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I need some Technical help for the Delta Electronics Axial Fan AFB0405MA-AFGE which is DigiKey part number: 603-2240-ND.
I tried the Application Engineering (AEChat) Chat but it just times out with no response! - Even after being forwared by one of the DigiKey Customer Support people!
This seems to be a special OEM Part Number for NVidia and I cannot find the details I need on the Delta Web site or in the Datasheet.
My questions are:
Is there a standard non-OEM equivalent available? - It must have 4 wires (incudong PWM and Tacho/FG) and be 5V or 12V and less than 1 W maximum Power.
What is the current taken by the PWM Input? - The 1nF Capacitance seems rather high requiring extra drive current to switch suitably quickly to suit 25 kHz PWM.
The Data Sheet says the Fan will start with 20% Duty Cycle. But can it keep running once started at say 5% or 10% Duty Cycle?
The Datasheet details Housing and Terminal connectors from LOTES (ABB-WAF-057-P08 and ABB-WAF-055-K01) and JWT (A2543H00-4P-DL and A2543TOB-2), but these do not seem to be readily available. So can you suggest equivalents that would be suitable and readily available?
Apologies for that. I’ve not the faintest clue whether that’s a systems issue or a people issue; either or both would be entirely plausible given all the present disruptions.
In response to the enumerated questions:
I don’t think this is a special/custom item in most senses; we have a part number for it, a link to a datasheet, and a few hundred on a shelf in the warehouse to sell to anybody with a credit card, none of which would be the case were the part number in question “special” by industry standards.
As you pointed out, the datasheet indicates a 1nF capacitance hanging on the input, which at 25kHz would have an impedance of about 64Kohm. Why the capacitance? Most likely it’s a means of providing a measure of protection against static discharge for the driver IC at minimal cost. The input impedance of the driver IC does not appear to be indicated, but I’d be surprised if it wasn’t at least a few hundred Kohm. Long story short, I wouldn’t expect any issue driving the PWM input to the fan directly from an I/O pin on any decent microcontroller.
Maybe; there’s a certain amount of stiction in the system that requires a bit of a kick to break free of when starting from a dead stop, which a person can often back off of a bit once things are moving. The minimum sustainable speed will change over time as things age and wear though, so there’s no good reliable answer to the “how low can you go” question. That said, since the thing has both a PWM and a tach output, it’d be possible to build an external feedback system to modulate the control signal in a way that allows more or less reliable control at very low rotational speeds. It’s not going to move much air at that point though, so a person really ought to ask oneself what the point in doing so would be, and if it’s really worth the trouble.
It seems to be a fairly common connector format for which functionally interoperable parts are available from a variety of suppliers. 61900411621 looks like one example of an equivalent housing that we have on hand; scrolling down that page a ways you should find links to mating board-side connectors and the associated contacts to go with the housing.
I contacted Arrow Europe, the UK representatives of Delta Electronics, who then got this reply from Delta Electronics:
This part number is an OEM P/N, you can check with the customer where he sourced the part, if it is from Digikey, he needs to check with them.
Hence it is difficult to get details and I am concerned, that despite your current high stock, that in a while it might become unavailable. The Datasheet says “Customer: Nvidia” (“Sample Issue Date: Jun.10.2019”), so I think it was specified by them and maybe Digikey bought up surplus stock?
I want to use the Nordic nRF52840-Dongle device and it’s GPIO specification says for “High Drive”:
Minimum Available Output Current (High or Low): 6 mA Typical: 9mA
Now say 10% Duty Cycle at 25kHz means the High is only 4 microseconds long and going by the above values (if Linear) for 1nF Load, the Output Rise/Fall time would be about 120ns which is 3% so fairly significant…
Also, simulating in LTSpice, changing by 5V in 120ns into 1nF takes over 40mA! - To keep below 9mA would mean it would be over 550ns or for below 6mA over 800ns!
So my conclusion is that at leat 100mA needs to be available to switch the 1nF load with a Rise/Fall time of say 50ns! - Not helpful really for a PWM Input when the Fan only takes 100mA Max current!
Yes, I think I may well have to use the feedback as you suggest, but I was hoping for some guide for the lowest Duty Cycle at which the Fan will run once started. I have seen other manufacturers specify 10% or even 5%.
