Using TRIAC for switching load

Thread Starter

milad.norouzi

Joined Dec 23, 2021
29
Hey.Sorry for my bad English. I'm using TRIAC and Opto-Coupler to switch loads(it can be laptop charger, lamps, and etc...).
The problem is that when i plug laptop charger to output , triac will switch on by itself. anybody have any idea to fix that?
I'm using the circuit below:
Screenshot 2021-12-23 202223.png
 

crutschow

Joined Mar 14, 2008
29,466
Low loads that may be non-ohmic, like your charger, may require a resistive load in parallel for proper operation, such as a 4 watt or greater incandescent night-light bulb.
This could also serve as a indicator that the output is on.
 

Thread Starter

milad.norouzi

Joined Dec 23, 2021
29
Thanks for your answer. but i don't want to add another element on my output like 4w bulb. is there any way to simulate that on my output?(Like adding another resistor or ... ?)
 

djsfantasi

Joined Apr 11, 2010
8,255
Thanks for your answer. but i don't want to add another element on my output like 4w bulb. is there any way to simulate that on my output?(Like adding another resistor or ... ?)
…may require a resistive load in parallel for proper operation
If it does require a resistive load in parallel, how are you going to do it without adding another element?

For simulation, you could add another resistor, rated at 5-6W. You can calculate the resistance required given the voltage supplied by the supply and the current draw needed for the laptop charger to activate. That value should be on the charger’s specifications.

I use an ATX power supply which requires a >100mA current draw on its sense wire. Which is effected by a 10W 10Ω resistor.
 

ericgibbs

Joined Jan 29, 2010
15,332
hi mn,
A Lamp is a Resistive type load.
Have you corrected the circuit as shown in post #2.?

If, yes, does it now work as expected.?
E
 

LowQCab

Joined Nov 6, 2012
1,913
A Solid-State-Relay, (SSR), is a much easier solution.
They will generally present an Input-Load that looks like an LED, ~4 to ~5-Volts at ~20ma.

And, they are available with a "Zero-Crossing" Output
so that they don't produce any Electrical-Noise when switching On or Off, or during operation.
( no Filter required, unlike an SCR )

Retail cost is around ~$19.oo for a 25-Amp, Zero-Crossing version.
https://www.digikey.com/en/products...s=N4IgTCBcDa4MwHYCMBaAygJVUsYCsKAckQCIgC6AvkA
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