Questions on SSR and PSU

Hi,

Firstly I couldn't find a more suitable subsection for these questions, if there is please let me know / or if admin could move the topic.

I'm not very good with electronics especially in this kind of setup (3D printing and it's components)
I'm building a CoreXY printer and I'm currently thinking of running a heated bed of the mains power (230v)
To do this I'd need a SSR.
The silicon heat mat I'm thinking of running is specced 500W@220v, this would equal ~ 2,3amp (right?)

So a SSR rated to 10Amp should be more then enough?

Secondly how can I guesstimate how big (or small) of a PSU I need when I will not run the heatbed of it?
I will run it on a 12v, would a 10A be sufficient? Or would even 5A do?

And lastly, how do I know how much inbound Amp a 12v 10A output PSU draws?

Thanks in advance.
BR//Amoniak

2.3A is correct, so a 10A SSR should suffice and it should not need a heatsink. I use a SSR-10DA to power the 230V 350W bed heater on my Kossel (see link in my signature). However, the SSR-25DA costs about the same as the SSR-10DA, so you could use that one too.

Pay attention to the following safety factors:

* Use highly-flexible cable to connect the moving bed and a fixed terminal block. The cables on silicone heaters are usually very flexible, but may be too short. The type of wire used for multimeter test leads wold be ideal and is readily available.
* Use strain relief (i.e. a cable clamp) at both ends of the cable, to guard against it fracturing where it enters the terminal block (or the heater).
* Connect the metal parts of the printer frame and the metal bed plate (if you have one) to mains ground.
* Make sure that no mains wiring is accessible to prying fingers.
* For added safety, power the printer via a RCD or GFCI (same thing, different name).

Regarding the PSU capacity, at 12V the calculation is something like this:

* Hot end heater current: 3.4A per 40W hot end heater, or 2.5A per 30W hot end heater
* Stepper motors: allow half the the current that you plan to run each stepper at (e.g. 4 steppers set to 1A each = 2A)
* Fans: allow 0.25A each (small fans will take less than this)
* Electronics: 0.2A

So a 10A PSU should be sufficient for a single-extrusion printer, but may be marginal or insufficient for dual extrusion.

I suggest you consider using 24V power instead, assuming you will be using 24V-capable electronics. This will help you get the maximum speed from your printer, especially if you are using 0.9deg/step motors.
.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for your answer.

Think I'll go ahead with the SSR-10DA. Don't see the point of going 25 which is then more then 10 times the necessary amps.
Would it be a good idea to put a separate fuse for the heat mat?
I'm thinking of having both separate fuse (2.5amp) and power switch for it.

Good safety tips as well. I'm most definitely thinking about these aspect when building my printer.

And I'm going single extruder so then 12v 10amp will do fine.

To be quite honest I haven't understood the benefit of going 24v vs 12v. Especially if you power your heat bed off mains.
Is there really such a difference? What stepper driver would you use for a 24v 0,9 deg/step setup?

Quote
Amoniak
Would it be a good idea to put a separate fuse for the heat mat?
I'm thinking of having both separate fuse (2.5amp) and power switch for it.

I don't. My delta printer uses an IEC mains inlet + switch + 3.15A slow-blow fuse to feed power to both the 350W bed heater and the 24V 5A PSU.

Quote
Amoniak
To be quite honest I haven't understood the benefit of going 24v vs 12v. Especially if you power your heat bed off mains.
Is there really such a difference? What stepper driver would you use for a 24v 0,9 deg/step setup?

Apart from making it easier to power and switch a large bed heater (which is not relevant when using a mains-powered heater), using 24V power instead of 12V means that the stepper drivers can maintain current, and therefore motor torque, up to more than twice the speed as with 12V. One some printers, the travel speed you can achieve will be limited by stepper motor toque at high speed, especially if you use 0.9deg/step motors (which generate around twice the back emf at a given speed, and need twice the drive frequency) and a 12V supply. This was very noticeable on my delta printer.

All the usual stepper drivers can run form 24V, but some 3D printer electronics boards are 12V only, e.g. most RAMPS boards.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].