The MK5 has an entirely different thermal landscape from the MK4 -
more metal to heat and higher distance between the heater elements and
thermistor mean it takes a lot longer for heat from the resistors to
get to the thermistor, which make the PID settings for MK4 much
different. I get a thermal swing of more like +2/-15 degrees but it
doesn't seem to affect printing much at all. I am looking to move to
a MOSFET board instead of a relay board to drive the heater, and that
should reduce the thermal swings some. I should also re-tune the PID
but I have no experience dealing with the proportional-integral-
derivative coefficients. I think the derivative coefficient should be
the one that helps to mute the temperature swings but I'm not really
sure.
On Aug 27, 4:56 pm, Marty McGuire <schmartiss...@gmail.com> wrote:
The M represents the giant spotlight I am shining in the clouds above
my city to attract the attention of MakerBot Industries so they will
tell us the PID settings they have been using with the MK5.
Too bad it's daytime and no one can see it. Maybe tonight they will
see it and help us.
On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: > mmm mmm > mm m m mm > mm m mm > mm m mm
> The M represents the giant spotlight I am shining in the clouds above > my city to attract the attention of MakerBot Industries so they will > tell us the PID settings they have been using with the MK5.
> Too bad it's daytime and no one can see it. Maybe tonight they will > see it and help us.
> HELP!
> Brendan
> -- > You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. > To post to this group, send email to makerbot@googlegroups.com. > To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. > For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
I've upgraded to the latest version of the extruder firmware on GitHub (compiled from source). This improved the relay "singing" a bit, but I still hearing some buzzing as it PWMs the relay from on-to-off as the heater crosses target temp.
Oddly, I can also hear that the heater doesn't turn off until the temperature has already overshot by about 3 degrees or so. Similarly, the heater doesn't turn back on until the temp has already dropped a few degrees below target.
I would expect it to anticipate the target-temp crossing and turn the heater on/off early. Is anyone else seeing this behavior?
Thanks, Marty
On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax
> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >> mmm mmm >> mm m m mm >> mm m mm >> mm m mm
>> The M represents the giant spotlight I am shining in the clouds above >> my city to attract the attention of MakerBot Industries so they will >> tell us the PID settings they have been using with the MK5.
>> Too bad it's daytime and no one can see it. Maybe tonight they will >> see it and help us.
>> HELP!
>> Brendan
>> -- >> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >> To post to this group, send email to makerbot@googlegroups.com. >> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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dirty hack : hook up the extruder as if it were a heated build plate ? I'm driving a HBP with relay, and its not humming so I assume its not PWM'd.
guess : maybe the reason it overshoots by 3 degrees is that is it using PWM and the duty cycle doesn't get large enough until its substantially out of range ? that doesn't really seem plausible, but maybe ?
On Sun, Aug 29, 2010 at 8:29 PM, Marty McGuire <schmartiss...@gmail.com> wrote: > My settings were close, at 5,0.35,36. Using Charles' settings of > 7,0.35,36, I still end up with greater than +/-10 degree Celsius > swings:
> I've upgraded to the latest version of the extruder firmware on GitHub > (compiled from source). This improved the relay "singing" a bit, but > I still hearing some buzzing as it PWMs the relay from on-to-off as > the heater crosses target temp.
> Oddly, I can also hear that the heater doesn't turn off until the > temperature has already overshot by about 3 degrees or so. Similarly, > the heater doesn't turn back on until the temp has already dropped a > few degrees below target.
> I would expect it to anticipate the target-temp crossing and turn the > heater on/off early. Is anyone else seeing this behavior?
> Thanks, > Marty
> On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax > <charles....@gmail.com> wrote: >> I have been using PID of 7, 0.35, 36 respectively.
>> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >>> mmm mmm >>> mm m m mm >>> mm m mm >>> mm m mm
>>> The M represents the giant spotlight I am shining in the clouds above >>> my city to attract the attention of MakerBot Industries so they will >>> tell us the PID settings they have been using with the MK5.
>>> Too bad it's daytime and no one can see it. Maybe tonight they will >>> see it and help us.
>>> HELP!
