need opinion about changing PSU fans

[fezder]

sorry, i took rated load as 36v/30A! little mis-understanding here.....(makes 1080w so 10% is 108w...)
yeah, this sunless time really takes toll from all of us
and oh man, i meant 108 WATTS not ohms, sorry there for typo

R = V/I = 36/3 = how many Ohms?
And how many watts will be dissipated by this resistor?

108w? 36/3=12ohms->12ohms x 3A^2 (sorry, don't know how to insert that small two on corner...)

 

[fezder]

and you are only 22...

23 actually, birhday comin' up next april ;D

 

[fezder]

load test currently running, inside temperature around 30'c , hooked mine 5amp/200w rheostat. it's quite hot, 130'c....rheostat i mean

 

[fezder]

ok here's the results:
room: 18.9
idle:20.1
load: sensor =40, IR meter (just checked for extra-reference)=45

 

[JimB]

OK, based on those figures I would be inclined to have the exhaust fans switch on when the exhaust air temperature is above about 40degC, and switch off again when the temperature has dropped to about 25degC.

You will need some hysteresis in the switching as I suggest above, otherwise you will get a situation where the fans are rapidly cycling on/off as the air is moved by the fans.

JimB

 

[fezder]

i was thinking also hysteresis-swicth, OR probadly much more complex to accomplish, like those what are used in computers, rpm rises according to temperature, if you catch my drift?

 

[tunedwolf]

Hey, how about using one of the TC65x devices from Microchip? They have pwm output for proportional fan speed. I'm sure there are other offerings out there too, from the likes of Maxim etc. That should simplify things considerably

 

[fezder]

wolf, worth a try, never used much more ''complex ic's, only discrete components

 

[fezder]

managed to repair one of mine linear psu's adjustable cv/cc (0...15v/0....10A) symptom was as follows: voltage swinged back and forth in its range, and the reason was loose contact on voltage knob (it was accident to find this one out, wire came loose so much i had to re-solder it back to it's place, and it was wiper-wire) other fault, was ammeter was reverse-installed (analog, so that too was kinda hard to see with small test load) and also, ammeter's adjustment trimmer's wire was loose. Now then, i place 10-turn pots for both voltage and amperage, just because 10-turn gives superb precision (and i have few in hand, salvaged from some school stuff year back or so)

decided to tell this, as this is already psu topic, so not big off-topic, no?

 

[JimB]

decided to tell this, as this is already psu topic, so not big off-topic, no?

This is your thread, you can take it in whichever direction you want.

...the reason was loose contact on voltage knob...
...other fault, was ammeter was reverse-installed...
...other fault, was ammeter was reverse-installed...

Who built that pile of junk!

JimB

 

[fezder]

Who built that pile of junk!

haha, good question, it's german made, so i doubt it's manufacturer's fault. I got this some time ago from school, so perhaps it got abused there, hehe?

 

[fezder]

hmm, i got an idea, dunno what you guys think but, i was thinking about using arduino-microcontoller, which reads data from temperature sensor via analog input, and switches fan on when temperature is higher than 45, and stops at 25. that should give hysteresis required
what do you think?

 

[JimB]

Sounds a reasonable idea.
If you have a spare arduino, try it and see what happens.

JimB

 

[fezder]

''trinket'' actually, 3 and 5v versions. They're super-small, perfect for this sort applications inside casing.