Powering on your cab without hitting the power button: the cap trick

[SirPeale]

Wrote a little how-to earlier.

http://www.pealefamily.net/tech/captrick/

[eccs19]

Wrote a little how-to earlier.

http://www.pealefamily.net/tech/captrick/

Good information. I think I'll put that in my bartop. 

Thanks!

[spystyle]

.

[ChadTower]

I like it.  Nice job.

[FunWithFire]

Can you figure out how to make the TV come on with a capacitor?

I saw a build on here a few days ago where they used a tv that if you have the power button held down, it didn't effect the normal operation. So they screwed a metal plate over the power button holding it down so that when the main power strip was turned on, it automatically turned the tv on.

[spystyle]

Yes, that is "jamming", it is not compatible with all televisions and makes the other buttons unusable while the power button is "jammed"

But the capacitor making the TV come on interests me.

Thanks,
Craig

[Stingray]

Cool trick, Peale.

-S

[shardian]

Yes, that is "jamming", it is not compatible with all televisions and makes the other buttons unusable while the power button is "jammed"

But the capacitor making the TV come on interests me.

Thanks,
Craig

If I understand correctly, this capacitor trick will work exactly like the "jamming" trick you speak of.

As a side note, wouldn't you need to set up your computer to only go to the shut down screen and not power all the way off with the cap trick? It seems it would turn right back on if this were not so.

[spystyle]

I would assume a capacitor turning a TV on would be differenet than holding a button down because there is an electrical current.

As for "shutting down" the computer - that's one more reason to use DOS, it dosen't need to shut down.

Cheers,
Craig

[ChadTower]

Depends on the button.

[shardian]

Depends on the button.

Now that you mention it, I do remember owning a tv that had a power button that was spring loaded, and delivered a "click" input. Kind of like a Propane grill starter. I am guessing this is what you meant. Holding the button did nothing after the click.

[ChadTower]

That's a two position button.

Most TVs now are momentary contact but not all of them are.

[davieboynj]

holy poo! 

would this work on an X-Box? 

[SirPeale]

As a side note, wouldn't you need to set up your computer to only go to the shut down screen and not power all the way off with the cap trick? It seems it would turn right back on if this were not so.

This setup is meant for you to flip a main power switch, not shut a computer down via Windows.

[shardian]

As a side note, wouldn't you need to set up your computer to only go to the shut down screen and not power all the way off with the cap trick? It seems it would turn right back on if this were not so.

This setup is meant for you to flip a main power switch, not shut a computer down via Windows.

So I guess you are shutting your computer down hot then (as in just pulling the plug with the computer in full operation)
If you actually shut windows down, the computer will power down. In this case, will the capacitor discharge, and then restrike, or will the computer stay shut down until the power is killed via power strip and then turned back on? If the computer restarts due to the capactitor before you could kill the power, then  you would have to set up the computer to not kill power to the MOBO on windows shut down. I had a windows 2000 machine that went to a black screen that said "you may now turn off the computer" when you powered down windows.

[Kevin Mullins]

This setup is meant for you to flip a main power switch, not shut a computer down via Windows.

So I guess you are shutting your computer down hot then (as in just pulling the plug with the computer in full operation)
If you actually shut windows down, the computer will power down. In this case, will the capacitor discharge, and then restrike, or will the computer stay shut down until the power is killed via power strip and then turned back on? If the computer restarts due to the capactitor before you could kill the power, then  you would have to set up the computer to not kill power to the MOBO on windows shut down. I had a windows 2000 machine that went to a black screen that said "you may now turn off the computer" when you powered down windows.

If your motherboard has both a "power" button and a "reset" button then you should be able to do it either way. Shut down Windows or shut down hot, personal preference.

