PWM to Analog converter circuit

I do somewhere. :)

I had looked at opamps but think you'd need a rail to rail power opamp and they tend to be a bit expensive, or you'd need to take a volt or two hit on the top end. Might take a look under simulation though and see how well it would work with say a slightly better opamp than a 741. The other tricky thing is that PWM on a PC is not always exactly 5v. I daren't probe my PC with my scope but putting a DMM across my PWM signal showed 3.3v at 100% duty.


In other news feast your eyes on this...

We had some 5mm black braid sleeve in work that needed a new home

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I also came across this while I was mooching. It looks more red in real life.

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Gave etching another go today.

Did the toner transfer method with ironing to get it to stick. I then patched it up with a 0.8mm paint pen.

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Need to get some nail varnish remover on it.

Not much point for this circuit really as it takes ages to print, iron, remove the paper, then touch up and then prepare and etch the copper and it doesn't actually reduce the footprint by much as the fan headers resrict the width. Nevertheless if I need to make a more complicated circuit it could be a way to avoid things like this.

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Here's a bit of a side project but in a similar vein.

I've often mentioned diodes as a way of reducing fan speed and this is an example of how to do it in the flesh.

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The design is modular so that the diodes amount can be varied between 2 and 5 and give a resultant voltage of 7v to near 10v. It's designed for a watercooling pump.

Anyway here is a video.

 
Nice!
Always enjoy your posts. :)

With this heatwave and nobody having any house fans to buy I built my own using 12v mains plug power supplies from dead gadgets and hooked a couple of 120mm and 140mm fans to them. They keep us cool and are quiet too. ;) Your PWM box with a couple amp 12v power supply and 4pin fan sockets on output would be perfect.
 
doyll said:
Nice!
Always enjoy your posts. :)

With this heatwave and nobody having any house fans to buy I built my own using 12v mains plug power supplies from dead gadgets and hooked a couple of 120mm and 140mm fans to them. They keep us cool and are quiet too. ;) Your PWM box with a couple amp 12v power supply and 4pin fan sockets on output would be perfect.
Click to expand...

I've been doing the same too with some spare fans. :)
 
Resident said:
I've been doing the same too with some spare fans. :)
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I think it works better than the ones they sell. Only problem is having a base to mount them on. I used some old kitchen wire cooling racks and taped the fans to them. Than set the racks on table, shelf, whatever directing the air where I want it.
 
I definitely think there's something to be said for ghetto mods. The 12" desk fans tend to be a bit noisy at night and I find blow a little too much even on lowest setting, so if this weather continues after the wet spell they've predicted I might put some of my 120mm fans to use with some PWM goodness to keep the noise down. My desk power supply buzzes a bit so would have to use an old router power supply or something.

I can only imagine the breeze those 11 fans would have created if I'd arranged them into a fan wall. The funny thing is I have another 6 or 7 fans that I could have used but ran out of space and connections. I've no idea why I have so many fans and why I've kept them all. Might be intersting to arrange them into a rough rectangle with cable ties for giggles. Maybe I could create one of those freefall simulators with them. :)
 
Tealc said:
Might be intersting to arrange them into a rough rectangle with cable ties for giggles. Maybe I could create one of those freefall simulators with them. :)
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When you get it working let me know. I've always wanted to play on one. :D

Edit: @lettuce, I'm sure Tealc will be along before too long.
 
Hello Lettuce.

Looks like it's picking up the PWM signal as stronger than the RPM tach feedback. This occurs when the fan is driven to low speed and voltage. I'm a little surprised to see it occuring at around 900RPM as normally it's seen when the voltage of the fan gets low enough that it can't make the signal strong enough and 900 I'd have thought would be fine.

My first advice is to increase the speed of the fan by adjusting the potentiometer a touch to see if it settles down. It may be a peculairity of the Gelid fans that causes this.

I also see the fan speed varying a lot between 900 and 2000. That is peculiar behaviour. All circuits I've built have been incredibly stable and vary only by just a few RPM here and there given a stable PWM.

