Freedombot Explores Your Fridge

March 21, 2011 by Chris Nelson 10 Comments

Freedombot is a neat little robot designed for exploring magnetic surfaces. It has two whiskers for detecting objects in its path and two rare earth magnets which allow it to stick to your fridge.

Overall Freedombot may not be anything revolutionary but its builder [skater_j10] does a good job of covering topics which my be interesting to robotics beginners. For example he goes through the process of modifying some HiTec HS- 55 Micro Servos for continuous rotation which allows them to act as the wheels. To control the bot he uses two 555 timers wired up in astable mode to generate the needed PWM for the servos. The proximity sensors are simple limit switches with some wire soldered on to the end. The end result is a neat little robot for roaming the front of your fridge. See a video of it in action after the break.

This happens to be [skater_j10]’s entry into the 555 timer contest. Unfortunately the deadline has passed for new entries but be sure to swing by and check out some more awesome 555 hacking.

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ASync-Firefly

March 11, 2011 by Noah Dunker 8 Comments

[dev_dsp] wanted to try his hand at creating a purely analog implementation of multiple synchronizing fireflies powered by a single battery and built from off-the shelf, through-hole components on inexpensive protoboard. In theory, even your local Radio Shack should still carry all of this stuff. He was obviously inspired by [alex]’s fireflies that we’ve covered in the past, but he wanted to see how far it could be taken without the use of a microprocessor.

In the end, [dev_dsp] relied on one crucial piece of digital ware, the ever-popular 555 timer IC, but he’s using analog discrete components to do the grunt work of adjusting the phase of each firefly by feeding a little extra current to the trigger capacitor whenever the flash of a nearby firefly is detected. After the jump, you’ll find schematics and a video demo of three ASync-Firefly modules in various stages of assembly playing with one another while [dev_dsp] discusses their operation.

A 555 Synthesizer

March 9, 2011 by Kevin Dady 12 Comments

Inspired by the memory of a childhood electronics kit, [Frank] decided to make a new 555 Synthesizer and enter it into the 555 contest. [Frank’s] remake is played with a stylus, and sports an attack and release envelope circuit, housed in a quick but effective acrylic case.

Using a single 555 timer, a hand full of capacitors, two transistors, and a healthy dose of resistors and potentiometers, the sound is quite impressive thanks to optional filtering, enveloping, and a lot of fine tuning. Full schematics, bill of materials, formulas, and board files are all available along with sources for some of the more specialized potentiometers.

Join us after the break for a ~13 minute long video, which is pretty cool, as it shows the device from prototype, and does some fast forward action though to the final product pictured above, though if you just want a demo of the 555 synth fast forward to 10:44

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Keypad Input Scanning By A 555 Timer

March 3, 2011 by Mike Szczys 17 Comments

[R-B] designed a 555 timer circuit to scan a keypad. Keypads are common interfaces for small projects and require row and column scanning by a microcontroller. [R-B’s] setup allows you to reduce the number of pins used on the microcontroller to just two. One is an interrupt that is triggered when any of the buttons are pushed, the other reads the frequency from the 555 chip. Each button has its own resistance which alters the frequency of the 555. The microcontroller reads the frequency for 100ms using a timer. The number of timer overflows that occur during that period directly correspond to the button press (five overflows for the numeral 5, zero overflows for the numeral zero).

We usually debounce our button presses for 40 ms, this is more than twice that amount of time but still not a staggering difference. It does make us wonder if you will miss quick button presses? The only really way to know is to try this out yourself. Check out the video after the break and don’t forget to leave a comment with your own experiences in working with the circuit.

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Earthquake Alert System

March 2, 2011 by Mike Szczys 15 Comments

[Roteno’s] submission for the 555 timer design contest is an Internet connected earthquake alert system. It monitors the USGS website for earthquake data and plays a tune when an earthquake occurs. The data is available as a feed in the form of a TXT file which is pretty easy to parse using cURL. He chose an LPCXpresso board (which is an ARM development platform that can run a Linux kernel) along with an XPORT module to handle the Ethernet traffic.

So where does the 555 timer see some action? It is responsible for playing the tone when an earthquake is detected. But playing just one pitch isn’t much fun. Instead, [Roteno] built the circuit above which creates a resistor network switched by a series of transistors. This way he can use GPIO from the microcontroller to choose different pitches. Check out the video after the break to hear the results. At power-up all eight pitches are played as a test, and the alert sound varies in pitch and tempo based on the magnitude of the earthquake.

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2-bit Full Adder Using Just Thirty Six 555 Timers

February 28, 2011 by Mike Szczys 12 Comments

This 2-bit adder was a lot of work to build. It uses a total of thirty-six 555 timers and it does have the option of adding or subtracting numbers. It’s a rather unorthodox use of the part, depending more on the chip as an inverter and taking advantage of the fact that there’s an NPN transistor built into it. [cpu86] did use some PNP transistors to give him the ability to turn off some of the 555’s to get everything working correctly.

He explains the use of two’s complement in the subtracting feature but the process is just touched on very quickly. Luckily there’s a huge eagle schematic available with his project writeup so that you can follow along and really grasp how this thing works. We’ve generated a PNG and embedded it after the break for your convenience. You’ll find it just after the two videos of the device in action.

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Analog Robotic Concepts

February 26, 2011 by Mike Szczys 20 Comments

Everyone’s getting on board with the 555 timer projects. But [Tom] didn’t just come up with one project, he shared a slew of ideas related to analog robotics. They’re center around servo motor control. You can see in the video after the break he has a pleasing way of sharing a lot of details while also making an easy to view demonstration video. He’ll put up a schematic for about one second and then move on, saving those that don’t care about the details by not droning on.

The first schematic that flashes by is the main circuit for controlling the servo motor. The rest of the concepts build from this circuit, using light, sound, flex, and other sensors as inputs. For instance, the setup above is using a light sensor. When the ball blocks the light the servo moves that vertical rod hitting it out of the way. When it swings back the process repeats. It’s striking how lifelike the reactions are, reminding us of insect movements. But this is really just the tip of the iceberg as he’s got a lot of future video ideas that we can’t wait to see.

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