Step down convertor question



  • I am installing a direct drive extruder and the part cooling uses a 5015 fan which is 12v, I am running 24v
    Can I run straight off the fan connector to step down to fan OR should I use a step down with an enable pin, which is then enabled by the fan output?
    TIA Paul



  • wiki has lots of info https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans#Section_Using_12V_fans_when_VIN_is_24V

    i would prefer one of those options to what you suggest.



  • @bearer Thank you, i shall investigate.
    P.



  • (enable pin may work, but the converters i have seen were with enable pins for input enable for power saving applications, you would need it to be an output enable for it to work well with speed control)



  • Some things I forgot to mention....
    Maestro board, 24v fans on all outputs.
    Fan 0 Part cooling
    Fan 1 Hotend cooling
    Fan 2 Case cooling.

    So if I read the wiki right, I am going to have to use Fan2 output for my part cooling fan. Not a prob I can mod cura.
    Remove the jumper, make a cable from jumper to Buck, out from buck into V_Fan. Then fan2 output feeds the part cooling fan.
    Bit of an issue if i need to reduce the speed..... Either way I do it, more investigating required. Only printing PLA so it is either on or off!!



  • I will have to find a 5015 fan 24v from somewhere!!!



  • The main question to what option one should use, from the Wiki (1, 2 or 3), is others fans - do they use 24V or 12V.

    On my printer, I only have a single 24V fan, which is happy to be always on (thus running straight off my power supply). My other fans are 12V since they are easier to source. For this I run power from my power supply, to the buck converter, and the positive output of the buck converter into the Fan voltage header - thus I wire the fans up as normal and they work (getting their 12V).

    The other method (typically if you have some that need 24V and others that need 12V), is to have the Fan voltage header at V_in (24V fans are wired as normal), and the buck converter (still directly to the power supply) output for the 12V fan positive wires, and their ground to the mainboard - these boards make use of N-channel mosfets (digital switches), which simply means they are between the load and Ground, so the PWM capability is kept in this configuration.



  • @bearer , @Jacotheron thank for your inputs
    It takes a while for things to sink and for me to understand.

    So wiring diagram if I have read the info correctly should look like this?0_1558258460300_IMG_20190519_103056.jpg
    The box on the right is the Buck convertor!

    Looks like I will get 2 buck convertors regulated to 12v output and 3 new 12v fans.
    As others have said in other posts and this one, 12v fans are easier to get hold of.
    I mentioned about speed control, I got my head round that also, it is controlled on the -ve side of the fan output.

    If someone could check my wiring idea, i would appreciate.

    TIA Paul



  • That should allow you to use the existing fan headers on the board with 12v yeah.

    You should also be able to use the same 12v converter for both V_FAN inputs, unless your fans draw more current than the single converter can handle.



  • @bearer Thanks for the sanity check, greatly appreciated.
    Just need a decent 5015 blower fan!



  • @paulhew MF50151VX-A99



  • Thanks to everyone for their guidance, greatly appreciated.

    Bought 2 x Pololu Item #2577 - S18V20F12 step downs from HobbyTronics and have installed one for the Filament cooling fan on port 2 on my Maestro, temporarily until I get to E3D to swap a 24v fan to a 12v.
    I was a bit nervous turning it all back on after making the changes, but no smoke!


Log in to reply