Controlling a Hot Plate’s Temperature for the Lab

When you need precise heating — like for the acetone polishing shown above — the control hardware is everything. Buying a commercial, programmable, controller unit can cost a pretty penny. Instead of purchasing one, try creating one from scratch like [BrittLiv] did.

[BrittLiv] is a Chemical and Biological Engineer who wanted something that performs well enough to be relied upon as a lab tool. Her design utilizes a plain, old hot plate and with some temperature feedback to run custom temperature ramps from programs stored on an SD card.

The system she developed was dealing directly with temperatures up to 338°F. The heating element is driven from mains, using an SSR for control but there is also a mechanical switch in there if you need to manually kill the element for some reason. An ATmega328 monitors the heating process via an MAX6675 thermocouple interface board. This control circuitry is powered from a transformer and bridge rectifier inside the case (but populated on a different circuit board).

She didn’t stop after getting the circuit working. The project includes a nice case and user interface that will have visitors to your lab oohing and aahing.

Disabling Tap To Pay Debit Cards

XRAY of Debit Card

Some people aren’t too crazy about the rush of RFID enabled credit & debit cards, and the problem is, you don’t really have a choice what card you get if the bank sends you a new one! Well if you really don’t like this on your card for whatever reason, it’s pretty easy to disable.

[James Williamson] recently got a new debit card with RFID technology — the problem is it was messing with his access card at work, the readers would beep twice, and sometimes not work. He decided to disable it because of this and that he didn’t really use the tap to pay feature, nor was he completely convinced it was as secure as the bank said.

Since these RFID chips use antennas made of copper wire, he could have just started slicing his card with a knife to break the antenna — but, since he has access to a CT scanner, he thought he’d scan it to figure out where everything was.

Simply make a small notch in the edge of your card, or snip off one of the corners. This breaks the antenna and prevents power to the chip when held near a reader — though if you don’t have access to a CT scanner you might want to double-check next time you buy something!

Now there is another side to this — maybe you actually like the whole tap to pay thing, well, if you wanted to you could get a supplemental card, dissolve it in acetone, and then install the RFID chip into a finger ring for Jedi-like purchasing powers!

Pole Climbing Device Runs Up Flags and Undies

Tubular Drive travels up and down poles

Driving a carriage up and down a cylindrical object isn’t the most popular activity but that is certainly no reason not to build such a device. Check out [Ryan’s] creation that does just that, he calls it a Tubular Drive.

There isn’t much going on here, basically there are 4 wheels that grip a pipe. Two of those wheels have integrated gears and are driven by a DC motor. The remaining two wheels are idlers. When power is applied to the motor, two of the wheels spin, which then moves the entire assembly down the pole. A quick reversal in polarity brings the unit back the other way.

With those 3D printed plastic wheels you may think that traction would be an issue but [Ryan] insists that it is not a problem. The ABS wheels were treated with an acetone bath to smooth out the print layers and the distance between the wheels can be adjusted using a couple of bolts. Together that allows enough surface contact and pressure to ensure slip-free traveling.

Although the wheels were made to grip 1/2″ electrical conduit, it would be very easy to adapt this design to fit around and climb up all sorts of cylindrical objects, maybe even rope! Perhaps v-wheels with a spring tensioner system would allow for traveling on different size tubes while also adjusting for any variation in the diameter of a single tube.

[Ryan] says version two will have a linear encoder and be driven by a stepper motor. Check out the video after the break…

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3D Printing Directly Onto Your iPad Screen

ipad 3d printing bed

Corning’s Gorilla Glass is very scratch resistant, shatter resistant, heat resistant, and even flexible material — it’s actually a perfect candidate to be used as a print bed material. The only problem is it’s not typically sold outside of consumer products, but that’s when [cvbrg] realized an iPad’s replacement screen would fit his maker-bot perfectly.

