PWM to Analog converter circuit
- Thread starter Tealc
- Start date
whoop! looking good thanks
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.
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.
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.
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.
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.
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.
Here's an older board that shows the correct way.
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.
Last edited:
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.
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.
Last edited:
It is designed to work with a massive range of fans. The version I sent you should cope with fans ranging from 0.05A up to 1A, or combinations of 1-20 fans within that current range.
The potentiometer acts like a valve and allows more, or less energy into the fan output circuit. It is meant to be adjusted to suit an individual need. Originally I used resistors and a switch to select 3 settings, low med high but I feel the potentiometer is a much more elegant solution and allows any user to swap and change cooling fans without needing to change the circuit. In some respects I've harmed my repeat business, but meh.
The switches were expensive (comparatively so) and a pain to solder up neatly.There are two main possibilities here.
1) The circuit has a fault and the PWM signal is not passing through the circuit.
2) The PWM signal from your motherboard is not actually changing when you adjust it in Speedfan and it is just sending 100% all the time.
I should be able to determine which of these two it is when I receive the board today/tomorrow.
Thanks for sending it back mate.
Last edited:
Right. Tested.
I don't think this broken ground wire helps much.
I also noted that a resistor was very close to the power rail so it may have been pushed down and shorted after heatshrinking, thereby popping the PNP. Once the PNP pops it goes short and you lose control. As a side effect when the PNP pops all PWM is cut and no current flows, protecting your PWM circuit and also running your fans at max. Always safety in mind you see.
For the broken wire:-
I will need to devise some sort of strain relief for these wires. I was at one time potting them with hot glue but since using adhesive shrink I haven't thought I needed to. I will either go with a cable tie securing the wires in a loop so any force acts upon the cable tie, or use a blob of hot glue over the opening where they come out. I could also go up a wire size to 22AWG which will make the connection stronger.
For the resistor:-
I will need to make sure I don't cut the track too deep and that will allow me to use a SMD resistor, which won't have any risk of shorting. I will need to use a smaller drill to cut tracks, or devise a different method of track cutting.
I'd expect that with the PNP replaced the circuit would work just fine, once I replace that resistor.
I don't think this broken ground wire helps much.
I also noted that a resistor was very close to the power rail so it may have been pushed down and shorted after heatshrinking, thereby popping the PNP. Once the PNP pops it goes short and you lose control. As a side effect when the PNP pops all PWM is cut and no current flows, protecting your PWM circuit and also running your fans at max. Always safety in mind you see
.For the broken wire:-
I will need to devise some sort of strain relief for these wires. I was at one time potting them with hot glue but since using adhesive shrink I haven't thought I needed to. I will either go with a cable tie securing the wires in a loop so any force acts upon the cable tie, or use a blob of hot glue over the opening where they come out. I could also go up a wire size to 22AWG which will make the connection stronger.
For the resistor:-
I will need to make sure I don't cut the track too deep and that will allow me to use a SMD resistor, which won't have any risk of shorting. I will need to use a smaller drill to cut tracks, or devise a different method of track cutting.
I'd expect that with the PNP replaced the circuit would work just fine, once I replace that resistor.
Last edited:
What I usually do is set the PWM at 20% or 30% and adjust until the fan speed is around 600rpm, or maybe higher if you run fast fans (greater than say 1500). Then it should ramp up speeds on a more or less linear fashion until it maxes out at 80-100% PWM.
You can also set max PWM and adjust until the fan just about reach their max speed. What'll happen is that the speed will increase gradually until it sort of hits a wall, this is the ideal point.
Remember that the fan closest to the cabling is the one that sends rpm. The others are just passengers.
You can choose to have your fans run a little faster at idle and have the max speed reached quicker if you choose. You can also have the fans never reach max speed by dialling down.
Look back to the first few pages of the thread and you'll see some graphs of fan speeds curves to get an idea of how adjustment affects the fan speed.
I may do a video on setting up eventually once I get my workbench set up.
You can also set max PWM and adjust until the fan just about reach their max speed. What'll happen is that the speed will increase gradually until it sort of hits a wall, this is the ideal point.
Remember that the fan closest to the cabling is the one that sends rpm. The others are just passengers.
You can choose to have your fans run a little faster at idle and have the max speed reached quicker if you choose. You can also have the fans never reach max speed by dialling down.
Look back to the first few pages of the thread and you'll see some graphs of fan speeds curves to get an idea of how adjustment affects the fan speed.
I may do a video on setting up eventually once I get my workbench set up.
Water cooling pumps are too power hungry for this particular design. I believe the D5 draws at least 2A at 12v. This circuit works up to 1A max. I also have no idea how slow the pumps are supposed to go, or how fast they go.
I have looked briefly into a high power version but I keep hitting the issue of the maximum voltage dropping to around 10v-10.5v at 2A.
I have also looked briefly at developing an IC based circuit that responds to PWM input and has a heavy duty FET on the output, that would drive a load of current but you'd lose tach output. You'd need to involve a micrcocontroller based solution to stretch the PWM or something to give a tach feedback.
+1 ocuk should be stocking these. i have 2 case fans on atm to test then my cpu fans will join in
You have to understand that this PWM converter is really quite simple, consisting of just 7 components, 5 of which are passives, a bit of wiring and some connectors. It takes time to put together of course.
A version that one would develop professionally would need to sense the current of the fans and determine it's own setting, rather than be adjusted by hand. Maybe if I were to develop a version with feedback and that level of control it would be worth considering. A professional board would be silkscreened so would not need the heatshrink.
Last edited:
I can make it shorter by taking the fan connectors off board. That saves around 30mm length. Reducing the width is mostly pointless as the width of the heatsink governs the width of the device. I can remove it but it would get hot under load of several fans.
As for creating a smart device. That might be a nice project for the warmer months.
As for creating a smart device. That might be a nice project for the warmer months.
What fans are using mate?
In all the time I've built these things, and we are going into the dozens of units and two years here, I've never heard a pop from them. Don't get me wrong I've blown transistors, had smoking potentiometers, scalding hot resistors and transistors but I've never had any audible feedback from the components.
I've seen fluctuating readings before but that's generally when the speed, and corresponding voltage, of the fan drops below around 4v or 5v and therefore leaving the PWM signal stronger, so the motherboard picks that up instead.
I've not really tested with PWM quite as low as 15%, it's generally designed for 30%+ PWM. I've never stated this because in a lot of cases you aren't able to go quite that low with PWM duty cycle.
In all the time I've built these things, and we are going into the dozens of units and two years here, I've never heard a pop from them. Don't get me wrong I've blown transistors, had smoking potentiometers, scalding hot resistors and transistors but I've never had any audible feedback from the components.
I've seen fluctuating readings before but that's generally when the speed, and corresponding voltage, of the fan drops below around 4v or 5v and therefore leaving the PWM signal stronger, so the motherboard picks that up instead.
I've not really tested with PWM quite as low as 15%, it's generally designed for 30%+ PWM. I've never stated this because in a lot of cases you aren't able to go quite that low with PWM duty cycle.
Ok mate. You could probably retweak the potentiometer if you find 40% too high for idle. Let me know if it remains stable at 30 or 40%.
I shall have to run some endurance tests on low PWM myself and see what effects it has. It's funny that I've never had thus issue before but I suppose its all good feedback and could help me develop it further and make it better.
I shall have to run some endurance tests on low PWM myself and see what effects it has. It's funny that I've never had thus issue before but I suppose its all good feedback and could help me develop it further and make it better.