Switching to 24v power supply



  • I've had my delta printer up and running for about 18 months and have decided that the time has come to upgrade from my Ramps 1.4 with 1.8deg steppers and 12v electrics to a Duet Wifi with 0.9deg steppers all running on 24v. I initially want to set up my printer with just one extruder before adding a second in the very near future.

    I have settled on using these stepper motors:

    http://uk.stepperonline.com/09deg-nema-17-bipolar-stepper-motor-2a-46ncm-17hm192004s-p-122.html

    which I intend to use for my three directional motors as well as the extruder(s). Hoping that I have made the correct choice regarding these motors I then moved on to considering a suitable power supply and this is where I'm struggling.

    Refering to both:

    http://reprap.org/wiki/Choosing_a_Power_Supply_for_your_RepRap
    https://duet3d.com/wiki/Choosing_the_power_supply

    Using the formula Power (Watts) = Voltage (V) x Current (A 😞

    Steppers (rated current x rated voltage + 50%) = 2 x 2.8 + 2.8 = 8.4 x 5 steppers = 42w
    Duet = 5w
    Heater cartridge = 40w x 2 cartridges = 80w
    Fans = 3w x 2 fans = 6w
    Panel Due = 3.5w
    Radial fans = ?

    Which totals 136.5w

    What I can't work out or find is the wattage needed for my heated bed:

    http://www.ebay.co.uk/itm/161744356159?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

    I read that "The Duet WiFi is able to supply 15A to a heated bed" (https://duet3d.com/wiki/Power_wiring) meaning a maximum of 24v x 15a = 360w.

    Should I therefore be thinking of 136.5w + 360w = 496.5w and so buy an LED PSU that can provide 600w at 25A? I'm thinking this is a huge wattage and I may infact have got the wrong end of atleast one stick. Any input or pointing out of the obvious would be gratefully received.



  • If you can foot the bill for the larger supply and have the room to house it…why not. Going too large however can in some cases make the supply a bit less efficient which will cost you a tiny bit more on your electric bill. Also keep in mind your peak wattage isn't going to be held all the time, once everything heats up the draw should drop significantly.

    Personally I would go for a bit of overkill in most cases. Also go with a good name brand, while the cheap supplies will work they won't hold up anywhere near as well in the long term. Worse case they can be grossly exaggerated in their specs, so that 600w supply might be more like 400w.

    Jeff


  • administrators

    The specification that Sintron gives on that web page leaves out one of the the most basic parameters, which is the resistance across the 24V connections, or equivalently the power consumption at its rated voltage. I suggest you ask them. My guess it that it draws no more than 130W and probably nearer 100W.

    So if you choose a MeanWell or similar quality PSU, a 300W PSU should be enough. If you choose a cheap Chinese LED PSU, then a bit more margin won't hurt. That said, my Ormerod with a 120W bed heater and dual heads has been running on a cheap 300W PSU for over two years.



  • @DC42,

    David. On a similar topic, I'm finding the noise from my PSU fan a little intrusive so I was looking at fan-less power supplies but of course, because there is no forced cooling, they tend to be on the small side as far as output is concerned. I'm guessing that using 2 and connecting them together in parallel is a big NO NO but just wanted to check. Cheers

    Ian



  • @deckingman:

    @DC42,

    David. On a similar topic, I'm finding the noise from my PSU fan a little intrusive so I was looking at fan-less power supplies but of course, because there is no forced cooling, they tend to be on the small side as far as output is concerned. I'm guessing that using 2 and connecting them together in parallel is a big NO NO but just wanted to check. Cheers

    Ian

    I would suggest against this at that power rating. Unless you can find some supply that's crazy efficient you need to pull that heat away. Convection cooling alone is just going to shorten the lifespan. A good compromise is to find a supply with a variable speed cooling system.

    Jeff


  • administrators

    The 300W PSU that I use in my Ormerod is fanless. So is the 120W one that I use in my delta (that printer has a mains-powered bed heater). The 300W PSU does have a lot of ventilation holes, which I am careful to keep clear. I hope I never spill coffee in it,

    The better PSUs have thermostatically-controlled fans.

    Connecting PSUs in parallel is indeed a big no-no. OTOH it's possible to use one PSU for the bed heater and another for everything else.



  • @ InSanity - I didn't mention a power rating (for which you suggest against).

    @dc42. 300W would be fine - I've not been able to find a fan less version of that wattage - do you have a link? (Meanwell's UK site has so many and searching for "fan less" doesn't yield any results). The bed is AC mains so it's only the hot end, X,Y Z steppers and fans. Even running 3 or more extruders I'm not likely to get close to 300W (but I do like to have plenty in reserve for who knows what the future holds).



  • two psu in // no no, but two 12V psu in serie is doable, some insulation to do with one of them.


  • administrators

    Ian Another option could be to replace the noisy fan inside your supply with a super quiet fan.



  • Thank you both dc42 and Jeff ((In)Sanity) for your quickly given and helpful advice.

