Plastic Optical Fiber Transmitter Ideas

121

00:47:25

Two Ideas how to make a Uart 5V Pulse Signal compatible to a POF Transmitter.
Top Example:
Inverted Transmitting, 
0 = LEDON, 1 = LEDOFF

Bottom Example:
Noninverted Transmitting,
1 = LEDON, 0 = LEDOFF

published 8 years ago

eekee

8 years ago

The top one is an emitter follower, amplifying current but not voltage. If you changed the PnP for an NpN with the emitter to ground (common emitter), it would actually be non-inverting because the LED would be on when the input is high. (Normally, common emitter is considered an inverter, and emitter follower is considered non-inverting. Connecting the LED to the positive supply inverts the logic, so common emitter becomes non-inverting.)

hurz

8 years ago

@eekee, the biggest issue you missed. Check the second circuit and measure the base current, or just think of what happens to a transistor if you apply 5V to the base emitter diode? LOL Ube>1.2V is problably nonsense.

eekee

8 years ago

Oh 300mA! That's 1.5W being dissipated in that transistor just to turn it on.

ElektroTinker

8 years ago

@eekee @hurz okey guys thaaaaank you for your help I will make it better next time.

eekee

8 years ago

Welcome! :) The usual way to drive the base is through a resistor. Or, if you use MOSFETs in EC, adjust the width if you need less than 600Ω from 5V signals.

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