I did test the circuits on my oscilloscope and PWM box before sending but I don't check the validity of the tach signal as that is totally fan dependant, so loading up one of my fans will not give a true reflection of the tach signal. Each fan will have their own hall sensor and circuitry to operate.

I wonder if this is somehow caused by the two fans on the Gelid. Can you check that only one tach wire comes from one of the two fans mounted on the cooler?

All being said I've made several (5 or 6) circuits for Gelids and not had any feedback thus far of any issues so maybe it is a wiring error on my part or something. If you have no joy then please contact me by email and we'll get this sorted.
 
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Seems more stable at the moment.

I should point out that for Gelid circuits such as yours all I do is solder it to another wire, insulate and run it off to the other side of the PWM converter, at no point does it form part of the converter circuit itself. The extra length could be picking up signals from elsewhere I suppose but it really shouldn't be that sensitive.

In addition, just in case you were not aware, the GPU doesn't care what the tach on fan is. All it does is vary the PWM duty cycle in the hope that there is something on the other end to listen to it. You can disconnect the tach and the graphics card will just go on modifying its duty cycle regardless.
 
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Hmm, it seems it could be related to MSI and the speed i have the fan set at for idle temps...

i6xq6eFVJrpah.jpg


If you look at the above, towards the end of the line graph you can see where i change the fan speed down from 30 to 25 and the tachometer went nuts, then i change it from 25 to 35 and it wasnt spiking at all?
 
Here's a small update.

Thought I'd shove a length of 6.4 heatshrink on the leads to see if it looks better than cable ties. I'm not sure. Maybe it will look better when properly shrunk and not done with a flame. Maybe I will try some smaller bands along the length.

heatshrink_zpsf0ae06d1.jpg


And I ordered some SMD resistors a few weeks back and thought I'd throw a circuit together. I'm a bit of a noob with SMD and as I made a few mistakes and made a bit of a mess. Makes the rear look simpler and aids assembly of the components on the other side. It also saves about 3mm off the height of the board. I really could do with a steadier hand or larger resistors, these are 1206 I think. I think the whole thing looks much better with the bulk of the resistors on the underside, even if it is more difficult to assemble. :cool:

smd_zps053680ba.jpg


I was thinking of videoing myself slapping one of theser together. Not sure how interesting it would be. :confused:


@bandyleg - Your converters are on their way to you mate. :)
 
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Tealc said:
Here's a small update.

Thought I'd shove a length of 6.4 heatshrink on the leads to see if it looks better than cable ties. I'm not sure. Maybe it will look better when properly shrunk and not done with a flame. Maybe I will try some smaller bands along the length.

http://i959.photobucket.com/albums/ae72/Tealc_wii/heatshrink_zpsf0ae06d1.jpg[ /img]

And I ordered some SMD resistors a few weeks back and thought I'd throw a circuit together. I'm a bit of a noob with SMD and as I made a few mistakes and made a bit of a mess. Makes the rear look simpler and aids assembly of the components on the other side. It also saves about 3mm off the height of the board. I really could do with a steadier hand or larger resistors, these are 1206 I think. I think the whole thing looks much better with the bulk of the resistors on the underside, even if it is more difficult to assemble. :cool:

[img]http://i959.photobucket.com/albums/ae72/Tealc_wii/smd_zps053680ba.jpg[/ img]

I was thinking of videoing myself slapping one of theser together. Not sure how interesting it would be. :confused:


@Bandyleg - Your converters are on their way to you mate. :)[/QUOTE]

Would it not be easier to braid the cables rather than a full heat-shrink wrap? Doesn't the HSW make the cable a little inflexible?
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Bit of an unneccesary update now.

Have been fiddling around with my Arduino development board and what it can do for me.

The following video shows one such experiment...


...and also has me wobble on about a possible project. ;)
 
Tealc said:
Have been fiddling around with my Arduino development board and what it can do for me.
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Perhaps a homebrewed open source fan controller?

The Tealc Controller: 20 Channels, 100W max, custom fan profiles, PWM to Voltage conversion with predefined fans (GT 1850s)

Im off to watch the video :)
 
I would be very interested in the electric scheme in order to build this converter, I can have it?There are problems with speedfan with the tachograph? Voltage min / max on the fan?
 
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