They are VERY small and very cute
As soon as I get some spare time I will assemble the first one and perform some testing. If it all works ok, then I will move it to the betatesters phase
First batch ordered!
15 PCB are on its way
If there is no problem with the design, I'll order about 50 more, wich would be enough for all the boards everyone asked for.
Anyone wants to betatest a board from this first batch once arrives?
And please leave a way to do it for the good old Duet 2 Wifi
This weekend I will update the post with schematics and simulations, and wait to see if more people are interested. If I have enough time I'll build a protoboard version and measure it with an oscilloscope and share it too.
I'm building a custom toolchanger with e3d toolhead and toolplates, and I was having problems with fans not reacting to PWM or being very whinny/loud/weak as soon as I PWM'd them, so I'm designing a very simple circuit with an low pass configured opamp and a transistor that should give a nice and stable analog voltage from the PWM signal from the duet.
Since I'm lowpass filtering in small signal, no inductors are needed, just a couple of resistors and capacitors, EMI should not be a problem, and the pcb should be very small.
My aim is just to use an all 24V system, but it would be rather easy to make the circuit voltage-agnostic so you could be able to mix and match fan voltages in the future.
Is anyone interested in such a circuit? I'm thinking about having some pcb boards manufactured, and since most services are about 20 pieces minimum order, I will have plenty of them...
That's the very reason I'm doing all of this: I'm driving 6 fans from a Duex 5 board, and I already calculated that the inductor for a LC filter would be huge, and I'd need 6 of them. That's why I went with this route. But thanks for the advice!
Have you determined what it is about your fans that cause them to not work with PWM?
I have dozens of different kinds of brushless fans from many different vendors and they all work fine with PWM.
Yes, I've done quite a lot of test. Some of my fans don't work at all as soon as you drop from 99% PWM. Most of them work, but PWM is not linear at all: 99% is already less than 25% airflow, and 50% PWM is no much less than that, and some of them kinda work with PWM, but whinning an awful lot, since they are connected to a Duex5 and I cannot change PWM frequency at all.
I suppose that 4010 fans, and even more, 4010 brushless radial fans are very tricky to get working with PWM.
By contrast, using my bench power supply, all of them work more or less linearly, at the very least from 12V to 24V.
In my other old printer (an old cartesian Marlin based custom one) I'm using 4020 and 5015 radial fans and managed to get some fans that work ok with PWM.
Yes, I've done quite a lot of test. Some of my fans don't work at all as soon as you drop from 99% PWM. Most of them work, but PWM is not linear at all: 99% is already less than 25% airflow
That doesn't make sense.
According to my oscilloscope 100% is pure DC and 99% is 99% "pure DC".
It seems strange that those 1% intervals where the power to the fan drops to 0 would reduce the airflow to 25%.
As @zapta said, brushless motors are driven by embedded electronics, they are not just inductors and magnets. And some electronics are very susceptible to supply anomalies. If you do something like this to an opamp, it will easily begin to oscilate. The 99% "pure DC" has 250 narrow gnd peaks per second, which generates infinite harmonics that can and indeed disturb most electronics. If you have an original e3d V6, try to PWM its 24V 3010 fan. It will stop as soon as PWM is activated, no matter the %. And if you have a 24V 4010 radial fan from TriangleLabs (if they have not changed the source) try to PWM it, and witness the speed fall once you go to a non-100% PWM.
mhh thats a bummer . I wanted to do 12V PWM to 5 V analog.
But as it seems you are a specialist in electronics. Do you have an idea why this simple optocoupler didn't work for that purpose:
Do you realize you could just use the PWM- from duet and 5V instead of Duet's Fan Vcc? You are not forced to use 24V/12V from Duet.
Here you have a example just with passive components:
Since your load is Arduino's analog input, and assuming it has quite a high input impendance (IIRC, 1MOhm) you could just pull-up with your 5V supply with a 1K resistor (5mA current draw) and use VFan- from Duet (which is a PWM open drain). You'll have a little offset from de resistive divisor around A1, but it would be small. According my simulations, 2.3V for 50% PWM, 0V for 0% PWM and 4.54V por 100% PWM. You can play with R2 and C1 values a bit more to achieve even better results (for example 10k-10u).
Of course you could also use my board, but I think your problem doesn't need it.
Do fan manufacturer provide graphs of CFM vs voltage? Is this something that can easily be measured?
Now that you have good control of the fan, would be interesting to know for example what 50% voltage means in cooling terms.
I don't even thing that the manufacturer expects you to run the fan at other voltage than nominal... If I had some way to measure air flow I could perform some measurements, something like displacement of a suspended weight or the like.
I'm trying to transition to TINA TI + KiCad
If paying for a subscription is an option for you, take a look at https://www.circuitlab.com/ . It has a more modern front end, works in a browser and has a cleaner user interface, and has nice feature such as sharing your schematic and simulation with others.
Most of my projects are digital so in the rare cases I need a simulator I use https://en.wikipedia.org/wiki/LTspice (free, powerful, dated user interface like most circuit simulators).
I'm trying to get used to TINA TI because it has most of TI spice models and it's fairly accurate (I do a lot of analog designs). Its transient analysis is the most accurate I've found to date. But thanks for the suggestions! I'll have a look
BTW, I think it's the last board I make with Ultiboard.
Most likely Kicad will give you nicer 3D renderings.
In fact, Ultiboard renders are VERY ugly xDD. In 1998, when I started using it, it was like "wooha!". But now it's 2021, and it's the very same render
It's just that I can go from Multisim to Ultiboard comfortably, and Multisim has a powerful analog spice simulator which I use a lot. I'm trying to transition to TINA TI + KiCad. I wish KiCad had a good spice simulator!
This is the new board:
It's a bit bigger so now the capacitor is included and the diode and the led are in top side. Also a bit more of space surrounding the in/out connectors.
BTW, I think it's the last board I make with Ultiboard. I have tested Kicad and its support for footprints is way better (I can directly import them from Mouser!)
@egon-net Out of interest. What would the cost be per board, delivered to the UK? Do you think they could be assembled with a fine tipped soldering iron, or only hot air?
Regarding cost, this is what I thought:
Regarding building the board with a fine soldering iron... It could be done since every part has its legs exposed and parts are not that small (SOIC8 & 0805 SMD), but it would be much more difficult.
Everything ready for the next batch of final boards!
Everyone who asked me for boards is already contacted for this batch. There are 23 boards finally requested, so I'll probably do a 25-board batch. Does anyone else need one before I place the orders to part suppliers?
I can also supply a STL/STEP file with the board and a basic box just in case you need
I have a original e3d Chimera+ in my custom printer. I do agree with the dual fixed nozzle being quite a problem. I've never had a completely clean two color print with it (it can be clean enough but not immaculate). But the worst part is that no matter how good you level both nozzles (it can be done, just quite time consuming) the inactive nozzle will mark the print if you use any kind of bed compensation. I grew very tired of having marks like a single ghosting line in every print.
Now I'm finetunning a toolchanger, and I really think that multihead is the only way to go if you want problemless many-material printing.