24V question!!
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Silly question guys. If I use a 24volt power supply can I still use my 12V fan and Hotend?
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nope. you can use a step down regulator for your 12v fans but the hotend must use a 24v cart. You will nuke your 12v cart on 24v and you can't use a step down on it.
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Figured that. Thanks
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If your upgrading from 12v you can delay buying new heaters by running both power supplies. 24v on the V_IN and feed the posative legs of the heaters with 12v leaving the ground legs connected to the duet.
You could also feed 12v to the fans using the fan voltage select pins, however if you do use a stepdown from 24v for these you can add one relay (with a flyback/freewheel diode) and you can get the duet to completely kill the power to the 12v heaters in the event of a heater fault.
Edit: If you do this run both power supplies from a single socket. I run a plug in RCD breaker and earth fault check sockets with a £10ish plug tester.
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i run a similar way as @DocTrucker suggested, i run a atx power supply and a 24v step up converter, but run 12v to my heater, as long as you supply the heater with 12v and pwm the negative its fine. then run the duet at 24v
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A Hot-end can still be stepped down, using a buck converter rated for the high current draw. Typical heater cartridges are 30-40W, which at 12V gives about 2.5-3.4A of expected current (using Ohm's Law). I would not run a heatbed through a buck converter, but a single hot-end should be fine.
I have seen buck converters rated for 5A, though they are usually a bit more expensive that the typical 2A units found everywhere. These buck converters are usually 90%+ effective (by basically doing PWM with an inductor and capacitor for smoothing). If you do decide to go with a buck, ensure that it have enough overhead capacity (going for a 5A rather than a 3.5A or lower), as the higher rated units should remain cooler.
Do not use a regular regulator, as they will need to use up the other 12V of the current you are drawing - which means it will be a second 30-40W heater (keeping that cool enough to let it keep doing its job, is simply not viable). These regulators are in this case under 50% effective.
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@jacotheron a buck converter may make controlling temperature more challenging. in my experience buck converters don't work well with pid tuned temperature control
