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Locking resistance issue on VTC Dual (SS mode) - Printable Version

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Locking resistance issue on VTC Dual (SS mode) - pi-xel - 01-06-2017

Dear all,

I am having a rather annoying issue with my Evic VTC Dual, which - to my opinion - could be rather easily fixed with a firmware upgrade.

I use multiple RTAs in SS TC mode whose resistances are rather close to each other. For that reason I have to frequently lock and unlock the resistances. My problem is that quite often the resistance does not really get unlocked on unlocking: If the resistance of the new coil is significantly higher than the one of the old coil, I am asked whether it's indeed a new coil. If the new resistance is significantly smaller the locked resistance is automatically adjusted and I don't even have to lock and unlock.

If the old and the new resistance are close to each other, however, the device keeps the old resistance even on un- and re-locking, i.e. when the device is turned on (after unlocking the old resistance) it reads the correct (measured) new resistance at room temp, but when I enter the menu to lock this resistance it jumps back to the previously locked resistance.

In such problematic cases as above I quite often have to use yet another (3rd) tank with a completely different resistance as an in-between step, i.e. go from 1.21 ohm to 0.6 and then to 1.3 because 1.21 to 1.3 is not possible. Is there any trick I am not aware of? If not, could you please explain to me why the unlocking of the resistance is not actually unlocking it and whether this can be fixed in an update?

Thanks in advance.

Best regards,
pi-xel


RE: Locking resistance issue on VTC Dual (SS mode) - Murray B - 01-07-2017

My mod is the eVic VTC mini with the version 3.04 firmware. As near as I can tell the display always shows the current ohms and activating the lock just copies the currently displayed value to memory to use as a constant. The lock symbol seems to mean that the value has been stored in memory but I can find no way to display the content of that memory location. It might help if you unlocked the resistance, changed atomizers, and then "locked" in the new value.


RE: Locking resistance issue on VTC Dual (SS mode) - pi-xel - 01-07-2017

(01-07-2017, 06:32 AM)Murray B Wrote:  My mod is the eVic VTC mini with the version 3.04 firmware.  As near as I can tell the display always shows the current ohms and activating the lock just copies the currently displayed value to memory to use as a constant.  The lock symbol seems to mean that the value has been stored in memory but I can find no way to display the content of that memory location.  It might help if you unlocked the resistance,  changed atomizers, and then "locked" in the new value.

Thanks for your reply. To my understanding temp control needs a base resistance reading at 21° C which is thereafter used as a reference that is compared to the higher resistance readings that occur at higher temperatures, thus allowing to determine the temperature of the coil.

My problem is however, that after unlocking I cannot lock another base resistance that is close to the one previously locked. Even if unlocked it reverts to the previously locked resistance once entering the menu in which power, resistance lock, etc. can be adjusted.

For instance: my previous coil was locked at 1.20 ohm @21° C. I unlock, remove the previous coil and put on a new one with say 1.25 ohm @21° C. The mod shows 1.25 ohm, but as soon as I enter the menu to lock the 1.25 ohm it reverts to the 1.20 ohm of the previous coil.


RE: Locking resistance issue on VTC Dual (SS mode) - Murray B - 01-07-2017

(01-07-2017, 07:20 AM)pi-xel Wrote:  [...] My problem is however, that after unlocking I cannot lock another base resistance that is close to the one previously locked. [...]

Sorry I did not make my previous post more clear, pi-xel. The lock symbol does not lock anything and the value of the displayed resistance is always the current value. The locking process only seems to copy the current resistance value to memory and there is no way I can find to read what that number is after it is stored. It does not matter though as long as the value is "locked" while the atomizer is cold. I think of the lock symbol as signifying that the value has been copied to memory and locked there as a constant.


RE: Locking resistance issue on VTC Dual (SS mode) - pi-xel - 01-07-2017

(01-07-2017, 08:07 AM)Murray B Wrote:  
(01-07-2017, 07:20 AM)pi-xel Wrote:  [...] My problem is however, that after unlocking I cannot lock another base resistance that is close to the one previously locked. [...]

