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397 Articles

Full-featured Battery Tester Puts Them Through Their Paces

April 14, 2011 by 10 Comments

When working on battery-dependent projects you want accurate performance information where a datasheet may not be available. [E. Lelic] set out to build a device that would meter internal battery resistance but ended up with a bench tool that can do much more than that.

A PIC 16F88 microcontroller takes center stage on the meter, taking voltage level readings, monitoring a DS1820 temperature sensor, and controlling an LM2575 step-down regulator. The components provide functionality for measuring Lithium Ion, Lithium Polymer, Nickel Cadmium, Nickel Metal Hydride, and Alkaline batteries. It is capable of fully discharging and fully charging the batteries, measuring time and power consumption during this cycle, and monitoring temperature changes for the NiMH and NiCad versions.

Look for the little red ‘Download’ icon at the bottom of the post linked above. That archive includes a schematic (which we’ve also embedded after the break), board layout in .LAY format, and a HEX firmware file.

If you enjoyed this build you might want to look at this other battery capacity tester.

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Temperature Sensing Mug Means Never Burning Your Mouth Again

April 12, 2011 by 14 Comments

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Some people tend to get awfully attached to their favorite mug. Like an old friend, the mug holds a special place in their hearts, and there’s a weird sadness when it finally gives up the ghost. Through the winter months [Ben’s] girlfriend is never without hers, and when it broke, he decided to give her a new one with some added functionality.

He built her a temperature sensing mug that uses a rather novel way of determining how hot or cold the contents are. Instead of using a thermistor to determine the drink’s temperature, he opted to use a simple diode since it is well known that a diode’s forward voltage varies with temperature. After determining the diode’s voltage range using hot and cold beverages, he hooked it up to the ADC of a PIC12F615 micro controller. The temperature is displayed via 10 LEDs, which are driven through a pair of 8-bit shift registers and buffers since his PIC did not have enough pins to control them on its own.

He had some PCBs made, and after a handful of setbacks got everything put together. He says the mug works pretty well, though the display changes a bit more slowly than he would like. He also mentions that if he builds a second version, he will be sure to select a different PIC that has enough I/O pins to do the job, as well as use a thermistor instead of a simple diode for sensing the temperature.

Continue reading to see a brief demo video [Ben] put together.

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PIC-based Temperature Logger With Onboard Storage

April 10, 2011 by 5 Comments

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Last summer, [Rajendra Bhatt] built himself a simple PIC-based temperature monitor with data logging abilities and recently got around to sharing it on his site. The sensor is based on a PIC12F683 micro controller and measures the ambient temperature on a set interval, storing the values on the MCU’s internal EEPROM.

He used a Maxim DS18B20 temperature sensor, which communicates with the PIC over a 1-wire bus. The sensor is read based upon the interval chosen by the user, and can be configured to measure the temperature every second, every minute, or every 10 minutes. The data is stored on the aforementioned EEPROM and can be uploaded to a computer via a serial connection. The PIC has the ability to store 254 readings before the data must be cleared from the device.

It’s a great beginner project, and has plenty of room for improvement. As [Rajendra] points out, an external EEPROM could be added to expand the recording capacity, and it would be nice to have a real-time clock on hand for accurate time stamping. If we were to build one ourselves, a means of wireless data transfer would be first on our list of potential enhancements.

PIC-based Ham Radio Autotuner

April 7, 2011 by 6 Comments

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A few years back, [Floyd, K8AC] built a high frequency autotuner as an addition to his Ham radio setup. Based off a design he saw in QST magazine back in the early ’90s, he has been using the tuner almost daily for the last few years, on both the 3.5 MHz and 7 MHz bands.

Built into the wall in his radio room, it is a pretty impressive sight. His “L” circuit is controlled by a pair of mechanically coupled inductors which are driven in concert by a pair of two-way motors. The positioning of the C and L components are monitored by a PIC controller which stores the tuning data for up to 30 predefined frequencies. A couple of button presses on his controller’s front end sends the tuner into action, dialing in his unit’s inductors and capacitor to their proper settings. The PIC monitors the tuner’s progress, informing him when the proper frequency has been tuned in, or if the frequency can not be set, indicating issues with the equipment.

His setup has undergone several revisions over the years, with the most recent iteration being the most automated of the bunch. Check out his site for plenty more details, or keep an ear out for [K8AC] on 40 or 80 meters.

[Thanks, Rich V]

Reverse Engineering LED Vodka Bottle Displays

April 6, 2011 by 10 Comments

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When [Tyler] heard about the LED matrix display that Medea Vodka was building into their bottles, he immediately wanted to get his hands on one. Who could blame him? Someone had finally combined two things we love dearly: booze and LEDs.

He struggled to find a bottle at any of his local stores for the longest time, but was absolutely stoked when he finally came across one of their reps promoting the brand while he was out shopping.

Once he got home, he pulled the display off the bottle and began poking around to see what made it tick. The display is made from a flexible PCB, and attached to the bottle with some clear elastic film. It is powered by two CR2032 batteries and controlled by a PIC16F chip, which pulls stored messages from a small Atmel EEPROM.

Once he figured out how to control the LED matrix, he uploaded his own fonts and added a LINX wireless module to remotely send messages to the board. He mounted it in a wooden frame and now uses it as a simple marquee display.

If you have one of these displays hanging around your house, be sure to swing by his site for schematics of his wireless interface board as well as the code he uses to drive the marquee. You can check out a video of the display in action there as well.

Gun Turret Built Into A Cake Box

April 3, 2011 by 17 Comments

Couch potatoes have a new line of defense thanks to this remote-controlled turret. The gun itself is a hacked down airsoft model. The mount started with a servo motor in the center of a plastic cake box. A thin strip of plywood was added, along with a couple of sliding furniture feet to stabilize the platform as it rotates. A second servo mounts to that platform, which allows the trajectory of the projectile to be adjusted up or down. A PIC 18F4520 controls both of the motors, as well as the firing of the airsoft module, all while listening for commands from an IR receiver. Just adjust the firmware to match an unused device on your universal remote and the power to annoy your roommates will be at the tips of your fingers.

You can see an overview of the build process, as well as a demonstration of the final project in the video after the break. The page linked at the top has a very detailed build log but some of the ‘next’ buttons on that page don’t work for us. Luckily you’ll see a table of contents in the right column which lets you navigate around these bad links.

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Super Pong Table Doubles The Fun

March 29, 2011 by 8 Comments

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While Pong has traditionally been a game played between two individuals, Instructables user [Brad] has put together a variation that doubles the fun.  His Pong coffee table has the ability to support up to four users at once, and makes for quite the living room centerpiece.

The table is made from sheets of MDF and incorporates a grid of 900 LEDs, all controlled by a PIC18 micro controller. The MCU is installed on a control board he designed, along with the other additional bits required to drive the LED array. A set of old Atari paddle controllers were disassembled and installed around the table, making this a true retro Pong experience.

As you can see in the video, the action is pretty frantic. It’s hard to tell who is winning until the game is over, but [Brad] says that a scoreboard will come in a future revision.

4-way Pong is a really cool idea! , but it looks like there are no open source schematics or code for the control board. We’re hoping someone sees this project and puts together a version for all to use, free of charge.

We were mistaken about the status of this project in relation to whether or not it was open source. [Brad] wrote to us letting us know that his code was not originally included with the Instructable as a result of a late night omission. As always, his projects are open source, and you can now download all of the source code and schematics at the page linked above (and in the first step of the Instructable, no less). Mea culpas all around, thanks for the update, [Brad]!

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