Rapid prototyping circuits like Arduino are a great resource when it comes to testing a design without having to worry about the setup of the base to test the design on. The same applies to the devices to be attached to Arduino itself : most of the times the I/Os are potentiometers, pushbuttons, LEDs, displays, IR emitters and receivers and sensors in general. And I don’t want to bother with soldering when the the source code (the ’sketch’) is there ready to run.
That’s why I developped and setup a few circuits ready to go with Arduino or general microcontroller based circuits : they come complete with wires, plugs to connect the Arduino and a few safety devices useful to protect the circuit and Arduino from possible wiring and programming errors. Connecting a switch in parallel to an output instead to an input might break the microcontroller or switching the three leads of a potentiometer might break it.
Many of my circuits are based on the original mini PCBs coming from consumer electronics, that’s why I never dispose or completely dismantle scrap TVs or printers on VCRs and all of the electronic devices I scavenge or get from friends (real friends ! ). I always save small PCBs with switches, motors and else together with the wiring and connectors.
The IR receiver in the picture above is on the original PCB froma Sony TV. The LED could be connected through an SMD transitor on the back of the pcb to the IR receiver to monitor the IR receiver output for received IR pulses.
The same for the IR emitter : a small LED on the collector of the transistor provides for a monitor of output IR pulses.
A better view of the schematic is here.
This is an example of protection device where the wiper of the potentiometer has a resistor in series : in case the wiring is switched and the wiper is incorrectly connected to a supply rail, the power supply is not shorted through the potentiometer burning the pot and possibly the power supply. Voltage drop across the resistor is not much of an issue as Arduino’s inputs leak very little current.
A capacitor at the wiper helps filter out wiper’s electric noise.
A better schematic is here.
The same for the pushbutton : however connected, no more than 5/220A (i.e. 20mA) are allowed to flow across the pushbutton (or an Arduino’s output pin). The board with the switches comes from an HP printer: as a bonus three LEDs are sitting there on the board along with the connector and wiring leads. The golden pins are from some PC board : heat shrink tubing helps keep the solder firm and lasting. This for male plugs.
Female sockets can be made easily with dismantled wire-to-PCB connector contacts and, again, heat shrink tubing.
On the left an RGB led with resistors (inside the heat shrink tubing. The piezo sensor on the right is a vibration/hit sensor. It doubles also as a piezo emitter. The schematic is here.
This is based on Arduino. Four displays show the time. At the time a modified relay strikes a fire extinguisher which provides a bell-like sound. It has to be a CO2 type : powder or liquid types do not work.
It looks a bit Al-Qaedian, so be careful as to where you display it.
Also, fire extinguishers are under pressure so be careful not to hit them too hard.
The circuit board:
This is the clapper made with a modified relay :
This is the schematic : the circuit is intended to be connected to an Arduino board. The name on connectors are Arduino’s.
This is the sketch to be downloaded into the microprocessor: Fire extinguisher striking clock
And this is a video of the clock in action :
I developed this infrared remote control decoder for Arduino on my Arduino-compatible STK500 evaluation board for Atmel’s AVRs.
The sketch is pretty much standard C code so porting to non-arduino dev systems is almost immediate.
I actually developed the code in C for a smaller ATtiny24 for a specific project underway thenI adapted it for Arduino and made available to anyone whom might need it.
The sketch expects the IR receiver on digital pin 8 and is in the form of a demo where 4 LEDs on digital output 4, 5, 6 and 7 are turned ON on my STK500 (microprocessor’s output connected to LEDs’ cathodes) when keys 1 2 3 and 4 are received from the remote. The power button on the remote turns all LEDs OFF.
The code also ouputs the received code to the serial port to be read on the serial console (9600 Baud-8-N-1) .
Any RC5 Philips TV remote control seems to be fine and the few programmable ones I tried work fine. Feedbacks are welcome.
…yes, one day I`m buying a real Arduino !
The sketch for Arduino is here.
IMPORTANT : should you experience problems with random resets, read Mark Arduino’s comment on Jan 24, 2010 at 1:06 pm.
Enjoy.