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PostPosted: Mon May 19, 2014 7:12 pm 
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kuraasu wrote:
KLucky13 wrote:
These High resolution picture I found on the link 2stimpy provided

Well, they're not that high-res, but enough for a first look. There is one resistor visible, R7, that seems to be not present on your board. Or is that just an optical illusion?

Good catch, It did not even occur to me... Now I see it too, indeed there is a resistor missing. This is not normal I assume?

That means in 1 order from reprap.me: a broken cork board and a incomplete power expander? Good reputation so far.. The reason I bought it assembled is because I don't know how to build it myself and then I get this.. Well last time I got no support at all about the broken cork board, wish me luck on this one...


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PostPosted: Tue May 27, 2014 9:26 pm 
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After some great support from reprap.me I have now a complete board :-) so this weekend i'll be testing it out for the first time :-)


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PostPosted: Thu May 29, 2014 6:20 pm 
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I've connected everything today and it works great. I'm using the 20v 9A laptop power supply for the heatbed.

Heating up to 50 degrees takes no time at all which is already very nice. Then I tried setting it to 100 °C and everything heats up quite fast until 85 degrees. Then it rises very very slow. 35 minutes in and it's at 90 degrees and it seems that it won't go over that number.

Can I get higher temperatures with a different power supply? Or is the limiting factor the heatbed itself?


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PostPosted: Thu May 29, 2014 7:47 pm 
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Hi Kenny,

KLucky13 wrote:
Can I get higher temperatures with a different power supply? Or is the limiting factor the heatbed itself?

actually both. The heatbed('s resistance) limits the current, and thus the maximum heating power for a given supply voltage.

In order to increase heating power, you need higher voltage. As you can see in this thread, 24 V is used most often, resulting in about 100 to 110 W heating power at room temperature and 80 to 90 W at ca. 90 °C. Since heating power increases with the square of the voltage, 20 V will result in about 70% power compared to those values.

Higher voltages may also be possible, but caution is required. Especially if the original ribbon cable is used due to its limited cross section.


Cheers,
kuraasu


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PostPosted: Thu May 29, 2014 8:03 pm 
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After waiting for a longer time the temperature came up to about 97 °C, it's already nice to begin with. When I come across a better power supply, I can still upgrade :-)

Here are some photo's of the completed upgrade:

Image

Image


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PostPosted: Fri May 30, 2014 7:39 pm 
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Hi Kenny,

I recently finished the upgrade for my bed heating. Perhaps you have read about it some posts earlier in this thread:
http://forum.velleman.eu/viewtopic.php?f=53&t=9598&start=180#p50306
Meanwhile I did some successful prints with ABS. At started with 90C printing on Kapton tape on glass, but often had problems with warping and my transformer got very hot.
The I treated the Kapton with some ABS/Acetone-Slurry, since then I did several prints without treating the tape again. Bed temperature could be lowered to 83C (perhaps lower is possible, did not try yet).

BTW for the first print I used a glass plate with hairspray, as you suggested for PLA prints. But the ABS sticked so much on this that I had to break the object to get it off.

regards

walo


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PostPosted: Fri May 30, 2014 7:49 pm 
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walo wrote:
Hi Kenny,

I recently finished the upgrade for my bed heating. Perhaps you have read about it some posts earlier in this thread:
http://forum.velleman.eu/viewtopic.php?f=53&t=9598&start=180#p50306
Meanwhile I did some successful prints with ABS. At started with 90C printing on Kapton tape on glass, but often had problems with warping and my transformer got very hot.
The I treated the Kapton with some ABS/Acetone-Slurry, since then I did several prints without treating the tape again. Bed temperature could be lowered to 83C (perhaps lower is possible, did not try yet).

BTW for the first print I used a glass plate with hairspray, as you suggested for PLA prints. But the ABS sticked so much on this that I had to break the object to get it off.

regards

walo


What really? ABS + hairspray sticks better then kapton? Nice, did not see that coming :p
I prepared a ikea mirror (the backside of it, and I sanded it) with acetone/ABS slurry. I did not tested it yet. What I did test was printing straight on kapton (sticked to ikea mirror) at 95 degrees. And with a brim, no problems. But I want to be able to print without those brims. To make ABS stick to the printbed it's not that big of a problem then I suspected before I started experimenting with ABS. I do have some other issues like I posted in other topics: I had a jam-up when I was printing for over an hour, the finned/cooled barrel of my E3D v5 hotend became very hot and caused ABS to stick to it inside. I don't know yet what I will do about that, probably a bigger fan or so. And the second problem (see ABS printing/config topic) is when printing small things, the layers tend to curl upwards. I think it is caused by the barrel cooling fan but I'm not sure :-)

Oh and btw, my power supply gets warm, but not hot.. But it really is a very big supply (in volume) almost twice as big as the original supply. Maybe that way it can get rid of the heat easier :-)


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PostPosted: Sat May 31, 2014 10:42 pm 
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KLucky13 wrote:
I had a jam-up when I was printing for over an hour, the finned/cooled barrel of my E3D v5 hotend became very hot and caused ABS to stick to it inside. I don't know yet what I will do about that, probably a bigger fan or so.

