More computer fan sillyness

[zevon8]

If I remember correctly, the transistor would pass the "10 second test" with only one of those small heatsinks that look like an aluminum IC.
Of course you could just use a small 1 x 2 inch scrap of alluminum.

( the 10 second test is - can you touch it for 10 seconds without cursing )

for your fan, I dont think will need much of a heatsink, something like this will do:

https://www.futurlec.com/Heatsinks/TO220S.shtml

since at lower speeds, the transistor is not on all the time, so on average the heat production is lower.

If you go the LM317 route, you will need a heatsink, like above picture, being on all the time, heat production is steady.

 

[ante]

Tim,

This very nice site : http://www.cpemma.co.uk/reg.html offers you serious speed controllers both temperature and manual regulated circuits.
Have a look!

Ante :roll:

 

[grrr_arrghh]

You can make your own voltage regulator with an op-amp driving a MOSFET. Either N-channel or P-channel will work, you would just change the output direction. This solution has no minimum regulator voltage dropout.

If the input is known to be a regulated 12V, you don't need a zener diode to create a known voltage, a resistive divider will do. Compare against the output voltage, and include a cap to slow down the feedback response a lot to prevent oscillation.

sounds great, but I don't really get it... :? Don't suppose someone could draw a quick circuit diag for me...? *smiles angelicly*

bmcculla and ante, both very useful, but I was hoping not to use any unusal parts, due the the high shipping costs of places like RS.

Cheers Zevon8, that was what I wanted to know.

 

[ante]

Tim,

An Op-Amp and a MOSFET is OK, if you want to create heat and loss of energy! You need PWM regulation to overcome this.

Ante :roll:

 

[grrr_arrghh]

An Op-Amp and a MOSFET is OK, if you want to create heat and loss of energy

lol, no that wasn't what I was going for...

I have decided to go with PWM for one fan, and low dropout regulator with a switch to go to full voltage for the other fan (a la the diag earlier in this thread)

Thanks for all the suggestions guys, I really do appreciate having a choice

Cheers,

Tim