I know my motherboard has both buttons in use.... therefore the "power" button only turns the pc on after an actual power down. (turning power strip off)
Without killing the power strip first, I have to use the "reset" button to re-boot. The "power" button does nothing no matter how many times you push it unless you actually shut the power strip down first.
So if the cap is on the "power" switch pins as Peale has mentioned then it should only kick it on the one time when power is turned on at the power strip. It should not reboot if you shut down through Windows before powering down the power strip.
(did any of that make sense  )
This of course is dependant on your PC setup and I know would work fine on mine

[diverdown]

Wrote a little how-to earlier.

http://www.pealefamily.net/tech/captrick/

Stupendously Simple

Im off to buy a capacitor today

[ac3]

Did anyone save this page by any chance? the link no longer works. 

[shardian]

And since you bumped this, it is worth mentioning that most mother boards have a 'turn on when power is detected' function. That is how I have my MAME PC set up. No need for this trick at all.

[SirPeale]

I did some site reorganizing lately and moved stuff around.  I thought I changed all the links here - guess I missed one.  Fixed.

[ac3]

Thanks Peale, great guide. 

[Zebidee]

Long ago I copied Peale's cap trick page into my mamedocs folder, which is full of heaps of interesting bits and pieces relating to arcade cabs & emulation. You can use this trick (or variants on it) for all kinds of electronic gear, form TVs to PCs to audio amplifiers.  It is just too good an idea.

[RandyT]

I'm as little confused about this one.  I understand how it works, but how is this better than simply jumping the "power on" (green) line with an adjacent ground line on the ATX power supply?

What am I missing?

RandyT



*edit* "Power On", NOT the "Power Good" line as mistakenly stated earlier.  "Power Good" is set to 5v as a way for the power supply to let the PC know that the supply is stable and ready to supply power (if anyone cares )

[Zebidee]

I'm as little confused about this one.  I understand how it works, but how is this better than simply jumping the "power good" line with an adjacent ground line on the ATX power supply?

What am I missing?

Firstly, the cap trick allows a pulsed signal to be sent, which simply shorting wires won't do.  Some devices require a pulsed, changing state to be detected in order to power up.  The cap trick allows a closed.shorted circuit, but then opens the circuit once the capacitor is powered up.  More than 'jamming' a button, it simulates pressing and releasing a button.

You might not need this for an ATX power supply, but older PCs need it and certainly TVs and amps need it quite often

[RandyT]

Firstly, the cap trick allows a pulsed signal to be sent, which simply shorting wires won't do.  Some devices require a pulsed, changing state to be detected in order to power up.  The cap trick allows a closed.shorted circuit, but then opens the circuit once the capacitor is powered up.  More than 'jamming' a button, it simulates pressing and releasing a button.

You might not need this for an ATX power supply, but older PCs need it and certainly TVs and amps need it quite often

Yeah, I get that

But as it is presented in the context of an ATX supply, it seems to be overkill and that is what was confounding me.  I haven't seen a PC with an ATX supply where simply grounding the "power on" (green) line on the supply has created an issue.  In fact, it's the only way one can use an ATX supply for anything other than a PC.  Most of the older Pre-ATX PCs just used physical on/off type switches (not momentary type) so this wasn't really an issue there either.

But for monitors and amps with soft power (and which don't have the ability remember the last state) I can see this as useful.  Perhaps the context should be altered?  Yes, it will work for an ATX box, but it's probably just extra work with little to no extra benefit for the trouble, IMHO.

RandyT

[SirPeale]

I'd hardly call it "extra" work.  Connect (in some fashion) a capacitor to the power on pins on your motherboard.  I used a feature connector, but if you really wanted "extra" work, remove the pins altogether and solder it in.

Some motherboards really don't like having the power on wire on the power supply connected to ground, and won't do anything at all.  I've seen several.

[Zebidee]

But as it is presented in the context of an ATX supply, it seems to be overkill and that is what was confounding me.  I haven't seen a PC with an ATX supply where simply grounding the "power on" (green) line on the supply has created an issue. 

Interestingly, I once argued your point in a thread Randy, but I changed my mind once I saw how broadly useful the trick could be.

