PWM to Analog converter circuit

Lettuce...

The converters can easily be hidden behind the motherboard, tucked into a drive bay or something. The board dimensions are around 70x20x20mm. I usually throw a few hundred mm of cable on the end to give flexibility.

It will act like a PWM fan once you tweak using the potentiometer to set the response but this is just a single time thing unless you add or remove fans.

CraigRobbo...

Sounds interesting. I've looked into PCB etching and have etched one or two boards (badly) but to be honest the difference in size wasn't that great as the fan headers take a lot of room, as does the transistor heatsink. Might be worth a little more effort and SMD components though.
 
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Thanks, so the PCB is too large to fit between the Gelid heatsink and GPU pcb??, as thats where i have tucked the wires from the gelid atm.....

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just though maybe have a really short wire on it and stick it between the heatsink and GPU PCB
 
I wouldn't have wiring in between cards like that unless you can help it. Better solution would be to have the PWM connector on the card go around the back where the converter is hidden, then the fan wiring gets hooked up to it there.

If the PWM converter PCB doesn't have a heatsink it might fit ok but it would run a touch on the warm side but would still probably be ok for the Gelid fans. The transistor gets warm once you start adding more and more fans. I can also minimise the height by using a fan connector on a wire rather than on board like most I make. There have been several I've made with connectors off board.
 
Tealc said:
I wouldn't have wiring in between cards like that unless you can help it. Better solution would be to have the PWM connector on the card go around the back where the converter is hidden, then the fan wiring gets hooked up to it there.

If the PWM converter PCB doesn't have a heatsink it might fit ok but it would run a touch on the warm side but would still probably be ok for the Gelid fans. The transistor gets warm once you start adding more and more fans. I can also minimise the height by using a fan connector on a wire rather than on board like most I make. There have been several I've made with connectors off board.
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Is it not possible to get hold of right-angled fan connector pins in an effort to minimise the height? Granted it may mean a slight adjustment to the board layout.
 
Yes mate I could look into right angle connectors. I could put three 3 ways in a row without much difficulty. I did have some kicking about too but straightened them into straight headers :)
 
Tealc said:
Yes mate I could look into right angle connectors. I could put three 3 ways in a row without much difficulty. I did have some kicking about too but straightened them into straight headers :)
Click to expand...

I don't need one obviously. The "Mk1" is still working like a beaut and there's plenty of space in the roof of my Phantom 410 where it's stored.

It was more just a thought from reading the last few posts.
 
So I'm making 2 converters for Dockie.

These look awesome and the neatest I've ever done I think. These support four fans each.

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New veroboard with white lines and some underside resistor soldering leave the topside looking quite neat.

With heatsinks fitted...

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These two board will be linked together to a single PWM and a single Molex for power, although I will be throwing an additional fan tach out in for the second board.
 
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Here's one destined to control the fans on a Gelid Icy Vision. PH series connectors at both ends so plugs into graphics card, snakes off behind the motherboard and then comes back to the card for the fan plugging.

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And I've added the wiring to the other one. Both these puppies work great as usual. Just needs its heatshrink now.

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Here's one of the GPU ones all dressed up.

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And for no particular reason I made a video.

 
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Just to let you know Lettuce and Dockie your converters are all packaged up and next to my front door ready for the Mrs to take to the Post Office. Hopefully she'll get the chance today.
 
Do you have a circuit diagram?

I was having a little play around, was gonna make one of my own as I have lots of components lying around.

You could try this op amp circuit with negative feedback. It will try and correct any voltage drop (Does a poor job in my simulation program). 100 ohm resistor is where the fans would go.



Larger Image :)


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1st Graph: Red is PWM @ 20KHz, Blue is smoothed PWM.
2nd Graph: Red is Op Amp output, Blue is voltage over load.

The Variable resistor allows you to tweak the output voltage depending on the input voltage via this formula.

Vout=Vin(1+(Rf/R1)

where:
Vin = smoothed PWM
Rf=Variable resistor
R1=10k fixed resistor
 
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