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BJT oscillators

A project log for Analog Blinken Grid

64 LEDs in a matrix on a wireframe controlled by 16 astable transistor oscillators to resemble a computer panel from a 70's TV show

matsengmatseng 01/25/2019 at 23:240 Comments

Since the LEDs are in a matrix I need to have the oscillators both push VCC into  columns and also connect GND to the rows. So I need two different types of modules for that

The oscillators themselves are just the bog-standard two-transistor, four resistors and two caps thingie.  And to be able to push and pull current I added a NPN driver transistor to eight of them, and a PNP driver to the remaining eight.

Using 1uF caps and 1M for the timing resistors I ot about 0.7Hz when running at 5 volts, slightly slower at 3 volts.

Schematics for the two types of oscillators
Schematics for the two types of oscillators

Eight of each of the two types of oscillators are needed for the 8x8 matrix.

Soldering the oscillators
Soldering the oscillators

I re-discovered the usefulness of using blu-tack to hold parts while soldering - but even  using that it took quite a while to freeform 16 oscillators with 9 parts each.

The oscillator with a NPN driver
The oscillator with a NPN driver

This is one of the NPN-driver oscillators that pulls a row to ground when active. The PNP oscillators looks more or less the same except for the top transistor that is in a slightly different position to access VCC instead of GND.

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