8×8 Audio/Video Switch

Frontalino assemblato con tutti i componenti.

An audio/video crosspoint switch based on the Maxim (now Atmel) MAX456 chip, with remote control serial port.

The detailed page about this project can be found HERE.


Infrared Repeater

irrepIt’s a little circuit to relay infrared remote signals from a room to another room.

Nothing fancy… no microcontroller, no firmware. Just a 555, a TMS5330 infared decoder (but almost any decoder should work), a long cable and an IR LED. That’s all.

I’ve used three of these circuits and I’m now able to use almost any remote in any room.

The trimmer on the circuit change the IR carrier frequency. It should be 38 Khz, but my appliances likes more a carrier of 42-43 Khz.

This is the schematic:


Multi-channel 12V light blinker

A PIC, 12 NPN transistors and a handful of other passive components.

This 12 channel light blinker has been connected to the lighting system of a train station scale model to simulate blinking light in different places and at different frequencies.

The “check panel” on the circuit, that shows with 12 mini-leds the output status, is very nice to see, but unfortunately I had not the chance to take a picture, but one day or another I’ll disassemble the full model to photograph the panel… :)

Dual channel train model variable power supply

trainpsI’ve built this for a friend. It’s a variable voltage stabilizer with dual indipendent outputs from 0 to 12 Volts, up to 1 Ampere each channel.

Each output have a switch to choose the output polarity and a potentiometer to set the output voltage. A trimmer on the circuit sets the maximum voltage for each channel.

This circuit uses the L272M dual power operational amplifier in a bridge configuration to switch polarity, so a single pole switch can be used to change train direction.

R/C Speed Controller

rcspeedThis is a really nice circuit that I use in my Tamiya RC car (I’ve also sold some of them). In short, it gets the servo signal from the receiver and uses it to drive the car electric motor. The hexfet H-bridge can handle more than 40 Amperes without problems. But the thing I’m very proud of is the “throttle” handling.

A little zone around the radio stick center position is the “dead zone”: the motor is free. All the “forward” zone is reserved to make motor go forward (its speed is of course proportional to the stick position). The upper half of the “backward” zone is the active braking position: the motor is short-circuited (sort of) and so the car stops in very little space. The lower half is obviously dedicated to make motor go backward.

The system is configured easily for any radio: just power on the car keeping the switch on the Speed Controller pressed, wait for the “beep” (No, it’s not a buzzer !!! My circuit uses the motor as a speaker :-) ) then put the stick full forward and press the button, put the stick full backward and press the button. That’s all. The configuration is written to internal eeprom and kept also if you disconnect batteries.

Another nice thing if you run indoor, or you’re learning the “art” of R/C car driving, is the “dummy mode”: with the car powered on you can press the button, and the controller reduce the maximum speed to about 1/4, keeping full speed proportionality and active braking.

High power LED display

leddispThis was my first “real” project years ago (I mean … someone asked me for it and paid me !!!)

It’s a 16×16 LED matrix, driven without multiplexing, with a little logic on board to allow a PC to draw on the display connected to the parallel port. It was really bright, with just 16 of the 256 leds turned on, it was impossible to look directly at the display.

I built then a stand-alone controller, with some image sequence stored on EPROM, and placed all in a custom built aluminium box. This was used as a sample to show display capabilities to potential customers.

Obviously the customer kept the 16×16 version But I kept for me the very first 8×8 prototype (the one in the picture), entirely wired by hand.