Question about "turning on computer" without a case.

[purbeast0]

I am not understanding how the LED can be powered on which means the circuit is complete (right?) but it's not jumping those pins? Or am I completely mis understanding it.

And I know I don't understand voltages and circuits and stuff as a noob, but the voltage starting around 3.5 or so and slowly going up seems odd.

 

[sdifox]

I am not understanding how the LED can be powered on which means the circuit is complete (right?) but it's not jumping those pins? Or am I completely mis understanding it.

And I know I don't understand voltages and circuits and stuff as a noob, but the voltage starting around 3.5 or so and slowly going up seems odd.

I am surprised as well. If you have a open circuit on that trace the led would not light up.

so in your collection of relays do you have one of these?

Electrical Buddy JQC 3F 73T DC 5V Coil 5 Pins Mini SPST Power Relay PCB Type 10PCS - - Amazon.com

Electrical Buddy JQC 3F 73T DC 5V Coil 5 Pins Mini SPST Power Relay PCB Type 10PCS - - Amazon.com

www.amazon.com

 

[purbeast0]

I am surprised as well. If you have a open circuit on that trace the led would not light up.

Could it have to do with the voltage being too low since it's only reading 3.5 something? I honestly didn't keep it on long enough to see the voltage grow all the way to 5 I just assumed it would since it was slowly growing.

 

[sdifox]

Could it have to do with the voltage being too low since it's only reading 3.5 something? I honestly didn't keep it on long enough to see the voltage grow all the way to 5 I just assumed it would since it was slowly growing.

when you hooked up the pins through the multimeter, it started right away no?

we could add a rc delay to the 5VDC driving the clock, so say 1 sec on that and 2 sec on the clock

 

[purbeast0]

I also just tried booting with a jumper on the motherboard pins and I can hear it start up and the fan is fast then slows down, then it goes back faster. I don't get this behavior when I have the circuit on there, it never slows down like that.

I also tried booting it up with the circuit on and this time it started right at 5.12v and I'm guessing because the cap had discharged fully maybe? But it still didn't do anything either.

 

[purbeast0]

I only have 1 type of relay too and it's this.

SRA-12VDC-CL datasheet

SRA-12VDC-CL datasheet, SRA-12VDC-CL equivalent, SRA-12VDC-CL cross reference

datasheetspdf.com

 

[Scarpozzi]

I also just tried booting with a jumper on the motherboard pins and I can hear it start up and the fan is fast then slows down, then it goes back faster. I don't get this behavior when I have the circuit on there, it never slows down like that.

I also tried booting it up with the circuit on and this time it started right at 5.12v and I'm guessing because the cap had discharged fully maybe? But it still didn't do anything either.

Motherboard runs through POST (Power On Self Test) and basically flexes its fans, etc. Multi-voltage fans sometimes need extra voltage to get started if they've not been running...kind of like those big capacitors that start an HVAC fan....but only 12v and less.

 

[sdifox]

I only have 1 type of relay too and it's this.

SRA-12VDC-CL datasheet

SRA-12VDC-CL datasheet, SRA-12VDC-CL equivalent, SRA-12VDC-CL cross reference

datasheetspdf.com

lol automotive is too hard to drive for logic level. oh well.

 

[purbeast0]

Motherboard runs through POST (Power On Self Test) and basically flexes its fans, etc. Multi-voltage fans sometimes need extra voltage to get started if they've not been running...kind of like those big capacitors that start an HVAC fan....but only 12v and less.

The board is never getting to the POST though because it never turns on via the circuit.

 

[purbeast0]

lol automotive is too hard to drive for logic level. oh well.

So based on these readings I've given you with the circuit and without, you can't really think of why they would be that way?

If the light turns off, wouldn't you expect pins PWRpin and GNDPin to read 0 once the light is off?

 

[sdifox]

So based on these readings I've given you with the circuit and without, you can't really think of why they would be that way?

If the light turns off, wouldn't you expect pins PWRpin and GNDPin to read 0 once the light is off?

I don't really understand why it is not working. 555 Pin 3 goes low after 1 second, and you saw that with the LED. But I don't get why it doesn't apply to the PWRPin - GDNPin

did you try adding another rc delay in front of the 555 circuit?


so from PWRPin which is the 5V before the 47KOhm resistor in the diagram, add a RC delay.


PWRPin - -- resistor parallel one branch to the 47KOhm in the picture and the other branch is capacitor then ground.
You'll need to double up the second RC delay so it is 2 seconds.

 

[purbeast0]

I don't really understand why it is not working. 555 Pin 3 goes low after 1 second, and you saw that with the LED. But I don't get why it doesn't apply to the PWRPin - GDNPin

did you try adding another rc delay in front of the 555 circuit?


so from PWRPin which is the 5V before the 47KOhm resistor in the diagram, add a RC delay.


PWRPin - -- resistor parallel one branch to the 47KOhm in the picture and the other branch is capacitor then ground.
You'll need to double up the second RC delay so it is 2 seconds.


View attachment 22917

What do you mean by "RC delay" is that just adding resistor?

Also I just checked pin3 of the timer right now.

I put the red of my multimeter on the +5V coming from PSU, and the black from the multimeter on pin3.

The voltage read 1.3v while the light is on, and once the light turns off, it reads 5.12v.

 

[Red Squirrel]

Try adding a small bleed resistor maybe? Though I would still lean towards using a relay for proper isolation. Even if grounds are the same, you just never know if a very small difference due to wiring can cause weird issues. If you have reed switches you could make a crude relay to test with.

 

[purbeast0]

Try adding a small bleed resistor maybe? Though I would still lean towards using a relay for proper isolation. Even if grounds are the same, you just never know if a very small difference due to wiring can cause weird issues. If you have reed switches you could make a crude relay to test with.

