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View Full Version : Is it possible to use SSRs directly from PI GPIO



andyhough
03-24-2018, 04:28 AM
I am sure this is simple, but I am hoping someone could point me to a good tutorial on how to connect my SSROZ boards to the PI GPIO?

Back in 2010 or so, I had a nice simple 64 channel display for a few years. I built about 36 SSROZs and then purchased a couple of never working prebuild Renard board to replace my Grinch and never saw a blink again. http://www.doityourselfchristmas.com/wiki/index.php?title=4_Channel_SSROZ_Assembly_Instructi ons

Now my daughter has a project where she wants to animate her doll house with some lights using python to control the PI GPIO. She is required to use Python for the class. I have an 8 port SanSmart relay that plugs right into the PI GPIO and works fine, except it is a bit loud loud. I have spent two days searching for directions on how I can get the PI GPIO to control the ssroz boards. Can anyone help?

My 2 years experience was just about soldering and using Vixen. Now I guess I need to know how the switches and buttons really work.

MartinMueller2003
03-24-2018, 10:08 AM
PI GPIO run at 3.3v. SSREZ (And the rest of the DIY SSRs) are designed to work at 5v. The GPIO may work if the wire run is short enough, but then again it may not. For two reasons, you really should put in a buffer:



Voltage shift will allow increased reliability and distance to SSR.
Buffer protects the GPIO from being damaged by things happening on the wire. Once a GPIO output gets damaged, it can take out more outputs and you will need to replace the PI. Replace $3 buffer / replace $35 PI. I go for a buffer in a socket.

frederic
03-24-2018, 11:42 AM
The SSR's we typically use are designed for 5V, but you can change that to 3.3V by calculating a new value for the inline resistor with the LED side of the optocoupler.

davros
03-24-2018, 11:58 AM
I suspect it would work but "students" and "AC" together make me nervous. GFI?

andyhough
03-24-2018, 06:42 PM
Thank you so much! What do you mean by a buffer? I get the concept, not the hardware.

andyhough
03-24-2018, 06:44 PM
Also, besides a buffer to protect everything, is it just a matter of sending 3.3v or 5v to the proper rj45 connection on the SSROZ or do I need something else.... besides a ground.

MartinMueller2003
03-24-2018, 06:52 PM
You Need +5, Ground and four active low signals (one per channel). The SSR is triggered when the channel control line is pulled LOW.

MartinMueller2003
03-24-2018, 06:53 PM
Thank you so much! What do you mean by a buffer? I get the concept, not the hardware.

Here is an example of a four channel device:

https://www.adafruit.com/product/1787?gclid=CjwKCAjw7tfVBRB0EiwAiSYGM26A7Ene4rTl3o-R_SvqzmGFa4luk036H2bS9ZXcd5RPbIFoyRy2ZRoCDx0QAvD_B wE

You can buy it cheaper elsewhere. There are also 8 channel devices around.

Here is a good description of a device and how to use it:

https://www.petervis.com/Raspberry_PI/CMOS_to_TTL_Logic_Level_Converter/CMOS_to_TTL_Logic_Level_Converter.html