Sorry I did not make my previous post more clear, pi-xel.  The lock symbol does not lock anything and the value of the displayed resistance is always the current value.  The locking process only seems to copy the current resistance value to memory and there is no way I can find to read what that number is after it is stored.  It does not matter though as long as the value is "locked" while the atomizer is cold.  I think of the lock symbol as signifying that the value has been copied to memory and locked there as a constant.

Isn't the currently stored / locked resistance value the one that shows when short-pressing the fire button at 21° C / room temp? And at least on my device the display does not always show the current resistance: whenever I enter the submenu in which I can change power etc. it shows the resistance at which I have last pressed lock / store, which often differs from the current reading outside that menu.

I am on the latest firmware 4.04 btw. (that afaik corresponds to 3.04 on Evic VTC Mini).


RE: Locking resistance issue on VTC Dual (SS mode) - Murray B - 01-07-2017

(01-07-2017, 08:19 AM)pi-xel Wrote:  Isn't the currently stored / locked resistance value the one that shows when short-pressing the fire button at 21° C / room temp? And at least on my device the display does not always show the current resistance: whenever I enter the submenu in which I can change power etc. it shows the resistance at which I have last pressed lock / store, which often differs from the current reading outside that menu.

I am on the latest firmware 4.04 btw. (that afaik corresponds to 3.04 on Evic VTC Mini).

There does not seem to be much documentation for the current version of the firmware and I can only observe and try to figure out what it is doing.  My current coil is 1.06 ohm at room temperature and rises to 1.23 at an indicated 340F.  if the coil was changed to one that is 1.05 ohms but the calculation was performed using the 1.06 value the temperature should still be close to what it was before.  When I change to a tank with a different atomizers I unlock the resistance and power off.  Then I attach the new tank, power-on, lock the resistance, and vape. That has been working well and has been producing a consistent vape even with the new MTM (?) coils.


RE: Locking resistance issue on VTC Dual (SS mode) - pi-xel - 01-07-2017

(01-07-2017, 11:32 AM)Murray B Wrote:  
(01-07-2017, 08:19 AM)pi-xel Wrote:  Isn't the currently stored / locked resistance value the one that shows when short-pressing the fire button at 21° C / room temp? And at least on my device the display does not always show the current resistance: whenever I enter the submenu in which I can change power etc. it shows the resistance at which I have last pressed lock / store, which often differs from the current reading outside that menu.

I am on the latest firmware 4.04 btw. (that afaik corresponds to 3.04 on Evic VTC Mini).

There does not seem to be much documentation for the current version of the firmware and I can only observe and try to figure out what it is doing.  My current coil is 1.06 ohm at room temperature and rises to 1.23 at an indicated 340F.  if the coil was changed to one that is 1.05 ohms but the calculation was performed using the 1.06 value the temperature should still be close to what it was before.  When I change to a tank with a different atomizers I unlock the resistance and power off.  Then I attach the new tank, power-on, lock the resistance, and vape. That has been working well and has been producing a consistent vape even with the new MTM (?) coils.

I agree that a 0.01 ohm difference does not make much of a difference in terms of vaping experience. However, the differences I am seeing are more in the 0.05-0.1 ohm range, which especially for subohm makes quite a difference, as there for instance the difference between an actual 0.6 ohm coil and a saved base resistance of 0.7 ohm is already 17%.

What I am consequently experiencing is that on the one hand it seems that a too high initial power is applied if the saved resistance is too high (but I am not entirely sure about that), resulting in a "burst" of vape. And on the other hand, a too high saved resistance leads to improper temp measurements, the coil can reach higher temperatures than allowed (this is definitely the case).

My main problem is that the mod does not behave as desired. My procedure is just as yours: I "unlock", replace the coil and "relock" to save a new base resistance. After "unlocking" the base resistance I should be able to save a new base resistance as the currently measured one. But right now this is simply not always possible.

Therefore I hope that this inconsistent behavior is fixed in a future firmware update. Or is there any situation that I don't see in which my described behavior is desirable?


