SSR doesn't wrok

I need change a relay:
relay

There are 3 GND
I tried with this board:
board

It doesn't work.
Because it's very simple i ask you where is my mistake
Do I need check the pcb?

Thank you for the answers

The relay you cite is mechanical, not a SSR.

I can't make heads nor tails of that board diagram.

Expand!

You need to explain in detail what it is supposed to do. Unless you know that it is difficult to figure out whether it does it or does not. :roll_eyes:

You are right
I need replace that relay (41.52) with a SSR; for that I made a new board with transistor Mosfet.
The relay 41.52 in the schematic, it's only a footprint (so it will be not present on the board) for help me to connect the new board where it was placed the old relay.
The new board will be a adapter SSR for the old relay 41.52

I'm sure it would be helpful to have inputs somewhere in that schematic. I don't see any of those.

Why is there a N + P channel dual MOSFET in there? A relay normally switches only one side.

One of the gates is left floating (due to Q1 held firmly off).

The old relay (41.52) switchs both: GND and VCC
Q1 (IMHO) it will be ON like second mosfet into U1.
The board (master) connected to this new board (SSR adapter) has +24V_IN always connected (to the coil), but the GNDS in floatting. When I press the switch GNDS is connected so:
I can measure 16.5V to pin 4 (U1) VGS -7.5V (second mosfet on)
I can measure 6V to pin 1 (Q1) VGS -6V (mosfet on) so also the first mosfet in U1 will be ON (VGS 12V)

When GNDS is floating:
24V to pin 4 (U1) VGS 0V (second mosfet off)
24V to pin 1 (Q1) VGS 0V (mosfet off) so also the first mosfet in U1 will be OFF (VGS 0V)

I thinking now if it needs a resistor between pin 3 Q1 and GNDA because when SSR must be OFF in that pin is three state

lex5555:
The old relay (41.52) switchs both: GND and VCC
Q1 (IMHO) it will be ON like second mosfet into U1.

OK, I saw Q1 wrong. That one is indeed properly ON, pulling G1to about 15V above S1. Still those large resistor values mean that switching on will be slow, and there is no way to switch that MOSFET off, even if there were a way of switching Q1 off (there isn't), as it would just leave the gate floating.

G2 is held at about 7V lower potential than S2. That's the p-MOS, so its ON at all times.

When I press the switch GNDS is connected so:

There is no switch in that schematic, or any other input that may change the state of these MOSFETs.

Your problem is indeed that the MOSFET you picked can only do 20V on VGS, that can be limited by e.g. a voltage divider or zener diodes. A voltage divider should have much smaller resistors than the values you picked so the gate is charged/discharged fast. You do have ~10 nC gate charge to deal with.

The switch is in a other board but i put into the schematic right now for avoid confusion

The 3 switch are only 1 switch
So you understand better (sorry)
I changed the resistor values

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That makes a lot more sense already - very different schematic this way.

Still extremely confusing with the two different GND and 24V nets. Drawing out the two MOSFETs in the tSM6502 separately and some rearrangement can go a long way here.

G1 is held at about +18V by the 24VA when both switches SW7 and SW? to the right of it (you forgot the annotation of two switches) are open through Q1's body diode. Is that really what you want?

SW7 switches on Q1, pulling G1 to GND,

That SW? doesn't seem to do anything useful.

The SW? to the left should switch G2 properly.

Unfortunately i can share the mainbord schematich so you have hard time to understand what I want.
Sorry
My goal is:
When i swtich SW (in schematich there are 3 but is only one):
Mosfet p channel ON =24V to D2
Q1 ON = approximately 12V to G1
If G1 12V n channel ON then GNDA GND are in shortcircuit

lex5555:
Unfortunately i can share the mainbord schematich so you have hard time to understand what I want.

You mean, you can't share the mainboard schematic?

OK, no problem. Goodbye! :grinning:

"OK, no problem. Goodbye! "

Channeling Grumpy Mike ?


When i swtich SW (in schematich there are 3 but is only one):
Mosfet p channel ON =24V to D2
Q1 ON = approximately 12V to G1
If G1 12V n channel ON then GNDA GND are in shortcircuit

Your schematic doesn't make any sense.
Your explanation doesn't make any sense.
There is nothing in your schematic that relates to an SSR.
Do you know what an SSR is ?

Yes, I must confess I tend to sometimes. :grinning:

And why not? :sunglasses:

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