Randy Glenn is possibly RoHS Compliant, but only by exemption.
Maxim has an interesting appnote on driving a bunch of LED displays using fewer I/O lines than normal
Charlieplexing: Reduced Pin-Count LED Display Multiplexing
An interesting approach to multiplexing the segment drives with the digit drives for multi-digit LED displays. It’s easy enough to implement on your own microcontroller, though unfortunately you don’t get the nifty constant-current driving that Maxim’s chips give you.
Continuing on my high-brightness LED kick, here’s a few designs for switch-mode constant-current supplies for high-power LEDs, courtesy of ON Semiconductor:
12V AC-DC MC34063 LED Buck Driver
The MC34063 is a nice chip to use purely based on price – it’s dirt cheap. You can also get a fair amount of efficiency from it, though apparently the darlington output stage is somewhat lacking. Still, it’s available in a DIP8 package, and did I mention… dirt cheap? $0.83CAD from Digikey in singles, drops to under $0.30CAD in the thousands.
Considering that any linear system (constant-current regulator, plain ol’ resistor) is going to give you something on the order of 50-60% efficiency, and this’ll give you on the order of 75-85%… not bad at all.
If you, like me, are using the excellent SCPlugin for Subversion on OS X, and also have your own Subversion server with a self-signed certificate, this thread is of interest in Getting The Damned Thing To Work™
An interesting appnote from Maxim, on building a rig to test the efficiency of power supplies:
Practical Data Acquisition using a Windows-based Power Meter
A neat rig all told, and shows of a few of Maxim’s cool parts, but it originally came to my attention when a former boss saw this line and felt the need to share:
"At 9600 baud, it takes more than one millisecond to transmit eight bits of data together with the start and stop bits. This is obvious in hindsight, but it can give the designer hours of undeserved enjoyment not only in wondering why data is not reaching the PC correctly, but also in illustrating the difference in operating speeds of the microprocessor and the RS-232 link."
The voice of experience rings loud and clear with that one.
This week, an appnote from Freescale on different ways to control high-brightness LEDs:
Bright Approaches to Microcontroller-Based LED Drivers
Driving these LEDs with constant current is really important for consistent results. Wavelength of the light is dependent on the current, so driving a precise value is crucial. However, forward voltage varies with current, and also experiences process variations, so the standard LED in series approach is pretty well useless if you want to control the colour of RGB LEDs properly. Thus, you need a constant current source that doesn’t depend on the forward voltage of the diode. This appnote presents a few solutions, though they head straight for the switching power supply that doesn’t work with RGB LEDs with a common supply terminal.
In Today’s lesson, we learn that if you use ls on a Linux system, and one of the directories in that directory is in fact the mount point for a Samba share on a computer that no longer exists… ls will return 1, rather than 0. If the directory is rather large, you’re not likely to notice that right off, and may suspect that someone’s rootkitted ls on your machine.
This week, from NXP, we have an appnote on building an all-software MP3 player using their LPC2148 ARM7TDMI microcontroller:
Realizing an MP3 player with the LPC2148, using libmad and EFSL
To compare: this solution uses the DAC built into the LPC2148, so it gets 10 bits of resolution for one channel. Adding an external audio DAC for a couple bucks brings that to 16 bits and two channels. The LPC2148 is running about $14 at Digikey in unit quantity right now.
Compare with the popular VLSI chips: the job is done for you, but the chips run $20 from Sparkfun, and 16 Euro from VLSI directly (!). Those prices include license fees, though, but you still need another controller to interface with your storage and get the data and commands to the codec chip. So this does have some cost benefit.
While not a company appnote per se, this document provides a decent overview of the different types of oscillators that can be used with a microcontroller. From AVRFreaks:
A bit AVR-centric, but it covers a number of useful topics, including how to properly size the loading caps on a crystal oscillator.
This week’s appnote comes from Winbond: a simple audio amplifier using a 2N2222 transistor to drive a small speaker.
It’s not going to be the best fidelity, but for driving a small speaker to generate tones coming out of a microcontroller, it sure beats having to put down an LM386 and such.
A neat application note from TI, which they no longer seem to host on their site:
Op Amp and Comparators – Don’t Confuse Them!
Interesting stuff, with notes on how to properly terminate unused opamps.