1
vote
2answers
962 views

Optocoupler | Why a resistor is required in the collector?

In this circuit, if the resistor in the collector R1 is 0 Ohms, the circuit doesn't work. That is, the output will be 12V DC signal as it is from the battery. And if R1 is non-zero, then the circuit ...
5
votes
3answers
959 views

Can LEDs or optocouplers be used without a resistor if PWM is used?

LEDs are often connected through a resistor and the purpose of this seems to be to lower the voltage across the LED to around 1.8V. Can PWM be used to lower the voltage instead of a resistor? If so, ...
1
vote
1answer
306 views

Alternative to optocoupler? Other switching devices?

I have a part that classifies what kind of power I get on ethernet by presenting different loads. For example, the part needs to have a 100 Ohm resistor across two of its pins, and the part will ...
4
votes
1answer
608 views

Zero Cross Detection Circuit for line voltage [duplicate]

Possible Duplicate: How can I detect a power outage with a microcontroller? I'm doing some research with the goal of eventually creating a light dimmer controllable from a micro controller. ...
1
vote
1answer
4k views

Choosing components for a triac's snubber

I'm interfacing the BT139-600 TRIAC with this MOC3051-M Opto-triac. I want to build a snubber circuit for the TRIAC as shown in the MOC3051M opto-triac's datasheet @ page 8, figure 12. The load ...