Transformer-based PSU Repair

September 13, 2011 by Mike Szczys 19 Comments

Repairing someone else’s design mistakes is much more difficult than starting from scratch. So whenever we come across someone who’s good at this type of trouble-shooting we pay attention. [Jim] had a Sangean HDR-1 in his home. It’s a tabletop HD radio that stopped powering up for some reason. He cracked it open and got to the bottom of the problem.

The first order of business is disassembly, which isn’t too hard with this model. With multimeter in hand he started probing the transformer and found that the contacts for the primary are an open circuit; signaling a problem. There’s no inline fuse for protection, and further study of the secondary winding let him to discover the use of 1N5817 diodes. These are underrated parts for this particular transformer. He replaced them with 1N4003 diodes to bring the device in spec. But there was still the issue of fuse protections. A bit of circuit free-forming allowed him add a fuse and varistor by soldering the directly to the transformer’s contacts.

Why stop there? While [Jim] had the case open he also swapped out the low-end op-amp and a few electrolytic capacitors to improve the sound quality of the radio. Op-amp replacement seems to be a popular way to improve the sound from HD radios.

Who Knew Jacob’s Ladder Builds Had So Many Options?

August 17, 2011 by Mike Szczys 20 Comments

[Grenadier] has a thing for the high voltage and, as you can see, he’s found multiple ways to build the icon of HV toys – a Jacob’s Ladder.

The three look similar, but they use different means of generation the voltages necessary to get a spark to jump through the air. The exhibit on the left uses a neon sign transformer, the one in the middle is based on a transformer from an X-ray machine, and the example to the right uses a microwave oven transformer. [Grenadier] discusses the pros and cons of each method, then links to his in-depth posts about working with each one them. There are also videos for all three. We’ve embedded the video for the microwave oven transformer after the break. That version of the Jacob’s Ladder requires some way to start the spark and in the video he’s doing it manually. There is always the option to add a solenoid to do the job but he does mention that you can’t just let it run because that cheap transformer will burn out before long.

If you like what you see here, perhaps you’ll be entertained when he runs HV through some soda cans.

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Tiny Transforming Beer Can Robot

June 8, 2011 by Mike Nathan 22 Comments

beer_can_robot

The next time you reach for a cold one, you might want to take a look at the can to ensure that your beer won’t suddenly sprout legs and start skittering across the table.

You might remember [Ron Tajima] from some of his previous creations, including this Roomba-based baby cradle and the PacMan Roomba mod. This time around, he has created a cool little transforming robot that fits inside a beer can.

The robot’s brains are stored just underneath the top of the beer can on a custom-built board. On one side of this board, you will find an mbed controller which is used to manage all of the robot’s functions, and on the other side, four batteries provide all of the device’s power. The robot’s three legs are controlled by six servos, allowing for movement in several different planes. The beer-bot’s movements are controlled with a Wiimote, so we’re assuming he has crammed a Bluetooth module somewhere in there as well.

[Ron] mentions that it moves a bit slowly when standing on end, but we think the robot is pretty awesome as is, and we can’t wait to see what improvements the next version might bring.

Stick around to see a video demonstration of the robot in action.

[Thanks Sascha]

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Transforming Robot Is More Than Meets The Eye

May 17, 2011 by Mike Nathan 15 Comments

transformer_copter

Let’s face it – building robust robots isn’t exactly easy. When designing them, builders often focus on a single method of locomotion in attempts to create a robust, reliable means of transportation. Whether it moves on the ground or in the air, there are always compromises to be made when designing a robot with the ability to travel over variable terrain. Looking to change that, researchers at the Center for Distributed Robotics have recently unveiled a robot that can travel on the ground with ease, then take to the skies in a matter of seconds.

The robot is rolls along the ground on a set of wheels mounted at either end. When it is time to fly, it pushes itself up onto one end before extending its rotors. As you can see in the video below, the transition occurs pretty quickly.

The current prototype is pretty fragile and carries quite the hefty price tag . More robust revisions are already in the works, so expect to see more in the coming months.

[Thanks Sandeep]

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3-phase Jacob’s Ladder

April 15, 2011 by Mike Szczys 18 Comments

Two sparks are better than one, a sentiment that was never more blindingly illustrated than with this three-conductor Jacob’s Ladder. The build centers around three-phase power, which uses a trio of alternating current sources sharing the same frequency, but offset by 1/3 from one another. If we’re reading the schematic correctly, [Jimmy Proton] is using normal mains as a power source, then connecting three transformers and a capacitor to set up the different phases. Two of the transformers, which were pulled from microwave ovens, are wired in antiparallel, with their cores connected to each other. The third transform is connected in series on one leg of the circuit.

The video after the break starts with the satisfying hum of power, only to be outdone by the wild sparks that traverse the air gap between conductors of the ladder. After seeing the first demonstration we kind of expected something to start on fire but it looks like all is well. We’ll probably stick to a less complicated version of Jacob’s Ladder.

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More High Voltage Experimentation With A Flyback Inverter

March 24, 2011 by Mike Szczys 16 Comments

[Electorials] actually makes working with a flyback inverter sound rather easy. This comes hot on the heals of the huge high voltage collection we saw the other day, but slows way down in the presentation of information. This makes the project very approachable for the newbie, especially considering that the majority of the testing is done with low voltages.

He’s using a flyback transform for this project, which can be pulled from an old CRT monitor. Once you have one in hand, all that’s required to figure out how to use it is a voltometer, a 9V battery, a MOSFET (also salvaged in this case), and miscellaneous components. Once he establishes what each external connection does electronically, [Electorials] builds his circuit on a breadboard, then uses it to create plasma in the bulb above as well as to light up a CCFL.

Building Linear Amplifier Prototypes

January 28, 2011 by Mike Szczys 15 Comments

We know way too little about this subject but hopefully [Bob4analog] helped us learn a little bit more this time around. He’s building his own linear amplifiers on what looks like sheets of MDF. This is an evolving design and the two videos after the break show two different iterations. He’s salvaged several components, like transformers from microwaves, as well as built his own components like the plate choke to the right of the tubes in the image above. In standby, the amp sits at 2800 volts, warming the filament before the unit is switched on.

So what’s he got planned for this? Good question, but it appears that there’s more than enough power to drive a long-range transmitter.

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