simon1974
Posts: 40
Joined: Mon Jan 22, 2018 7:08 pm

solid state relays

Wed Oct 17, 2018 7:26 pm

hi all
I have just purchased 2 8 channel solid state relay and it is written on the circuit board that they are high level trigger.
my question is do I have to use the interface board that I am currently using with my 16 channel relay board.

link below
https://www.ebay.co.uk/itm/12V-8-Channe ... 2749.l2649

drgeoff
Posts: 8611
Joined: Wed Jan 25, 2012 6:39 pm

Re: solid state relays

Wed Oct 17, 2018 7:39 pm

The "high level trigger" or "low level trigger" usually refers to the logic polarity, not the absolute voltage, which determines if the relay is operated or not.

If your current 16 channel relay is 12 volt low level trigger you can use your current interface board but will need to add a logical inversion to the software controlling the RPi GPIOs.

pcmanbob
Posts: 4461
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: solid state relays

Wed Oct 17, 2018 7:40 pm

The information on the eBay page is some what confusing as you say it says high level trigger but it lists the 12v version activation as

12V low-level trigger module: 0-4.5VDC relay connect (ON), 5.5-12VDC relays disconnect (OFF)

Which is active low ! It also requires 5.5v to 12v to switch the relays off.

So I doubt very much you will be able to drive this directly from you pi gpio.

If it were me I would do my own testing to determine how these relays activate and the voltages required to drive them.
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