Current Limiting Diode Use and Tutorial

Current limiting diode 1

Not that this happens often, but what do you do when faced with a repair where you don’t know the power source but you do know you have to drive LED backlighting? When faced with this dilemma [Eric Wasatonic’s] solution was to design for ambiguity. In this interesting hack repair [Eric] needed to restore backlighting for an old car stereo LCD display. First he guaranteed he was working with a DC power source by inserting a small full-wave bridge rectifier. Then knowing he needed 4 mA to power each LED for backlighting he used some 1978 vintage current limiting diodes designed to pass 2mA each regardless of voltage source, within limits of course.

Sure this is a simple hack repair but worthy of being included in anyone’s bag of tricks. Like most hacks there is always knowledge to be gained. [Eric] shares a second video where he uses a curve tracer and some datasheets to understand how these old parts actually tick. These old 1N5305 current limiting diode regulators are simply constructed from a JFET with an internal feedback resistor to its gate which maintains a fixed current output. To demonstrate the simplicity of such a component, [Eric] constructs a current limiting circuit using a JFET and feedback potentiometer then confirms the functionality on a curve tracer. His fabricated simulation circuit worked perfectly.

There was a little money to be made with this repair which is always an added bonus, and the recipient never reported back with any problems so the fix is assumed successful. You can watch the two videos linked after the break, plus it would be interesting to hear your thoughts on what could have been done differently given the same circumstances.

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Hacking a Christmas Tree for Less Blinkyness

Hacking a Christmas Tree to Blink Slower

What good is a fiber optic self-lighting Christmas tree if it flashes so fast it will put you into an epileptic attack? The answer is “Not very good”, if you ask [Mads Nielsen] a.k.a [EcProjects]. So [EcProjects ] started a little project to slow the Christmas tree’s blinkyness down to a more reasonable rate. The task didn’t seem too difficult at first but turned into a quality tutorial building a variable frequency H-bridge motor control.

After opening the base of the tree [EcProjects] found a 12 volt AC geared synchronous motor turning a multi colored translucent plastic disk. A bright spotlight was shining upwards through the turning disk into the ends of hundreds of small fiber optics. This mechanism dumps loads of multi colored light out the ends of the fibers at the tips of the Christmas tree branches as the disk turns.

His goal was to slow down the motor; however, the rotation was based on the 50 Hz mains signal. In order to continue using this motor a lower frequency AC power source was needed. What follows in the video is an excellent lesson on how an AC synchronous motor works plus how to build a variable frequency control and H-bridge using some transistors, resistors and CMOS 4069 inverter chip.

In the end the frequency drive could only be lowered to about 30 Hz before the synchronous motor would stall and reverse using his design. [EcProjects] was bold enough to include several fails which always provides more opportunity for learning and is greatly appreciated.

If you believe you have a better solution please share your idea in the comments. I’m sure the first proposal will include an Arduino and servo modified for continuous rotation, but any solutions would be fascinating including modifications to his design. You can join us after the break to watch the video.

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Xbox One Headset 2.5 mm Plug Adapter

In all of Microsoft’s grand wisdom they found it necessary to make the new Xbox One headset adapter without a standard 2.5 mm headset jack. People have invested great amounts of money in quality headsets for previous game platforms that now cannot jack into the Xbox One controllers. This may seem like a déjà vu hack from a week ago but it is different and adds more solutions for the annoying Xbox One headset compatibility problem.

[Jon Senkiw] A.K.A [Xandrel] wasn’t having any of this Microsoft nonsense so he cracked open the headset adapter case that plugs into the Xbox One controller. He photographed the PCB and wiring and realized he could fit a 2.5 mm headset jack from an old donor cellphone into the case. A dap of hot glue, some AWG 30 jumper wires and a bit of plastic trimming was all it took to get a jack inside the headset adapter just the way Microsoft should have done from the factory.

Previously when [octanechicken] added a 2.5 mm female phone adapter at the end of the cable he did not connect the black wire to anything being it was the 2nd side of a push-pull speaker. However, from looking at [Jon’s] photos he connected the speaker output wire to a solder pad on the PCB where the black wire originally connected, marked HPL, and he had nothing connected to the HPR pad. This seemed to work for [Jon] just fine, but is the opposite of what [octanechicken] did last week when he connected the blue wire to the speaker output which would have traced back to the HPR pad on the PCB.

This hack makes these controllers backwards compatible without too much issue being reported. If you have issues please report here or on [Jon’s] SE7ENSINS thread. He has also made comments on the thread that he is willing to help mod headsets, so if you’re not able to hack this yourself [Jon] might be willing to help.

2.5 mm Jack Adapter for the Xbox One Headset

As most everyone knows the Xbox One came out last week and if you were one of the lucky few to get one you might have noticed the headset is quite uncomfortable and covers only one ear. [octanechicken] has a possible adapter solution that lets you plug-in an older more comfortable chat headset like a Turtle Beach. It is being reported as a functional hack by others in the comments; however it may still be questionable. We say questionable because the first release of this Instructable clearly had a flaw in the wiring, but updated text seems to have fixed that problem. Using a female 2.5 mm stereo inline jack [octanechicken] was able to get the Xbox One headset controller to work with older Xbox 360 chat headsets having a male 2.5 mm plug.

The photos on the instructable are still incorrect so following the text instructions one simply unsolders the wires from within the ear piece and then solders the white wire to the tip connector, blue wire to the middle ring connector and the bare wire to the rear sleeve connector of the female 2.5 mm stereo inline jack. Remember to leave the black wire disconnected and covered with a bit of tape. If you cut the wires instead of unsoldering them, remember to scrape any varnish off before soldering. But what about that black wire?

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Simple Dremel TRIAC Hack Repair

Dremel Repair

It’s a wonderful thing to see a clever hack repair instead of disposing of a product. The best repair approach is finding exact replacement components, but sometimes exact components can’t be sourced or cross-referenced. Other times the product isn’t worth the shipping cost for replacement parts or you just don’t have time to wait for parts. That’s when you need to really know how something works electronically so you can source suitable replacement components from your junk bin to complete the repair. This is exactly what [Daniel Jose Viana] did when his 110 volt Dremel tool popped its TRIAC after he plugged it into a 220 volt outlet.

[Daniel] knew how the TRIAC functioned in the circuit and also knew that a standard TRIAC of sufficient specifications could be used as a replacement even if it didn’t have the correct form factor to fit the PCB layout. For [Daniel’s] tool repair he had to think outside the box enough to realize he could use some jumper wires and snuggle a larger TIC206E TRIAC that wasn’t meant for the device but still applicable into the housing where there was enough free space. A little shrink-wrap and all was good again. Sure the fix was simple, but let’s not trivialize the knowledge he needed for this repair.

And if you’re wondering if it worked, he notes that he’s been using this tool for three years since the repair. We thank [Daniel] for sharing this tip and allowing us to add this to our tool belt of Dremel repair tricks.

Retrotechtacular: WWII Paraset Spy Radio Used by French Resistance


[Robert Sumption] a.k.a [W9RAS] takes on the daunting challenge of building a WWII spy radio called the Paraset as the topic of this week’s Retrotechtacular. It was originally a tube based CW (Morse code) transmitter/receiver used by the French underground to communicate with the Allies. Many of these radios were dropped behind enemy lines and could run on European AC or 6 V DC with the added advantage of being able to use most anything for an antenna, including fence wire. These small, low power and highly mobile radios tuned in the 3 to 8 MHz range were instrumental in the resistance. But they still make for a really fun scratch-built radio project.

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