Dear All,
My ceramic heater is dead, which one should I get as replacement? I get a lot of information from reprap and the internet but a couple of things get confusing between reads.
Quick Background:
Before I killed my heater, I was preparing to heat up to 230 to do first test of extruding ABS. I had already done some heating before without filament and it worked fine but it was not on for long. Our fans were slowing the heating process a bit so I but kapton tape to protect the block from wind, this could have reduced the heat disipation and help increase the temp faster, but could it have also killed the ceramic heater? I don't know what was rated at but from the looks of it could have been a 8w heater.
Also notice that when I reached the temperature and extruded ABS was coming out very slowly. Then, as soon as I hit the home button for the steppers to move to reposition the hotend, the PSU shuts down (Ouch!). Turn off and on again, reach the temp and try again, same thing, PSU shuts down. I knew I should not keep going but then I decided to test the heater alone while waiting for a friend to lend me another PSU. Before he arrived the heater reached 200 and then down hill from there to a silent death.
Considerations:
I am using a SainSmart Megatronics 2.0 board which has 4 MOSFETs (25A) according to the datasheet. It is running the heater at 12v with a 16AGW cable. I do not have a heatbed connected so the amps of a 450ATX (12V - 16A) should be sufficient for heater, steppers, fans and some to spare on a 20x4 LCD. Right? PSU's are not hard to come by, this one might be just too old or something else.
Heater Availability:
I could just get the ones that I see on eBayEbay ceramic heater reprap, those that say for reprap from China, but they might take too long to reach. Those look exactly like the one in the hotend and most of them are: 8w at 4.7ohms.
Looking at the ones I have available in my vicinity I see:
1w, 5w, 10w, 20w and 25w.
Most of them have 4,7 ohms, 5.6 ohms, 6.8 ohms, and 10ohms.
Situation:
I get into a lengthy and often heated discussion with some friends (engineers) about what heater to get at which resistance and wattage. I want to buy a new heater to try the difference but one of my friends thinks that we should do more research to avoid damaging the board. As much as I hate to say it, he is right and it is a wise and safe choice. So, in order to humour him, using a different PSU what should I consider in terms of heater choice to give the board a proper working chance?
Ohm's Law:
I am trying to understand and sometimes I think I do until I get confused by reading things pointing in different directions which adds to the turbulence of our first build.
I am not going to explain Ohm's Law because it is explained widely on the web and quite frankly I might just add more confusion to others. This formula wheel seems to be helpful and clear enough for me. (http://diyaudioprojects.com/Technical/Ohms-Law/Ohms-Law-Formula-Wheel.png)
Quick questions for the knowledge intensive contributors.
True or false? Ohm's Law helps me calculate which resistance (ohms) to use to maintain a constant feed of amps though my fixed 12v line.
True or false? If I use more amps, does the hotend heats up quicker...
True or false? ...and so will other things like my board/MOSFET/PSU.
True or false? When I multiply the amps times the volts I get the output power in watts.
Wattage and resistance in heaters:
What is the relation of this power to the wattage of a heater? Heating resistors have a power spec in watts and a resistance in ohms (i.e. 20w 10ohms). I am told that the wattage on the heaters is the output that it can be capable of giving as heat, which is concurrent with what is found on this forum about heat dissipation (referenced further down). In accordance with ohm's law, if the ohms on a resistor is lower more amps can be drawn with the same amount of volts. However, in one post I see an inverse claim where the author contrasts the behaviour of a resistor with that of a transistor. (reprap forum) "...As the resistance decreases, more power is radiated from the transistor (I assume that's what you're using?), and less from the resistor". To try to understand this for a resistor I have to think about passing more and more amps through a thin cable. The cable will offer resistance and also heat, right? If the statement is true I would be better getting a:
- 10ohms heater which would allow 1.2amps at 12volts capable of producing ~14watts.
On the same topic I also see a reference to ohms law and the following statement "...the power dissipation (heat production) of a resistor goes UP as the resistance goes down FOR A CONSTANT VOLTAGE." This is more in line with what I was given to believe initially by Ohm's Law. So if this is right, I should get a:
- 4.7ohms heater that can pass 2.55amps at 12volts producing ~31watts.
The 31w are more than the 14w, therefore the second statement seems to be 'truer'. Answering which one is it, would only answer part of my dilemma. The rated wattage on the heater, what does it mean? In the two examples above, either 10ohms or 4.7ohms, will output more than 10w. So I should get a 20w heater, right?
I find this comment about a hotend design with a glass nozzle (at reprap.org) "...I also went to get some more 1W resistors. This time I got 3.3 Ohm resistors so that I could use 2 in series and have the heater leads come out the same side of the block." What are the benefits of using a couple of 1w heaters? I can't assume he is using 12v but it makes me think that if I did that, it will be equal to passing ~44w through a heater that is rated at 1w. Not to mention the almost 7amps for two of them. So again what does it mean?
More quick questions for the knowledge intensive contributors of this forum:
If the heater says 1w:
True or false? Will it produce a maximum of 1w of heat?
True or false? Will it die if more than 1w goes through it?, or
True or false? Will it produce what the volts*amps passing through it give?
True or false? Is it a rating of how much heat it can dissipate?
True or false? Does the size mean it can dissipate more heat?
True or false? If it is attached to the aluminium heating block does it increase the heat dissipation?
I have also seen 40w heating cartridges which seem like are just covered in aluminium to increase heat conductivity to the block and thus dissipation. Makes me think about adding thermal compound or thermal grease which I commonly use on my CPU heat sink, to increase conductivity on the block and increase the wattage/heat up quicker.
But before this...I need to get a new heater.
