Why a two-wire meter cannot see a milliohm A two-wire ohmeter pushes current through a pair of leads and reads the voltage across that same pair, so it measures the device plus the copper, crimps, clip jaws and oxide in the path. Across 10 kΩ that is irrelevant. Across 10 mΩ it is the entire […]
Using simple wires to measure signals with the oscilloscope would result in unreadable plots on the scope, the main reason being the noise coupled onto the “probe” itself. The first line of defense against that would be to use a coaxial cable as a probe, which would prevent external noise coupling. 1. Introduction An unwanted
Compensation of Oscilloscope Probes Read More »
The ATtiny24, 44, 84 series only has 1 external interrupt (INT0) [Page 48 of the datasheet]. This is the interrupt that we are most familiar with using on the Arduino. You can simply use this interrupt by saying “attachInterrupt()” While it only had 1 interrupt, I wanted to have two buttons on my clock: one
What a buck module actually exposes The LM2596 modules sold for a couple of dollars are a fixed-frequency (150 kHz) step-down regulator with an internal switch, an inductor, a Schottky diode and two capacitors. The feedback pin is held at 1.23 V, and the output voltage is set by the divider from Vout to that
How to control LM2596 buck-converter with microcontroller Read More »
What the clock fuses actually select An ATmega32 does not start until the fuses say how fast to run. Four bits in the low fuse byte, CKSEL3..0, pick the source: 1111–1010 crystal or ceramic resonator, 1001 a 32.768 kHz watch crystal, 1000–0101 external RC, 0100–0001 the calibrated internal RC oscillator, 0000 an external clock on
Externally clocking (and overclocking) AVR MCUs Read More »
According to TI’s website, these LM2596 step-down (buck) regulators are sold for $1.8 each for a quantity of a thousand. So how a finished converter could be sold for just above a dollar each is quite a mystery to me. Anyway, the picture below is the board I received. It appears that there are a
LM2596 DC-DC Converter Module Testing Read More »
The ATMega168 is a great general purpose 8-bit AVR microcontroller from Atmel. It has 23 GPIO pins, but sometimes (as I have found) you can run out of I/O pins as your design grows. This happened to me recently when, of the 23 GPIO pins available, 2 were taken up by an external ceramic resonator,
Read multiple switches using ADC Read More »
Have you been using float or double variables to perform mathematical operations on embedded systems without a Floating-Point Unit (FPU)? You are doing it wrong! That’s incredibly inefficient. Use fixed-point representation instead. An FPU is an hardware block specially designed to carry on arithmetic operations on floating point numbers. Even though the C/C++ code may work without
The Art of Representing Floating-Point Numbers as Integers Read More »
emon-server RESTful service converting ‘flashing lights’ or ‘pulsing magnets’ on electricity and gas meter to JSON using the trustful 555 timer chip, Python, NodeJS and a Raspberry PI Summary A cheap 555 timer chip acting as Schmitt trigger combined with a phototransistor or LDR is taped to the ‘flashing light’ or ‘pulsing magnet’ on the
Emon-server – 555 Timer as power usage sensor Read More »
Our ECE 4760 final project is to build a microcontroller based smart medicine box. Our medicine box is targeted on users who regularly take drugs or vitamin supplements， or nurses who take care of the older or patients. Our medicine box is programmable that allows nurses or users to specify the pill quantity and day
Smart Medicine Box Read More »
