SST03 problem

[peranders]

Does it work properly with 24 VDC?

What is the voltage across the zener when having 230 VAC in?

[h3ndrix]

Across DZ1 I am reading:

- 3.97 V DC
- 0.79 V AC

I measured both just in case.

Also the 120 ohm resistors are reaching 78 degrees celsius...is this normal?

[peranders]

B1 is mounted right? Not broken? Does it work with 24 VDC?

You should have 48 mA through the caps and the 120 ohm resistors so the total power will be 0.27 W per resistor. That's OK for 600 mW resistors. You have only a few volts you say and that means that the load is too heavy. Where does the current flow? You should first check with 24 Volts with current limitation so you don't fry any parts.

[h3ndrix]

I have been trying to solve the problem, I even tried to do some simulations in proteus (isis), but I get weird results:

- when the switch is open I get 30V.

- when switch is closed (circuit working) I get 163V.

[h3ndrix]

An here is the switch open:

[h3ndrix]

Just discovered something weird, I figured I should check if there is any continuity  in the relays when the power is supplied, so I checked and there seems to be problem. It seems like the relays first work and then jump back, so thats why I get no voltage in the output. Why would that be, seems like the relays are working and then jumping back.

[peranders]

Have you tested with 24 VDC? D4 working? Mounted correctly?

[h3ndrix]

So I finally found a AC transformer with 24V out and tried it, here is what I found:

- When the circuit is swithed ON or OFF, it doesn't matter, I get 5V AC at mains out,
- Both of the relays receive 2.78V at their coil contacts,
- The LED does not turn on, if I turn the switch on and off a few times, every once in a while I get a very fast flash on the LED (I guess thats the caps)
- DZ1 measures 2.1V DC and 175mV AC

What do you think?

[h3ndrix]

Another thing I don't understand, when I try to apply 24V directly to the K2 relay coil, I get sparks, I tried both ways just to make sure I dont mix anode and cathode and its the same.

[peranders]

You should have used a DC source with current limitation. If you apply AC directly to the coils you may destroy the D4. I think something if not correct mounted and possibly also broken. Could you please try to get a DC source for testing? You could also take a close-up photo and upload. Maybe there is something obvious?

[h3ndrix]

I applied 24V DC to the coils, not AC, as I mentioned, one of the relays work and the other does not. I will try to take a photo today. Thanks.

[peranders]

Voltage across R13 when you have 24 VDC?

R14?

R10?

[h3ndrix]

Found it! :)

I checked the voltages like you said and found out that the resistor in R13 was broken, for some reason. I changed it and it works:)

Thanks for all the replies and help.

[peranders]

Good! I was a bit worried because noone has failed to get this design working.