My ceramic heater is dead, which one should I get as replacement? I get a lot of information from reprap and the internet but a couple of things get confusing between reads.
Quick Background:
Before I killed my heater, I was preparing to heat up to 230 to do first test of extruding ABS. I had already done some heating before without filament and it worked fine but it was not on for long. Our fans were slowing the heating process a bit so I but kapton tape to protect the block from wind, this could have reduced the heat disipation and help increase the temp faster, but could it have also killed the ceramic heater? I don't know what was rated at but from the looks of it could have been a 8w heater.
Also notice that when I reached the temperature and extruded ABS was coming out very slowly. Then, as soon as I hit the home button for the steppers to move to reposition the hotend, the PSU shuts down (Ouch!). Turn off and on again, reach the temp and try again, same thing, PSU shuts down. I knew I should not keep going but then I decided to test the heater alone while waiting for a friend to lend me another PSU. Before he arrived the heater reached 200 and then down hill from there to a silent death.
Considerations:
I am using a SainSmart Megatronics 2.0 board which has 4 MOSFETs (25A) according to the datasheet. It is running the heater at 12v with a 16AGW cable. I do not have a heatbed connected so the amps of a 450ATX (12V - 16A) should be sufficient for heater, steppers, fans and some to spare on a 20x4 LCD. Right? PSU's are not hard to come by, this one might be just too old or something else.
Heater Availability:
I could just get the ones that I see on eBayEbay ceramic heater reprap, those that say for reprap from China, but they might take too long to reach. Those look exactly like the one in the hotend and most of them are: 8w at 4.7ohms.
Looking at the ones I have available in my vicinity I see:
1w, 5w, 10w, 20w and 25w.
Most of them have 4,7 ohms, 5.6 ohms, 6.8 ohms, and 10ohms.
Situation:
I get into a lengthy and often heated discussion with some friends (engineers) about what heater to get at which resistance and wattage. I want to buy a new heater to try the difference but one of my friends thinks that we should do more research to avoid damaging the board. As much as I hate to say it, he is right and it is a wise and safe choice. So, in order to humour him, using a different PSU what should I consider in terms of heater choice to give the board a proper working chance?
Ohm's Law:
I am trying to understand and sometimes I think I do until I get confused by reading things pointing in different directions which adds to the turbulence of our first build.
I am not going to explain Ohm's Law because it is explained widely on the web and quite frankly I might just add more confusion to others. This formula wheel seems to be helpful and clear enough for me. (http://diyaudioprojects.com/Technical/Ohms-Law/Ohms-Law-Formula-Wheel.png)
Quick questions for the knowledge intensive contributors.
True or false? Ohm's Law helps me calculate which resistance (ohms) to use to maintain a constant feed of amps though my fixed 12v line.
True or false? If I use more amps, does the hotend heats up quicker...
True or false? ...and so will other things like my board/MOSFET/PSU.
True or false? When I multiply the amps times the volts I get the output power in watts.
Wattage and resistance in heaters:
What is the relation of this power to the wattage of a heater? Heating resistors have a power spec in watts and a resistance in ohms (i.e. 20w 10ohms). I am told that the wattage on the heaters is the output that it can be capable of giving as heat, which is concurrent with what is found on this forum about heat dissipation (referenced further down). In accordance with ohm's law, if the ohms on a resistor is lower more amps can be drawn with the same amount of volts. However, in one post I see an inverse claim where the author contrasts the behaviour of a resistor with that of a transistor. (reprap forum) "...As the resistance decreases, more power is radiated from the transistor (I assume that's what you're using?), and less from the resistor". To try to understand this for a resistor I have to think about passing more and more amps through a thin cable. The cable will offer resistance and also heat, right? If the statement is true I would be better getting a:
- 10ohms heater which would allow 1.2amps at 12volts capable of producing ~14watts.
On the same topic I also see a reference to ohms law and the following statement "...the power dissipation (heat production) of a resistor goes UP as the resistance goes down FOR A CONSTANT VOLTAGE." This is more in line with what I was given to believe initially by Ohm's Law. So if this is right, I should get a:
- 4.7ohms heater that can pass 2.55amps at 12volts producing ~31watts.
The 31w are more than the 14w, therefore the second statement seems to be 'truer'. Answering which one is it, would only answer part of my dilemma. The rated wattage on the heater, what does it mean? In the two examples above, either 10ohms or 4.7ohms, will output more than 10w. So I should get a 20w heater, right?
I find this comment about a hotend design with a glass nozzle (at reprap.org) "...I also went to get some more 1W resistors. This time I got 3.3 Ohm resistors so that I could use 2 in series and have the heater leads come out the same side of the block." What are the benefits of using a couple of 1w heaters? I can't assume he is using 12v but it makes me think that if I did that, it will be equal to passing ~44w through a heater that is rated at 1w. Not to mention the almost 7amps for two of them. So again what does it mean?
More quick questions for the knowledge intensive contributors of this forum:
If the heater says 1w:
True or false? Will it produce a maximum of 1w of heat?
True or false? Will it die if more than 1w goes through it?, or
True or false? Will it produce what the volts*amps passing through it give?
True or false? Is it a rating of how much heat it can dissipate?
True or false? Does the size mean it can dissipate more heat?
True or false? If it is attached to the aluminium heating block does it increase the heat dissipation?
I have also seen 40w heating cartridges which seem like are just covered in aluminium to increase heat conductivity to the block and thus dissipation. Makes me think about adding thermal compound or thermal grease which I commonly use on my CPU heat sink, to increase conductivity on the block and increase the wattage/heat up quicker.
But before this...I need to get a new heater.