Bolt Action Pneumatic Spud Gun

April 9, 2011 by Jesse Congdon 44 Comments

No one should ever make a potato cannon. They are wildly unsafe, powerful, and can easily shatter your neighbor’s gaudy bay window, you know the neighbor with the mean dog.

That said, [Jeremy Cook] made a minature bolt action spud gun! Using a custom machined Delrin bolt, a fitted Delrin reducer, and some PVC, the spud gun is capable of quickly loading custom shaved potatoes with the greatest of ease. Pushing the bolt (literally a bolt) forward forces the spud through the reduction coupling and into the barrel. Lock the bolt to the side, pull the trigger (an air blower) and two expansion chambers toss compressed air behind your starchy projectile. The design is reminiscent of a common bolt action rifle, but all that Delrin reminds us of paintball markers.

[Jeremy] is writing up the project in multiple posts, so check his blog for info. We are also no strangers to the strange, dangerous and wonderful world of potato launching tech.

Stick around for a video of the launcher in action!

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Light-sensing Circuit For Power Saving Applications

April 8, 2011 by Mike Nathan 6 Comments

light_sensing_circuit

Instructables user [MacDynamo] was thinking about home security systems and wondered how much electricity is being wasted while such systems are powered on, but not activated. He pondered it awhile, then designed a circuit that could be used to turn a security system on or off depending on the time of day, but without using any sort of clock.

His system relies on a 555 timer configured as a Schmitt trigger, with a photoresistor wired to the reset pin. When the ambient light levels drop far enough, the resistance on the reset pin increases, and the 555 timer breaks out of its reset loop. This causes the circuit to power on whatever is connected to it. When the sun rises, the resistance on the reset pin drops and the 555 timer continually resets until it gets dark again. He notes that this behavior can be easily reversed if you were to put the photoresistor on the trigger pin rather than the reset pin.

We like the idea, though we are a bit wary about using this for any sort of real security system. An errant insect or debris could cause the system to be turned on, and we’d feel pretty foolish if someone disabled our alarm with a flashlight. That said, this sort of circuit still has plenty of practical, power-saving applications outside the realm of home security.

Sticky Sweet Animatronic Peep Show

April 7, 2011 by Mike Nathan 14 Comments

peeps_peep_show

With Easter quickly approaching, [Kyle] decided to finally build a project that is as tasty as it is wrong.

Behold, the Animatronic “Peep” show! Using nearly a dozen marshmallow Peeps, he constructed a stage for his “performers” and a seating area for their “clients”. The structure was built mostly from balsa wood and foamboard, featuring a retractable curtain, stage lighting, and music.

Once triggered, the embedded Arduino gets to work animating the stage lights and blaring “Cherry Pie” while the sugar-coated onlookers await their entertainment. The curtain is drawn back and a trio of winged dancers emerge one by one, ready to entertain the crowd. The onlookers even offer up dollar bills to the dancers via a servo-mounted arm.

The project uses a total of 10 servos driven by the Arduino, along with an audio decoder chip to provide the proper ambiance for the marshmallow debauchery. [Kyle] says that he put together about 650 lines of code to get the whole thing running, but there doesn’t seem to be any way to download it at the moment – hopefully we’ll see something posted soon.

It might not be high-brow, but it sure beats blowing up old, stale Peeps in the microwave!

Stick around for a trio of videos demonstrating the Peep show as well as revealing some of the stage’s inner workings.

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Geiger Counter Built In An Ohmmeter Enclosure

April 7, 2011 by Mike Szczys 4 Comments

Here’s a Geiger Counter that makes itself at home inside of an old Ohmmeter (translated). [Anilandro] set out to built this radiation detector in order to learn how they work. Like other diy Geiger Counter builds we’ve seen, this project assembles a circuit to interface with a gas-filled tube which serves as the detector. [Anilandro] takes a few paragraphs to discuss how this works; the Geiger tube is basically a capacitor whose electrical characteristics change as an ionizing particle passes through it.

Once he had the theory worked out he scavenged some parts to use. A broken emergency light donated its transformer to provide the high voltage needed. The rest of the circuit was built on some protoboard, and a speaker was added to output the clicking noises that have become a familiar part of the detector hardware. The tube itself is housed in a wand that attaches to the base unit through a cable. Check out some test footage of the finished unit after the break.

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Shift Register Is All It Takes To Make A 3-wire Serial LCD

April 7, 2011 by Mike Szczys 11 Comments

This hack is a bit older, but one aspect of the setup makes it worth sharing. Shift registers are a common component to include in a project when you need to increase the number of I/O pins available. We’ve used them to drive LCD screens before, but we never realize you could use a 595 chip to make a 3-wire serial LCD interface. That’s because we’ve always thought of shift registers as having three control pins which must be addressed: data, clock, and latch. But it seems that’s not the case. This hack gangs the pins for clock and latch (called the storage register clock input on this chip) together. This causes the shifted data to be latched to output register one clock cycle after it is shifted into the chip.

This means you can operate the 595 chip with just two pins, but alas, you do need one more connection to drive the LCD properly. This is an HD44780 compliant display. It is being used in 4-bit mode; four of the shift register pins provide that data, while a fifth controls the Register Select pin. Since the shifted data from the 595 appears on the pins after each clock strobe, you must control the Enable pin on the LCD separately or it will behave sporadically.

So there you have it, control an HD44780 display with just 3-pins by using a $0.42 part. Are we going a little too fast for you? Check out this 595 tutorial and give the shift register simulator a try. That should bring you up to speed.

[Thanks Rajendra]

Circuit Building With A Hammer And Nails

April 6, 2011 by Mike Nathan 34 Comments

real_breadboarding

[Collin Cunningham] over at Make recently wrapped up another edition of “Collin’s Lab” – this time around, the subject is breadboards. He starts off by discussing a common solderless breadboard, something you are no doubt familiar with. What you might not know however is how breadboards got their name.

Way back when, before there was a RadioShack in every strip mall across the country, fancy prototyping supplies like your solderless breadboard did not exist. Amateur radio operators would prototype circuits on wooden boards, often using whatever was around as a substrate. Many times, this meant that the family’s cutting board ended up as a makeshift prototyping station.

One popular method of building circuits was to drive small nails into the breadboard, using wire wrapping to connect things together. [Collin] demonstrates this technique in the video, constructing a simple LED flasher circuit.

He says that the process works decently enough, and was kind of fun to do. He does mention however that building any sort of circuit requiring an IC would likely be out of the question.

If you have a few minutes to spare, check out the video embedded below – [Collin’s] take on technology is quirky and entertaining as always.

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Everything You Need To Know About Wall Warts

April 6, 2011 by Kevin Dady 25 Comments

If you work with electronics at any skill level you need juice. [Jon] has a great, and clearly worded tutorial about Wall Wart Power Supplies with pretty much everything you need to know about those little black boxes hanging off of your outlets.

The whole thing starts off with the basics like transformers, rectification smoothing and regulation, then moves on to the different basic types, dedicating a page to linear, regulated and switching types, giving output performance charts under different situations.

Also included is a run-down of DC barrel jack structure so you get the right plug every time, wall wart type identification, a random sample comparison test, and a good selection of formulas to even keep the old hats reading along. Although you might want to set aside a little time at 9 pages and some Q/A in the comments, it might take a moment to read.