ciruits and chematics


Posted on Feb 7, 2014

This is the current schematic for the Boost converter. The negative power is connected to the emitters and LED cathode. With the values shown, the circuit draws about 18 mA and drives the LED to 5 mA or so. Higher input voltage, up to 3 volts assuming white LED use, pulls more current and therefore produces more light. Changes in values will chang


ciruits and chematics
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e performance. Attention should be paid to the inductor, as it is the key in most cases. It needs to be capable of dealing with peak currents and not saturating. This is the schematic for the Low Drop Out (LDO) regulator circuit based on the LM334. The transistor boosts the available current (limited to 10 mA by the IC) to higher levels needed to drive the LED. In the example above the 47 ohm resistor (which is always in circuit) sets a basic current of about 1. 5 mA. When the switch is not in the center position (open circuit) either the 10 ohm or 2. 2 ohm resistor is put in parallel with it, raising the total current. This gives low, medium and high levels, each regulated.




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