Fan only full-OFF or full-ON. Tried 12V, & 24V fans. Hm?...

[Swami]

Greetings Makergear community,

Looking forward to learning, and contributing. Anywho...

Never saw a MG M2 before a week ago, but fixing one for a friend:) Great machine, w/ great documentation, and a significant support community. Have managed to get the printer printing, but still have some issues - one being the fans: only respond to S0, or S255. Have read might be due to incorrect voltage rating. Two fans were missing and I wasn't sure which voltage to get. I know very little about the history of this particular unit, or about MG in generally, but did see a date of Dec. 2014 on an SD card and assessed the required fans were 12V. Ordered/installed fans, then discovered the issue. Investigated a bit online, and on the unit: read that improper voltage could be culprit, plus took multimeter, and scope to things. Got 24V out of power supply; and got PWM waveform across fan showing values higher than 12V. So, ordered 24V fans... same behavior:( (FYI, at some point when digging into electronics box, noted that that fan is 12V).

OK makers, what am I missing? TIA.

Swami
3D printing, & laser specialist at Factur makerspace (in Orlando, FL).

P.S. From SD card dates, and looking at various image/videos/user manuals, I surmise the unit is an original MG M2 V4 (no rev.). The filament drive motor, and printer head have been "upgraded", though, so other things might be different, too, but I just haven't recognized them as such. FYI, hot end is V3b.

[insta]

The original fans (drive cooling and electronics cooling) were 12v units in series. It's... not a great setup. Fine if you're running dumb resistive loads like lamps, but not so much for smart devices. The part cooling fan (the big one) is a 12v (running at PWM'ed 19v) for really old units, or 24v on anything with a 24v power supply.

Use 24v fans on the drive & electronics, and put them in parallel across the connector, instead of in series. Same end result, far better performance for the electronics. If you have them, whack a 680uF 35v capacitor across the fan leads in the box for smoother voltage out.

I suspect the on/off behavior is a firmware configuration. You have to explicitly enable fan PWM on non-MG firmware.

(your first 3 posts are moderated, don't post spammy ones to get your post count up)

[Swami]

Thx for the prompt reply, Insta.

I will follow your directions. As noted in OP, PSU is 24V, and I have 24V 40mm, & 50mm fans.

As for ON/OFF behavior, I can check firmware, but I did scope the 50mm fan and got a PWM waveform (if they wanna call it that:)).


(Whoa, image looks big in Preview, but source rather small: 800x600. Apologies, if too big.)

FYI, just now diving into firmware, so may have questions. Nice to have a helpful community:) Also, FYI, was programmer in past life.

[insta]

The firmware isn't hard if you have any development experience. Just stick to Configuration.h and Configuration_adv.h. You *may* need to branch into pins_RAMBO.h, but shouldn't have to go outside of that.

Your waveform looks really messy. Whack some capacitors across things.

[Swami]

Thx.

Yeah, I'm OK w/ delving into the firmware realm, and am already in a bit. As for the waveform, yeah, poor excuse for a square wave:) Will clean it up w/ a cap - suggestions on were, and values? TIA.

Having fun:)...

[insta]

I've never done it (I have too many wires in my boxes as it is), but I'd put it in the wire clamps directly. Use 680-1000uF @ 35v, 105C if you can find one.

[Swami]

Thx:)

[jk42]

Swami,
If you email us at support.makergear.com we can help you get the right fans and firmware for your configuration.

[ednisley]

whack a 680uF 35v capacitor across the fan leads in the box for smoother voltage out

Which will kill the MOSFETs when they're trying to apply PWM, because they short the cap energy to ground.

It's time to stop applying PWM to fans: viewtopic.php?f=7&t=6310#p35393

As a consequence, it's time to stop putting fans in series to "divide the supply voltage".

[insta]

A 680uF isn't going to blow up a mosfet, Ed. The BLDC controllers are designed, to an extent, to respond to variable input voltage. They do not like being in series though.

I can give it a shot this weekend on a standalone RAMBo if there's no new answer by then.