LittleArduinoProjects#222 Stair-step Generator

Once again I'm inspired to go and build a circuit by yet another great tutorial from w2aew.

This circuit generates a stairstep waveform by an ingenious combination of 3 circuit elements:
  • a "high" (265Hz) frequency pulse (555 timer) provides the charge to step-up the output
  • the step pulse feeds an OpAmp pulse integrator/accumulator
  • a low frequency pulse generator (OpAmp oscillator) provides the reset pulse that clears the accumulator and resets the 555

As always, all (more...)

LittleArduinoProjects#221 XOR with Resistor-Transistor Logic

Exclusive OR (XOR) operation is true only when the inputs are different.

An XOR may be constructed using combinatorial logic: an OR ANDed with a NAND. But can it be done with even more basic discrete components?

This circuit uses a diode-bridge and a single transistor - quite neat. It does mean however that there is no output buffer, in fact the output is powered from the inputs. I'm using an Arduino to drive the (more...)

LittleArduinoProjects#220 Arduino gcc toolchain

The Arduino IDE is the most convenient way to get started with Arduino, but it does obscure the underlying mechanics of building software for an Arduino.

How to do it from scratch? This is my experiement and guide to building software for an Arduino from the command line. I use a Mac and homebrew, so it is somewhat MacOSX-specific.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo (more...)

LittleArduinoProjects#219 DS18S20 1-Wire Reading

Another way to measure temperatures, this time the DS18S20 - an inexpensive 1-Wire digital thermometer with a range of -55°C to +125°C, at ±0.5°C accuracy from -10°C to +85°C.

It comes in TO-92 packaging and may be powered directly (using three pins), or take parasitic power from the data line (using two pins). This makes it ideal for pin-starved microcontrollers that need a decent ambient temperature reading. In this project, I'm just exercising the (more...)

LittleArduinoProjects#218 MPU-6050 3-Axes Accelerometer Gyroscope Module

I'm planning to build a controller that needs motion detection, so got hold of an Invensense MPU-6050 3-Axes Accelerometer Gyroscope Module to see if it would do the trick. The module conveniently operates on 3-5V. All I've done so far is a simple sketch to confirm I can read raw values from the MPU-6050 using the Arduino Wire library.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo (more...)

LittleArduinoProjects#217 Basic AVR-controlled Buck Converter

Buck converters are switching power supplies configured such that the output voltage is lower than the input voltage.

Since the primary components (inductor and capacitor) ideally consume no power, high conversion efficiencies are possible. In practice of course, components are not ideal and there is some power loss. More significant however is any power consumed in the control and feedback circuits.

This circuit is a demonstration and exploration of the basic buck configuration with a (more...)

LittleArduinoProjects#216 OSHChip driving SPI LED module

How easy is SPI with the OSHChip? I thought I'd find out by first controlling a module that has a very basic SPI-ish slave interface.

I'm using the LEDx16Module that I designed in the KiCad like a Pro course from Tech Explorations. It has dual 74HC595 shift registers that can be driven with SPI to control 16 onboard LEDs.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo (more...)

Feature Lifecycle Analysis with PivotalTracker

Can you trust your agile planning process to deliver the best result over time?

In an ideal world with a well-balanced and high-performing team, theory says it should all be dandy. But what happens when the real world sticks it's nose in and you need to deal with varying degrees of disfunction?

Feature Lifecycle Analysis is a technique I've been experimenting with for a few years. The idea is to visualise how well we are (more...)

LittleArduinoProjects#215 OSHChip yotta toolchain

After bruising myself on the raw gcc toolchain - and although I got a program running - I think I want my toolchain to do more of the hard work for me!

So next I tried yotta, the software module system used by mbed OS. Building a simple program using the Official Yotta target for OSHChip and gcc on MacOSX proved quite straight-forward.

As always, all notes, schematics and code are in the Little Electronics (more...)

LittleArduinoProjects#214 OSHChip gcc toolchain

Can I build a program for the OSHChip using the gcc toolchain and Nordic Semi SDK on MacOSX?


Here are my notes and scripts for compiling and deploy a simple program, but there remain a few rough edges. There are probably easier ways to do this ... like using the Official Yotta target for OSHChip using gcc ... but I was curious to see how far I could get with just gcc and the Nordic (more...)

