Heh, the guy built monstrous cooling system... then, so some random reason decided to add chipamp to it
Putting aside that this isn't necessary in this application, the question is still a valid one for other uses!
A solution that might not seem easy but isn't that bad would be a micro-controller. TI's MSP430 line of chips goes for about $1.80 a chip when purchased by itself and 3 lines of code could make it check for line voltage and if it's not present anymore, run the fan relay for X more seconds.
A solution that might not seem easy but isn't that bad would be a micro-controller. TI's MSP430 line of chips goes for about $1.80 a chip when purchased by itself and 3 lines of code could make it check for line voltage and if it's not present anymore, run the fan relay for X more seconds.
Yes, the point of the question was "how to continue cooling, even if the power source is disconnected"....like a power outage, or someone pulls the AC plug.And supply the msp430 & fan with battery?
.....so it's run by either a battery or a supercap.
BTW....I have some APEX PA04 high volt/current opamps .....where the matching heatink can be liquid-cooled. I'm slowly gathering parts to use these in a "stupid-powerful" chip-amp.
http://www.apexanalog.com/wp-content/uploads/2012/10/HS11_E.pdf
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Yes. And my point, as the point of some people already commented is that "after someone pulls the AC plug" the system will "continue cooling, even if the power source is disconnected".
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Yes. And my point, as the point of some people already commented is that "after someone pulls the AC plug" the system will "continue cooling, even if the power source is disconnected".
you got it....
It may not be entirely useful in a chipamp situation....where passive cooling is adequate.
But in a situation where the movement of air "is the only" method of cooling.....a reasonable method of continued cooling....is a good path to explore......even if only for future reference.
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And supply the msp430 & fan with battery?
I was thinking water tower and turbine, but I'm willing to consider an enormous flywheel as well.
My old post.
I've thought about this for years now.
There are differing opinions in this thread.
I still believe there could be a need to continue active cooling after shutdown, maybe not in my particular use.
It's more about the theory now.
Scenario:
Hot object is connected to a thermal mass (fat heatsink) and is actively cooled to maintain a non-destructive temperature.
Upon shutdown, the active heat transfer is stopped and cooling becomes passive.
I (still) think....that when the active cooling is stopped, the thermal dissipation process (a fan) is stopped too. And the larger the heatsink, the more it will reverberate back into the object being "protected".
There is an easy test....thermally measure the heatsink when active, shut the entire system off, and see if the heatsink temp rises momentarily, without the fan or power.
This is what nerds think about, lol.
I've thought about this for years now.
There are differing opinions in this thread.
I still believe there could be a need to continue active cooling after shutdown, maybe not in my particular use.
It's more about the theory now.
Scenario:
Hot object is connected to a thermal mass (fat heatsink) and is actively cooled to maintain a non-destructive temperature.
Upon shutdown, the active heat transfer is stopped and cooling becomes passive.
I (still) think....that when the active cooling is stopped, the thermal dissipation process (a fan) is stopped too. And the larger the heatsink, the more it will reverberate back into the object being "protected".
There is an easy test....thermally measure the heatsink when active, shut the entire system off, and see if the heatsink temp rises momentarily, without the fan or power.
This is what nerds think about, lol.
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For thin conducty stuff like metal, it will just cool.
BUT. I had a hot-air furnace mis-adjusted for too much fire and not enough air. When the house thermostat was satisfied the fire would shut-down. A minute later the air-fan shut-down (it had its own temp-switch). Then a minute later, the air-fan would start-UP again, and run about 30 seconds.
The thick asbestos(?) lining in the firepot held and slowed heat.
Frankly, if you are running an audio amp THAT hot, you should re-consider its cooling. The unlikely thermal surge at shut-down is probably much less wear/tear than the hours of hard work before it.
BUT. I had a hot-air furnace mis-adjusted for too much fire and not enough air. When the house thermostat was satisfied the fire would shut-down. A minute later the air-fan shut-down (it had its own temp-switch). Then a minute later, the air-fan would start-UP again, and run about 30 seconds.
The thick asbestos(?) lining in the firepot held and slowed heat.
Frankly, if you are running an audio amp THAT hot, you should re-consider its cooling. The unlikely thermal surge at shut-down is probably much less wear/tear than the hours of hard work before it.
I agree, that's a major design flaw. It would be much better to improve the cooling concept with i.e. heatpipes, bigger heatsink mass/surface, cooling tunnel etc. instead of let it run longer. If you still want to realize a fan switch off delay three vaiable solutions come to my mind:
- Plain time delay. The 555 usggestion is ideal for that and adjustable. Also a very easy solution is a discharging capacitor controlled switch.
- Energy storage delay. A big capacitor or battery which lets the fan run until it's out of charge. A very crude solution but got one big advantage, it's still working if the power is cut. If a battery is used, maintenance is needed like checks for leakage, remaining maximum charge, if the charging and its safety functions still work. (really, burning or exploding batteries are no laughing matter)
- Temperature or combined time/temperature switch off. The most refined solution, can be extended to other parameters or functions like check for fan, its speed and current but the most complex and difficult to implement solution, may need modifications to the amp board too, depending on what it should be able to control.
Forced cooling is only needed after switch off under the following condition:
Something in the thermal path between the original heat source and ambient has a maximum temperature which will be exceeded under passive cooling; note that this requires something between this element and the original heat source to have significant thermal mass. In any case the original heat source will be safe.
For a car it is the coolant fluid which has a maximum temperature, and the block which has the thermal mass. The heat source is hot gasses, but they have all gone.
For a chip amp (or any other electronics?) the heat source is the chip junctions. There will normally be nothing downwards from there on the thermal path which has temperature problems. The only significant thermal mass is the heatsink.
In some cases continued forced cooling after switch-off can cause problems, because it can lead to too-rapid temperature change which can cause mechanical stress.
Something in the thermal path between the original heat source and ambient has a maximum temperature which will be exceeded under passive cooling; note that this requires something between this element and the original heat source to have significant thermal mass. In any case the original heat source will be safe.
For a car it is the coolant fluid which has a maximum temperature, and the block which has the thermal mass. The heat source is hot gasses, but they have all gone.
For a chip amp (or any other electronics?) the heat source is the chip junctions. There will normally be nothing downwards from there on the thermal path which has temperature problems. The only significant thermal mass is the heatsink.
In some cases continued forced cooling after switch-off can cause problems, because it can lead to too-rapid temperature change which can cause mechanical stress.
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