The part you suggested just seems to be a Housing (no pins). I think from that Series I would need one of the following Wurth Parts to mate with the Plug on the Fan:
I’ve no clue what the origin story on this particular item is, other than that it was added to our listings roughly a year ago, to all appearances as a regular production, standard item available to anybody. All parts eventually go obsolete, and sometimes somebody will come in and buy up whatever stock we have on a given P/N. So yes, there’s always some risk of not being able to obtain product on short notice. Our sales folks can work with you to set up scheduled orders, if you’d care to hedge your bets on that front.
But this is a 40mm fan of which we speak, and those are not uncommon; we have other listings for products of a similar general profile here. 12V versions appear to be somewhat more numerous, as higher rotational speeds generally require higher input voltages and it’s more common for folks to be concerned with getting enough airflow to do a job, than being able to to throttle down to near-nothing.
Many potential points of discussion arise herein, but the question of instantaneous versus average values seems to be one of significance. Yes, charging even small capacitances rapidly can require fairly high instantaneous currents for short periods. Yes, an nRF52840’s limited drive capacity will probably distort things somewhat. But does it really matter? If so, why? Filling a 1nF bucket to the 5V line and dumping it out 25K times a second takes 125uA on average, which isn’t much compared to the supply current. And that 100mA “maximum” figure? It might not mean what you think.
Such a specification does not strike me as particularly common insofar as it’s a thing that will change over the life of the fan as the bearing system degrades, and given the device’s purpose as an air mover, spending extensive time characterizing how closely one can operate to the point of not moving air seems to be an exercise of limited practical utility.
That it is, offered for purposes of comparison with the similar housing indicated in the fan datasheet. Compatible contacts and mating board-side connectors are, as mentioned, linked under the “Associated Product” and “Mating product” headlines further down the product page.
I need to power 2 off Fans and an nRF52840-DONGLE from a USB 2.0 Port which has a standard Power available of 2.5 W maximum at 5 V.
So from your link the only Stocked Fan that might be suitable is “AFB0412VHA-DU48” (Digikey: 603-2030-ND) which has 1.08 W Power (1.44 W Max) consumption at 12V (which I could obtain from a DC/DC Converter) and that has a very different PWM Input circuit, as well as recommending a signal at only 2kHz! - Its Datasheet is on the Delta-Fan web site!:
It specifies 7 to 12V DC, so will it take less Power at 8 or 9 V? Will it spin slower at a lower Voltage?
Also its FG signal does not recommend a Capacitor.
Note - AFB0405VHA-AYGF, as well as being non-Stocked has a minimum Start Duty Cycle of 30% which is definitely too high!
Yes, maybe once proved, we could consider scheduled orders, to ensure continuity for a period of time, but our volumes are going to be low!
Yes, I understand about the average versus peak current. My concern is not the current taken by the Fan (which will not go through the Controller Output Pin), but to switch 1nF at even 120nsec takes 40mA peak versus the nRF52840 GPIO Output specification of 9mA Typical. So it will either switch even slower or break the device, hence I am designing an interface circuit using Transistors.
Noted
Ah! - Sorry I had not scrolled down the link page to the Mating Products!
If you’ve not already done so, I’d suggest entering “affinity laws” into your search engine of choice. Long story short, to a first approximation flow, pressure, and input power are proportional to rotational speed to an exponent of 1,2, and 3 respectively.
The basic design for fans of this sort puts a permanent magnet on the rotor, and uses a combination hall-effect sensor/switch IC to sense rotor position and drive the stator coils with the appropriate timing to achieve motion; higher voltage means faster current rise times and stronger fields, thus faster rotation, and higher input power requirement. In general, the PWM frequency is not particularly critical. IIRC in some examples I’ve studied it appeared to more or less just modulate the drive voltage directly; filter that and ta-da, one gets a variable supply voltage from a fixed-voltage source… Weird things can start to happen if one gets too far off the recommended value (like using a 100Hz PWM freq on a fan that suggests 25K) but a few minutes playing with a function generator attached to the PWM input will give a person a good idea of what is and isn’t within the realm of feasible.
Also, this page has a fair bit of info that might be helpful.
Just wondering how you got on with (4) - the mating connector? The connector on the AFGE fan looks a little unusual in that the the raised ribs which force alignment with the mating connector are located roughly in line with pins 1 and 3, unlike the usual arrangement where they would be at either end ie pins 1 and 4. This precludes the more common mating connectors as the rib aligned with pin 3 would foul the tab.
Back last July, I did a lot of research for my customer about suitable fans and how they could be controlled.
But I am afraid that the project has been put on the “back burner” for now as other higher-priority projects need to be completed/progressed and we have limited resources. So, although I got to the stage of specifying the main components required, we have not proceeded to order, let alone test to date.
