Wind simulator fans

Sorry the Ruck didn’t work out for you. The SeaFlos are fine, but muffin fans don’t really put out much air at much velocity.

There’s maybe another option, though. Have you looked at the fans used on auto radiators? Those are 12V, high power, and I think generally ball bearing. Significantly different form factor, though, but high velocity and lots of air and I think with a lower RPM and noise. Would be a swap for SeaFlos other than form factor.

Thats actually a good idea. A quick look tells me that could work, but the form factor.. they are generally much larger in diameter. I would prefer adding pipes or ducts to put the fan on the side of my rig. I might google a bit see if i can find 1.

I would need to look at the board again where I could see the traces and my fans are mounted up. I knew what they were back when I first did this but didn’t make notes. I need to partially disassemble anyway to hook up the tach wires in my Arduino box and will look again to get the component designators.

And exactly on the resistance. If you can solder another same value resistor on top of the stock R, you would cut the time constant in half. The engineer thought that it would be ok but obviously there’s always a chance for disaster. It’s easy to find, though. You just trace the wire for PWM input to the connector on the circuit board, and from there it goes straight to the resistor and you’ll see a cap right on the other side.

I missed that but yeah, that Ruck is slow.

Squirrel cage fans might be a solution too. Lots of those have 4” or 6” outputs, ball bearings, etc. might be quieter than SeaFlo fans too aside from the actual wind noise.

I opened mine up today while I had some other stuff off the rig. I think I’m in the right area but wasn’t able to figure out exactly which of the extremely tiny surface mount resistors is the one we want.

I think part of the problem is the probes on my multimeter are kind of big for this application & it’s hard to get any readings - even directly across one resistor... is there some kind of coating on there?

anyway, if you open yours up and figure it out let me know. Attaching some close up pics of the area in question... I think it might be C210 & R216.

@lbwski - I haven’t had a chance to open mine up but I was thinking the R/C parts were on the top side of the board. Could easily be wrong, though. And there probably is a coating. Since those fans are in the air flow, it wouldn’t surprise me at all if they add a conformal coating. There’s definitely a solder mask but in those shots it looks like there could be a clear conformal coat. Sharp probe tips should pierce it no problem, though.

I was digging back into the code to add the “100% slam” bit but not done yet. Was also going to light up the on board LED whenever the slam was active to give a visible indication. But I keep getting re-tasked with domestic duties. Hopefully soon (sometime this week?) will have some progress to report.

As an aside, are you able to load and run this code? https://www.xsimulator.net/communit...rmoto-and-arduinouno.6876/page-33#post-213758 I can just post the code but .ino seems to be easier for others (and me )

Haven't had a chance to play with this code yet; been busy.

Was cleaning up the driveway the other day and realized this Ryobi 18v blower would probably make for a great wind sim. Moves a lot of air & you can vary the output anywhere from 0-100% very smoothly. Plus, it can go from nothing to maximum and back in a second or two. A bit of PWM noise at lower speeds, but otherwise checks all the boxes.

Now... I don't think I'm going to sacrifice my blower any time soon (these things are great for cleaning up the garage, etc!) but thought I'd mention it here in case it gets someone thinking.

@Zed
I know this is a few years on, but I wanted first to say thanks for all the info. I was about to go down the bilge blower route but your post has definitely made me think the inline duct blower with PWM is the way to go.

Hoping I can ask you a couple of simple questions.

1) In terms of connecting my current PWM output to the input of these fans (like the Terrabloom), is it in theory just joining the two together? I notice you mention a level shifter? So I think you're going PWM output to Level Shifter, Level Shifter Output to PWM of fan?

2) What do you need the Level Shifter for / How do you know you need one?
I've a 12v pwm output, going to a 220v Pwm mains-powered inline fan, much like the Terrabloom

(https://www.symprojects.com/categor...controllers-fan-controller/fan-controller-new)

Grateful for any advice!

Thank you sir.

Hey Scott, glad the info was helpful!

The level shifter is needed in my setup because I use an Arduino to send the PWM signal. Those only do 5V PWM but the Terrablooms need a PWM banging around 12V (next paragraph very important though - the Terrablooms just interpret the 12V PWM as an analog signal.) The electronics in the Terrablooms don’t (or didn’t) respond properly to 0 to 5V PWM so I use the level shifter to convert a 0-5V PWM signal into a 0-12V PWM.

What’s actually going on is the Terrabloom control electronics are just looking for a voltage that ranges from 0 to 12V with 12V being full speed. I used PWM since the input to the Terrablooms has a low pass filter on it and in effect what the PWM does is become a dirt cheap digital to analog converter. A 50% duty cycle square wave is the equivalent of a 6V analog signal after the filter in the fan electronics and will cause the fan to run at about half speed. Your fan may or may not have similar input characteristics.

The Arduino handles USB communications and fan settings. If you already have a 12V PWM signal, that should work directly without the level shifter but the level shifter may still be handy depending on the 12V PWM output characteristics and the control input electronics of your fan. The level shifter can deliver a fair amount of current so the Terrabloom input doesn’t load it. Depending on the output resistance of your PWM source and the impedance of the control input circuit, you might get loading and not be able to hit full speed - if that matters.

Since you aren’t using Terrabloom fans, though, I can’t say if this would work for you. The way to know if the fan signal input is loading your output is to check the voltage on the PWM signal at 100% duty cycle. If there is a loading issue that voltage will be lower. Say 10V instead of 12. If your fan is expecting a PWM signal and has a wide voltage tolerance on the PWM input, you should see full speed anyway. If, however, your fan is really expecting an analog signal, that loading would reduce the voltage of the square wave and even at 100% duty cycle won’t run at full speed. That 10V example would be somewhere around 80% speed.

That may all be clear as mud. Let me know if it makes sense or not and what is still confusing. I talked with the Terrabloom engineers to figure out I could control their fans this way since it’s not the normal way to control them. The stock control supplied with the cheap version of these fans is just a potentiometer and that’s what the Arduino PWM output combined with their input filtering approximates.

Caveats - the time constant on that input filter is fairly long and part of what limits how fast you can change the fan’s speed. The next thing in the chain that limits how fast the fan can change speed are the control electronics themselves. They don’t have lots of power to dump into the fan motor and that time constant is part of how they protect the electronics from overcurrents. As a duct fan, it’s meant to spool up in a reasonable time and stay there. Luckily that reasonable time is fairly quick. One person here tried these fans for auto racing simulation and that lag was too long for him. I understand. I can come to a complete stop before the fans stop blowing, or rocket out and there’s no wind until they come up to speed too. Airplanes are more forgiving. But since yours isn’t a Terrabloom that may or may not apply.

One other thing of note is I bought and replaced bilge blower fans when their bearings would start squealing after about a year both times. You can tell when I switched to Terrablooms by the post dates (looks like 2020), but that original set is still running daily and doing just fine. And they are still much quieter.

Hopefully I answered to some extent. I’m not familiar with your hardware so can’t say for certain but I think it’s likely it would work from a 12V PWM signal without the level shifter but loading could affect that.

Let me know if other questions. Cheers!

And the proverbial caution - you mentioned 220V. If you aren’t already aware of the potential (arh, arh, arh) for injury and death if you get across that, please don’t attempt anything I may have said without the help of someone who knows what precautions to take around such voltages.

Just wanted to acknowledge the awesome reply straight away so it didnt look like I hadnt spotted it.
Currently travelling away for the weekend, so will come back to reply properly as soon as I can sit at a keyboard.
Very grateful for all of that, thanks again!

@Zed

I've sent you a private message about this build, that I'm also trying to embark on, if you have any time to answer I would be very appreciative