>>> Brendan
>>> -- >>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>> To post to this group, send email to makerbot@googlegroups.com. >>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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I'm getting same behavior and temp ranges. Got both MK5 and HBP
through relay. Updated to RepG18, MB at 2.2, Ex Control at 2.3.
You can watch the leds on the extruder board to see when it cuts off
current to the relay and it's 3 degrees above target easy. The temp
then continues to drift to >10 degree overshoot on low temps (<100C).
At higher temps (230) it starts to cut out at 3 degrees above, then
led is fully off by 235. (OK, so that PWM business is apparent in
brightness of the LED, but I don't get the relay noise). Then, on the
way back down, the led kicked on, not full brightness, two degrees
below. Didn't hit full brightness till 10 degrees below or so and
temp continues to drift down at that point (bottomed at 213 at a 230
setpoint for me).
PID is now 7, 0.347, 36
Beta = 4066, TR = 10000, base temp = 25
I've played with a few different PID settings but nothing good yet.
Since it's 5 degrees above and 15 degrees below at the temps we care
about, I'm going with 235 as a target so the range is 220-240. Still,
it's pretty disturbing since the MK4 never drifted more than a degree
or two out and this supposedly has more mass and should be more temp
stable.
hmm... it sounds like PWM is not only questionable for noise/relay lifetime problems, but is also confusing the firmware's model for stabilizing temperature. I feel like this could be fixed easily by changing the temperature control on the extruder to something that more closely resembles that used on the HBP. Unfortunately, I am not familiar with the software, don't have a MK5 extruder, and am feeling too lazy to dig through the source code. I guess I'll hold off on trying to upgrade until this gets patched.
On Sun, Aug 29, 2010 at 9:07 PM, Brendan <bren...@whatsnewla.com> wrote: > I'm getting same behavior and temp ranges. Got both MK5 and HBP > through relay. Updated to RepG18, MB at 2.2, Ex Control at 2.3.
> You can watch the leds on the extruder board to see when it cuts off > current to the relay and it's 3 degrees above target easy. The temp > then continues to drift to >10 degree overshoot on low temps (<100C). > At higher temps (230) it starts to cut out at 3 degrees above, then > led is fully off by 235. (OK, so that PWM business is apparent in > brightness of the LED, but I don't get the relay noise). Then, on the > way back down, the led kicked on, not full brightness, two degrees > below. Didn't hit full brightness till 10 degrees below or so and > temp continues to drift down at that point (bottomed at 213 at a 230 > setpoint for me).
> PID is now 7, 0.347, 36 > Beta = 4066, TR = 10000, base temp = 25
> I've played with a few different PID settings but nothing good yet. > Since it's 5 degrees above and 15 degrees below at the temps we care > about, I'm going with 235 as a target so the range is 220-240. Still, > it's pretty disturbing since the MK4 never drifted more than a degree > or two out and this supposedly has more mass and should be more temp > stable.
> Brendan
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This is *really* experimental (haven't tried it myself), but I've just created http://wiki.makerbot.com/pid-controller-tuning outlining the Ziegler-Nichels control system tuning method and embedded three Wolfram-Alpha widgets to do the calculations.
Using a T=60 and L=10.286 I was able to generate KP=7.0, KI=0.34 and KD=36.
I had to set T=30 and L=7.2 to get KP=5.0 and KI=0.35, which sets KD=18.
If I set T=55 and L=12, I get KP=5.5, KI=0.23 and KD=33. I'd suggest using these as a starting point since lowering both KP and KI should make for a more stable controller. - If this has the opposite effect of taking too long to reach temperature or settling the wrong temperature (steady-state error), try decreasing the Delay Time (L) value in 0.1 decrements from that L=12 value. That will have the greatest influence on increasing the KI term.
> I've upgraded to the latest version of the extruder firmware on GitHub > (compiled from source). This improved the relay "singing" a bit, but > I still hearing some buzzing as it PWMs the relay from on-to-off as > the heater crosses target temp.
> Oddly, I can also hear that the heater doesn't turn off until the > temperature has already overshot by about 3 degrees or so. Similarly, > the heater doesn't turn back on until the temp has already dropped a > few degrees below target.
> I would expect it to anticipate the target-temp crossing and turn the > heater on/off early. Is anyone else seeing this behavior?
