Heatbed to 24V Question

[critical_limit]

Hi All,

my Max V2 is still on Order, not shipped yet and I hope it will not take years to have it shipped to Germany.

I want to upgrade my Heatbed to 24V from the beginning. So I have a question:

Is it just to put on the 24V to the Heatbedrail of the Rambo and run the PID-Setting Procedure?
Or do I have to tell the Board that the Heatbed-Rail is on 24V? Any changes to be made to the Firmware/Software?

Hope it will help changing to 24V to speedup the heating. I´ve read that the original Setup needs to go to 90°C more than 30 mins.

Any comments are highly appreciated.

Cheers from Berlin-Germany
Dirk

[mhackney]

Dirk, firstly congrats to Germany on a great World Cup win!

I run my Onyx directly from 24V through the RAMBo with no problems (over 18 months now). However, I and most here recommend isolating it through an SSR. That allows you to keep 12V on the RAMBo and 24V through the SSR to power the Onyx.

In either case, there is no firmware or other configuration to make. Simply do the PID tuning. Mine heats to 60°C in about 45 seconds with a 2mm aluminum heat dissipator plate. Takes a little over a minute to get to 80°C. No waiting!

cheers,
Michael

[critical_limit]

Dirk, firstly congrats to Germany on a great World Cup win!

Hi Michael.

Thanx for the quick reply.
Have you seen the final? Great game! And after whole Germany was on Party! I went to bed at 4 in the Morning after a lot of beers

Ok, so I will setup my max V2 to 24V heatbed. But I don´t want to use a SSR. I´ve read that Rambo 1.2 can handle up to 15A over the Headbed-Rail.
My 24V Powersupply only delivers 10A, so it will be ok for the Rambo to handle it.

Now I´m waiting and waiting and waiting........

cheers
Dirk

[mhackney]

Yes, my family watched ALL of the World Cup games, we're big soccer fans. My daughter is studying at Hiedelberg and was able to enjoy watching the games with her friends.

10A should be fine for RAMBo to handle.

cheers,
Michael

[Jimustanguitar]

Hey Michael, did you have any trouble with the LED on the heated bed? Is there any need to change the resistor so that you don't overload the LED?

[mhackney]

I didn't install it. It didn't do anything for me!

[Hansen]

Ok, so I will setup my max V2 to 24V heatbed. But I don´t want to use a SSR. I´ve read that Rambo 1.2 can handle up to 15A over the Headbed-Rail.
My 24V Powersupply only delivers 10A, so it will be ok for the Rambo to handle it.

Mmmm, you should remember the good old Ohm's law (V = R * I) The Onyx has an internal resistance of about 1 ohm. This means that if you apply 24V to it, it will draw 24A from the power supply. If this is the case, the 15A fuse on RAMBO will blow. However, it seems your power supply is rated for 10A only, so your power supply will be overloaded by the current to the Onyx, and it will not be able to deliver that kind of current.

So... depending on the topology of your power supply, it will either shut down entirely, decrease the voltage (and maybe turn unstable) to about 15V or BURN .

You can not connect the Onyx to a 24V power supply, and have 24V AND 10A at the same time. In other words it is not possible to run the Onyx at 24V directly from RAMBO.

What I do not understand is... some people state that they ARE actually using 24V with the Onyx directly through the RAMBO MOSFET (and through a 15A fuse)... are you sure that you are actually getting what you think?

[critical_limit]

Hi Hansen,

you are absolutly right with your calculations. If you let it uncontrolled it will draw 24A at 24V.

But my 24V-Source is constant current limiting. It will hold 24V and limiting to 10Amps max constantly.
Should work I guess.

But whats with the LED?? Is a bigger resistor needed? Don´t know which Resistor and LED is used in the Kit.
But if I use a 4,7k Resistor it should be ok at 24V ??

Thanx
Dirk

[Hansen]

Hi Dirk

But my 24V-Source is constant current limiting. It will hold 24V and limiting to 10Amps max constantly.
Should work I guess.

If your power supply really is built for permantly limiting current, then that should be OK. The thing is, though, the only way the power supply can limit the current to 10A is by decreasing the voltage. So... you will not get 24V but somewhere in the range of 15-17V (the resistance of the Onyx might increase, when it gets hot).

All this doesn't really matter as long as you don't damage anything, and the Onyx gets hot. My worry is primarily that you will destroy your power supply, if it is not built for limiting the current permanently. The RAMBO should protect itself from over-currents (the fuse will blow).

