IPV D2 reading much lower ohms on ni200 coils then estimated by Steam Engine?

[collinsmcrae]

Here's the deal. I just purchased my first TC device a few weeks ago, which is the ipv D2. Well, straight away I built an 8 wrap, 3mm inner diameter, 28 gauge ni200 spaced coil and installed it on one of my subtank minis. First ni200 build and I nailed it, the IPV D2 read the coil as .13 ohms and the vape was spectacular. It worked flawlessly actually. No rattle snaking, no dry hits, strong vapor production; perfect.

Anyway, I love to tinker and I wanted to practice my ni200 building some more, so after a few days of tc vaping bliss I decided to rebuild the thing, even though I could probably have gone a month without changing the coil. Only this time, the resistance is coming in much lower, and I,m doing the build exactly the same way as the original. I've built 4 since then, and they all come in much lower than that original coil. Now, I get .093-.095 ohms on an 8 wrap, around .103 on a 9 wrap. These resistances are all significantly lower than what steam engine estimates.

I do insure that all contact points are clean and tight. In fact, I wrap the leads around the post screws on the subtank mini rba deck. So what do you think might be causing this? Could a 10 degree variance in temperature in my house make that sort of diference? Could a hot spot or touching coil rings (I build ni200 spaced) cause the discrepancy? Any suggestions would be greatly appreciated.

 

[edyle]

that's really only a 10 to 20 % difference.

the main thing to watch for is if the coil is touching the metal above or on the sides.

check the coil ohms with the coil totally exposed,
then check the coil ohms after you put on the barrel and the top.


touching wraps could cause lower resistance i suppose initially.
shorter legs could cause lower ohms.

 

[collinsmcrae]

that's really only a 10 to 20 % difference.

the main thing to watch for is if the coil is touching the metal above or on the sides.

check the coil ohms with the coil totally exposed,
then check the coil ohms after you put on the barrel and the top.


touching wraps could cause lower resistance i suppose initially.
shorter legs could cause lower ohms.

Thanks for the suggestion. A 10-20% may not be much, but everyone else seems to be getting around .1-.15 ohms with the same buil, which is a bit troubling. It's really hard to know if my device just went defective. I will try what you have suggested here, because by all accounts this build should be .1 ohms or over, which it was on the first one.

 

[IMFire3605]

Well several factors, a dedicated Ohm reader or Digital Multimeter really is suggested instead of relying solely on your mod, the mod works in a pinch, but can be off on calibration just like an ohm meter can, having two reference readings gives you a ball park, what steam engine gives is a guestimated figure, but...

1) Variances from one batch of metal can be different from another
2) Not all Ohm readings are 100% accurate unless you spend almost $9kay on a precision Ohm reader that reads in the nano-ohms, you need at least 2 decimal slots more than what you are shooting for, 0.00 you need readings at 0.0000 to be anywhere close to 95% accurate
3) Just like on Ohm readers, many mods have a variance they are off like stated above, I've seen this with mods and Ohms readers alike, one will read a 0.35ohm while another will read 0.30 or 0.40 ohms

I right now on my only TC device I have, the coil I have in it, has stayed stable at 0.12 for the last several weeks, 12wrap on a #14 Machinist screw for spacing with 28awg Ni200 annealed, if I'm over 0.10 I am happy with it though my device will do 0.05, it's still a crap shoot to hit accurately even with Kanthal and Nichrome higher resistance wire.

 

[edyle]

an 8 wrap could be a 7/8 or an 8/9
a 9 wrap could be an 8/9 or a 9/10

depending on what angle you are looking from

tightening or loosening your510 connector can cause differences in the ohms measured.
tightening or loosening the coil head from the subtank base can also cause variation because the bottom pin of the coil head has to contact the top of the tank's main 510 centerpin.

 

[collinsmcrae]

Well several factors, a dedicated Ohm reader or Digital Multimeter really is suggested instead of relying solely on your mod, the mod works in a pinch, but can be off on calibration just like an ohm meter can, having two reference readings gives you a ball park, what steam engine gives is a guestimated figure, but...

1) Variances from one batch of metal can be different from another
2) Not all Ohm readings are 100% accurate unless you spend almost $9kay on a precision Ohm reader that reads in the nano-ohms, you need at least 2 decimal slots more than what you are shooting for, 0.00 you need readings at 0.0000 to be anywhere close to 95% accurate
3) Just like on Ohm readers, many mods have a variance they are off like stated above, I've seen this with mods and Ohms readers alike, one will read a 0.35ohm while another will read 0.30 or 0.40 ohms

I right now on my only TC device I have, the coil I have in it, has stayed stable at 0.12 for the last several weeks, 12wrap on a #14 Machinist screw for spacing with 28awg Ni200 annealed, if I'm over 0.10 I am happy with it though my device will do 0.05, it's still a crap shoot to hit accurately even with Kanthal and Nichrome higher resistance wire.

