Aftercooler problems using NE556

[Sceadwian]

For semi conductors in particular electron vs hole flow is important, never however be fooled into thinking holes actually exist, they're just the absence of what could be there, which is the electron, IT'S transfer is what actually does the work.

 

[Reloadron]

For semi conductors in particular electron vs hole flow is important, never however be fooled into thinking holes actually exist, they're just the absence of what could be there, which is the electron, IT'S transfer is what actually does the work.

This is really moving off topic but out of curiosity does it matter? I guess what I am saying is that if a person looks for example at a full wave bridge of diodes and understands how the alternate half cycles of an AC waveform are rectified does it really matter how they see electron flow or stationary holes? The point is they understand how it works. If they can use a diode in a circuit does it matter? It's fine to understand it both ways, that being a good thing but I just don't see where it matters. I can see what you are saying as to importance with semi-conductors but as long as someone understands what is actually going on in a circuit be it a semi-conductor or a vacuum tube I don't see where it matters. I guess it's just me.

We now return you to the regular thread.

Ron

 

[Sceadwian]

Which is why it's something that should be noted and moved on from =)

 

[mgeno216]

Alright, so when the LTSpice version of my schematic is run, for some reason, the both transistor's collector is only getting a few hundred nano amps, but the full 5v. Why is this? The file is in post #31. Shouldn't the second transistor (Q1) allow as many amps through as the fan needs.

Thanks,
Mike

 

[mneary]

Make sure the current in FAN is the same as the current in Q1 collector. There might be a gap in a conductor.

 

[mgeno216]

It is the exact same in terms of shape, but the fan is 4 nano amps less.

Mike

 

[mgeno216]

Any1 got any ideas?

 

[Sceadwian]

Nano amps of current in a simulation like that means the circuit isn't designed properly. I have a hard time following a circuit I didn't build so I can't really tell you what's wrong as I don't feel like tinkering with it. None of the values in it seem quiet right 'just off the top of my head' What's the purpose of the pulse voltage source?

 

[mgeno216]

I didn't make the LTSpice drawing, mneary gets credit for it. I designed the original circut and here is the premise that I think it should work on.

There are three voltage sources in the xbox, a 3.3v, 5v and a 12v. The 12v is not used in this circut. The 5v is on regardless if the console is on or off (so long as the console is plugged in). The 3.3v is used as a reference signal so that the circut only kicks in when the console is off.

The are two transistors, they are both power PNP transistors. Q2 controls wheather the 555 gets power. Its base is controlled by the 3.3v and the resistors limit the current to 8ma. I chose 8ma because I am using 80ma for the 555, and I thought the rule of thumb was 10:1 collector:base current. So when the 3.3v turns off (aka the console turns off) the 555 starts timing. It is set up in a monostable fashion.

The output of the 555 is connected to the base of the second transistor (Q1). Since Q1 is a PNP, the output from the 555 is inverted. The two diodes are used for protection. I am not sure what damage can be cause if the 3.3v flows into the output of the 555, or if the 555 output flows into the 3.3v when it is off.

I hope this helps you understand how I am trying to acheive the aftercooler.

Mike

 

[Sceadwian]

Your fan isn't 12volts? Most are.
If the purpose is to simply turn the fan on or off depending on the state of the 3.3V line then I think there's some confusion because you don't even need a 555 for that, all you need is a single transitor. Or is the 555 supposed to be there so that the fan is only on for a short time after the 3.3V goes low?

 

[Mikebits]

From what I read, the fan voltage starts out at 5.4 vdc and ramps up to 11.8vdc in 30 seconds.
See page 5 of this ref https://www.electro-tech-online.com/custompdfs/2010/06/Xbox_360-HandC-V1_4.pdf

 

[Sceadwian]

What does this have to do with the fan(s) they are using in the aftercooler? The aftercooler itself is outside of anything related to the xbox itself, they said they wanted to use the 3.3V line trigger to turn the aftercooler on, this shouldn't have anything to do with the stock Xbox system itself.

 

[Mikebits]

What does this have to do with the fan(s) they are using in the aftercooler? The aftercooler itself is outside of anything related to the xbox itself, they said they wanted to use the 3.3V line trigger to turn the aftercooler on, this shouldn't have anything to do with the stock Xbox system itself.

According to the original post. Unless I am misunderstanding they plan to use same fan.

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.

