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Ticker 16x8 logo

Text ticker with 16*8 LEDs and an ATtiny- or an ATmega-Controller

4 Power supply

Power supply for the low-LED-current ticker The software can switch 128 LEDs on simultanously, so that the power supply has to drive up to 384 mA. If a 2x7,5V transformer is used, hte transformer has to drive 2.9VA. The next higher power category of commercial transformers is at 4.8VA.

As electrolytic capacitor we select a 4.7mF with 16V. The 5V regulation uses a standard 7805, which drives up to 1 A. That is sufficient.

Power supply with a 4.8VA transformere These are the load/unload curves of the power supply with a 4.8VA transformer with 450mA load. There is enough voltage left for the regulator. The heat sink of the voltage regulator can either be none or a small 20 K/W: the max thermal power is at 1.4 Watt.
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