12vdc 10 minute Off-Delay Timer - Need help please.

Hi folks.

I'm new to this whole forum posting lark so please be gentle with me. From reading a ton of different posts within these forums, I reckon that you clever guys here are likely to be able to help me solve this.

Project brief:

To create an off-delay circuit for an external cooling solution for an Xbox 360 games console.

Basically, I have an Xbox 360 console which used to have a problem with the 3RLOD, I decided to remove the stock heatsinks and install a Koolance external water cooling system. This has remedied the fault with the console superbly (the console now operates at a max. load temp. of 43 deg. C.) and the 3RLOD hasn't returned in over 6 months of use since the mod was completed.

The issue which I have however, is that the external cooling solution must first be powered on from it's own seperate 12vdc power supply before the console can be powered on, aswell as having to remember to also switch off the cooling solution once I have had enough of getting my butt kicked at Halo3 by some grotty little 5yr old. I am concerned that either I might forget to do this one day or somebody else will come along and have a play but forget to turn on the cooler, which will most certainly lead to my Xbox 360 burning out.

I would like to create a circuit whereby upon powering on the Xbox 360, an off-delay timer circuit of some sort, fed from the Xbox 360's internal 12v supply, switches & holds on the seperate 12v supply to the cooler using a latching relay, then upon powering down the Xbox 360, the circuit will hold in the seperate 12v supply to the cooler for an additional 10 mins or so to allow it time to dissipate any residual heat from the system. I have read in places about using a 555 timer but i'm unsure exactly how to accomplish this.

Although the Xbox also operates using 12vdc which can be used to power the circuit, the seperate 12v supply must feed the cooler. I wouldn't like to run the risk of overloading the Xbox 360's PSU.

I would be very appreciative of any help that you guys could offer.

Thanks, WinMXer.

I wouldn't worry about residual heat. A soon as you turn off the Xbox, no more heat is generated and it won't get any warmer. It can just cool down from there by normal convection.

Thus all you need is a 12V relay controlled by the Xbox supply to switch the power to the cooler.

Hi crutschow.

Thank you very much for your response. I'm not so concerned about the residual heat from the console's processors, more-so the heat lying within the Koolance Exos. Although the Exos is good at removing heat when it's fans are running, the heat tends not to dissipate well upon power-down. I have found that up to 30 mins after I have finished playing the Xbox, the Koolance system is still reading a temperature of around 40 deg. C. from it's probe which is placed directly next to the CPU DIE.

It may seem over-zealous of me to want the cooler to remain on for an extra 10 mins, but i'd rather be overly cautious for the sake of spending a tenner on components to look after what is already a flaky piece of manufacturing to begin with.

Plus... where's the fun in taking the easy way out?! lol

Well, I follow the KISS school of engineering, so I never add parts unless they are really needed. And I don't see any problem if the Koolance system sits at 40 deg. C indefinitely. That's a fairly mild temperature as far as electronics go.

Yeah, I get where you're coming from, but when it comes to an Xbox 360, which has less than an admirable record for it's construction quality, i'd like to avoid having any residual heat hanging around which could potentially wear out the system's components over time.

If anyone would be able to help me out I would be extremely grateful.

Why not just spend $19.95 on a cooler?
**broken link removed**

Are you kidding, lol. Those things cause more damage than anything else. I've read countless reports as well as seen first hand that these 'coolers' can fry an Xbox.

I'm simply looking to improve upon my existing cooling solution which works tremendously, but could just do with a tweak or two. This circuit is one that I would definitely like to incorporate, I just can't figure out the schematic for it.

WinMXer said:

I would like to create a circuit whereby upon powering on the Xbox 360, an off-delay timer circuit of some sort, fed from the Xbox 360's internal 12v supply, switches & holds on the seperate 12v supply to the cooler using a latching relay, then upon powering down the Xbox 360, the circuit will hold in the seperate 12v supply to the cooler for an additional 10 mins or so to allow it time to dissipate any residual heat from the system.

Click to expand...

The following circuit will do what you want. The X-box 12V supply will discharge the capacitor and turns ON the MOSFET to power the cooler.

When the X-Box is off, the capacitor slowly charge and after about 10 minutes, the cooler turns OFF. This simple circuit has the problem of running the cooler upon power up for ten minutes even with the XBox OFF initially. If that is not acceptable, then the second circuit will address this problem. A power ON reset circuit is added so that the cooler will remains OFF during timer power up.

Hi L.Chung.

Thank you very much for taking so much time to create the schematic that you posted. I feel bad for saying that I think it is a bit too complex & expensive for my needs.

I'm basically looking to create a simple 555 timer relay circuit that will be powered by the Xbox's 12v supply. Upon applying 12v from the Xbox to the circuit, the relay will energise, pulling in the N.O. contacts. Upon loss of power, ie. turning off the Xbox, I want the 555 timer circuit to hold in the relay for an adjustable period of time, between 5 to 15 mins'ish.

Should the Xbox be turned on again within this Off-Delay period, the circuit is to reset to it's standard state.

I know that this is possible, but have no idea how to draw up the schematic.

The problem is that you can't power the "555 timer relay circuit" from the Xbox's 12v supply because it will turn off as soon as you turn off the Xbox. You need to power it from the cooler's 12V supply. Yes, you could use a 555 and a relay, but it'll cost as much as L. Chung's circuit and be just as "complex".

Hi kchriste.

That's not quite true. I've seen in a Velleman Start/Stop Timer Kit - K2579, where the 12v supply charges a 100uF electrolytic capacitor, which upon activation of a momentary start button powers the relay coil for a period of time adjustable using a variable resistor.

