PWM to Analog converter circuit

pob9 said:
whoop! looking good thanks :)
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It's on its way to you. Mrs Tealc posted it.

When you get it you may need to adjust so get a small slot screwdriver and turn the little screw. Clockwise to add more power.

I find it best to set PC at idle and adjust until you get the idle speed you want. As you ramp up PWM the attached fans will increase linearly until they reach max speed.

Once set you can tuck it away and forget. My converter has needed no adjustment since installing over a year and a half ago.
 
smsmasters said:
Hi Tealc received it today many thanks.

Which way shall I turn the screw for max speed?

Kind Regards
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You need to turn it clockwise mate. Beware of turning it too far though. It won't break or anything but you may find your idle speed is too high. You need to find the sweet spot for your fans, then once that's done tuck it away. :)
 
I'm not sure what happened.

At first my fans spun at ~1600 RPM and now after turning the screw, all fans now only spin at ~1250 RPM with all 4 fans attached and only ~1400 RPM with one fan attached, even after turning the screw back.

P.S. Okay to cut some heatshrink tubing off since the fan connector won't fully stay in place unless I do?
 
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smsmasters said:
I'm not sure what happened.

At first my fans spun at ~1600 RPM and now after turning the screw, all fans now only spin at ~1250 RPM with all 4 fans attached and only ~1400 RPM with one fan attached, even after turning the screw back.

P.S. Okay to cut some heatshrink tubing off since the fan connector won't fully stay in place unless I do?
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Are those speeds the maximum you are seeing the fans spin at full PWM duty cycle or at 20% duty cycle?

Yes cut away. It's only there to stop the thing shorting out to other things and to make it look a little more attractive.
 
Tealc said:
Are those speeds the maximum you are seeing the fans spin at full PWM duty cycle or at 20% duty cycle?

Yes cut away. It's only there to stop the thing shorting out to other things and to make it look a little more attractive.
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My motherboard is set to full PWM speed so yes these are the maximum speeds I'm seeing the fans spin at.

Could I have turned the screw too much?:confused:

Kind Regards
 
Not really mate. It will keep turning but will make no further adjustment beyond a certain point. I find the fine control of these potentiometers over 3/4 turn ones quite useful but can see how it is difficult to understand where you are adjusting to.
 
Hi mate,

Turned the screw about 20 times clockwise,

1 fan = ~1450 RPM
2 fans = ~1350 RPM
3 fans = ~1300 RPM
4 fans = ~1250 RPM

Is this to be expected?

Also what would happen if you accidentally short one of the 3 pin connections or plug it the wrong way round?
Thanks :)
 
They should be oriented so that the ears on the connectors are pointing toward the PWM connector. I actually forgot to draw it on then this time.

Here's an older board that shows the correct way.

panyan1.jpg


Reversing the connectors made them go really slow if I remember correctly.

You should be getting top speed near enough at 100% duty cycle. I tested the circuit with 4 fans and verified the output using my oscilloscope as I changed the PWM using my PWM box. I set it so it worked 6v-12v at the time but obviously your fans may be more power hungry, or less, hence the adjuster.

So I don't know. Try turning it the other way and see how you get on? Never had an issue before.
 
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Tealc said:
They should be oriented so that the ears on the connectors are pointing toward the PWM connector. I actually forgot to draw it on then this time.

Here's an older board that shows the correct way.

panyan1.jpg


Reversing the connectors made them go really slow if I remember correctly.

You should be getting top speed near enough at 100% duty cycle. I tested the circuit with 4 fans and verified the output using my oscilloscope as I changed the PWM using my PWM box. I set it so it worked 6v-12v at the time but obviously your fans may be more power hungry, or less, hence the adjuster.

So I don't know. Try turning it the other way and see how you get on? Never had an issue before.
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Would plugging in the molex into a split molex connector lower the current and thus the fan speed? The molex connector I plugged the PWM cable into is shared by my sound card, pump and cold cathodes.
 
Not very likely. A Molex can provide several amperes of current.



What happens if you adjust the PWM duty cycle? Try dropping it down to 20% or 30%. Do the fans adjust speed at all?
 
Tealc said:
Not very likely. A Molex can provide several amperes of current.



What happens if you adjust the PWM duty cycle? Try dropping it down to 20% or 30%. Do the fans adjust speed at all?
Click to expand...

I use speedfan to adjust the PWM duty cycle and turned the screw clockwise again a few more times.

With all 4 fans connected:

100% PWM duty cycle = ~1300 RPM
20% PWM duty cycle = ~1250 RPM

It seems it didn't drop by much.

P.S. My motherboard is the G1 Z87 Sniper
 
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I've got a spare circuit all built up here. I will heatshrink and then do the test after that and send it to you. I will get it to the post office Friday afternoon so you should get it Saturday with a bit of luck.

I'm not sure what has gone wrong with that one. This is the first one I've had a problem with out in the field, as it were, but it seems to be not receiving PWM properly. As I said it was tested but admittedly that was done before I fitted the heatshrink so maybe the extra pressure of the heatshrink has opened a connection somewhere.

I will do the testing before after heatshrink in future to be sure. ;)
 
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