SSR for controller

Hello, I need to select an SSR for a RADDS 1.3. The SSR will be connected to the D08 port on the controller. I found a decent SSR: [fr.farnell.com] however, I have been told that this won't work when connected to the D08 port because of AC voltage at the port or PWM or something like that.

Can you please tell me whether this will in fact work or NOT work. If it will work then just say that it will, and if not then please explain to me why and what I can do to make it work.

Thank you

---

The (getting better) Noob

Zapadee zoopidee.

That's an AC SSR. What kind of heated bed are you planning to use, how many watts, with what power supply?

Also, before anything else, please read through this thread: [forums.reprap.org]

and take a look at various other threads in the Safety forum.

Edited 1 time(s). Last edit at 04/21/2015 01:32PM by AndrewBCN.

The heated bed I am using will be a silicone heat mat running directly from 230V mains supply. 2400W at 20 deg-C and 1700W at 150 deg-C.

I am using thick wires so it shouldn't be a problem.

---

The (getting better) Noob

Zapadee zoopidee.

I should also probably mention that I am not using a RADDS but an Azteeg x3 pro.

---

The (getting better) Noob

Zapadee zoopidee.

You are seriously planning to use a 2000W mains AC powered heater under most of your 3D printer mechanics? I honestly hope you fully understand the issues associated with this as well as the safety risks involved ( including risk of death).

My only advice in this case would be: don't. Normal MK2B 100W PCB heatbeds are already dangerous enough as they are.

I understand that I will need to include many safety features in order to avoid certain death. The reason the bed takes up so much power is because it is 700x700mm and needs to reach as high as 150 deg-C. It's the only way for the application I am using it in.

---

The (getting better) Noob

Zapadee zoopidee.

Hmmm, I see you have already gone through this:

[forums.reprap.org]

My recommendation, if you intend to go ahead with this, is to get the help from a certified, qualified electrical technician. It would be irresponsible from me or anybody else in this forum to make any other suggestion at this point.

Okay thank you very much.

---

The (getting better) Noob

Zapadee zoopidee.

Quote
AndrewBCN
It would be irresponsible from me or anybody else in this forum to make any other suggestion at this point.

Andrew, I suggest you speak for yourself, you shouldn't presume to speak for others.

3DPrintingNoob, I recall that you already indicated in another thread that this is a collaborative project in a university or similar teaching environment, and that the design will be checked by a qualified electrician.

I agree that for that size bed, AC mains power is the only practical option. I also agree that around 2KW is around the power level you will need to heat a 700x700mm bed to 150C in a reasonable time - but do you really need as high as 150C?

That SSR should do the job quite adequately. However, it will dissipate around 15W, so you need to pay attention to keeping it cool enough. For my large delta printer with a mains-voltage heated bed, I fitted an aluminium tray to the bottom of the printer, and mounted the SSR and the printer PSU on that so that the tray helps to remove the heat.

You will need to take account of at least the following safety issues in the design, in order to make it safe enough for your electrician to approve it. You should present the design to him/her before you commence construction.

1. All the AC main connections need to be adequately insulated and protected from prying fingers.

2. The cables connecting the moving bed to the SSR and mains supply need to be highly flexible, and rated at 10A @ 240VAC or more. The sort of cable used for multimeter test leads is widely available and is one possible choice. Curly mains leads may be another possibility.

3. Those cables need strain relief at both ends.

4. The underside of the bed needs to be thermally insulated so that the flexible cables cannot come into contact with a hot surface.

5. Feed the mains supply through an RCD to give additional protection against electric shock.

6. Implement protective grounding for the bed and all other metal parts of the printer.

7. With that amount of heating power, I suggest a thermal cutout to protect against uncontrolled heating due to software failure etc. The sort of thermal cutout used in microwave ovens may be suitable, and they are widely available.

8. Make sure that all the AC mains wiring is accessible when covers are removed, so that it can easily be inspected by your electrician and for subsequent safety checks.

9. Any 3D printer is a fire risk, and IMO should not be left unattended without at least a smoke alarm and someone able to respond quickly with the right sort of fire extinguisher. But yours will be more of a risk than most, because of the large heating power. So you need to be able to turn the power off easily from a safe distance, and have suitable fire extinguishers on hand.

This is only a list of the most obvious points. A proper hazard analysis can't be done until there is a design.

Edited 1 time(s). Last edit at 04/21/2015 04:04PM by dc42.

---

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].

Quote
dc42

Quote
AndrewBCN
It would be irresponsible from me or anybody else in this forum to make any other suggestion at this point.

Andrew, I suggest you speak for yourself, you shouldn't presume to speak for others.

...

I never presume to speak for others, but it is common sense to not give any irresponsible advice on a forum regarding any technical issue where there is a clear indication of risk of death or other serious harm to the person asking for advice or other innocent bystanders - which is definitely the case here.

