We do what we must because we can!
The Renard SS-16 Christmas Light Controller board comes equipped with an on board 5V supply. Having several high current 5V supplies on hand, I decided to use them, sparing the expense of the transformers, regulators, caps, diodes, etc.
Mostly Complete Renard SS-16
It turns out it is very easy to add a good old fashioned analog meter to your next digital microcontroller project. Simply, drive the meter with a PWM source with proper buffering and current limiting. This post will discuss the circuit theory, resistor calculations and programming necessary to achieve this end.
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This week’s chip is also coupled with a Gizmo Of The Week, the ShiftBright, a RGB LED with the Alegro A6281 and a carrier board.
Alegro has this to say about their chip…
The A6281 is a 3-channel constant current LED driver that has a wide range of output currents. The A6281 controls LED brightness with a Pulse Width Modulation (PWM) scheme that gives the application the capability of displaying a billion colors in an RGB cluster. The maximum current is set by an external resistor.
Product homepage.
Product datasheet (PDF).
The company, MaceTech has three products based around this chip, the Shiftbright, which houses a fairly standard single LED; the Megabright, which has three 100mA 40,000 MCD LEDs, one of each color, and the Shiftbar, which is simply a A6281 breakout board to add your own LEDs. Also related, but not based on the A6281 is the Octobright, an 8 channel RGB LED board based on the Texas Instruments TLC5947 24-channel 12 bit PWM controller. More details on that chip at a later date.
I plan to use the Megabright for a RGB LED mood lamp based on an Ikea Lampan table lamp. I was simply going to use the same code as I plan in the Ikea Spoka hack, but I want to try this chip and off load the PWM generation and such from the PICmicro.
Completed the Larson Scanner”. Named after Glen A. Larson, the creator of both Battlestar Galactica (1978) and Knight Rider (1982), it is a simple LED sequencer that mimics the “eye” of the Cylon or the hood scanner on KITT in Knight Rider.
So what’s so special about about a LED sequencer? A couple of logic gates would do it, a microprocessor isn’t even necessary. This sequencer accomplished the sequencing of 8 (12 capable) LEDs with a chip with only 6 I/O lines, and only 4 were used.
This feat was made possible by “Charlieplexing” the LEDs, saving I/O pins and not overly increasing complexity. In using a microcontroller, the pattern and speed can be easily changed. With two left over I/O pins, other functions can be added. Mark-II of this circuit will include left scanning, right scanning, and a “sync” signal for multiple pumpkins scanning in unison.
STEP 0 – The Motivation
The Motorola Syntor was a synthesized 32 channel radio for VHF or UHF. Manufactured in the early 1980s they came after the crystal controlled Micor radio and shared many accessories. The RF frequency information was held in a one-time programmable PROM chip, and the PL tone / DPL code information in a second chip. These chips have since become impossible to find.
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PART 1: Getting It -IN-The Air
A few years ago I bought a HF6V, or rather, a pile of tubing purporting to be a complete 6 band vertical and safely stowed it away, never getting to it, till now. A few days ago I gathered the necessary pieces parts, attempted to assemble the antenna, and got my old AEA CIA-HF antenna analyzer working again.
While working on various data acquisition projects, I realized that making my applications aware of the date would be a necessity. PCs by definition are already date aware, but I am working on small stand-alone data acq projects without a real time clock. Enter the Maxim (Dallas) DS1307 64 x 8, Serial, I2C Real-Time Clock. Maxim has this to say about their chip…
The DS1307 serial real-time clock (RTC) is a low-power, full binary-coded decimal (BCD) clock/calendar plus 56 bytes of NV SRAM. Address and data are transferred serially through an I2C, bidirectional bus. The lock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply.
So couple this chip with a 3V lithium coin cell battery, a crystal and a couple of resistors, and your next microcontroller project will be date aware.
COST: $3.74 USD (Digikey)
Just a simple “cylon” or “knight rider” style light chaser this time around. I whipped this up in about an hour, as an exercise in “CharliePlexing“, a method whereby LED connections to a microcontroller are greatly reduced.
Prototyping boards are usually fscking expensive, $20 – $30 for a good Vero board. The folks at ProtoStack have reasonably large, reasonably priced protoboards for $8.40. Check em out.