You're right that the ATX usefulness of the cap trick is limited.  The cap trick is very useful for PCs (eg with AT power supplies) that, for some reason, can't be set to auto power on when power is applied.  However, vaguely modern PCs runing WinXP on an ATX machine can do auto power-up anyway so it is irrelevant.  

Now, so that noone gets the wrong idea, I'd better tell you that you can't use the ATX pin 14 (the green PSON wire) as a momentary power-on switch.  This is purely an on/off.  Short this pin to GND to switch power supply ON, and while it is shorted the PC is on.  However, disconnect from GND and the PC will IMMEDIATELY switch OFF.  The cap trick will NOT WORK with pin 14.

A PC's Momentary on/off is actually controlled by the motherboard, which is why you need to use the cap trick on the power on/off switch on the mobo (look for the front panel header), not from ATX green pin 14.  I believe that this is the way that Peale has described the cap trick on his site.

[Zebidee]

I'd hardly call it "extra" work.  Connect (in some fashion) a capacitor to the power on pins on your motherboard.  I used a feature connector, but if you really wanted "extra" work, remove the pins altogether and solder it in.

You can "install" the cap just by shoving the pins into the back of the power switch connector on the motherboard.  Would take about 2 seconds, I reckon!

[RandyT]

I'd hardly call it "extra" work.  Connect (in some fashion) a capacitor to the power on pins on your motherboard.  I used a feature connector, but if you really wanted "extra" work, remove the pins altogether and solder it in.

Some motherboards really don't like having the power on wire on the power supply connected to ground, and won't do anything at all.  I've seen several.

Well, one method requires a cap and the other requires a sharp fingernail (in its crudest form )  Maybe not a big deal if you happen to have a bunch of capacitors of the right value laying around, but most, I would guess, won't.  Measuring for polarity, etc, also takes time, effort and expertise with a meter.  It's quite different than jumpering the green wire to the black wire next to it (and jumpers don't explode when you reverse the polarity.)

Would you happen to know which boards don't work with the ATX power on jumper?  It seems odd to me that a piece of electronics could refuse to operate when given power, but nonetheless, I'd be interested in steering clear of them.  BTW, some power supplies need a hefty load on the 5v supply for them to turn on.  Just having a motherboard attached might not be enough.

RandyT


*edit*  It seems like an item like this would be a good one to have on your store.  Just plug in the pre-attached connector and problem solved

[RandyT]

A PC's Momentary on/off is actually controlled by the motherboard, which is why you need to use the cap trick on the power on/off switch on the mobo (look for the front panel header), not from ATX green pin 14.  I believe that this is the way that Peale has described the cap trick on his site.

Actually, you kind of have this a little twisted.  The "Momentary" is simply the nature of the switch.  When you press it, it completes a very low power circuit which, you guessed it, pulls the "power on" line low (same as connecting it to ground) while waiting, as it always does with power applied, for the ATX supply to raise the "power good" line to 5v.  At that time, it starts the system.  The mobo doesn't care if you release the switch because it is now holding the "power on" line low with it's own circuitry.  Your job is done

RandyT

[SirPeale]

Would you happen to know which boards don't work with the ATX power on jumper?  It seems odd to me that a piece of electronics could refuse to operate when given power, but nonetheless, I'd be interested in steering clear of them.  BTW, some power supplies need a hefty load on the 5v supply for them to turn on.  Just having a motherboard attached might not be enough.

I didn't make a list, no.

*edit*  It seems like an item like this would be a good one to have on your store.  Just plug in the pre-attached connector and problem solved

Unfortunately it's not as 'cut and dry' as that.  I've found that different motherboards require different caps.  I used an old dried-out cap on my boys cab for years that I salvaged from a cap kit I did.  I wish I'd had a meter to measure the ESR.  It finally stopped working after several years.  I replaced it with a 10uf 16V cap, and it doesn't work.  I would work with it to see what does, but I haven't had the time.
See above.

[Zebidee]

A PC's Momentary on/off is actually controlled by the motherboard, which is why you need to use the cap trick on the power on/off switch on the mobo (look for the front panel header), not from ATX green pin 14.  I believe that this is the way that Peale has described the cap trick on his site.