 

[Sceadwian]

No fan runs on a swept voltage range over 30 seconds.. That's the response of the Xbox fan driver itself... Probably as the system powers up and heats up.
First off he needs to use fans that run directly off 5Vs, the idea of using a 9V battery to supply the fans is ludicrous from the start. When the circuit loses the 3.3 V signal it turns on for a set time, you need a 555 for that for the one shot, but the one posted so far does not function.

The hardest part of this I see is finding fans that run well off 5V directly. ALL PC fans I have ever seen use 12 volts, and require over 5 volts to start. (hence the 5.4 to 11.8V ramp seen)
The system starts, starts the fans off on low. 5.4V, ramps up to 11.8 as the system generates heat. Pretty simple.

The only other option I see is using a giant capactior with a diode to prevent it from discharging into the supply from the 12V supply to a 12V fan, when the 3.3V signal is lost it'll trigger a transistor from the capacitor to the fan turning it on, but that will only be a for a few seconds unless you spend more money on super caps that are worth more than this entire project.

 

[mgeno216]

From what I read, the fan voltage starts out at 5.4 vdc and ramps up to 11.8vdc in 30 seconds.
See page 5 of this ref https://www.electro-tech-online.com/custompdfs/2010/06/Xbox_360-HandC-V1_4-1.pdf

That is not true. I haven't put a multimeter there to give you exact numbers, but there is a cap on how high the xbox will let the fans go. Many people 12v mod their fans and it then sounds like a jet engine. There is a huge audible difference between a stock fan and a 12v modded fan. That being said, the fans are rated for 12v, but you will only see the 12v once the xbox is overheated. They will run for 10secs and then the whole console shuts itself down.

No fan runs on a swept voltage range over 30 seconds.. That's the response of the Xbox fan driver itself... Probably as the system powers up and heats up.
First off he needs to use fans that run directly off 5Vs, the idea of using a 9V battery to supply the fans is ludicrous from the start. When the circuit loses the 3.3 V signal it turns on for a set time, you need a 555 for that for the one shot, but the one posted so far does not function.

The hardest part of this I see is finding fans that run well off 5V directly. ALL PC fans I have ever seen use 12 volts, and require over 5 volts to start. (hence the 5.4 to 11.8V ramp seen)
The system starts, starts the fans off on low. 5.4V, ramps up to 11.8 as the system generates heat. Pretty simple.

The only other option I see is using a giant capactior with a diode to prevent it from discharging into the supply from the 12V supply to a 12V fan, when the 3.3V signal is lost it'll trigger a transistor from the capacitor to the fan turning it on, but that will only be a for a few seconds unless you spend more money on super caps that are worth more than this entire project.

Here is the problem with that. Only 5v once the console is shut off. When the console shuts off so does the 12v source. I agree that a battery is a bad idea. I have seen 5v at RadioShack so picking one up won't be hard. I will go test now if the fans will run, but for now lets assume they do.

Mike

 

[Mikebits]

Ya I want monostable, and it is set in monostable.

Mike

I missed this response. No your timer is not set for monostable. It is set for astable as you have pin 2 tied back to pin 6. Just to verify this I bread boarded your 555 as shown in your schematic and it runs all the time. I tested without the transistors, just 555 part.

 

[mgeno216]

Oh, I though that the only difference was the resistor from the resistor from power to pin 7. So to make it monostable, what should pin 2 (trigger) be connected to.

Thanks, that might be the problem with the circut.

Mike

 

[Mikebits]

Okay, I thunked on this a bit and I think I came up with a circuit that will do what you want.
See attached. The way it works, or supposed to work is as follows:

On pwr up, IC1A is reset and not triggered. Xbox_12vdc is present and provides power to fan through D2. On power off, Xbox_12vdc goes low and enables max1896 5v to 12v converter and the 12v is is supplied to the fan via D1. After preset time IC1A /Q goes high and disables max1896 thus fan shuts off. See diagram. I did not work out all the values and such but this is a starting point. Let me know if your interested in me going further with this.

https://www.electro-tech-online.com/custompdfs/2010/06/MAX1896.pdf
**broken link removed**

BTW, D1 and D2 should be of schottky type.

 

[mgeno216]

Thanks Mike

I do understand how this works, but I do have a few questions. What is the item that connects Pin 2 on the 74LS123D to ground. It looks like it is labled C1P, but I can't really read it.

And how will the fans get the nessacary amps. They run on .4 amps each (there are two), but the Max 1896 only outputs .3amp at 12v. I am not opposed to running only one fan, because that would definetly make the cool down more gradual

Mike

 

[Mikebits]

C1P is the power pins for the LS123. Eagle Cad does it that way. Did not know there were 2 fans, darn.