Building a solid state relay module

[EasyGoing1]

So they sell these on Amazon pretty cheap:



I looked at the different pics that they post from different angles and I got all of the values of the components on the circuit board, but I'm obviously not exactly sure what the schematic would look like so I came up with this:



But, I'm not exactly sure that it will work, or even if my configuration of the components makes sense in terms of a "stable" circuit given the desired function of it ... I have all of the components but I'm wondering if anyone can take a quick look at my schematic and offer any comments? The power source is 5V

[R_J]

Re: Building a solid state relay module

Here is a similar device with schematic http://wiki.sunfounder.cc/index.php?..._Trigger_Relay
Solid state relay using a mechanical relay?
These are SSR as an example

[EasyGoing1]

Re: Building a solid state relay module

Here is a similar device with schematic http://wiki.sunfounder.cc/index.php?..._Trigger_Relay
Solid state relay using a mechanical relay?

Interesting ... ill play with it on a breadboard and see what I can come up with.

Thank you!

[EasyGoing1]

Re: Building a solid state relay module

Here is a similar device with schematic http://wiki.sunfounder.cc/index.php?..._Trigger_Relay
Solid state relay using a mechanical relay?
These are SSR as an example

So here's something interesting ... on the other side of the relay, I have a separate 6v source connected to a resistor and an LED ... and when I bias the transistor, the relay switches on and the LED lights up through that separate power source, but when the transistor goes off, the relay doesn't open ... its like it just stays latched ... even if I disconnect the input of the relay and bring both pins to ground, it sill allows current to flow through the relay until I disconnect one of the output pins, where it will stay disconnected until the inputs of the relay are brought high again. I have several of those relays and I tested a few of them and they all exhibit the same behavior.

[budm]

Re: Building a solid state relay module

What is the spec of the relay/ What is on the output side TRAIC, SCR, Transistor? If they are TRAIC or SCR, they will latch on since those kind of outputs are made for AC.

[EasyGoing1]

Re: Building a solid state relay module

I just did a google and apparently the relay requires the voltage at the output to go to zero before it switches off ... so it can only drive an AC load

[budm]

Re: Building a solid state relay module

Yep.

[EasyGoing1]

Re: Building a solid state relay module

What is the spec of the relay/ What is on the output side TRAIC, SCR, Transistor? If they are TRAIC or SCR, they will latch on since those kind of outputs are made for AC.

I wonder what would happen if I used it to switch on a circuit that is pulse width modulated ....

[budm]

Re: Building a solid state relay module

Current has to drop to 0 (or Less than Holding current) for it to be off.
https://cdn.badcaps-static.com/pdfs/...758642a941.pdf

[EasyGoing1]

Re: Building a solid state relay module

Current has to drop to 0 for it to be off.

which would the be the case with PWM ... although the frequency is much higher than an standard 60Hz AC signal ... wonder how fast those triacs are

[EasyGoing1]

Re: Building a solid state relay module

Current has to drop to 0 (or Less than Holding current) for it to be off.
https://cdn.badcaps-static.com/pdfs/...758642a941.pdf

Didn't work ... at least not with an arduino PWM source from an analog pin

[budm]

Re: Building a solid state relay module

You need SSR DC output (I.E. MOSFET) if you want PWM output.

[EasyGoing1]

Re: Building a solid state relay module

You need SSR DC output (I.E. MOSFET) if you want PWM output.

A potentially interesting find ... if I use an analog pin as the PWM source to the LED, and then open the relay, but immediately after opening the relay, I tur that pin off then back on ... it still remains powered (it keeps the triac latched) so I started playing with delay times between turning that pin to 0 and then back on and discovered that if I delay by as much as 12 microseconds ... it stays latched... but at 13 microseconds, it trips the triac and breaks the circuit ... so at least we know it takes somewhere between 12 and 13 microseconds to break the triac connection.

[EasyGoing1]

Re: Building a solid state relay module

You need SSR DC output (I.E. MOSFET) if you want PWM output.

What do you mean SSR DC output? you talking something like using a 555 with a MOSFET to generate the pulse?

[budm]

Re: Building a solid state relay module

They make SSR with MOSFET on the output side.
I.E. http://www.ssousa.com/MOSFET-Output-SSR
Also Look at CRYDOM again, see what DC output is.

[EasyGoing1]

Re: Building a solid state relay module

They make SSR with MOSFET on the output side.
I.E. http://www.ssousa.com/MOSFET-Output-SSR
Look at CRYDOM again, see what DC output is.

I see what you're saying ... I was just going to google to see if they made DC load capable SSRs

[budm]

Re: Building a solid state relay module

It is right there in the link, it can handle AC and DC, or DC only.

[Curious.George]

Re: Building a solid state relay module

I see what you're saying ... I was just going to google to see if they made DC load capable SSRs

Depending on circuit topology. you can fashion an AC/DC SSR out of a bridge and a "switch". The bridge ensures the switch always sees the same polarity signals across it. But, this increases the drop across the SSR.