Hear that? It’s a 555 Timer AM radio

555_timer_am_radio

[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

baby_swing_tube_amp

[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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Punch tape musical synth

synthanola

[Jeri Ellsworth] sent over a 555 design contest entry that struck her as particularly interesting. The Synthanola is a three-channel music synthesizer that accepts input from an old Heathkit paper tape reader. While this hack might seem overly retro, it’s actually an extremely appropriate use of technology, as the Heathkit H-10 and the 555 timer were both popular tech in the 70′s. This retro-focused synth uses fourteen 555 timers, twelve of which are dedicated to synthesizing audio. If this entry does not win the contest, it certainly must be a strong contender for most 555 timers used.

[Thrashbarg] gives a detailed explanation of the logic used to drive the music playback from the punch tape, as well as full circuit diagrams for his entry. So far he has encoded MP3s of Bach’s Invention and Fugue in D Minor to tape, with hopefully more to come. In order to truly appreciate his efforts, the Synthanola should be seen as well as heard. Stick around for a pair of videos of the synth in action.

If you’re interested in seeing more 555 contest entries, be sure to check out some of our previously featured projects.

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Screamer doll prank toy

screamer_doll

While it is only the middle of February, it might be a good time to start thinking about your plans for April Fool’s day. [Dino's] Screamer Doll is his submission to the upcoming 555 Contest.  This fun little circuit can be used to easily annoy your cube or house mates and is perfect for all of the April Fool’s day pranksters out there. He fit all the components into a small plastic toy, replacing the eyes and mouth of the doll with three photo cells, and swapping the nose out for a bright LED. When light hits the photo cells, a loud high-pitched squeal is emitted, and the LED blinks furiously until the light source is removed. Shielding the device from light will cause both the sound and LED to slow down, but the brightness of the LED ensures that the toy still makes noise when covered.

It would be great to see a version of this project that is completely silent in the dark, allowing it to be hidden at night, greeting its victims come morning.

If you want to see video of the device in action, read on – just be sure to keep your speaker volume at a reasonable level!

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555 Timer circuit simulation software

ltspiceiv_demo

[FightCube] wrote in recommending a very helpful piece of circuit simulation software for those of you still constructing entries for the 555 design contest.   LTSpiceIV, available from Linear Technology, allows you to construct moderately complex 555 driven circuits including common components such as capacitors, resistors, diodes, FETs, and more.  Once you have constructed your circuit, you can view the results in an easy to use visualization window, without ever having to touch your soldering iron or a breadboard.  According to [FightCube], the software is fairly easy to use, and best of all, it’s free.

He has shared one basic circuit he built as a demonstration of the software’s capabilities, and promises to share more in order to motivate others to enter the contest.

Beginner concepts: 555 push button toggle

PIC, AVR, and Arduino are ubiquitous in projects these days and a lot of the time it’s easy to over-complicate things with their use. In this case, [Tod] wanted to use a momentary tactile switch to turn something on and off. Instead of going with a microcontroller he built the circuit around a 555 timer. What he really needed in this case is a flip-flop but lacking a chip for that he went with the 555 because it has one built-in. Three resistors and a capacitor later he’s in business, adding another resistor and a transistor to deal with the load switching. We’ve embedded video of the circuit controlling an LED after the break. This IC ends up in a lot of projects so dig through your parts bin and give this circuit a try.

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