Aftercooler problems using NE556

[rocket8080]

Hi Im newbie at this stuff and need help. Ive been building a aftercooler for my computer using a schematic and veroboard layout downloaded from the net. It uses a 5v standby supply (1A) and a 12v switched supply (0.5A?). The idea is when I power off the computer the timing cycle starts and clicks in a relay to change the fans over from the motherboard to a 9v battery for 4-5 minutes. At first it didn't work as it was using a 5v relay so I changed it to a 3v as the ne556 can only out put 3.3v using a 5v supply. All was working well until today when it just stopped working and I cant figure out why. Any help would be great as rapid hair loss is starting to occur! Here is the schematic and vero layout. I noticed aswell there are a few difference with the two, when building it though I followed the vero layout.

 

[Mikebits]

So wait a minute, your 556 has a 5v supply and your putting 12v on the inputs? You probably fried the part, hopefully you did not damage your MB.

 

[crutschow]

You realize that the aftercooler has no practical purpose. Once you turn off the power and the fans stop, the computer components will get no hotter than they were with the computer on and the fans running.

 

[Reloadron]

No, they route the 12 volts (normal fan power signal) through the normally closed relay contacts. When the system powers down the 556 timer configuration (running on the PC 5 volt standby power) pulls in the relay and the fans now run off the 9 volt battery for a short duration determined by the 556 timer circuit.

Does the little LED work that signifies the 556 has output? That would eliminate the relay being at fault? The most likely failure item would be the 556. There really isn't much there. Do you have a meter to poke around with?

<EDIT> I also agree with crutschow as to it being practical or needed. </EDIT>

Ron

 

[rocket8080]

aftercooler

Ive been using this for two months and not had any problems at all with the board. The points Ive taken the supplies from are just infront of the psu connector. Forgot to mention when i say computer I mean my xbox 360. The aftercooler stopped working earlier and my xbox is still running good. I tested it first on a broken motherboard for like hours just to make sure I didnt screw up my working one.

 

[rocket8080]

Yeah the little led worked fine all the time. Now the led doesnt come on anymore . Although when having a poke around with my meter I triggered the timer by accident and the led came on . Did this a couple times, seems like its doesnt do this automatically anymore, do know why

I think it is pratical as the heatsinks put in there are crap and cant be relied on for passive cooling as there stretched as it is. The gpu and cpu temps go up like 10-15c when switched off and there hot enough as it is.

 

[Mikebits]

No, they route the 12 volts (normal fan power signal) through the normally closed relay contacts. When the system powers down the 556 timer configuration (running on the PC 5 volt standby power) pulls in the relay and the fans now run off the 9 volt battery for a short duration determined by the 556 timer circuit.

Does the little LED work that signifies the 556 has output? That would eliminate the relay being at fault? The most likely failure item would be the 556. There really isn't much there. Do you have a meter to poke around with?

<EDIT> I also agree with crutschow as to it being practical or needed. </EDIT>

Ron

Maybe I am missing something. From the schematic, it looks like 12v is directly tied to pin 2 and 6 of the 556. I see a potential latch up condition here.

 

[Mikebits]

The gpu and cpu temps go up like 10-15c when switched off and there hot enough as it is.

Have you verified this with a test? Have you compared your temp data with the data sheets of the CPU? If the heat sink is inadequate, why not install a better one?

 

[Reloadron]

Maybe I am missing something. From the schematic, it looks like 12v is directly tied to pin 2 and 6 of the 556. I see a potential latch up condition here.

No, you didn't miss anything Mike. I did!

There certainly is 12 volts applied to the 556, I can't say I would have done it that way.

As to thermal rise when the system is shut down it happens because the fans have stopped on the CPU & GPU HSF assemblies. At this point neither is powered and after a brief peak those temperatures will drop. I don't believe this will be harmful.

Ron

 

[rocket8080]

I cant install any better heatsinks than what there is as its a xbox360. I verified the temps using a infra red thermometer. Theres two reasons Im wanting to do this design.
1- the 360 I have is of the older model type which is plagued by heat issues. On the newer consoles this design has been inbuilt to the board so microsoft must of thought it had some value
2- This has really sparked off my intrest in electronics and I HATE quitting!!!

I did some more poking around lastnight after reading what mikebits said about the 5v supply and the 12v inputs. From my understanding the 556 is being used as a inverter and timer cycle. when powering off the 12v line the led would come on click in the relay and then time out but It doesnt do this anymore when powering off. when having a look last night after I powered it off I accidently grounded pin 6 (trigger) and the timing cycle started and clicked over the relay. Does this mean mike was right and I fried the inverter side of the 556?
would dropping the 12v to 5v for the inputs on the inverter side rectifiy my problem? Any ideas or suggestions for improvement I would be most grateful!!