I'd like to know how I could construct a similar circuit without incorporating the momentary switch, where instead the capacitor acts as a backup supply to the relay coil upon loss of the 12v from the Xbox. Then after the period of time, set using a variable resistor, the relay coil will de-energise.

I also have all the parts required for the 555 timer circuit to hand, I believe, so if possible i'd be alot happier to use them rather than shelling out for a load of other components.

WinMXer said:

I also have all the parts required for the 555 timer circuit to hand, I believe, so if possible i'd be alot happier to use them rather than shelling out for a load of other components.

Click to expand...

OK. We did not know you have all the parts ready and wants explicitly a 555 circuit. BTW, the above circuit I proposed is much simpler, cheaper and more reliable than a 555+relay circuit.

Let's restate your problem:

"I want to control a 12V cooler on a separate +12V power supply using 555 and a relay. The cooler is to run immediately when there is +12V DC signal coming in (from X-Box) and I want it to continue running for a further 10 minutes (adjustable from 5 to 15 minutes) when the input signal has gone. Then the cooler will turn OFF and the circuit will go into standby."

The following circuit uses a 555 and a relay. You can ignore V2, which is simply a simulation signal for the circuit. I hope you'll find the circuit useful.

Hi L.Chung.

Thank you again for providing such an excellent & well drawn out circuit diagram for me to use.

I've given this circuit a try using pretty much exactly all the same components that you suggested, apart from exchanging the 47uF capacitor for five 10uF capacitors in parallel to provide 50uF. As well as using a 220uF & 100uF capacitor in parallel instead of the 330uF capacitor. I also went for the 2Mohm variable resistor which I was able to use from the Velleman start-stop timer kit. I worked on the assumption that all three references to 12v were from the same supply.

So, upon connecting it all up i'm not sure where i'm going wrong? The circuit exhibits no timing functions & merely energises the relay when 12v is applied to the circuit & then when the 12v is disconnected, the relay also de-energises without holding in for any delay period.

From your level of expertise I am pretty confident that your circuit is sound, so do you have any suggestions as to where I may have gone wrong?

Thank you again.

These are the steps for circuit debugging:

I worked on the assumption that all three references to 12v were from the same supply.

Click to expand...

I know it is kind of misleading to have two 12V mentioned in the circuit.

There are 12V power supply(for 555 timer & cooler) and there are 12V XBox signal in the circuit. Do not confuse the two. One is a separate power supply which needs to be presented all the time, while the other is a control signal only. It can be there or not. No power is taken from the control signal.

Do not connect the "XBox 12V signal" to the cooler circuit 12V supply circuit yet.

1. Do not use a large value 330uF capacitor for testing. Use a 22 or 47uF cap for testing. The cooler does not have to be connected.

2. Check for the correct direction of the diode 1N4148. Turn the 2Mohm POT all the way to near minimum resistance.

3. The 12V supply for the 555 needs to be presented always for the circuit to work. No connection to the "12V XBox control signal" is needed for testing. Just leave it open and unconnected.

4. Power up the 555 timer circuit. The relay will energize and then drop OFF after a while. Waits until this happens. Now the circuit is into standby mode.

5. Temporarily connects 12V via a jumper wire to the circuit input marked "12V control signal from XBox". The relay will immediately energize.

6. Remove the jumper, the relay will stay ON and then drop OFF after a short time delay

7. Increase the resistance on 2M POT and confirm that the drop out delay time interval increases.

8. Change the capacitor back to 330uF or 470uF and repeat step(5) until you have about 10 minute delay

Now the 555 timer is confirm working:

9. Power OFF the 555 circuit and connect "XBox 12V singal" to the input marked "12V control signal from XBox"

WinMXer said:

Hi kchriste.
That's not quite true. I've seen in a Velleman Start/Stop Timer Kit - K2579, where the 12v supply charges a 100uF electrolytic capacitor, which upon activation of a momentary start button powers the relay coil for a period of time adjustable using a variable resistor.

Click to expand...

If you remove power from that circuit, the relay will drop out immediately because it has no source of power to hold it in. The capacitor is just for timing. It does NOT power the relay; the 12V supply does. That's why you are having problems with L. Chung's circuit above.

if i may suggest i use this with my watercoolers and it makes everything very easy to use. plug the xbox into the main outlet and the watercooler into the other and it will auto switch them on at the same time. cheap also

**broken link removed**

This is just a thought,my Volvo has a switch with a built in timer incorporated in it,it switches the rear dimist on for 12 mins & the heated mirrows on for 6 mins,I think you could use this to turn your cooler on-off.You could get one from your local car-breaker's for a few pence. Good luck Terry

WinMXer said:

Hi kchriste.

That's not quite true. I've seen in a Velleman Start/Stop Timer Kit - K2579, where the 12v supply charges a 100uF electrolytic capacitor.... ...where instead the capacitor acts as a backup supply to the relay coil upon loss of the 12v from the Xbox.

Click to expand...

a 100uF capacitor won't run your 555 and relay for any period of time at all, in fact it would discharge so fast you wouldn't know it was even there lol, capacitors have to be in the farad range to have any "battery" like longevity, and most supercaps are low voltage so you have to buy several and run them in series (i have a maxwell supercap and it's like 2.5v 10F for example)

not sure that really added to this conversation but i figured i would inform you on the capacitor thing

ever looked inside an electric toaster?,you will find a very interesting timer circuit.Toaster circuits are not PWMs, they don't regulate the ampage,they just time how long your bread has been in.So you decide just how burnt you like it.The same principle applies to any thing you wish to time.other appliances have similar timing circuits.