    I'm pleased to know that I was at least on the right lines. I have sent a message off to Sintron so I'll see if I get a reply and take it from there. No reply and I'm happy to take dc42's estimate of 100w-130w as a base and then I guess it's a question of how much damage I can justify doing to my already battered wallet. Cheap, big and bulky and undoubtedly less efficient or not quite as big and bulky, well made and reliable but 4 times the price:

    http://www.ebay.co.uk/itm/PSU-ENCLOSED-300W-24V-Part-No-SP-320-24V-By-MEAN-WELL-/351590956671?hash=item51dc743e7f:g:CZAAAOSwg3FUhe~6

    http://www.ebay.co.uk/itm/DC-12V-24V-5V-Power-Supply-for-LED-Strip-Universal-Regulated-Switching-CCTV-UK-/191733870857?var=&hash=item2ca43ab109ⓂmPu7fe3VbWXi0A1quJ78VWg

    Life in a nutshell really.

    Steve


  • administrators

    @deckingman:

    @ InSanity - I didn't mention a power rating (for which you suggest against).

    @dc42. 300W would be fine - I've not been able to find a fan less version of that wattage - do you have a link? (Meanwell's UK site has so many and searching for "fan less" doesn't yield any results). The bed is AC mains so it's only the hot end, X,Y Z steppers and fans. Even running 3 or more extruders I'm not likely to get close to 300W (but I do like to have plenty in reserve for who knows what the future holds).

    If the bed heater is mains powered, you don't need anything like 300W. I use a 120W PSU in my delta, and it's only that high because I wanted the possibility of supporting dual nozzle extrusion.



  • Mains powered bed heater really would change the game, with that I don't see why fanless would be an issue. For most using 300+ watts I'm not sure I would want a fanless power supply. The meanwell I'm using is just temp controlled, but still loud when the fan is on. Fannless would be fine if the caps and such are of good quality and temp rating. If anything I think a good temp controlled power supply would be best with slow ramp and only turning on when really needed i.e. max load.

    Really it all boils down to the load on the supply and the efficiency. Find a 90% plus efficient supply and heats less of an issue.

    Jeff



  • Looks like TDK, Sampu, and some others have 300w fanless supplies. I'm still not crazy about the idea but sure would be nice to have less noise.



  • @dc42

    David,

    I'm working on a design for a 6 colour active mixing hot end. It may not come to anything but who knows….......

    So my calcs go like this:
    X and Y motors 2 amp each but being driven at 40% (CoreXY - build area 400mm x 400mm, big, heavy XY axes 600mm long, 400mm travel) =1.6 amp @ 24V = 38.4W. (Z is intermittent and won't run concurrently with XY so has been ignored)

    6 off extruders 1 amp rating but driven at 40% =2.4 Amps = 57.6 W

    Hot end 2 x 40 W heater cartridges (it'll be big with 6 inputs and a big melt chamber is anticipated) = 80W

    Mixing motor, fans, lights,electronics etc = 30W (guestimate)

    Total = 206 Watt. Use 80% capacity so spec at 257 Watt. Hence me thinking that 300W (or 250 if I could find one) would be a good choice. The motor currents are actually set at 80% of their rating but I'm guessing that they actually draw about half this, hence me using 40%. Am I way off ?

    Cheers

    Ian


  • administrators

    The motors won't take that much power, especially with a 24V supply. See https://duet3d.com/wiki/Choosing_the_power_supply#Total_power_needed.



  • I'm using a Mean Well HLG-600H-24B, which supplies 25A @ 24V (600 W). It's somewhat expensive, heavy, and quite overkill for my current printer, but it's fanless, elegant and works great. There are less expensive ones with lower output power, of course.



  • Ahhh. Using rated voltage instead of supplied voltage brings it down a LOT - of course it does now that I thing about it. Sorry for being thick. 2 amps at 2.8V =5.6W and 50% x 2 steppers =16.8W instead of 38.4. Doing the same calcs for the 6 extruders brings the total down from 206 to 155W so 200W should be fine for all likely future requirements. Thanks



  • Don't forget you always have to factor in the quality factor, 300w no name supply vs 300w top quality brand name supply. The cheaper no name or off brand supplies will almost always overrate their specs where as often the top brand name supplies might underrate a bit. In the end you get what you pay for.

    I'm posting this more for others that might read this post then those who have already posted.

    Jeff



  • I'm happy to say that I received a reply from Sinton today saying 'if you use 24v , the resistance should be around 2.8~3 ohm.' So, using

    Current = Voltage / Resistance
    Power = Voltage * Current

    Gives me between 192v and 206v which was a bit more than I was expecting. Coupled with my previous workings out that means I'm going to need 136.5w + 206v = 342.5v with a bit of wiggle room so lets say 350v. Shame really as I had just about settled in my mind on a MeanWell 300w PSU.

    Steve



  • I'm wondering if buying a different heated bed with a higher resistance would be the better way to go:

    http://www.ebay.co.uk/itm/3D-Printer-Aluminium-Heated-Bed-Heatbed-MK3-12V-For-RepRap-Prusa-Delta-rostock-/231358142820?hash=item35de051964:g:5l4AAOSwPe1UDscs

    With 4 ohm of resistance that equates to 144w and so a total of around 280w with a happy amount of wiggle room lending itself nicely to a MeanWell 300w PSU. Possibly I have just answered my own question….......


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