One of the biggest problems people encounter with 3D printing usually involves the print bed. Sometimes the prints don’t stick, the edges peel, or it even gets stuck on there too well when it’s done! A popular solution is a borosilicate glass bed, which typically helps with adhesion and surface finish — but again, sometimes the prints don’t want to come off! Sometimes parts can even tear up pieces of the glass bed when you’re trying to remove them. People usually counteract this with Kapton tape, which can become a headache in its own right — trying to apply it bubble free, tearing it, doing it all over again…

Using an iPad’s screen (only about $15 on eBay), means you can hack and jab at the print bed all you want without fear of breaking it – It even has a bit of flex to it to help pry your parts off. Did we mention it also has a very uniform flatness, good thermal conductivity, and resistant to pretty much all solvents?

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Simple Hack Puts an RFID Tag Inside your Mobile Phone

RFID security systems have become quite common these days. Many corporations now use RFID cards, or badges, in place of physical keys. It’s not hard to understand why. They easily fit inside of a standard wallet, they require no power source, and the keys can be revoked with a few keystrokes. No need to change the locks, no need to collect keys from everyone.

[Shawn] recently set up one of these systems for his own office, but he found that the RFID cards were just a bit too bulky for his liking. He thought it would be really neat if he could just use his cell phone to open the doors, since he always carries it anyways. He tried searching for a cell phone case that contained an RFID tag but wasn’t able to come up with anything at the time. His solution was to do it himself.

[Shawn] first needed to get the RFID tag out of the plastic card without damaging the chip or antenna coil. He knew that acetone can be used to melt away certain types of plastic and rubber, and figured he might as well try it out with the RFID card. He placed the card in a beaker and covered it with acetone. He then sealed the beaker in a plastic bag to help prevent the acetone from evaporating.

After around 45 minutes of soaking, [Shawn] was able to peel the plastic layers off of the electronics. He was left with a tiny RFID chip and a large, flat copper coil. He removed the cover from the back of his iPhone 4S and taped the chip and coil to the inside of the phone. There was enough room for him to seal the whole thing back up underneath the original cover.

Even though the phone has multiple radios, they don’t seem to cause any noticeable interference. [Shawn] can now just hold his phone up to the RFID readers and open the door, instead of having to carry an extra card around. Looking at his phone, you would never even know he modified it.

[Thanks Thief Dark]

Stuffing an RFID Card into a Finger Ring

[Benjamin Blundell] loves wearable technology — but isn’t very happy with commercial offerings — at least not yet. He wanted to take one of his personal RFID cards, and fit it into a much smaller form factor, a 3D printed RFID ring.

The cool thing with most RFID cards today is they are made of a plastic that is quite easily dis-solvable in Acetone. Simply soak the card for about 30 minutes (depends on the card) and the plastic will simply peel away, revealing the microchip and copper antenna coil. It kind of looks alive when it’s melting…

The problem is, the antenna coil is generally the size of the card — how exactly are you going to fit that into a ring? [Benjamin] managed to find some surrogate RFID key tags, with a much smaller antenna coil. A little bit of solder later and he was able to attach his RFID microchip onto the new antenna! He mentions it is possible to wind your own antenna… but to get the frequency just right might be a bit challenging.

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[CNLohr] Demos His Photoetch PCB Process

etch

If you’re going to learn something, it only makes sense to learn from a master. [CNLohr] is known around these parts for his fablous PCBs, and he’s finally started to document his entire fabrication process.

[CNLohr] is using a photoetch process, where a mask is created with a laser printer on overhead transparencies. He covers the copper clad boards with a Riston photosensitive mask—available here, and they accept Bitcoin—sent through a laminator, and exposed with the laser printed mask and a UV grow bulb. After the mask has developed, [CNLohr] drops his boards into a ferric chloride bath that eats away the unexposed copper. He then removes the photomask with acetone and cuts the boards with a pair of aircraft snips, and they’re ready to be soldered up with components.

Yes, home PCB etching tutorials are pretty much a solved problem, but [CNLohr]’s work speaks for itself. He’s also the guy who made a microcontroller/Linux/Minecraft thing on a glass microscope slide. Learning from a guy with these skills means you’re learning from one of the best.

Video below, and there’s also a video going over the design of a PCB using KiCAD (!) and TopoR (!!!) available here.

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