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I'm trying to design a computer-controlled power ON/OFF system for the device I'm working on. what I need is that I can turn device on or off with computer, and I have the means to apply 5v digital output from my computer (by using a DAQ). I found something about AQH3223 on the internet and bought the IC, tested it initially, and designed my PCB. But it seems like I tested it sloppy, because the device turns on, but does NOT turn off. I apply digital trigger to Power ON pins (pin 2), the input supply goes in pin 8 (VCC-IN), and is feeded to my device from pin 6 (VCC). Also, I have positive and negative supply voltages, thus the double design.

the part of my circuit with AQH3223

Now like I said, when I apply trigger, both SSRs work fine and turn on, but when I put it off (by turning digital output to zero) they're still on. I even tested the ICs on breadboard (this time thoroughly), and got the same result. I apply 5v to trigger and an input feed to pin 8, and a LED is connected to pin 6 that is grounded. this time, the LED is always on unless I take down the feed voltage on pin 8. I also did some search and found this topic Triac BTA316 does not turn off but they didn't find any answer either.

is there an easy fix for this? or better, another way to do this turning on and off? thanks.

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1 Answer 1

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On the top of the front page of the data sheet the part is described as: -

Ideal for AC load control

This must have sounded alarm bells somewhere when you read the data sheet?

It uses a triac and this cannot be commutated off when operating at DC unless the load current drops below 25 mA (holding current).

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  • \$\begingroup\$ True, and since I have both positive and negative voltages, it should be able to support AC voltages. don't you agree? \$\endgroup\$
    – jimiweber
    Commented Jan 12, 2017 at 8:27
  • \$\begingroup\$ If the load current naturally falls below the holding current (25 mA) as specified in the data sheet then the triac will switch off. What you say about positive and negative voltages in your design is irrelevant because THIS DEVICE is an AC load device. \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2017 at 8:33
  • \$\begingroup\$ But my LED setup on breadboard hardly consumes even 10 mA. It's just one LED! also,my device doesn't use that much power either. \$\endgroup\$
    – jimiweber
    Commented Jan 12, 2017 at 9:00
  • \$\begingroup\$ Go read about triacs if you don't believe me. \$\endgroup\$
    – Andy aka
    Commented Jan 12, 2017 at 9:03
  • \$\begingroup\$ I'm not saying that, it's just that LED doesn't consume that much power, so it's below holding current (which is 25mA as you said). \$\endgroup\$
    – jimiweber
    Commented Jan 12, 2017 at 9:37

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