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.

DIY PCB Exposure Box Looks Professionally Made

August 17, 2011 by Mike Nathan 10 Comments

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[Stynus] was frustrated with the fact that he would have to flip his PCBs over mid way through the exposure process, so he decided the best course of action would be to build his own double-sided PCB exposure box.

He scored some UV LEDs on eBay, and after waiting a few weeks for PCBs to arrive, he was ready to start construction. The box contains a sliding glass shelf, which is positioned between two sets of LED panels. The setup lets him simultaneously etch both sides of any PCB, up to 20cm x 30cm in size. The exposure box is run by a PIC 16F628P and features an LCD status panel as well as a small handful of controls. [Stynus] programmed the box to retain the length of the last exposure, making it easy to replicate his results time after time.

Towards the end of the build log he shows off some pictures of the completed exposure box, which looks very professionally done. It’s a great job all around, and we would gladly take one for our workshop in a heartbeat.

Power Up With Knowledge

August 15, 2011 by Kevin Dady 18 Comments

The LM317 is a favorite for many people who want quick, cheap, reliable and ajustable power. It only takes a few parts to set up and it does its job rather well. Sometimes though, you just need a power supply.While there are a million tutorials out there, not many go as in depth as [Phil] does in his 2 newest videos.

Covering everything from the wall outlet to the final output, [Phil] explains each part step by step, stating what it does and the math and formulas behind it all to produce quality results. He then goes over to a working model and reviews each part showing its real output on a oscilloscope, which is very handy if you do not have one yourself.

In the second video he takes that knowledge and builds it all up into a professional looking bench top model with LCD meter readout and varnished paper to complete the front look. If you’re looking to build your first bench supply or want a better grasp on what exactly is happening in the one you have now, you should join us after the break for these 2 quality productions.

Continue reading “Power Up With Knowledge” →

Make Your Own Custom Hot Glue Sticks

August 14, 2011 by Kevin Dady 63 Comments

Hot glue guns can be very handy tools for bonding all sorts of surfaces, while getting you accustomed to plastic burns. The one thing they lack though is color, and while yes, you can on occasion find colored glue sticks, there is usually only a limited selection and they cost way more than the normal amber or clear sticks.

[Ken] solves the blandness problem of hot glue sticks in his kitchen, as shown in this cool slideshow. In a melt and recast process, glue sticks and crayons in a 3:1 ratio are slowly heated on an electric stove in a old can. Metal tubing is lined with silicone parchment paper to act as a release agent. The now vivid and scalding hot glue is poured into the tube and left to cool.

You might be wondering how mixing colored wax into ethylene-vinyl acetate effects the glue’s strength . According to the author if you need decrease the mix viscosity, you can add up to 10% paraffin wax by weight without effecting the bond strength. Color and viscosity control? Hot glue just keeps getting better!

Juice Bridge Powers Your Breadboard In A Snap

August 13, 2011 by Mike Nathan 28 Comments

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[Quinn Dunki] got tired of messing around with wires when connecting things to her benchtop power supply, so she built herself useful little power bridge that plugs directly into any standard breadboard.

The board is small and simple, but quite useful all the same. It was built to power both sides of the breadboard, and it can be easily switched between an unregulated power supply and a regulated 5v supply. An ammeter can be attached to the board via a pair of pins she set aside, allowing her to easily measure the current draw of the entire circuit.

We think her “Juice Bridge” would be very useful to anyone who frequently prototypes on breadboards. In fact, it would be a fantastic beginner project since it involves etching and developing PCBs as well as some simple soldering, while resulting in a handy takeaway tool at the same time.

If you want to build one of your own, [Quinn] has the schematics and Eagle PCB files available for download on her site.

DIY Smart Tweezers Make SMD Work A Cinch

August 10, 2011 by Mike Nathan 22 Comments

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[Noel] does a lot of SMD work and wanted a pair of “smart” tweezers that could be used to place components as well as for reading their capacitance and resistance values on the fly. As we have seen, these things can be somewhat costly, and not really necessary if you already have a good multimeter. With that in mind, he figured he could build his own for almost nothing.

He started off with a pair of kids’ “training” chopsticks which are durable, but more importantly, non-conductive. He took a second pair of tweezers, this time made of metal, and split them in two. He soldered wire to a set of ring terminals, mounting one on each leg of his broken tweezers. The final bit of assembly involved using zipties to mount everything on the plastic chopsticks along with the addition of banana plugs to the end of his probes.

[Noel] says that the tweezers work quite well, and with such a low price tag, we can’t argue.