Blew a fuse! replacing 7.5A fuse for 10A (Duex5)?

honeycris

I blew the 7.5A fuse on the Duex5 board. From what I can gather, the fuse is for the V_IN itself. I blew it when I was running an 800W heated bed and 2 chamber heaters (250W and 100W) at the same time. The heated bed is wired through the Duet board while the chamber heater is wired through the Duex5 heater input.

I think 7.5A might be too low for what I have going on here. Is there any issue with replacing the 7.5A fuse with a 10 or 15A? The V_IN screw terminal is rated for 25A I believe.

Nurgelrot

@honeycris I think you be better off replacing the fuse with the same size that blew. Then move that 800W bed onto its own external mosfet and power line.

honeycris

@Nurgelrot

I don't think I understand what you mean. Here is a picture of the wiring setup. The red circle is the heated bed and the yellow circle is the chamber heater setup which consists of two separate heating elements that are 250W and 100W.

alankilian

@honeycris I'm confused.

800 + 100 + 250 = 1,150 Watts.

At 12 Volts, that's almost 100 Amps.
At 24 Volts, it's almost 50 Amps.
At 48 Volts, that's almost 25 Amps.

How are you planning on powering this much stuff using a 10 Amp fuse?

Nurgelrot

@honeycris Right. Get your self some external mosfets. Just google bed-heater mosfet or something select a good one (or two) and wire your bed or chamber heater to the mosfet and the mosfet direct to your PSU then wire the Bed out/chamber heat out on the Duet Boards as the signal line to the corresponding mosfet. Get that current off your expensive Duet boards.

https://www.amazon.com/heatbed-mosfet/s?k=heatbed+mosfet.
https://3dprint.wiki/reprap/electronics/heatbed_mosfet

Just the first googles that came up may not be the best sources. Do your research...

mrehorstdmd

@nurgelrot Heaters don't require regulated DC power at all. Why not go all the way and get that current out of the DC power supply by using line powered heaters with SSRs? That will reduce the power supply to something that delivers <200W and doesn't need a cooling fan or a truck to haul it. It will be cheap, small, and quiet.

Nurgelrot

@mrehorstdmd For that 800W bed heater I 100% agree. I'd have that on mains with a SSR. Prob the big chamber heater too. Didn't think of it right a the moment -and I don't really feel great about telling people to go play with high voltage in a forum unless I'm pretty sure I know what they(and myself) are doing.

Phaedrux

@honeycris said in Blew a fuse! replacing 7.5A fuse for 10A (Duex5)?:

I was running an 800W heated bed

Is this actually a DC bed heater, or is it AC powered through SSR? Can you even GET an 800w DC bed heater?

dc42

@honeycris The heater outputs on the DueX are good for 5A each, max 7.5A in total unless you increase the fuse. A 24V 250W chamber heater will draw a little over 10A. A 24V 100W heater will draw a little over 4A. So the 100W one would be OK by itself, but the 250W one isn't.

Use an external mosfet or SSR to drive the chamber heater. Alternatively, if you are already using a SSR to drive the bed heater, you could drive the chamber heater from the Duet bed heater output.

honeycris

@dc42

So would it be safe to replace the Duex5 fuse with a 15A one and run the heaters as I have it set up? Or would that potentially draw too much power for the Duex heater output?

The bed heater is AC powered through an SSR.

I guess I'm confused again. I am currently driving the bed heater with the SSR but I am still using the Duet bed heater output for the bed itself. I have the heated bed screw terminals connected to the SSR input. So how can I use this output for the chamber heaters?

The system is 24V. It's an E3D tool changer. The only things that are different is I'm trying to set up a chamber heating system and there is a liquid cooling system that is also currently being powered from the same power system.

Below is the heating element I'm using. One 250W and the other 100W wired in the same circuit.

https://www.amazon.com/Fdit-Constant-Temperature-Heating-Element/dp/B07JKNKK7J/ref=pd_sbs_3/142-6312925-1470019?pd_rd_w=yqFT0&pf_rd_p=a5925d26-9630-40f3-a011-d858608ac88b&pf_rd_r=WR8TCF09MQXHXVNAXFB0&pd_rd_r=a293fa7e-119d-4317-aacd-727f39a10930&pd_rd_wg=YjRj2&pd_rd_i=B07JKNKK7J&psc=1

Also, the PSU I have is 400W so it seems like I need something beefier, huh.

dc42

@honeycris said in Blew a fuse! replacing 7.5A fuse for 10A (Duex5)?:

I guess I'm confused again. I am currently driving the bed heater with the SSR but I am still using the Duet bed heater output for the bed itself. I have the heated bed screw terminals connected to the SSR input. So how can I use this output for the chamber heaters?

If you are using RepRapFirmware 3 then you can configure any output on the system to drive the bed SSR, for example one of the outputs on the DueX. That will free up the output labelled "Bed heater" for your chamber heaters.

honeycris

@dc42

Got it. And that is because the SSR is controlled by the board but the power from the PSU doesn't run through the board, rather it runs through the SSR?

Sorry for the basic questions. I am learning...

I ordered a more powerful PSU (1000w) and an external MOSFET so once those come in I'm going to re-wire everything and try this out.

Phaedrux

@honeycris said in Blew a fuse! replacing 7.5A fuse for 10A (Duex5)?:

Got it. And that is because the SSR is controlled by the board but the power from the PSU doesn't run through the board, rather it runs through the SSR?

Correct.

@honeycris said in Blew a fuse! replacing 7.5A fuse for 10A (Duex5)?:

Sorry for the basic questions. I am learning...

We all start at zero.