I don't have one of those and you are talking a bit over my head lol

Also just for reference, I used the diagram on that page below to hook up my breadboard pretty much identical to this, where the +5v powering the resistor is my PWRPin and tried both making GNDPin be right at pin3 of the timer and also being the ground of the LED. And I'm assuming those green/yellow lines are just any old wires in that diagram.

 

[sdifox]

I don't have one of those and you are talking a bit over my head lol

Also just for reference, I used the diagram on that page below to hook up my breadboard pretty much identical to this, where the +5v powering the resistor is my PWRPin and tried both making GNDPin be right at pin3 of the timer and also being the ground of the LED. And I'm assuming those green/yellow lines are just any old wires in that diagram.

I am assuming the 5v at row 6 is not connected to PWRPin right?

 

[purbeast0]

I am assuming the 5v at row 6 is not connected to PWRPin right?

Nope. Just the one at 16 is going to PWRPin. The one at 3 and 6 are coming from the ATX PSU.

 

[purbeast0]

Kind of bad pic but here it is.

First row abcde is power from PSU (don't mind black wire - had to extend solid core to get it into breadboard).

First row fghij is ground from PSU.

A28 and A29 are going to PWRPin and GNDPin.

And I disconnected the LED/Resistor when I was just testing it out now which is why you see those going to nothing in the pic.

 

[sdifox]

put this between the Red wire on Pin 14 and the resistor at Pin 14. Of course you don't want the resistor on Pin14 to be connected to the red wire directly now, it has to go through the new resistor first.




also, double up on the existing resistor and capacitor, resistor in series, capacitor in parallel so that RC Delay is 2 seconds.

 

[purbeast0]

put this between the Red wire on Pin 14 and the resistor at Pin 14. Of course you don't want the resistor on Pin14 to be connected to the red wire directly now, it has to go through the new resistor first.

View attachment 22919


also, double up on the existing resistor and capacitor, resistor in series, capacitor in parallel so that RC Delay is 2 seconds.

Sorry was busy yesterday and now just getting around to this.

I added that part you diagrammed there and no different results. Light was on maybe a little longer. The readings between PWRPin and GNDPin stayed the same where it keeps rising.

And I think I did the second thing you mentioned but nothing happened even the light didn't turn on so I don't know if I did it correctly.

 

[purbeast0]

So I just put everything back to how it looks in the link and have the +5V coming from the PSU and all grounds coming from the PSU as well.

I then put my multimeter on the +5V and then on the pin3 of the timer chip.

The readings I get while the light is on is 1.3v and then as soon as the light turns off it goes to 5.12v.

But when I change the +5v going to the resistor to the PWRPin and the GNDPin going to pin3 of the timer, the readings are where it starts at like 3.5v and slowly keeps creeping up.

 

[sdifox]

So I just put everything back to how it looks in the link and have the +5V coming from the PSU and all grounds coming from the PSU as well.

I then put my multimeter on the +5V and then on the pin3 of the timer chip.

The readings I get while the light is on is 1.3v and then as soon as the light turns off it goes to 5.12v.

But when I change the +5v going to the resistor to the PWRPin and the GNDPin going to pin3 of the timer, the readings are where it starts at like 3.5v and slowly keeps creeping up.

can we test your relay to see if it will operate on 5V? you can use a different section of the breadboard (top right per your last pix)

+5V and ground from PCPSU go to the coil pins, PWRPin to Normal Open, Ground to Normal Closed, Common to Resistor + led to PWRGND and for Signal just have a wire sticking to it.

Power up circuit, then touch the signal wire to +5 from PCPSU.

 

[purbeast0]

can we test your relay to see if it will operate on 5V? you can use a different section of the breadboard (top right per your last pix)

+5V and ground from PCPSU go to the coil pins, PWRPin to Normal Open, Ground to Normal Closed, Common to Resistor + led to PWRGND and for Signal just have a wire sticking to it.

Power up circuit, then touch the signal wire to +5 from PCPSU.

Sorry man just been busy today.

Can you elaborate a little bit on the relay stuff I'm not completely following.

I got the +5 and ground from ATXPSU to the foil pins. And PWRPin to the NO.

Is "Common" the pin between the coil?

And is "Normal Closed" the one opposite to the NO? I've never wired anything to the NC and just want to be sure.

And when you say "signal" do you just mean pin3 on the timer? It sounds like you mean on the relay but this relay only has 5 pins on it and that would be the 6th one you mention.

 

[Red Squirrel]

Relays usually have 3 pins for the contacts, one that is normally open and one that is normally closed. When power is applies it basically transfers to the other.

 

[purbeast0]

Relays usually have 3 pins for the contacts, one that is normally open and one that is normally closed. When power is applies it basically transfers to the other.

Yeah here is a pic of mine they have a diagram on the bottom.

I know the top/bottom left are the coil and the pin between them is the common.

And the top right one is NO so that means the bottom right one is NC so thanks for that.

But I am not sure what he means by "signal" then.

 

[purbeast0]

Okay I hooked up the relay like mentioned and ignored the signal thing because this relay doesn't have a signal wire, and when I just put the ATX PSU in standby mode the LED turns on. I don't even have to turn the PSU "on" for the LED to light up.

I also don't know if this matters or not but when I turn the arcade cabinet on and the PSU powers on, the motherboard doesn't turn on and the fans don't slow down at all. And if I pull the harness off the PWRpins and put it back on, the light goes off and comes back on as expected, but the motherboard still never turns on as if it's jumping the 2 pins. I'm not sure if that is expected or not.