LittleArduinoProjects#213 OSHChip blinky

I heard about the OSHChip on the podcast #146 and immediately wanted one!

An ARM Cortex-M0 32 bit micro processor (nRF51822) with 2.4 GHz Radio and other goodies all in a breadboard-compatible DIP16 package .. how could you say no?!

So far, so good. Literally 5 minutes to the first blinking LED, and hours of fun followed .. this is an awesome little package.

As always, all notes, schematics and code are in the (more...)

LittleArduinoProjects#212 Stay Creative!

A simple project inspired by Make your own LED Sign VU Meter by GreatScott!. The catch-phrase should be familiar if you subscribe to his channel;-)

It's a VU meter, but rather than doing the "bar graph" thing à la LM3915, it pulses the intensity of all LEDs to the volume of the incoming audio.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

LittleArduinoProjects#211 Buck Converter Modules

There are many super-cheap buck converter modules available, often based on the LM2596S-ADJ. The "BuckConverterModules" project is where I've recorded notes on the individual units I get to see. So far I've tested four. Two perform really well; two are OK but I have my doubts about the specs of the converter chip.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

LittleArduinoProjects#210 Pump up the Jam!

This is a super cheap amplifier kit built around the TDA7297 15+15W dual bridge amplifier chip. All the other parts in the kit are essentially the basic supporting components for the TDA7297.

Performance is very good, although my impromptu speaker boxes don't do it justice. They need better baffles at least, but I can hardly blame Straits Preserves for not making marmalade boxes to the specification of speaker enclosures!

As always, all notes, schematics and (more...)

LittleArduinoProjects#209 a funky little LED display

I found this interesting LED display at Sim Lim Tower, and grabbed one to test. The LED unit combines 7 x 7-segment display (no decimal points) and 7 indicator LEDs (Red-Green-Yellow).

It is marked as "72R02PHIL T9717". I have no idea what that means(!), and of course there's no sign of a datasheet on the net, so pinouts needed a bit of reverse-engineering. All in all, an interesting display unit for a combination of (more...)

LittleArduinoProjects#208 Single Stage FM Transmitter

I've been experimenting with FM, and the hardest thing to get right tends to be the hand-wound coils. So to get a baseline, I picked up a 1-transistor kit during a recent visit to Sim Lim Tower.

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

LittleArduinoProjects#207 Frequency Counter

Testing a CMOS frequency counter circuit with a 100Hz - 5MHz range.

I found this circuit published in Electronics magazine (Sep 16 1976). It's a classic demonstration of the CD4026 "bucket-brigade" and CD4047 astable oscillator.

The frequency counter is governed by a CD4047 oscillator. Since this offers a clean 50% duty cycle, it is ideal for flipping the circuit between two modes: sampling period; display period.

As always, all notes, schematics and code are in (more...)

LittleArduinoProjects#206 CD4047 Astable Oscillator

The CD4047 is capable of running in astable or monostable configurations, with operating frequency configured by an external RC network. So in one sense, sounds like the 555 timer!

Unlike the 555, the CD4047 provides a fixed 50% duty cycle with good frequency stability (+/- 2% @ 100KHz).

As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub.

LittleArduinoProjects#205 Triac Dimmer

A triac is a "bidirectional thyristor" because it conducts in both directions and is typically used in AC applications.

The basic behaviour of a triac can be summarised in two rules:
  • Rule 1. To turn ON, a gate current ≥ IGT must be applied until the load current is ≥ IL (latching current).
  • Rule 2. To turn OFF (commutate), the load current must be < IH (holding current) for long enough for the device to return to the blocking state.

This project is a test of the classic AC dimmer circuit (more...)

LittleArduinoProjects now with fancy catalog!

I keep finding new uses for GitHub Pages - situations where in the past I would otherwise have spun up a web site on heroku or similar. But if the site can be static, and especially if you are already hosting the git repository at GitHub, Pages are perfect.

For a long time, I've maintained the LittleArduinoProjects project index as a simple table in the README. But it wasn't particularly nice or usable, so I (more...)