> Thanks, > Marty
> On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax > <charles....@gmail.com> wrote: >> I have been using PID of 7, 0.35, 36 respectively.
>> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >>> mmm mmm >>> mm m m mm >>> mm m mm >>> mm m mm
>>> The M represents the giant spotlight I am shining in the clouds above >>> my city to attract the attention of MakerBot Industries so they will >>> tell us the PID settings they have been using with the MK5.
>>> Too bad it's daytime and no one can see it. Maybe tonight they will >>> see it and help us.
>>> HELP!
>>> Brendan
>>> -- >>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>> To post to this group, send email to makerbot@googlegroups.com. >>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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"The future is already here. It's just not very evenly distributed" -- William Gibson
On Sun, Aug 29, 2010 at 23:59, Andrew Plumb <and...@plumb.org> wrote: > Hi Marty,
> This is *really* experimental (haven't tried it myself), but I've just created http://wiki.makerbot.com/pid-controller-tuning outlining the Ziegler-Nichels control system tuning method and embedded three Wolfram-Alpha widgets to do the calculations.
> Using a T=60 and L=10.286 I was able to generate KP=7.0, KI=0.34 and KD=36.
> I had to set T=30 and L=7.2 to get KP=5.0 and KI=0.35, which sets KD=18.
> If I set T=55 and L=12, I get KP=5.5, KI=0.23 and KD=33. I'd suggest using these as a starting point since lowering both KP and KI should make for a more stable controller. > - If this has the opposite effect of taking too long to reach temperature or settling the wrong temperature (steady-state error), try decreasing the Delay Time (L) value in 0.1 decrements from that L=12 value. That will have the greatest influence on increasing the KI term.
> Andrew.
> On 2010-08-29, at 8:29 PM, Marty McGuire wrote:
>> My settings were close, at 5,0.35,36. Using Charles' settings of >> 7,0.35,36, I still end up with greater than +/-10 degree Celsius >> swings:
>> I've upgraded to the latest version of the extruder firmware on GitHub >> (compiled from source). This improved the relay "singing" a bit, but >> I still hearing some buzzing as it PWMs the relay from on-to-off as >> the heater crosses target temp.
>> Oddly, I can also hear that the heater doesn't turn off until the >> temperature has already overshot by about 3 degrees or so. Similarly, >> the heater doesn't turn back on until the temp has already dropped a >> few degrees below target.
>> I would expect it to anticipate the target-temp crossing and turn the >> heater on/off early. Is anyone else seeing this behavior?
>> Thanks, >> Marty
>> On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax >> <charles....@gmail.com> wrote: >>> I have been using PID of 7, 0.35, 36 respectively.
>>> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >>>> mmm mmm >>>> mm m m mm >>>> mm m mm >>>> mm m mm
>>>> The M represents the giant spotlight I am shining in the clouds above >>>> my city to attract the attention of MakerBot Industries so they will >>>> tell us the PID settings they have been using with the MK5.
>>>> Too bad it's daytime and no one can see it. Maybe tonight they will >>>> see it and help us.
>>>> HELP!
>>>> Brendan
>>>> -- >>>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>>> To post to this group, send email to makerbot@googlegroups.com. >>>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
>>> -- >>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>> To post to this group, send email to makerbot@googlegroups.com. >>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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> --
> "The future is already here. It's just not very evenly distributed" -- William Gibson
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Using Wolfram|Alpha's a bit of a moving target, being beta and all. If you keep the equations relatively simple they seem to survive better, hence the splitting up the PID term calculations into three separate widgets.
Andrew.
On 2010-08-30, at 9:27 AM, Charles Edward Pax wrote:
> On Sun, Aug 29, 2010 at 23:59, Andrew Plumb <and...@plumb.org> wrote: >> Hi Marty,
>> This is *really* experimental (haven't tried it myself), but I've just created http://wiki.makerbot.com/pid-controller-tuning outlining the Ziegler-Nichels control system tuning method and embedded three Wolfram-Alpha widgets to do the calculations.
>> Using a T=60 and L=10.286 I was able to generate KP=7.0, KI=0.34 and KD=36.
