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Physical Computing
IV-6 VFD vacuum fluorescent tube email counter
Written by blog   
Thursday, 16 December 2010 00:00

Authors: blog


The star of the show is the Soviet IV-6 vacuum fluorescent display tube, brand new from old stock. I picked it up on ebay for $1 delivered unit cost.

Digit segment switching is via 7 2N3904/3906 NPN/PNP transistor pairs. I didn't want to use a VFD driver chip because a) they are scarce/obsolescent b) they are expensive c) they are overkill for a single 7-segment tube and d) most don't have a thruhole package option anyway.

The section to the right of the tube is a boost converter circuit to generate the ~25V to drive the grid and segments. Since it is a single digit tube, it is a direct DC drive. The IRF730 power MOSFET is modulated by the PWM output of the Atmega8 on the left side of the board.

Power and communication is via an FTDI FT232R USB-serial cable, which I will replace with a cheap PL2303 cable (when it arrives from Hong Kong). I'm also gonna move this to one of those fancy new transparent breadboards, because I think that look will really complement the vacuum tube. I might rethink the layout to see if I can cut down on the tangle of wires.

by coreylcoreyl

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Last Updated on Thursday, 16 December 2010 01:10
Motion-sensing bathroom noisemaker
Written by admin   
Friday, 10 December 2010 00:00

Authors: admin

Mike Hord from Hack Factory built a motion-sensing device for a local pizzeria’s restrooms. For the purpose of annoying them while they “rest”.

Recently I was approached by an architecture/design firm to help with an electronic install at a client site. The client had requested a system that interacts with users in the bathroom- “interacts” meaning, hassles them when they come and go.

The system has three events- enter, exit, and “loiter”, and sounds in different folders on the USB drive will be played for each event, allowing users to change the sounds later if they wish.

Motion-sensing bathroom noisemaker - [Link]

Last Updated on Friday, 10 December 2010 01:34
Meet the DC Motor Plug
Written by jcw   
Tuesday, 07 December 2010 00:00

Authors: jcw

Here’s a new I2C plug to drive two small DC motors. The DC Motor Plug has 2 H-bridges on board, which can drive each motor in forward or reverse. An additional 4 I/O pins are available, for limit switches, quadrature encoders, whatever:

Dsc 2310

Here is a test setup with a couple of (different) geared motors, driven from a 4x AA battery pack, plus the usual AA Power Board for the JeeNode itself (these could also have been combined):

Dsc 2309

All I/O is done via I2C, using the MCP23008 expander chip (same as used on the EP, LP, and OP plugs).

Here is a sample sketch called dcmotor_demo.pde which briefly drives each of the motors in both directions:

Meet the DC Motor Plug

One notable detail about this plug is that it uses TC4424 chips which are in fact not DC motor drivers at all but MOSFET drivers… it turns out that these are also well suited for small DC motors, and should be able to handle up to 1.5A @ 4.5..18V.

A small bipolar stepper will probably also work, but I haven’t tried that yet. This board has a jumper to select between I2C addresses 0×26 and 0×27, so two of these can be daisy-chained on a single port.

Speed control should be possible using software PWM, but not at very high rates, since the I2C bus will be the limiting factor.

One use for this in the context of home automation would be to drive small highly-geared 12V motors to adjust the position and raising/lowering blinds.


Docs added to the café and kit in the shop, as usual.

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Last Updated on Tuesday, 07 December 2010 02:42
1-Wire Barometer
Written by admin   
Tuesday, 07 December 2010 00:00

Authors: admin

This project is a 1-wire barometer which will work on a Dallas Semiconductor Corporation 1-Wire network. The components used are: A Motorola MPX4115 Silicon Pressure Sensor, A Dallas Semiconductor DS2438 Smart battery Monitor, a Voltage regulator, an operational amplifier, a diode, some resistors, some capacitors etc. Check details on the link below.

1-Wire Barometer - [Link]

Last Updated on Tuesday, 07 December 2010 02:48
Relay Solar Tracker
Written by admin   
Sunday, 05 December 2010 00:00

Authors: admin

This project is a solar tracker based on light depended resistors, relays and opamps. Check the installation of circuit solar tracker to diseqc motor.

Relay Solar Tracker - [Link]


Last Updated on Sunday, 05 December 2010 03:44
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