Similarly, I wouldn't dispense any advice on any forum regarding the manufacturing of high voltage devices, rockets, weapons of any kind, etc... Obviously, feel free to post whatever your conscience dictates you can.

The only responsible advice in this thread is to refer the OP to a qualified, certified electrical technician, which I did and you did too. The rest is irresponsible "free" advice, because it will be up to a qualified, certified electrical technician, acting as a professional, to determine in situ all the technical details and requirements to insure the safety risks are minimized, and she/he will take responsibility for it.

now the main question.... Do i need an SSR to control the wood burning stove under my heat bed? It puts out around 20K BTU....... 200C should be within reach...

---

My Personal Blog. Build blog.
[engineerd3d.ddns.net]

Modicum V1 sold on e-bay user jaguarking11

Quote
jaguarking11
now the main question.... Do i need an SSR to control the wood burning stove under my heat bed? It puts out around 20K BTU....... 200C should be within reach...

Yes, Solid State Relays are good for wood or coal, but obviously not suitable for liquid (e.g. kerosene, petrol) or gas (propane, oxy-acetylene) heated beds.

Quote
dc42

2. The cables connecting the moving bed to the SSR and mains supply need to be highly flexible, and rated at 10A @ 240VAC or more. The sort of cable used for multimeter test leads is widely available and is one possible choice. Curly mains leads may be another possibility.

Actually, the OP never said that the bed moved. And I'd suggest that moving a 700x700 bed would be a extraordinarily problematic.

dc42

Thanks for all that info, I have a question. Firstly, I read some forums regarding the SSR connected to the board, now my SSR can handle 50/60Hz as it will be connected to mains supply which will have the same frequency. However, the PWM was mentioned to have frequencies as high as 60kHz, so is this not too high for the SSR to handle?

Andrew

Don't worry about it, it will be my responsibility, or... the electrical technician's responsibility ;P

Frank

dc42 has been helping me with my project a lot so he has lots of info regarding it, and so he knows already that the bed will be moving vertically. I don't think it will really be a problem as the bed will be moving extremely slowly anyway. Also, we will be using three powerful motors to do the job.

---

The (getting better) Noob

Zapadee zoopidee.

A zero crossing AC SSR can cope with very slow PWM e.g. 1Hz or lower. Heated beds are typically driven in bang-bang mode and so don't use PWM.

---

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].

I forgot to answer your question, dc42. Yes, I need it to be as high as 150 deg-C because it will be operating at 130 deg-C often. Furthermore, it was required to add future sustainability to it in order to use new materials in the future (which may need higher bed temperatures).

---

The (getting better) Noob

Zapadee zoopidee.

So technically, I shouldn't have a problem with the SSR working with the Azteeg x3 pro then? Are you basing these statements on experience or theory?

---

The (getting better) Noob

Zapadee zoopidee.

I am basing these statements on theory, as an engineer with a lot of electronics experience behind me. I use an AC mains SSR to power the heated bed of one of my printers, but I drive it in bang-bang mode, which is the default for the firmware I use and quite adequate for that printer. Slow PWM has been used to control heaters via triacs (a triac is the guts of many AC SSRs) for more than 40 years, it's called burst-fire control.

I don't know the Azteeg X3 pro. Whether PID is used for the bed and what its frequency is will depend on what firmware you run on that board. Someone mentioned on one of these forums that Marlin uses (or can use) slow PWM for the bed, but I don't use Marlin so I haven't looked into this.

Edited 1 time(s). Last edit at 04/22/2015 03:43AM by dc42.

---

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].

I plan to not use PID for the heatbed, as bang-bang mode should suffice. Okay, thank you dc42, helpful as always. They should really make a system where you can thumb up or increase the rep of a user.

---

The (getting better) Noob

Zapadee zoopidee.

Quick question, does the SSR I posted in this thread have an optocoupler within it? If not, then can someone point me towards an SSR with the same capabilities plus includes an optocoupler integrated.

This one: [fr.farnell.com]

Thank you

---

The (getting better) Noob

Zapadee zoopidee.

Quote
3DPrintingNoob
Quick question, does the SSR I posted in this thread have an optocoupler within it? If not, then can someone point me towards an SSR with the same capabilities plus includes an optocoupler integrated.

This one: [fr.farnell.com]

Thank you

Yes (and so does every other SSR I've come across), the datasheet shows it.

---

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].

If you look at it's datasheet, you'll see the attached image. The two sides of the circuit are separated by an phototriac which would serve as the optocoupler, isolating the AC mains voltage from the DC printer voltage.

Oh my, I looked at the datasheet yet missed the diagram by a mile. Thank you.

---

The (getting better) Noob

Zapadee zoopidee.