Sorry for what I assume is a really basic post but I’ve been looking to install another 40mm to help cool PLA prints on my Taz 4. I’ve tried quite a few replacements (using the existing fan cabling) but all seem to have issues powering up at lower fan speeds. They’d need to be set to speeds > 240 to move and then if the speed falls bellow 220 they stop spinning and get very hot.
I’ve tried to look for a fan that’d match the included fan but can’t seem to find one in the UK.
What fans have others used/anyone know any specific models or UK sellers? Any help would be really appreciated!
I do not know of a place in the UK, but I decided to contact Pelonis and buy some myself. The latest fans I got elsewhere have the same issue as yours, so I asked today and that is why they get these. Besides these are lower cost than the ones I just got.
None of the ones I have tried work unless you set the percentage to 70% or more. Pelonis wants me to order 200 minimum. So I will have to continue looking.
These Zener diodes can drop ~6V each, at up to ~1.85A (3W power dissipation each). Two can be wired in series to drop 6V, and this is remarkably effective at ‘converting’ 12V fans to operate across the full range of 24V PWM input.
A user posted a duct design which circled the nozzle. It was a good design, the flaw was a second duct which cooled the hotend barrel on the buda. Modify the design and block off the duct to cool the hotend that should allow the single fan to cool the extruded filament in all directions… not just along the X.
Could also try a relay to supply direct power from the PSU, bypassing any limitations of the Rambo.
I’m also interested in adding a 2nd filament fan and upgrading the tiny throat fan.
I thought the existing Filament Fan was 12v and the throat fan was 5v.
DicoJon’s example was 12v.
Piercet says it’s 24v
The RAMBo board can support both 12v and 24v. You need to understand what your power supply is providing to the RAMBo board. I know that the TAZ 5 uses 24v.
The real problem is the range of voltages the fan can operate at. Many of the fans I have tried only work within 20% of the 24 volts supplied. Or a fan rate of 75% to 100% and not the ~34% and up that the older fans and Pelonis fans can.
Or you lose the fan speed control you need for reliable cooling of the extrusion when needed.
I have some nice 12v Noctua fans I’d like to use, but they are 12v. Could you explain how to connect the Zener diodes to allow these 12v fans to work at 24v? I’ll be putting 2 fans on my TAZ in parallel (one on each side).
Best regards,
PCH
PS - you said that they drop 6v each and then you say that 2 in series will also drop 6v. Wouldn’t that be a 12v drop for 2?
I guess that works if you want them running at full speed all the time.
mirage335 answered my question via PM. I thought I’d copy it here in case others are interested -
Connect two zener diodes in series. Make sure the band marked on both diodes faces the same way. Connect the lead with the band to the positive lead (usually a red wire).
Now, since the two reverse-biased zener diodes drop 12V, the voltage between the other side of the diode pair and ground (usually a black wire), will be 12V.
Now connect your fans in parallel to that. They will see 12V.
Take care to thoroughly understand what you are doing. If you mis-wire, mis-understand, or short-circuit something, you may cause severe, expensive damage. Also, beware the power supply can supply upwards of 20A. As with a car battery, short-circuiting that much current can cause dangerously bright flashes, burns, and fires. Safety first.