>> I had to set T=30 and L=7.2 to get KP=5.0 and KI=0.35, which sets KD=18.
>> If I set T=55 and L=12, I get KP=5.5, KI=0.23 and KD=33. I'd suggest using these as a starting point since lowering both KP and KI should make for a more stable controller. >> - If this has the opposite effect of taking too long to reach temperature or settling the wrong temperature (steady-state error), try decreasing the Delay Time (L) value in 0.1 decrements from that L=12 value. That will have the greatest influence on increasing the KI term.
>> Andrew.
>> On 2010-08-29, at 8:29 PM, Marty McGuire wrote:
>>> My settings were close, at 5,0.35,36. Using Charles' settings of >>> 7,0.35,36, I still end up with greater than +/-10 degree Celsius >>> swings:
>>> I've upgraded to the latest version of the extruder firmware on GitHub >>> (compiled from source). This improved the relay "singing" a bit, but >>> I still hearing some buzzing as it PWMs the relay from on-to-off as >>> the heater crosses target temp.
>>> Oddly, I can also hear that the heater doesn't turn off until the >>> temperature has already overshot by about 3 degrees or so. Similarly, >>> the heater doesn't turn back on until the temp has already dropped a >>> few degrees below target.
>>> I would expect it to anticipate the target-temp crossing and turn the >>> heater on/off early. Is anyone else seeing this behavior?
>>> Thanks, >>> Marty
>>> On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax >>> <charles....@gmail.com> wrote: >>>> I have been using PID of 7, 0.35, 36 respectively.
>>>> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >>>>> mmm mmm >>>>> mm m m mm >>>>> mm m mm >>>>> mm m mm
>>>>> The M represents the giant spotlight I am shining in the clouds above >>>>> my city to attract the attention of MakerBot Industries so they will >>>>> tell us the PID settings they have been using with the MK5.
>>>>> Too bad it's daytime and no one can see it. Maybe tonight they will >>>>> see it and help us.
>>>>> HELP!
>>>>> Brendan
>>>>> -- >>>>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>>>> To post to this group, send email to makerbot@googlegroups.com. >>>>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>>>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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>> --
>> "The future is already here. It's just not very evenly distributed" -- William Gibson
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I've tried going through several sets of values, taking the time constant all the way down to 30 and up to 90 (from the original 60), and adjusting the delay time to bring the Kp value into the 5.0 - 7.0 range.
These changes seem to produce some changes in the relay buzzing. Higher time constant values led to shorter periods of buzzing as the PWM transitioned from 0 - 255 (or back). Lower time constants produced longer periods of buzzing, with a slower transition from 0 - 255 (or back).
However, none of the sets of values I tried actually led to a stable temperature. At best, the heater would only begin to change state at about 3degC too late. At worst, it would get 10degC too high or low before attempting to switch the heater off.
It seems like only a few people are experiencing this behavior. I was wondering if folks with successful MK5 setups could describe their configuration in detail. I'm interested in knowing:
* How your MK5 is connected * Whether you have an HBP and whether it is powered through the relay board * What firmware versions do you have on the motherboard and extruder controller * What PID settings you're using
Sorry to keep pushing on this thread, but I am at a loss to explain why I am seeing this behavior with my 'bot. If I recall correctly, part of the point of PID is that the proportional control will predict and compensate for overshoot, so the behavior of waiting until after the target temp has been crossed before reacting seems pathological.
> Using Wolfram|Alpha's a bit of a moving target, being beta and all. If you keep the equations relatively simple they seem to survive better, hence the splitting up the PID term calculations into three separate widgets.
> Andrew.
> On 2010-08-30, at 9:27 AM, Charles Edward Pax wrote:
>> Wow, Andrew, that looks really good. I didn't know about the embeds.
>> On Sun, Aug 29, 2010 at 23:59, Andrew Plumb <and...@plumb.org> wrote: >>> Hi Marty,
>>> This is *really* experimental (haven't tried it myself), but I've just created http://wiki.makerbot.com/pid-controller-tuning outlining the Ziegler-Nichels control system tuning method and embedded three Wolfram-Alpha widgets to do the calculations.