Actually, you kind of have this a little twisted.  The "Momentary" is simply the nature of the switch.  When you press it, it completes a very low power circuit which, you guessed it, pulls the "power on" line low (same as connecting it to ground) while waiting, as it always does with power applied, for the ATX supply to raise the "power good" line to 5v.  At that time, it starts the system.  The mobo doesn't care if you release the switch because it is now holding the "power on" line low with it's own circuitry.  Your job is done

RandyT

No, I haven't got it twisted at all.  I think that you have.

If you use pin 14, The PC will only stay on while the pin is shorted.    It is not a momentary response.  If you are using a momentary button, then the PC will shut itself down as soon as you take your finger off the button.  You could have a hard on/off switch, but that doesn't really seem like a good idea with a modern PC runnign WinXP, as they like to shut themselves down.

This is simply the technical specification, even if you happen to find an exception yourself somehow.    And to top it off, I have tried to do it before myself and had exactly the response I have described - the PC stays on only so long as you keep the button pressed (ie keep grounding pin 14).

[RandyT]

If you use pin 14, The PC will only stay on while the pin is shorted.    It is not a momentary response.  If you are using a momentary button, then the PC will shut itself down as soon as you take your finger off the button.

Nobody has suggested using it like this.  I'm not exactly sure why you think they have.  It doesn't make much sense to argue about something that isn't really part of the discussion.

You could have a hard on/off switch, but that doesn't really seem like a good idea with a modern PC runnign WinXP, as they like to shut themselves down.

Regardless of what you think seems like a good idea, it works, is part of the ATX specification and causes no ill effect.  If you are really worried about doing it this way, simply disable the power handling options in either the BIOS or in Windows.  Most will want to do this for a cabinet anyway.

This is simply the technical specification, even if you happen to find an exception yourself somehow.    And to top it off, I have tried to do it before myself and had exactly the response I have described - the PC stays on only so long as you keep the button pressed (ie keep grounding pin 14).

I have deployed many a commercial kiosk in my past and this is what we did on every one of them.  You can infer that you don't think it works or isn't correct, but my experience has provided evidence to the contrary.   As for whether it stays on after removing the ground, of course it doesn't.  Nobody suggested using a switch here, rather you are supposed to jumper the wires.  The whole point is to eliminate the switch .

RandyT

[Zebidee]

If you use pin 14, The PC will only stay on while the pin is shorted.    It is not a momentary response.  If you are using a momentary button, then the PC will shut itself down as soon as you take your finger off the button.

Nobody has suggested using it like this.  I'm not exactly sure why you think they have.  It doesn't make much sense to argue about something that isn't really part of the discussion.

You could have a hard on/off switch, but that doesn't really seem like a good idea with a modern PC runnign WinXP, as they like to shut themselves down.

Regardless of what you think seems like a good idea, it works, is part of the ATX specification and causes no ill effect.  If you are really worried about doing it this way, simply disable the power handling options in either the BIOS or in Windows.  Most will want to do this for a cabinet anyway.

This is simply the technical specification, even if you happen to find an exception yourself somehow.    And to top it off, I have tried to do it before myself and had exactly the response I have described - the PC stays on only so long as you keep the button pressed (ie keep grounding pin 14).

I have deployed many a commercial kiosk in my past and this is what we did on every one of them.  You can infer that you don't think it works or isn't correct, but my experience has provided evidence to the contrary.   As for whether it stays on after removing the ground, of course it doesn't.  Nobody suggested using a switch here, rather you are supposed to jumper the wires.  The whole point is to eliminate the switch .

RandyT

I just deleted everything else I wrote in this post to say one thing to Randy - The whole point of this thread was to discuss the cap-trick (not wire-shorting), and that was what I was discussing with regard to pin 14.  If you want to talk about something else, then start a new thread.

I know what I am talking about Randy. I suspect that you do as well.  But attitude won't solve anything.  I'm bored with this discussion and want to move on now.

Thanks.