Simple Transistor Tester Makes Sorting Easy

September 2, 2011 by Mike Nathan 26 Comments

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Hacker [Dino Segovis] is back with yet another installment of his Hack a Week series, and it’s looking like he isn’t too worse for wear after hunkering down to face hurricane Irene.

This week, it seems that [Dino] is having some problems separating his PNP transistors from his NPNs. After Albert Einstein proves to be less than useful when it comes to sorting electronic components, [Dino] decided to build a simple transistor tester to help him tell his PNPs and NPNs apart without having to resort to looking up product data sheets.

The tester itself is relatively simple to build. As you can see in the video below, it consists of a power supply, an LED, a few resistors, a pair of known transistors, and not much else. When everything is hooked together, the NPN/PNP pair causes the LED to light up, but the circuit is broken whenever one of the transistors is removed. Inserting a new transistor into the empty spot on the breadboard immediately lets you know which sort of transistor you have inserted.

Sure you can tell transistors apart with a multimeter, but if you have a whole drawer full of loose components, this is a far more efficient option.

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Repairing An Old Pick And Place Machine

September 1, 2011 by Mike Nathan 15 Comments

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Professional-grade pick and place machines are quite pricey, so when the crew at Null Space Labs picked up an old Juki Placemat 360 for only $1,200, they were stoked. When they finally got it in-house however, they realized that the seller’s definition of “working” was a bit different than theirs. The machine’s compressor is busted, and there are all sorts of other bits that require some TLC before they can get things up and running again. They have put together a “build log” showing off their work as the machine is taken from an ancient, mostly-working relic to a lean, mean, picking and placing machine.

So far, they have torn the thing down and inspected the upgrades and damage the machine has been subjected to over the years. The crew started making a few small repairs, and have even replaced the unit’s laser with machine vision, which seems to be working well thus far during testing.

While you might not have any similar machinery in your workshop, it’s still fun to watch as they tear it down and revamp it, bit by bit.

Building A CNC Router To Call My Own

September 1, 2011 by Jeremy Cook 17 Comments

As with most writers for [HAD], I enjoy doing projects as much as I like writing about them. As a mechanical Engineer that writes for a blog mostly about electronics, a CNC router seemed like something I needed in my garage. Building a router like this requires a bit of expertise in both electronics and mechanics, so it seemed like a good challenge.

This router kit, made by Zen Toolworks, comes fairly complete frame-wise, but requires a lot of knowledge on the electrical side to get things running correctly. In order to make it look decent and work correctly, I had to rely on some zip-tie and basic diagnostic skills that I’ve honed as a former engineering Co-op and technician. Also, I had to figure out a way to cheaply stack everything in my garage as we park two cars there (the footprint is 14″ x 22″, so I consider that a success).

One of the bigger challenges that I still have to overcome with this project is learning “G-code” and how to use software to generate it. Although I’ve done some basic programming already, as seen in the video after the break, there’s still much to learn. I’d hope that having this tool around can lead to better projects as I won’t have to be restricted to simple milled lines and circles anymore.

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How To Build A Vacuum Form Table That Gets It Right Every Time

August 31, 2011 by Mike Nathan 27 Comments

[James] builds all sorts of robots and superhero costume replicas at home, so he is always searching for a better way to get consistent results when using his vacuum table. A lot of people use their oven or exposed heating coils from electric frying pans to warm the plastic sheets, but [James] wasn’t really interested in going down that route. He cites that he would rather not heat plastic in the oven where he cooks his food, nor is he really keen on the idea of exposed heating elements.

Instead, he opted for a slightly pricier, though completely reasonable setup that produces consistent results every time. Most of the forming table was built using MDF sheeting, as you can see in the video below. His heating apparatus was the most expensive part of the rig, since it’s an off the shelf quartz-based room heater. He lays the heater on its back side, and directs the heat up through an MDF frame using aluminum foil as a reflector. The plastic sheeting mounted at the top heats evenly, and in no time, he has a perfectly vacuum formed prop that is ready to be painted.

Sure, it might cost a bit more than some other vacuum formers we’ve looked at before, but spending a bit more up front to get consistent results is well worth it if you ask us.

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Large 7 Segment Display Made From Glue

August 25, 2011 by Kevin Dady 50 Comments

We here at Hack A Day love LED’s, and all things LED related, but one of the biggest problems with LED’s are the small size. We want bigger and brighter, matrices the size of our TV, seven segments as big as a wall and a single white led the size of a baseball, and brighter than the sun!

I was recently commissioned to make a device which uses a pretty large number display, and I went out shopping. The seven segment we liked best was still quite pricey, and would not fit our enclosure correctly anyway. We ended up going a different route, but it really got me thinking… What if you wanted to make something with a fairly large display? And how could one go about doing it cheaply at home?

I first thought about acrylic rods, but no one near me had any of small diameter, or at a decent price. Never mind that I don’t have that many tools on hand, and I could just see me trying to drill out the end of a thin plastic rod using a electric hand drill, and my knees as a clamp. Looking around the HQ I found my stash of glue-sticks. I thought would make an interesting display and it is easy to work with.

Before I knew it I had a working (serial and expandable) 9 inch tall 6 inch wide 7 segment display. I will be the fist to admit, its not spectacular in quality, or brightness, though the display itself did only cost four dollars in material. A quick and easy project, especially if you need a quick scoreboard or large clock.

Join us after the break to see how the display and the controller circuit are made.

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Home Tanning Lamps Become Organ Donors For A PCB Exposure Bed

August 23, 2011 by Mike Szczys 4 Comments

Some projects benefit greatly from the parts a builder is able to find. Take this UV exposure bed for photo-resist copper clad boards (translated). It looks like a commercial product, but was actually built by [TabascoEye] and his fellow hackers.

The main sources for parts were a flatbed scanner (which acts as the case) and two self-tanning lamps that use UVA flourescent bulbs. By sheer luck the bulbs and their reflectors are exactly the right size to fit into the top and bottom cavities of the scanner. The control hardware centers around an ATtiny2313 micorocontroller, which takes input from a clickable rotary encoder, and displays exposure information on a character LCD. The finished product deserves a place right next to other professional-looking exposure boxes that we’ve looked at.

MilliOhm Measurement Made Easy

August 17, 2011 by Nick Schulze 8 Comments

When [Kerry] wanted to measure some very small resistances very accurately he did not want to fork out the big bucks for a high end multimeter or a mico-ohmmeter, so he decided to build one himself. Measuring resistance is a simple enough concept, it directly implements Ohms law (V=IR). The problem with very small resistances is that when you apply a sensibly sized constant current to the load, the voltage to be measured is too small for conventional multimeter.

To overcome the problem [Kerry] designed a constant current source of very high accuracy using the AD8276 unity gain difference amplifier and the AD8603 high precision opamp. Then to boost the voltage across the load he used the LMP8358 programmable gain precision opamp, this allowed him to easily change the gain for different magnitude resistance, the circuit diagrams are all available on his site. Finally he used four point probes to eliminate probe wire resistance errors, ending up with the ability to measure small resistances with very high accuracy.