 

[DirtyLude]

As to thermal rise when the system is shut down it happens because the fans have stopped on the CPU & GPU HSF assemblies. At this point neither is powered and after a brief peak those temperatures will drop. I don't believe this will be harmful.

The core of the CPU/GPU never gets any hotter than when it's turned on. If a heat increase is measured after the system is shut off, it's an increase in the temperature of the heatsink, which is soaking up the residual heat from the core and can't remove it that quickly.

Cooling the system after it's been turned off does nothing.

 

[3lectrokid]

I'm not sure but if you want to cool the CPU quicker and take the heat to the heat-sink use something called a peltier plate. this makes it very cold on one side and warm on the other side. They can be got from ebay and many other places.

However I though the new xbox's just have a thing that if the temperature of the CPU rises the fan spins faster. When I turn my xbox of the fans stop spinning. I have recently got my xbox

 

[mgeno216]

It definetly does something. The xbox without a after cooling system would just bake in its own heat after the console is turned off. Firstly you have to understand how badly the xbox 360 was built. In my opinion Microsoft took the idea of "the lowest bidder gets the job" to a new extreme. The solder they used to hold the chips to the board is very weak. When that becomes broken or the warping of the board lifts it away, the xbox Red Rings of Death. We all know how common that problem is. The warping is a huge problem for the xbox. The xbox has these standoffs that hold screws to keep top half a case attached. These standoff rise up from the bottom of the motherboard chasis and put pressure on the bottom of the motherboard. The pressure is significant because the two standoffs that hold the top case down are 2mm to high. That might not sound like alot, but after 1 or 2 years combined with the shitty cooling you have a problem. This after cooler wouldn't be needed except for alot of people that damage has been done, and they now a very damaged console. Every little bit counts. Instead of debating if it is nessacary, why don't you just help him out.

Mike

 

[crutschow]

. Every little bit counts. Instead of debating if it is nessacary, why don't you just help him out.

The debate is how best to reduce the heat problem with the X-box, and there are likely better ways than keeping the fans on after the power is turned off, which would have only a marginal effect on this problem.

 

[rocket8080]

I have done all other mods to reduce the heat problem. I have lapped the heatsinks, used artic silver thermal paste, done the fan shroud mod, increased fan voltage to 9v, install xcm core cooler v2, used the team hybrid improved x-clamp fix. This is last mod that I can do to improve my chances of avoiding the dreaded ROD. I will be happy to debate this with anyone but Im really looking for help to my problem first.

 

[3lectrokid]

as i said yesterday look at peltier patch while the machine runs. It keeps the chips super cool and makes the heat-sink super warm. look on ebay as they are quite cheap

 

[DirtyLude]

as i said yesterday look at peltier patch while the machine runs. It keeps the chips super cool and makes the heat-sink super warm. look on ebay as they are quite cheap

From what they said, they are looking to keep the supporting components cooler to prevent warping/expansion/contraction, not just the chip. So that would do the opposite of what they want.

 

[mgeno216]

Also peltiers can cause consensation around the cool side.

**broken link removed**

What does everyone think about this. The IC is a 555. The 3.3v is used as a signal from the motherboard to determine wheather the console is on or off. The 5v is a standby voltage that is present so long as the xbox is pluged in. Both transistors are PNP. When the 555 output is low the fans are on, the only problem is that while the console is off it is sipping power, in order to keep the fans off. 80ma to be exact.

Mike

 

[rocket8080]

Yeah I would rather not use a peltier as I heard about the condensation problems that they cause. Plus its just moving heat from one area to another inside the case, Im wanting to exhuast residual heat inside the case when the power is switched off

 

[Mikebits]

Well, it seems that Microsoft has acknowledged a reliability issue on the mobo. Most notably that the CPU bga device loses connectivity of some pads due to rapid temp changes after CPU is turned off resulting from board warpage, so I wonder if adding a cooling fan would only hasten the warpage due to a rapid cooling.

Other questions I have are; Is not that cpu fan rated for 250ma @ 12vdc, how well will it run at 5vdc and how much current will it draw? Secondly, what is the power sequence timing? That is when is 12v de asserted in relation to when 5vdc standby is asserted, and lastly what is the current drive of the standby 5vdc ?
These are issues that I think should be addressed prior to any tinkering or your red button of death, or whatever it is called may occur sooner than if left alone.