My line following robot is another step closer to being completed. I finished soldering all of the components and connected the battery to test the circuit. The next and hopefully last steps are to attach the circuit board and motors to the body.
I got that RN-42 carrier board populated and working! Its ready for the GyroSkirt driver board, once I get that built.
There are a few errors on the board. TX and RX are swapped somewhere. Either on this board or on my USB to TTL-Serial board or in the RN-42 documentation. Also it seems the LEDs were meant to go to Vcc rather than ground. As a result my LED indication for connection status and RF traffic is inverted.
I can live with the errors as the actual data transmission works like a champ. To test the tranmission I hooked the carrier board up to a PC via a USB to TTL serial converter configured to operate at 3.3V. The venerable Hyperterminal program was used to open the virtual com port on the PC. Then I downloaded Sena’s Bluetooth terminal program to my Android phone and used it to form a Bluetooth serial connection between my phone and the modem. The result: keys pressed on my phone’s keyboard appeared inside the Hyperterminal running on the PC and keys pressed on the PC keyboard appear inside the Sena Bluetooth terminal running on my phone. Bi-directional data flow at 115,200 baud.
Now that I have proven my wireless link works, I need to update the GyroSkirt/GryoBelt firmware to allow me to adjust the gain and the deadband over the Arduino’s serial port. (In addition to actually making a driver board that has a spot for the modem.)
I got my first batch of iTead Studio boards in! iTead Studio is a pcb printing shop that offers absurdly cheap prototype boards. The new boards look great. I’ll definitely use them again. It only took 2 1/2 weeks to get here. For the price its an awesome service.
The particular board shown is a carrier board for the RN-42 Bluetooth modem, which is only $15 from Sparkfun if you buy it in its surface mount form. For another $15 I now have
10 12! carrier boards that allow me to adapt the surface mount device to through hole technology as well as control infrequently utilized device specific features such as factory reset, BT Master mode, force 9600 baud and more. The more you know the cheaper electronics gets.
The carrier, populated with the modem, etc., is destined for the GyroSkirt. The idea is that I’ll be able to adjust the gain and deadband processing on the gyro sensor reading wirelessly from a program on my Android phone via the Bluetooth radio in my phone and one of these boards affixed to the GyroSkirt driver. The GyroSkirt will again be driven by an Arduino, so I hope to leverage the Amarino library to speed my development time.
Alert others to your presence outside, in style!
Today I stopped by the makerspace to etch the circuit board for my second robot. The robot is a very simple line follower that uses a LM393 dual comparator IC. The complete design and build instructions can be found in the book Robot Building for Beginners by David Cook.
My cat has been telling me she wants to get more into 32 bit ARM processors. So when ST started freely offering their discovery development board for their new Corex M4, I jumped at the chance. My luck was in and the board arrived today! The STM32F4 on the board has a full meg of flash and a single precision floating point unit! Oh and like a bazzilion hardware timers and lots more. The board itself has a number of sensors and a big LED on it.
My cat is looking forward to spinning up a compiler and putting the device through its paces. She is especially looking forward to the demo app where the board pretends to be a mouse.
A time lapse video complied from the Milwaukee Makerspace CCTV system. 7 hours of video compressed into 4 minutes. All events took place between 4:30 and 11:30 PM Thursday, September 29, 2011.
- Rich welding
- Chris and Rich working on their electric cars
- Chris driving his electric car in and out of the shop
- Tom, Adam, and Royce working in Diptrace
- Bret, Rich, Royce, and Adam blacksmithing items with the forge
- Various people working on misc. projects and chatting
- Royce, Brant, and Adam etching and tin-plating circuit boards
- Pete working on his Makerbot 3D printer
In addition to the usual hackery and makers working on their electric cars, Bret fired up the forge again last night. Rich turned some horseshoes into hangers, Adam flattened a steel rod, and Royce folded a metal bar.
In preparation for BarCampMilwaukee6 (this weekend!) Royce and I have been mass producing circuit boards for a “learn to solder” class we’ll be holding. The boards are 1.5″x1.5″ square and include a battery, two resistors, traces in the shape of our logo, and two red LEDs for eyes. The copper traces were tinned using “Tin It” to prevent oxidation and make it easier to solder. We’ve made 65 of the “tie pins” so far and the project gave us an opportunity to tweak our methods for PCB etching. We prefer etching with ferric chloride, but muriatic acid and hydrogen peroxide are looking more attractive as they’re cheaper chemicals, can be obtained locally, and etch much faster without heating. Also, red Sharpie markers seem to work really well at cleaning up traces with the muriatic acid solution. Specifically red, not sure why.
This is the prototype of the tie pin we plan to make for our own little Learn-to-Solder sessions. It’s inspired by the Makershed tie-pin. We don’t have any RGB flasher LEDs at the moment, and won’t in time forb BarCamp. But the red LEDs still look pretty cool.
At some point we’ll put an order out to a real PCB shop and get a circuit board with red solder mask and black silk screen. But these boards are plenty of fun for now.
A few months ago I started collaborating with Jordan Waraksa on a project that is currently on display at the Haggerty Museum of Art, in a show running until the end of December. He sculpted a pair of wooden acoustic horns called Bellaphone 5 & 6 out of walnut. Each horn rests on a redwood base that houses a small speaker. If you visit the Haggerty, you’ll hear the speakers playing songs by Jordan’s band, The Vitrolum Republic. If you really love the Bellaphones and amplifier, know they are for sale.
I developed and built the electronics for the horn’s amplifier, whose chassis Jordan also sculpted from redwood. Because the chassis is wood and has no vents (for aesthetics), electrical efficiency became a high priority in order to prevent overheating. I chose to use a Maxim 98400A class D amplifier driven by a high efficiency switching 15V DC power supply. I added a digital signal processing chip from Analog Devices to increase the bandwidth of the horn and smooth out its frequency response (i.e. to improve the audio fidelity). Analog’s ADAU1701 is a remarkably powerful chip – it is more than capable of these tasks. In addition, the 1701 prevents bass notes (frequencies below 100 Hz) from reaching the small speakers (which are incapable of reproducing these low notes), which would otherwise emanate from the horns as distortion. Finally, the 1701 also adds a small amount of compression, which prevents distortion at the loudest output levels. The 1701 is actually real-time programmable via a USB connection to a computer running Analog Device’s free SigmaStudio software. It’s a tremendously user friendly GUI environment with drag and drop audio processing blocks.
Check out the inside of the amplifier as it was being assembled, prior to the addition of many ferrite beads which eliminate the audible noise from the three high efficiency switching power supplies: One powering the amp, one powering the DSP board, and one continuously charging a Motorola Cliq XT handset playing songs from the Vitrolum Republic.
And one of Bellaphone five and six:
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