another Adafruit offering that holds your hand each step of the way from designing, to sewing, to wiring it up. This will go great with that glowing unitard he’s been working on.

[Alan Yates] has also done a spectacular job with his Tron backpack seen on the left. He picked up his EL wire on clearance at a place called “big-W” after Christmas last year. They were selling 3 meter segments (each with their own inverter) for just $3. We’re happy he got a deal and even more pleased that he found a use for it.

[Thanks Drone]