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What is the voltage of an optocoupler gate?
Assuming that a single HCT output is only feeding this optocoupler, a logic 1 voltage of about 4.9V can be presumed. The output current available from a HCT gate to drive the optocoupler input is limited to 4mA, which is quite low for driving an optocoupler.
How does the optocoupler work as a switch?
No, the optocoupler does not act as a switch. The LT4430 compares the feedback to a reference, and drives the optocoupler to whatever photocurrent it needs to maintain the feedback = reference. So it will regulate the output voltage to the desired setpoint.
What kind of current does an opto coupler need?
As the current available from typical computer input/output ports may only be a few µA, as computer port lines are usually designed to drive some type of logic input, the input to this motor drive circuit is via a HCT Schmitt inverter gate, which only requires an input current of 1µA, with the 12V 40mA motor being driven by a 2N3904 transistor.
What is the voltage of a pc817 optocoupler?
In this case however, a popular PC817 optocoupler from Sharp will use voltages and currents available from HCT logic. Assuming that a single HCT output is only feeding this optocoupler, a logic 1 voltage of about 4.9V can be presumed.
What is the purpose of an optocoupler interface?
The main purpose of an optocoupler interface is to completely isolate the input circuit from the output circuit, which normally means there will be two completely separate power supplies, one for the input circuit and one for the output.
Why do you need an optocoupler to drive a microcontroller?
The optocoupler’s isolation gives you the advantage that you can place its output transistor anywhere you like, independent of the microcontroller’s supply voltage. Driving the opto-coupler means driving its LED. If the microcontroller can’t drive it directly you’ll need a small transistor for that.
What is the forward current of an optocoupler?
It consists of collector-emitter voltage (VCE) and collector current (IC) as a function of the base current (IB). With optocouplers, the emitter forward current (IF) is approximately equivalent to the transistor’s base current (IB) and is plotted as forward current (I F) in various steps.
What are the voltage ratings of optocoupler isolators?
As well as detecting DC signals and data, Opto-triac isolators are also available which allow AC powered equipment and mains lamps to be controlled. Opto-coupled triacs such as the MOC 3020, have voltage ratings of about 400 volts making them ideal for direct mains connection and a maximum current of about 100mA.