But whats with the LED?? Is a bigger resistor needed? Don´t know which Resistor and LED is used in the Kit.
But if I use a 4,7k Resistor it should be ok at 24V ??

As far as I can see from other threads in this forum, the stock resistor actually is 4.7k. The LED will be fine with this resistor at both 12V and 24V (which your PSU will not provide anyway).

BR
Hansen

[Eaglezsoar]

Hi Hansen,

you are absolutly right with your calculations. If you let it uncontrolled it will draw 24A at 24V.

But my 24V-Source is constant current limiting. It will hold 24V and limiting to 10Amps max constantly.
Should work I guess.

But whats with the LED?? Is a bigger resistor needed? Don´t know which Resistor and LED is used in the Kit.
But if I use a 4,7k Resistor it should be ok at 24V ??

Thanx
Dirk

http://ledcalculator.net/ has a resistor calculator for leds.
For one led you can put in 1.2 voltage drop across led
current through led would be 15ma (they can handle more than 15ma but I don't run them at their limits.)
The resistor value calculated should be close, the actual value can vary by up to 20%.

[PowderLab Drew]

Hi Dirk

But my 24V-Source is constant current limiting. It will hold 24V and limiting to 10Amps max constantly.
Should work I guess.

If your power supply really is built for permantly limiting current, then that should be OK. The thing is, though, the only way the power supply can limit the current to 10A is by decreasing the voltage. So... you will not get 24V but somewhere in the range of 15-17V (the resistance of the Onyx might increase, when it gets hot).

All this doesn't really matter as long as you don't damage anything, and the Onyx gets hot. My worry is primarily that you will destroy your power supply, if it is not built for limiting the current permanently. The RAMBO should protect itself from over-currents (the fuse will blow).

But whats with the LED?? Is a bigger resistor needed? Don´t know which Resistor and LED is used in the Kit.
But if I use a 4,7k Resistor it should be ok at 24V ??

As far as I can see from other threads in this forum, the stock resistor actually is 4.7k. The LED will be fine with this resistor at both 12V and 24V (which your PSU will not provide anyway).

BR
Hansen

Sorry to jack your thread, but I too have been thinking about going with a 24 volt PSU. If I ran an SSR and just used the trigger from the Rambo to turn it on, would that actually send the full 24 volts to the Onyx?

Thanks,
Drew

[critical_limit]

Sorry to jack your thread, but I too have been thinking about going with a 24 volt PSU. If I ran an SSR and just used the trigger from the Rambo to turn it on, would that actually send the full 24 volts to the Onyx?

Hi Drew,

yes it will. But as mentioned, your PSU needs to be able to delivered min 24A steady.

[imagebuff]

Is there any way to run 24v to the Onyx while limiting current to under 15A? Like others I'm evaluating picking up a 24v / 15A PS for what appears to be quite an improvement in bed heating time. Someone mentioned using an SSR. What is an SSR?

Thanks
Chris

[Eaglezsoar]

Is there any way to run 24v to the Onyx while limiting current to under 15A? Like others I'm evaluating picking up a 24v / 15A PS for what appears to be quite an improvement in bed heating time. Someone mentioned using an SSR. What is an SSR?

Thanks
Chris

An SSR is a Solid State Relay which come in AC in and AC out on the Output or DC in and DC out on the Output.

You would need the DC - DC output type. These links I found on Amazon.com Always remember that the SSR will need a heatsink.

http://www.amazon.com/Single-Phase-Soli ... =DC-DC+ssr
http://www.amazon.com/Aluminum-Solid-St ... r+heatsink

The output for the bed from the rambo goes to the bottom of the SSR, observing polarity.
The output positive side from the 24VDC Supply goes to the right top of SSR, the Left top of SSR connects to the positive side of the heatbed.
The negative side from the 24VDC power supply would connect to the negative side of the heatbed.

When the heatbed needs to turn on that signal goes to the input of the SSR and turns on the SSR allowing the 24VDC to go to the Heatbed.
I hope that this all makes sense. Also the resistor on the heatbed for heatbed LED should be reduced as mentioned in this topic.

[Jimustanguitar]

I hooked up a 24v 20A supply this evening, and wow. I can't believe that I didn't do this sooner. I went from a 15 minute warm up time to only 2 minutes. It will be much more convenient to print now.

