I’ve been collecting goodies from China and adafruit to use during the holidays. Hooray for me time.
Enter the Dragino
The Dragino v2 was just released. This little device runs OpenWRT, supports wifi and mesh networking, and has remote flash of AVR (or Arduino) devices. The power consumption is rated at 1 watt…which is really good. This makes it feasible to run this from solar power.
This device has dropped to a great price point: $45. This makes it equivalent to a raspberry pi. It’s a nice price point to do home automation or remote DAQ.
Edit 12/23: The Dragino is now starting to show up Amazon Prime. This sounds a lot of effort arranging shipping from China,
Fun with the 74HC4046 PLL
Most hobbyist skip over the section on understanding Phase Locked Loops. The problem with PLL’s is that they are generic. There are many things you can do with PLL’s, so many that it’s hard deconvolute what a basic PLL does.
The 4046 has been around for decades. The 74HC4046 is a modernized (but by no means modern) version that can be used at higher frequencies. The built-in oscillator works up to 12mhz.
The 4046 has two basic sections: a voltage controlled oscillator (VCO) and a phase comparator. The VCO takes a voltage input (zero to Vdd) at pin 9 and outputs a signal on pin 4. This oscillator (VCO) can be used without using the rest of the chip.
I configured a test circuit with C1 = 20pf and R1 = 10K ohms.
Here are the frequencies generated at different pin 9 voltages.
1V 1.0424 mhz
2V 2.883 mhz
3V 4.348 mhz
4V 5.403 mhz
5V 5.551 mhz
C1 = 68pf
1V 0.358 mhz
2V 1.214 mhz
3V 1.902 mhz
4V 2.442 mhz
5V 2.512 mhz