Thanks for the reply. It's just strange that out of 5 of the exact same builds, the first one was on point and the rest have been dead on at around .095. But they do remain stable and the temp control seems to preform just as well. I do need to invest in a dedicated ohm reader to check against. Anyway, thanks for the advice!

 

[Bunnykiller]

Thanks for the suggestion. A 10-20% may not be much, but everyone else seems to be getting around 1-1.5 ohms with the same buil, which is a bit troubling. It's really hard to know if my device just went defective. I will try what you have suggested here, because by all accounts this build should be .1 ohms or over, which it was on the first one.

1 - 1.5 with Ni200??? must be some huge coils to get that.... 1 - 1.5 sounds more like Kanthal builds

 

[Darkstarncw]

1 - 1.5 with Ni200??? must be some huge coils to get that.... 1 - 1.5 sounds more like Kanthal builds

Based on his original numbers I think he meant .1 to .15 ohms.

 

[collinsmcrae]

1 - 1.5 with Ni200??? must be some huge coils to get that.... 1 - 1.5 sounds more like Kanthal builds

Yeah, I rock a 140 wrap ni200 coil in a custom barel section for the subtank mini that I had made at a local machine shop. I have wired a foot pedal switch to my IPV D2, and all of this is mounted to my recliner in my living room. Lol, just kidding. That was a typo. Thanks for pointing it out to me.

 

[GeorgeS]

I've never purchased a vape centeric ohm meter - IMHO a waste of money as whatever your mod reads is what your base resistance for vaping is going to be. If your mod reads it wrong you may not be happy with your vape.

I hand wrap my Ni200 coils, the 28AWG is 'springy' enough to almost perfectly auto-space the windings, you do have to make sure none of the windings are touching - if you wrap the wire all the way around the posts there is a tendency of the wire to bind with the post and deform the coil while tightening the screw, 28awg need not be wrapped around the screws.

I let the coil 'hang' at least 1/3 to 1/2 below the the level of the screws - mount to high and the windings will contact the top, to low and it will contact the air hole. 1/16-3/32" above the airhole is where I try to get it.

With the ONLY RBA and subtank base I'll attach to the mod and check the resistance with no wick or hood - just the bottom, open RBA and coil. Then I'll add the wick and check again and finally add the walls and hood and check again. 3mm leaves very little room, 2.5mm works better for me.

 

[collinsmcrae]

I've never purchased a vape centeric ohm meter - IMHO a waste of money as whatever your mod reads is what your base resistance for vaping is going to be. If your mod reads it wrong you may not be happy with your vape.

I hand wrap my Ni200 coils, the 28AWG is 'springy' enough to almost perfectly auto-space the windings, you do have to make sure none of the windings are touching - if you wrap the wire all the way around the posts there is a tendency of the wire to bind with the post and deform the coil while tightening the screw, 28awg need not be wrapped around the screws.

I let the coil 'hang' at least 1/3 to 1/2 below the the level of the screws - mount to high and the windings will contact the top, to low and it will contact the air hole. 1/16-3/32" above the airhole is where I try to get it.

With the ONLY RBA and subtank base I'll attach to the mod and check the resistance with no wick or hood - just the bottom, open RBA and coil. Then I'll add the wick and check again and finally add the walls and hood and check again. 3mm leaves very little room, 2.5mm works better for me.

Thanks for the advice! I do wrap the wire around the screws, and yes it is a PITA indeed. And I do have trouble with keeping the coil from deforming while tightening the screws. I like your suggestion about placing the coil below the screws in order to leave clearance for wrapping the leads around the screw. Two questions: Do you hang the coil upside down, rather than right side up? Seems like it might be easier that way. For my next question, 8 spaced wraps comes out wider than the the than the terminals, so there seems to be no way to place the leads without them pinching against the outside coils, unless you place the coil in at an angle, rather than horizontal. Do you just put it in slanted? Or do you have some trick , such as bending the leads, in order to get it perfectly horizontal without the the leads touching the coils?