I decided to connect directly to the Rambo like Michael Hackney did and not use an SSR. No trouble to report. I do plan to add a second cooling fan on the board though.

[Eaglezsoar]

I hooked up a 24v 20A supply this evening, and wow. I can't believe that I didn't do this sooner. I went from a 15 minute warm up time to only 2 minutes. It will be much more convenient to print now.

I decided to connect directly to the Rambo like Michael Hackney did and not use an SSR. No trouble to report. I do plan to add a second cooling fan on the board though.

Did you have to change the automotive type fuse to a higher value one?

[Jimustanguitar]

Did you have to change the automotive type fuse to a higher value one?

Not yet I got it hooked up for the first test last night, so I've only heated it up twice. This weekend will tell the tale of whether or not it will work continuously.

[CaptInane]

What PSU are you using for your 24V? Like several others, I'm also considering doing the same thing. My heat bed will never get above 103C and takes a decent chunk of time to get to 90C. I originally got one of the Rev 2 beds with my kit which turned out to be some what defective (it would get to about 75-80C in 20-30 minutes). I received the Rev 5 as a replacement. It works a whole lot better but the heat up time is still 15-20 minutes or so to get it up to 85C.

Has anyone looked into putting two power supplies in series to 24V? I've looked into it some, but I've always been a bit jumpy about doing much to a PSU. It's probably from having that power cord blow up in my hand when I was about 12. I never let my brother-in-law cable the power in any of my PCs again, that's for sure. Even if I did, I'd certainly let him plug it in.

Jimustanguitar, how's your still working with the 15A fuse? All this really makes me wish I would have paid a lot more attention in my Energy Conversion class, or at least not be so hungover every time...

[Renha]

If I want to use both 12v and 24v power supplies without SSR, 24v for heated bed and 12v for anything else, do I need to connect their black wires together?

Another question, am I need to use SSR with Azteeg X3 Pro and 600w 24v power supply?

[Jimustanguitar]

If I want to use both 12v and 24v power supplies without SSR, 24v for heated bed and 12v for anything else, do I need to connect their black wires together?

Another question, am I need to use SSR with Azteeg X3 Pro and 600w 24v power supply?

I'm scheming to do something similar to this. I want to run the printer on 12v when I'm mobile, and I want to run it on 24v when I'm at home with my power supply. My plan was to use two automotive relays with their trigger coils in series so that when 24v is applied, it flips the 12v output from the Rambo to trigger the SSR. I have the wiring diagram in my head, but I'll have to draw it out to share.

The NC state of the relay would pass the 12v from the Rambo directly to the Onyx, and when 24 is present, one relay would divert that power to the SSR trigger and the other relay would connect the SSR's output to the bed. I plan to put all of the grounds together.

The plan is to make the presence of 24v cause all of the switching to happen automatically. No 24v and it would operate "stock" on 12v. I'll let you know how it works!

[CaptInane]

What are you using for the 24V supply? I have 2 ATX PSUs running in series. I'm currently using a 500 or 600W to run everything else, then I'm feeding its +5V to the ground of a second supply. So, theoretically my input voltage is 17V, but I'm only seeing 15.1V across the bed.

I've tried running the 24V but when it gets to a set temp, say 110C, I can hear relays in the secondary PSU clicking like crazy as the head bed turns on and off. All that clicking just makes me think about how soon I'll be replacing a relay.

[Jimustanguitar]

What are you using for the 24V supply?

I've got a more industrial style 24v supply that's rated at 20A continuous. I'll have to look at the model and manufacturer...

[Demolishun]

Old thread, but figured I would chime in:
http://forum.seemecnc.com/viewtopic.php?f=55&t=5406

It covers just about everything on 24VDC conversions for the heated bed.

[Eric]

Something I wrote on another thread, but it applies here:

Fuses are safety devices, not precision instruments. For massive current loads, usually caused by short circuits, they'll blow almost instantly. For more reasonable overloads, they take time to blow. 110% rating would likely take hours to blow. 150% rating will take a number of minutes. 200% is still a number of seconds. I'm generalizing here, real numbers will vary by fuse line. Ambient temperature is a factor (ratings are at 25C, colder increases rating, warmer decreases). Active cooling (fan blowing on board) may increase the rating.

So if your bed reaches the target temperature before the fuse blows, you're "getting away" with using a 15A fuse, at least so far. Once the bed is at temperature, the overload is effectively gone because the software throttles the power-over-time to what's required to maintain the temperature.