Are you sure that the fan didn't stop for a while for some reason? Today I did a larger print, an Eifel tower (not so big as yours, but still challenging ;) ) and I checked the temperature after 4 hours of printing at 230C. It was still at 39C between the lowest two fins, which is the usual temperature. Weeks ago I was testing how much cooling is needed there and I was running the fan with down to 6Volts, resulting the temperature being still <50C. So the cooling doen't seem to be a sensible point there as long as the fan is running a little bit.
Quote:
Oh and btw, my power supply gets warm, but not hot.. But it really is a very big supply (in volume) almost twice as big as the original supply. Maybe that way it can get rid of the heat easier :-)
Oh, good. My transformer is designed for a duty cycle of 50% only, this is why I avoid heating the bed to 90C. The heating would be on all the time.

regards

walo


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PostPosted: Sun Jun 01, 2014 12:17 pm 
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Since the fan is so loud I would have noticed it when it would have stopped :p So I don't think so. Yeah I really don't know why it overheated... I have no temperature sensor to test it but I burned my fingers on it half way up, so it must have been very hot at that time. I had no issues with this before.. But I notice you print at 230 degrees instead of 245, I don't think this will make the major difference but I could try it..


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PostPosted: Wed Jun 18, 2014 10:13 pm 
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thev wrote:
could the velleman 15V replaced with a strong 12V ATX Power Supply?


You mean the -12V and the +12V combined from such a PS.


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PostPosted: Wed Jul 02, 2014 10:32 am 
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Hello

I had the same problem with low temp and it took forever to reach 60 deg.

Now I have bought and mounted a silicone heatpad from http://www.keenovo.com/products/silicone-heater.html

I must say its fantastic! 22 -> 110 deg in less than 2 min. I bought it on ebay and a SSR to go with it. The relay 12v DC to 220v AC.

This is the best upgrade Ive made to my K8200 :D


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PostPosted: Thu Jul 10, 2014 1:44 pm 
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I find a simply solution using a 12V 30A Relay. Then I convert the heatbed output of the controller from PWM to Digital 0/1.
Untill now it works fine and I printed for 12hours at 110°C without problems. Using a 12V 150W power supply for both controller and hotbed.
It is not clear why Velleman decided to have the heatbed output in PWM instead of a common 0/1 output.
Is there some reason?
The original Marlin Firmware is built to work in "bang-bang" mode (ON / OFF) for the hot bed.
Inside the firmware into the pins.h file , all the other board have this code:
#define HEATER_0_PIN 10 //E0
#define HEATER_1_PIN 12 //E1
#define HEATER_2_PIN -1
#define HEATER_BED_PIN 6 //BED

Velleman converted in
#define HEATER_0_PIN 10 //E0
#define HEATER_1_PIN 12 //E1
#define HEATER_2_PIN 6 //BED

So the hotbed works like a thirth extruder, using PWM output controlled with a PID.
And this causes the need to built complex electronics schemas instead of using a normal relay.


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PostPosted: Wed Jul 16, 2014 2:45 pm 
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I just finished installing a 24VDC power supply to heat the heat bed and did not use any additional electronics. Look at the controller schematic and you will see that the MOSFET for the heat bed is used to sink current. I simply connected the +24 volt supply directly to the heat bed (through the ribbon cable ) and made the new power supply share a common ground with the controller. When the heat bed MOSFET turns on it completes the path to ground. No other modification is needed. Very simple and is working great!


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PostPosted: Fri Jul 18, 2014 8:04 am 
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Just to avoid to destroid my controller, did you connect the parts as the following schema? I did in Italian but
"PIATTO" means PLATE and "ALIMENTATORE" means "power supply"
Image


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PostPosted: Fri Jul 18, 2014 9:36 pm 
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Mikeb69 wrote:
Just to avoid to destroid my controller, did you connect the parts as the following schema? I did in Italian but
"PIATTO" means PLATE and "ALIMENTATORE" means "power supply"
Image


You understand perfectly what I did. It works!!!!

There is absolutely no reason to add additional circuitry to add in the second 24 volt supply. I have been working in electronics for many years and this will work without any issues.

Tim


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