Circuit design for multiple UART connections

[Bill Porter] has a tip for designing circuits that have multiple connections to a single microcontroller UART. This stemmed from a review of a friend’s circuit design that used the UART in the project, but also called for an FTDI chip in order to reprogram via USB and a bootloader. Unlike the schematic above, the circuit called for straight connections without any resistors. With that design, a conflict will occur if two devices are connected and attempting to communicate at the same time.

The fix is easy. [Bill] discusses how to prioritize the connection by adding the pair of current limiting resistors seen above. This helps to ensure that damage will not occur, and that the FTDI chip will take precedence. Now the external hardware will not preclude the FTDI chip from accessing and programming via the bootloader. The tutorial is intended for those rolling their own boards out of an Arduino-based prototype, but it will work in any situation where you need multiple connections to a single set of UART pins.

Keep all eyes on your kegerator with this light up gauge cluster

kegerator_gauge_cluster

A few years back [Evan] built a kegerator from a mini fridge and was quite happy with his new beer chiller. Like many of us do, he started thinking up ways in which he could improve the project as soon as it was completed. While it took a couple of years, he recently got around to adding the temperature and capacity gauges he always wanted.

He added a temperature probe to the refrigerator, and then constructed a pair of tools that he could use to measure how much beer was left in the keg. The volume monitors include a scale built using a pair of pressure sensors from SparkFun, and a flow sensor installed in the beer line.

[Evan] scored an old Chevy gauge cluster and cleaned it up before installing a pair of analog meters which he used to show the keg’s temperature and “fuel” level. Since he feels no project is complete without some LED love, he added a few of them to the display without hesitation. The LEDs calmly pulsate when the keg sits idle, but spring to life and begin flashing when the flow sensor is activated.

As evidenced by this pair of keg monitoring systems, we think that you can never have enough information when it comes to your beer stash, so we really like how this project came together.

Be sure to check out his kegerator’s gauge cluster in the video below.

[Read more...]

Maker Faire KC 2011: In Photos (Part 1)

As a writer for Hackaday, I get to see CNC machines, Prototypers, Tesla coils, and much more on a nearly daily basis. However, there are an uncountable number of people that don’t usually get to share in these technical wonders. Maker Faires provide the chance for the public to see and interact with the inventions, kludges, and geniuses that put together the things we write about on Hackaday.

Follow along after the break for some photos of the interesting things I got to see and enjoy.

[Read more...]

[Bunnie's] archives: Unlocking protected microcontrollers

A few years back [Bunnie] took a crack at cracking the security fuses on a PIC microcontroller. Like most of the common 8-bit microcontrollers kicking around these days, the 18F1320 that he’s working with has a set of security fuses which prevent read back of the flash memory and EEPROM inside. The only way to reset those security fuses is by erasing the entire chip, which also means the data you sought in the first place would be wiped out. That is, if you were limited to using orthodox methods.

[Bunnie] had a set of the chips professionally uncapped, removing the plastic case without damaging the silicon die inside. He set to work inspecting the goodies inside with an electron microscope and managed to hammer out a rudimentary map of the layout. Turns out that flash memory can be erased with ultraviolet light, just like old EPROM chips. Microchip thought of that and placed some shielding over the security fuses to prevent them being reset in this manner. But [Bunnie] managed to do so anyway, creating an electrical tape mask to protect the rest of the data stored in the chip while bouncing UV light underneath the shielding at an angle.

Want to uncap some chips of your own without enlisting the help of others? Give this method a try.

[via Dangerous Prototypes]

Solder paste dispenser hacked to run off compressed air cans

solder_paste_dispenser_air_can_hack

[John] got a shiny new solder paste dispenser for a steal, and before he hooked up the tool, he decided to take a look inside to make sure everything was on the up and up. Aside from a few questionable wiring practices he didn’t approve of, everything else looked to be in good working order.

The only thing that was bothering [John] is that he wasn’t too keen on keeping his noisy and large air compressor in his workshop, so he set off to find a different way to provide compressed air to the device. He settled on air dusters like those used for cleaning the crumbs out of your keyboard, but he needed to find a way to reliably get the air to his solder dispenser. He heated the air can’s nozzle until he was able to screw his dispenser’s hose barb into it, creating a tight seal. The modified nozzle was reattached to the can and placed in a simple jig that keeps the nozzle held down continuously.

[John] fired up his dispenser, and the 80 psi coming from the duster was plenty to get the solder paste flowing. Sure the rig might not be the most high tech solution, but we think it’s a pretty good means of getting quiet compressed air anywhere you need it.

Tiny hardware-based DSLR intervalometer

diy_dslr_intervalometer

Most DSLR cameras have the ability to take pictures at set intervals, but sometimes the menu system can be clunky, and the options are often less than ideal. [Achim] is a big fan of time lapse photography and has been hard at work creating a hardware-based intervalometer to suit his needs. He has just finished the second revision of the controller which is just about small enough to fit inside the housing of a 2.5mm stereo plug. The timer is not 100% universal, but so far he has confirmed it works on Nikon, Canon, and Pentax cameras.

Based on a PIC10F222, the circuit’s operation is quite simple. Once the dongle is connected to your camera, you simply need to take two pictures anywhere from 0.4 seconds to 18 minutes apart. The intervalometer “watches” to see how long you waited between pictures, and proceeds to take shots at that interval until the battery dies or your memory card fills up.

As you can see in the video on his site, the timer works a treat. If you want to make one of your own, swing by his site to grab schematics and code – it’s all available for free.

*Whoops, it looks like we’ve actually covered this before. Our apologies.

Teamspeak button uses tattoo machine foot switch

As an avid gamer, [Pat Norton] uses Teamspeak with his friends when playing World of Warcraft. [Pat]‘s friends were annoyed with the voice-activated option for Teamspeak and the constant squeaking of dog toys, and [Pat] was annoyed with the questionable usability of a push-to-talk key. Dissatisfied with his options, [Pat] built footswitch-controlled teamspeak button using a Teensyduino and a broken tattoo machine foot switch.

The Teensyduino is an incredibly small Arduino compatible board that was perfect for this project. Since the teensyduino can operate as a USB Human Interface Device, it’s very easy to have the board appear as another keyboard to the computer. After borrowing some code from the hardware button of a DIY photobooth, [Pat] hooked up the foot switch to two pins of the board. From there, it was very to adapt the code so the foot switch would act as a third ‘Control’ button. The results look very professional, like a factory-made game controller. We’ve seen a few foot switch keyboard devices before, and while this probably isn’t the most efficient way to have a foot switch button control something on a computer, it’s certainly the smallest we’ve seen.

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