Hall Effect to Trigger Light Switch

[eneuro]

Can you use triacs for 12vDC applications, or is a MosFet more appropriate?

Probably the most important thing is how much power do we need to switch and if it is inductive or resistive 
By choosing proper resistors I used BTA16 and MOC3041 to switch 18VAC electromagnet solenoid easy.

There is only 500 pages of very good intros and even Spice simulation models source code to help with semiconductors in many electronic circuits
http://www.allaboutcircuits.com/pdf/SEMI.pdf

Triac is on page 343, after SCRs on 331 .
Worth to see while this book can save a lot of burned semiconductors 

[ceamiclover]

I will definitely look into it.  Thanks

[eneuro]

After reading those 500 pages probably you might looking for something like this 

I use similar circuit 24h a day with small heat sink on BTA16 triac it drives small air conditioning 230VAC fan.

However, at 5V I put 330 Ohm resistor to get around 11mA current on left side of MOC3041 (about 1.2V voltage drop on internal MOCxxx 1-2 pins diode), since this is not low current version (MOC3043 has lower typical 5mA) and in place of one 360 Ohm resistor I put two 1W 180 Ohm, to minimalize a chance to get any arcing on short one small 360 resistor.

Note: Did not tested it with LPT-I used classic LM7805 as 5V power supply, no need for PC controll in my case.

[WarSim]

That cct is very commonly used in remote and isolated dimmer switches.  Of course the real cheep ones skip the snubber.  Good cct to use if the part cost is low enough.  Just be sure to heed the power dissipation advice given by the others. 


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[rs20]

After reading those 500 pages probably you might looking for something like this  .

Practically identical circuit to what I linked back at #31, just for the record

[ceamiclover]

Having problems with this project.  It worked reliably for a couple of months and then discharged the batteries suddenly in the 2 projects I had.

I made 2 circuit boards with HC-SR501 Ir motion detectors to trigger opto-triac MOC363 to trigger Triac BTA16 to jumper a light switch.

I replaced the batteries and they worked again.  I had been flipping off a power strip that provided the 120vac constant when I didn't want the lights turning on.  I flipped the power strip on. the lights flicked on for an instant, and went out.  The battery had went from 9v to 1v suddenly.

This seems like the issue caused by a "brown-out" or surge.  I am wondering how I should protect my projects from this.  Do I need capacitors? Diodes?

In automotive, we use a clamping diode between the power and ground sides of a relay.  No idea whether that is applicable here, though.

Any help appreciated.