RE: Locking resistance issue on VTC Dual (SS mode) - Murray B - 01-08-2017

(01-07-2017, 08:27 PM)pi-xel Wrote:  [...]I agree that a 0.01 ohm difference does not make much of a difference in terms of vaping experience. However, the differences I am seeing are more in the 0.05-0.1 ohm range, which especially for subohm makes quite a difference, as there for instance the difference between an actual 0.6 ohm coil and a saved base resistance of 0.7 ohm is already 17%.[...]

Sorry, pi-xel, but I did not realize we were talking about using coils that were not supplied by Joyetech. That adds a couple more things to check.

The first step to accurate temperature control is to set the correct "M" value. For Joyetech TC products that number appears to be derived by multiplying the TCR value of the coil wire by a constant. For some models the firmware sets the correct "M" value when the wire type is chosen. Those values are for wire types supplied by Joyetech and may not apply to other brands. The composition of metal alloys can vary even when they are of the same type as illustrated by the composition table in the document posted at http://www.aksteel.com/pdf/markets_products/stainless/austenitic/316_316l_data_sheet.pdf

Type 316L stainless steel alloys with different compositions would be expected to have slightly different TCRs and, therefore, different "M" values. The "SS316" setting in the firmware may only work for the alloys Joyetech supplies and other types of SS316L may need to have their "M" value entered manually. Until the correct "M" value is entered no amount of patching the firmware will correct TC problems.


RE: Locking resistance issue on VTC Dual (SS mode) - pi-xel - 01-08-2017

(01-08-2017, 04:54 AM)Murray B Wrote:  
(01-07-2017, 08:27 PM)pi-xel Wrote:  [...]I agree that a 0.01 ohm difference does not make much of a difference in terms of vaping experience. However, the differences I am seeing are more in the 0.05-0.1 ohm range, which especially for subohm makes quite a difference, as there for instance the difference between an actual 0.6 ohm coil and a saved base resistance of 0.7 ohm is already 17%.[...]

Sorry, pi-xel, but I did not realize we were talking about using coils that were not supplied by Joyetech.  That adds a couple more things to check.

The first step to accurate temperature control is to set the correct "M" value.  For Joyetech TC products that number appears to be derived by multiplying the TCR value of the coil wire by a constant.  For some models the firmware sets the correct "M" value when the wire type is chosen.  Those values are for wire types supplied by Joyetech and may not apply to other brands.  The composition of metal alloys can vary even when they are of the same type as illustrated by the composition table in the document posted at http://www.aksteel.com/pdf/markets_products/stainless/austenitic/316_316l_data_sheet.pdf

Type 316L stainless steel alloys with different compositions would be expected to have slightly different TCRs and, therefore, different "M" values.  The "SS316" setting in the firmware may only work for the alloys Joyetech supplies and other types of SS316L may need to have their "M" value entered manually.  Until the correct "M" value is entered no amount of patching the firmware will correct TC problems.

Murray, I am aware of TCR and I don't have any issues with setting the correct M value. However, while the M value defines the "slope" of the temperature measurement, I am having issues with setting the "offset", that is, the base resistance. And this has nothing to do with the M values.


RE: Locking resistance issue on VTC Dual (SS mode) - Murray B - 01-08-2017

(01-08-2017, 05:04 AM)pi-xel Wrote:  Murray, I am aware of TCR and I don't have any issues with setting the correct M value. However, while the M value defines the "slope" of the temperature measurement, I am having issues with setting the "offset", that is, the base resistance. And this has nothing to do with the M values.

It is becoming increasingly clear that you are not technical, pi-xel. The zero offset is not nearly as important as the span value. In this case the span multiplier makes far more difference to correct operation than the offset. Where are you getting your "M" value for your wire from if you are not using Joyetech coils? It is highly unlikely that Joyetech's SS316 setting is going to work for other brands of wire. Was your wire marked with a TCR value or are you just guessing as to the correct value? If you only use Joyetech products together then your problems should disappear.

Since I do not owe you anything I will unsubscribe from this thread now. Good luck.