>>> Using a T=60 and L=10.286 I was able to generate KP=7.0, KI=0.34 and KD=36.
>>> I had to set T=30 and L=7.2 to get KP=5.0 and KI=0.35, which sets KD=18.
>>> If I set T=55 and L=12, I get KP=5.5, KI=0.23 and KD=33. I'd suggest using these as a starting point since lowering both KP and KI should make for a more stable controller. >>> - If this has the opposite effect of taking too long to reach temperature or settling the wrong temperature (steady-state error), try decreasing the Delay Time (L) value in 0.1 decrements from that L=12 value. That will have the greatest influence on increasing the KI term.
>>> Andrew.
>>> On 2010-08-29, at 8:29 PM, Marty McGuire wrote:
>>>> My settings were close, at 5,0.35,36. Using Charles' settings of >>>> 7,0.35,36, I still end up with greater than +/-10 degree Celsius >>>> swings:
>>>> I've upgraded to the latest version of the extruder firmware on GitHub >>>> (compiled from source). This improved the relay "singing" a bit, but >>>> I still hearing some buzzing as it PWMs the relay from on-to-off as >>>> the heater crosses target temp.
>>>> Oddly, I can also hear that the heater doesn't turn off until the >>>> temperature has already overshot by about 3 degrees or so. Similarly, >>>> the heater doesn't turn back on until the temp has already dropped a >>>> few degrees below target.
>>>> I would expect it to anticipate the target-temp crossing and turn the >>>> heater on/off early. Is anyone else seeing this behavior?
>>>> Thanks, >>>> Marty
>>>> On Sun, Aug 29, 2010 at 6:10 PM, Charles Edward Pax >>>> <charles....@gmail.com> wrote: >>>>> I have been using PID of 7, 0.35, 36 respectively.
>>>>> On Sun, Aug 29, 2010 at 15:46, Brendan <bren...@whatsnewla.com> wrote: >>>>>> mmm mmm >>>>>> mm m m mm >>>>>> mm m mm >>>>>> mm m mm
>>>>>> The M represents the giant spotlight I am shining in the clouds above >>>>>> my city to attract the attention of MakerBot Industries so they will >>>>>> tell us the PID settings they have been using with the MK5.
>>>>>> Too bad it's daytime and no one can see it. Maybe tonight they will >>>>>> see it and help us.
>>>>>> HELP!
>>>>>> Brendan
>>>>>> -- >>>>>> You received this message because you are subscribed to the Google Groups "MakerBot Operators" group. >>>>>> To post to this group, send email to makerbot@googlegroups.com. >>>>>> To unsubscribe from this group, send email to makerbot+unsubscribe@googlegroups.com. >>>>>> For more options, visit this group at http://groups.google.com/group/makerbot?hl=en.
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>>> --
>>> "The future is already here. It's just not very evenly distributed" -- William Gibson
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> --
> "The future is already here. It's just not very evenly distributed" -- William Gibson
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I was wondering last night whether the thermistor values would contribute to this problem. I've got a "thermocouple kit" from Adafruit on the way so I can get the right calibration values for the thermistor, which should be good, regardless.
My gut (probably incorrectly) tells me that no matter how off my thermistor values are, the extruder should be able to reach a steady state for whatever it "thinks" is the target temperature. However, I'm sure that is a misleading intuition, so I want to go ahead and remove that variable. :)
Thanks, Marty
On Mon, Aug 30, 2010 at 4:51 PM, Charles Edward Pax
<charles....@gmail.com> wrote: > Marty, I think you should consider that your thermistor values may be > a contributing factor.
>> * How your MK5 is connected > - I have the MK5 connected directly to my extruder controller board. I > am on an experimental Gen4 extruder controller using a thermocouple.
>> * Whether you have an HBP and whether it is powered through the relay board > I have an HBP connected directly to my extruder controller board. > Again, an experimental Gen4 board.
>> * What firmware versions do you have on the motherboard and extruder controller > I'm not sure. My bot is on loan, so I can't check. However, I am > entirely confident that I am running whatever is most recent.
>> * What PID settings you're using > PID = 7, 0.35, 36
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I just thought of something you could try. Instead of driving both resistors in parallel using a relay, break the parallel connection and drive one 5 Ohm resistor with the main Heater channel and the other 5 Ohm with the Valve or Fan channel.