 

[GeorgeS]

I'll leave the coil on the mandrel or drill bit while placing it, 8 or even 10 wraps of 28awg can have a very slight space (enough to slide a thin piece of paper) and fit with in the screws. I like using the outside edges of both screws and with the drill/mandrel in place some bending can happen where the ends can be bent in to fit the outside edges of the screws without forcing the coil to compress and coils to make contact.

Here's a 9 wrap Ni200 in the STM RBA:

Note, I'm capturing the legs on the outside edges, the coil is pushed down (not inverted but the wires are coming off the middle of the diameter rather than the top or bottom), the leg on the top left takes a sharp left turn as it exits the screw as well as the bottom right leg takes a right turn.

I'll screw one leg down and using the drill/mandrel push+bend+twist+compress the coil until I can secure the 2nd leg. Then I can push+bend+twist some more until the spacing is even and the coil is centered.

While I started with 0.10-0.20ohm target I've been using 32awg to get higher base resistance.

(RBA v1 shown)

 

[Completely Average]

When you say there is a 10 degree temperature difference in your house, what was the temperature when you built your first coil and what was it for the rest?

And yes, when working with Ni200 temperature can have a definite effect on the resistance. That's precisely how TC works, by measuring the changes in resistance as the wire heats up. If your house is 10 degrees colder it could very well result in a .03-.04 ohm drop in resistance.

 

[Scotticus93]

Mine reads higher. I have given up with ni200 for now for other reasons. Maybe part of it is steam engine doesn't take into account the spacing we put in but yours is reading low which is weird

 

[collinsmcrae]

I'll leave the coil on the mandrel or drill bit while placing it, 8 or even 10 wraps of 28awg can have a very slight space (enough to slide a thin piece of paper) and fit with in the screws. I like using the outside edges of both screws and with the drill/mandrel in place some bending can happen where the ends can be bent in to fit the outside edges of the screws without forcing the coil to compress and coils to make contact.

Here's a 9 wrap Ni200 in the STM RBA:

Note, I'm capturing the legs on the outside edges, the coil is pushed down (not inverted but the wires are coming off the middle of the diameter rather than the top or bottom), the leg on the top left takes a sharp left turn as it exits the screw as well as the bottom right leg takes a right turn.

I'll screw one leg down and using the drill/mandrel push+bend+twist+compress the coil until I can secure the 2nd leg. Then I can push+bend+twist some more until the spacing is even and the coil is centered.

While I started with 0.10-0.20ohm target I've been using 32awg to get higher base resistance.

(RBA v1 shown)

Thanks! This is almost exactly what I do, beat for beat. A few small differences, but pushing the coil below the screws is a great addition and I will be doing that from now on. On a side note, I've even been thinking about making a jig that can just hold the coil in place while I tighten my leads, which would be quite useful. Freeing up the one hand that has to hold the drill bit (or whatever anyone uses) would be quite useful.

 

[collinsmcrae]

When you say there is a 10 degree temperature difference in your house, what was the temperature when you built your first coil and what was it for the rest?

And yes, when working with Ni200 temperature can have a definite effect on the resistance. That's precisely how TC works, by measuring the changes in resistance as the wire heats up. If your house is 10 degrees colder it could very well result in a .03-.04 ohm drop in resistance.

I can't recall lol. I live in Orlando and it is stupid hot here during the summer. We can cool the house down to below 76 at night time efficiently, but during the day I'm lucky to hit 79. Sometimes I set the thermostat up high on my way to work to save money, and neglect to dial it down when I get home. Also, I have a window unit in my room which keeps it at 71 degrees, because I can't sleep any other way lol. I build in my room sometimes, so I could be building my coils in an environment that is anywhere between 71-85 degrees, at any given time. So that really could definitely be part of it.

 

[GeorgeS]

Thanks! This is almost exactly what I do, beat for beat. A few small differences, but pushing the coil below the screws is a great addition and I will be doing that from now on. On a side note, I've even been thinking about making a jig that can just hold the coil in place while I tighten my leads, which would be quite useful. Freeing up the one hand that has to hold the drill bit (or whatever anyone uses) would be quite useful.

Glad its helping.

The last bit that I do is when I'm almost ready to tighten the near screw I'll hold the mandrel+coil against the far wall so when I push-shove it back to the near side (to secure+tighten the far side) I now have some 'slack' in the coil to allow the coil to be wider than the screw hold points.

Good idea about using a jig - I've tried a thin piece of cardboard between the coil and air hole as a spacer but it kept falling out. Having a bit of slack and pushing the coil+drill bit down also sort of unwinds or unbinds the coil on the mandrel making it easier to remove. (depending on if you mount it windings going down or windings going up)

Good Luck!