A trio of last-minute 555 timer projects

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[Bob] has been busy lately putting the finishing touches on three different projects that he plans on entering into the 555 Design Contest.

His first entry is a low-power H-bridge, which can be used to drive small servos. While he admits that it is a bit odd to build use a 555 timer to construct an H-bridge, they are cheap and plentiful enough to justify their use. Check out the video below to see the simple H-bridge controlling a servo.

[Bob's] second entry is quite a bit more complex than his H-bridge. His secret knock detector listens for a pattern of knocks, triggering a relay if the proper cadence is detected. If a knock is heard, the first 555 timer starts, listening for another knock within a specific time range. If a knock is heard during this period, the next timer is triggered, and the process is repeated. Subsequent knocks must be timed correctly, or the circuit halts, waiting for a reset timer to expire before listening is resumed. It’s a bit hard to get the knocks just right, but that should be fixable with a few small tweaks.

The third entry he sent us is a project that is pretty common, though with a somewhat uncommon implementation. Class D amplifiers are often built as low-power headphone amps for personal audio applications. He liked the idea of a Class D amplifier, but wanted to build something with enough power to listen to his music in a small room. To accomplish this task, he looked over the internal block schematics of a 555 timer and constructed a pair of high-power 555 timers himself, using discrete components to mimic those usually found in the 555 package. His results were decent, though admittedly not of the highest quality, and could be tweaked a bit to provide better sound fidelity.

Continue reading to see videos of each project in action.

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Alien life form synth toy

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We were sent [Dr. Offset’s] most recent project, a kid’s toy that is half sculpture/half noisemaker, but 100% cool. The device uses several 555 Timers and is his entry into the 555 Design Contest, which wraps up in just a few days. To really enjoy his creation, you need to suspend disbelief for a moment, and indulge the space fantasy he creates. In other words, let yourself be a kid again, if only for a few minutes.

What he has built is a containment unit for an alien life form found during an outer space exploratory mission. The creature has fused its organic bits with electronic components in order to survive in the stark, empty world it used to call home. The containment unit allows you to zap the “bug” with various frequencies to see how it reacts. The “bug” is light sensitive, so it always offers a varying experience, day or night.

It’s definitely one of the most artistically creative entries into the 555 Design Contest we have seen yet. Continue reading to see a thorough walkthrough and demonstration of his project.

[Thanks Rich Decibels]

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AM/FM SOS beacon saves your bacon

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[BadWolf] sent us a device called the “Bacon Beacon“, which is his 555 Design Contest entry. In short, it’s a life-saving device that emits an S.O.S. signal in Morse code over both the AM and FM bands. The device uses five 555 timers to get the job done, each of them dedicated to a specific task. Three of the timers are used for clocking and Morse generation, while the remaining two are used to produce and transmit an audible signal over the air waves. Currently, the signal can be received about a mile away from the source, which would theoretically allow for a search and rescue team to locate you with a simple radio and directional antenna.

The current design is still a bit rough around the edges, but the final plans would have the circuit built into a flashlight-like device equipped with red and green signaling LEDs. It’s a clever project and would make for a great tool if you got lost while hiking, or in the event of a zombie apocalypse.

Stick around for a quick video of the Bacon Beacon in action, and swing by [BadWolf’s] site if you want to know why his project has such a strange moniker (hint: it’s not because it can “save your bacon”).

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DIY lightning special effects

Halloween may have come and gone but thats no reason not to take a look at this neat little special effects setup.  Basically it uses an analogue circuit to monitor an audio signal and triggers some camera flashes using 5V relays.  The idea is that you can play lightning strikes and other spooky sounds, and the system will trigger camera flashes to coincide with the lightning strikes. Adding in some color organs in addition to the camera flashes will dim your lights to help achieve a thunder like effect. Unfortunately there aren’t any schematics for the color organs (which technically might be just light organs) but that doesn’t detract from the seemingly well designed analogue signal processing. Check it out in action after the break.

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DIY hot air hand dryer – an OCD sufferer’s best friend

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[haqnmaq] admits that he suffers from Obsessive Compulsive Disorder and on occasion, can be found washing his hands up to 20 times an hour. Very distrustful of cloth towels, he exclusively uses paper towels to dry his hands, to the tune of 2-3 rolls a day. In an effort to lessen the impact his OCD has on the environment and his wallet, he decided to build an automated hot air hand dryer using a 555 timer, which doubles as his entry in the 555 Design Contest.

The concept behind his project is to use a hair dryer as a hot air source, relying on a phototransistor and a pair of IR LEDs to detect when hands are placed under the dryer. When a pair of hands are detected, a relay is triggered and the hair dryer is turned on. Once the dryer has run for a pre-determined but adjustable time, the relay is opened, and the hair dryer turns off.

It’s a pretty simple project, but one that is quite useful, whether you suffer from OCD or not. The only thing he might want to watch out for is the restricted air flow to the dryer, since it is mounted in a sealed plastic container – a few seconds with a hole saw should remedy the problem quite easily.

Want to see the hand dryer in action? Keep reading for a short video demonstration.

[Thanks Ryan]

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Hear that? It’s a 555 Timer AM radio

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[Eric] recently built an AM radio based on a 555 timer, and posted a few pictures to the Hack-a-Day Flickr pool. He used the 555 timer as an AM demodulator and power amplifier in order to drive the speaker. A hand-wound inductor is used to tune the signal which is then superimposed over the ramp signal produced by the circuit he built. [Eric] points out that he chose a CMOS 555 timer because of its superior performance in this particular application since the timer is used in a bit of a nontraditional manner. He shared his circuit diagram as well as a great video walking through each part of his design, finishing off with a demonstration of the radio, which can be seen below.

This is yet another great project that will be entered in the 555 Design Contest – simple and elegant. We love seeing these, so keep them coming!

If you want to see more cool projects made by Hack-a-Day readers, be sure to check out our Flickr pool as well as the forums.

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555 Two-fer – Baby swing upgrade and a Headphone tube amp

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[Jason] sent in two 555 timer driven items that were worth sharing, both of which are entries in the 555 Design Contest.

The first item is a circuit that automatically resets an infant swing. [Jay], who built both items, has an infant swing for his daughter that spins a mobile and plays music. It’s great but it only works for 7 minutes and 15 seconds before a button push is required to trigger it again. He found this limitation to be annoying, and as I have owned the same swing, I can echo his frustrations. He probed the swing and found that a 5v pulse was required to reactivate the mobile, but it had to be sent after it turned off to have any effect. He put together a simple circuit that would do the button pushing for him, as you can see in the video below.

[Jay's] other entry is a headphone tube amp using a quartet of 6DJ8 vacuum tubes. The 555 timer in the amp is used to drive a FET and the hand-wound transformer he built for the amp. You can see a video of the amp in action below as well.

The projects are lacking a thorough write-up, but he does provide schematics for both the swing reset switch and the tube amp for those looking to replicate either item.

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