You'll have to check to see what the steady-state temperature is when the Valve/Fan-connected resistor is on. If it's lower than your target extrusion temperature it should be trivial to add activate and deactivate commands to your skeinforge start and finish gcode. Then all the Heater-connected resistor has to do is heat the difference as required.
Be prepare to add heatsinks and/or an always-on fan to the FETs to keep them cool.
> I was wondering last night whether the thermistor values would > contribute to this problem. I've got a "thermocouple kit" from > Adafruit on the way so I can get the right calibration values for the > thermistor, which should be good, regardless.
> My gut (probably incorrectly) tells me that no matter how off my > thermistor values are, the extruder should be able to reach a steady > state for whatever it "thinks" is the target temperature. However, > I'm sure that is a misleading intuition, so I want to go ahead and > remove that variable. :)
> Thanks, > Marty
> On Mon, Aug 30, 2010 at 4:51 PM, Charles Edward Pax > <charles....@gmail.com> wrote: >> Marty, I think you should consider that your thermistor values may be >> a contributing factor.
>>> * How your MK5 is connected >> - I have the MK5 connected directly to my extruder controller board. I >> am on an experimental Gen4 extruder controller using a thermocouple.
>>> * Whether you have an HBP and whether it is powered through the relay board >> I have an HBP connected directly to my extruder controller board. >> Again, an experimental Gen4 board.
>>> * What firmware versions do you have on the motherboard and extruder controller >> I'm not sure. My bot is on loan, so I can't check. However, I am >> entirely confident that I am running whatever is most recent.
>>> * What PID settings you're using >> PID = 7, 0.35, 36
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"The future is already here. It's just not very evenly distributed" -- William Gibson
well i don't have a successful MK5 setup, but i'll go ahead and share
* How your MK5 is connected
thru relay w/ thermistor installed per MK5 instructions
* Whether you have an HBP and whether it is powered through the relay
board
yes, powered thru relay
* What firmware versions do you have on the motherboard and extruder
controller
mobo fw 2.2 (mobo v1.2), extruder fw v2.3 (extruder v2.2) [batch 15]
* What PID settings you're using
default were:
5 / 0.1 / 5; then tried - sinusoidal from 208-229 (220 target)
7 / 0.35 / 36 - same result
went ahead and did some other target temps:
160 (sinusoidal from 152-174)
250 (sinusoidal from 239-255 [255 might be a false low value, looked
flat, maybe a detection threshold)
whether the HBP was on or off made no difference. was a little
surprised changing the PID settings made no difference -- reset the
extruder, powered off and on the whole machine -- and the PID settings
were saved -- still made no difference.
brief "behavioral analysis":
at 212 going down - buzz, click, buzz
209 down to 208 and back - quiet
210-220 - pulsating buzz
220 - click
224 - click
229 - ting noise
228-212 - quiet
Installed relay board, used RepG 18, set PID using the values here. Tons of buzzing on the relay as temperatures approached 220. WILD swings in temperature from 235 down to 209, which usually means the proportional constant is off
Relay fried on the relay board. Totally dead, and it died in the stuck on position .. head reached a temp of 245 before I shut it down.
PWM + Relay is just a stupid idea. Relays just aren't meant to be driven by high speed PWM.
I'm either going to design and use a board with power FET's which -are- designed to take the beating of PWM .. or I'm going to switch PWM off entirely.
In the thread titled "Status of Plastruder MK5 or MK6 or???", Zach
said
the heater is going to be 2.5 ohms. at 12v that pulls 4.8A
for a total of 57.6W of heater action. there's a bigger thing to heat
up.
chances are that the current mosfets will not be able to handle this.
the
gen4 extruder controller will have much better mosfets that are
designed
with this in mind.
of course you could use a smaller heater or only run one of the
resistors or
use 2 mosfets, or a couple other hacks to get it working using stock
parts.
It's possible/likely the MakerBot folks who've been field testing the
MK5 have done so on the Gen4 extruder controller. If no one can find
operable PID settings that work through the relay, this may become a
discussion of what's the easiest or best hack that'll work till gen4
electronics are out.
I was thinking of soldering the contacts of two of the mosfets on the
extruder controller together then joining wires on the outputs as a
way of sharing load across them. I know very little electronics --
could someone who knows more comment if this is likely to work?
My electrical engineer friend noted that while what you suggest is possible, you should not attempt it given you limited EE knowledge. You would have to do more than just put them in parallel.
On Tue, Aug 31, 2010 at 10:02, Brendan <bren...@whatsnewla.com> wrote: > In the thread titled "Status of Plastruder MK5 or MK6 or???", Zach > said
> the heater is going to be 2.5 ohms. at 12v that pulls 4.8A > for a total of 57.6W of heater action. there's a bigger thing to heat > up. > chances are that the current mosfets will not be able to handle this. > the > gen4 extruder controller will have much better mosfets that are > designed > with this in mind. > of course you could use a smaller heater or only run one of the > resistors or > use 2 mosfets, or a couple other hacks to get it working using stock > parts.
> It's possible/likely the MakerBot folks who've been field testing the > MK5 have done so on the Gen4 extruder controller. If no one can find > operable PID settings that work through the relay, this may become a > discussion of what's the easiest or best hack that'll work till gen4 > electronics are out.
> I was thinking of soldering the contacts of two of the mosfets on the > extruder controller together then joining wires on the outputs as a > way of sharing load across them. I know very little electronics -- > could someone who knows more comment if this is likely to work?
> Brendan
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> My electrical engineer friend noted that while what you suggest is
> possible, you should not attempt it given you limited EE knowledge.
> You would have to do more than just put them in parallel.
> In the thread titled "Status of Plastruder MK5 or MK6 or???", Zach > said
> the heater is going to be 2.5 ohms. at 12v that pulls 4.8A > for a total of 57.6W of heater action. there's a bigger thing to heat > up. > chances are that the current mosfets will not be able to handle this. > the > gen4 extruder controller will have much better mosfets that are > designed > with this in mind. > of course you could use a smaller heater or only run one of the > resistors or > use 2 mosfets, or a couple other hacks to get it working using stock > parts.
> It's possible/likely the MakerBot folks who've been field testing the > MK5 have done so on the Gen4 extruder controller. If no one can find > operable PID settings that work through the relay, this may become a > discussion of what's the easiest or best hack that'll work till gen4 > electronics are out.
> I was thinking of soldering the contacts of two of the mosfets on the > extruder controller together then joining wires on the outputs as a > way of sharing load across them. I know very little electronics -- > could someone who knows more comment if this is likely to work?
> Brendan
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I've got a PCB milling now, based on a speed controller for an model aircraft motor of all things. It has six power FET's running in parallel, with the gates tied together. Should be able to handle 12V 5A with ease, and be PWM-a-ble. Soldering it will have to wait for the weekend, but I'll post the results on flickr and here.
so the oscillations are definitely attributable to the relay as i
plugged in my mk4 and ran it through the relay and got a similar
behavior -- though its oscillation period is much shorter (yeah, i'm
sure this isn't shocking but it was nice to confirm).
also had issues with setting my PID values back to their defaults
after switching back to the MK4:
1) P parameter wouldn't "stick" to what i set (0.1 becomes 0.09765625)
2) temperature would hold at ~-7C below target -- raising P to 0.2
(becomes 0.19921875) brought the temp up to target
-- hope this isn't any sort of death knell, can anyone put my mind at
ease?
On Thu, Sep 2, 2010 at 8:01 PM, Graham <gmarqu...@gmail.com> wrote: > so the oscillations are definitely attributable to the relay as i > plugged in my mk4 and ran it through the relay and got a similar > behavior -- though its oscillation period is much shorter (yeah, i'm > sure this isn't shocking but it was nice to confirm).
> also had issues with setting my PID values back to their defaults > after switching back to the MK4: > 1) P parameter wouldn't "stick" to what i set (0.1 becomes 0.09765625) > 2) temperature would hold at ~-7C below target -- raising P to 0.2 > (becomes 0.19921875) brought the temp up to target > -- hope this isn't any sort of death knell, can anyone put my mind at > ease?
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