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Offline Lotuswins

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  • Roseburg, oregon
Re: Testing TCB Firmware with Stock Arduino Mega
« Reply #210 on: July 31, 2020, 01:09:05 PM »
Hi Luke,

2.1 amps....back in 18......must have been an abused smoker  8)

I seem to have melted a few down too..... :-\

So I pulled out two new, one used Taigen V2 smokers out of the spares bin and messed around for a little while. 

I hooked up my FatFingersV2 board, and put the Fluke in series measuring amps in the AVG (average) mode.  At 80 percent setting at idle, I got 0.56 to 0.60 amps on all three smokers.  It goes up a bit when increasing the throttle to 100% as set up on the board, but not much.

So I then plugged the smokers directly into the battery at 7.89volts unloaded 6 cell NiMh.  This yielded 0.73 to 0.80 amps.   

A curious thing is happening though when you let the smoker run for a while.... The current reading, starting at 0.6 amps, would slowly rise.   At roughly the 2 minute mark, the amps had increased a little over 10%.  The front of the smoker got hot, could hardly touch it....I wonder if my previous readings were maximums with a very warm smoker?  Perhaps.....

So the resistor in the stock Taigen V2 units is a NiCr wire, wrapped around a fiberglass or silicone fabric cylinder, right?  Small, but effective..  I've seen them, after much use, turn all black, burnt to a crisp.  I wonder if the heating action eventually turns the insulator to carbon, reducing the resistance causing even more current to flow?  Right now, I've given up on the smokers, just replace them as they fail since they are cheap.   HL now has a newer version though, that has an improved resistor configuration (V6.0 I think) which has the wire wrapped piece inside an insulating tube, which wicks up the fluid.  The resistor is smaller than the Taigen version, and instead of a wad of cotton to wick the fluid up, they use a little sponge.  I have one in my JS2, and so far it hasn't failed me.  I haven't done a current read on it yet, but the resistance is in the same ballpark as the Taigen IIRC.

Thanks for doing the current calcs, at least it looks like the board will survive a stock smoker.  No temperature rise on the traces was detectable after the 2 minute run above.


Offline LukeZ

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  • Edinburgh, Scotland
Re: Testing TCB Firmware with Stock Arduino Mega
« Reply #211 on: July 31, 2020, 03:53:31 PM »
Thanks for measuring that Jerry, those numbers are much more reasonable thankfully! That sounds closer to what I would have expected, and well within the tolerances of your board even with 1 oz copper which is good to know. Who knows what you must have done to that poor old smoker to have it draw over 2 amps! But these things are cheap and who knows what can happen. Maybe the little air-pump got gummed up with old fluid.

I am not surprised the current rises slightly over time as the smoker gets hot, there is definitely a relationship between the resistance of a conductor and its temperature, which principle as you know is used in reverse with thermistors to measure temperature! I've only taken apart a handful of older version Heng Long smokers and I thought they just used an actual resistor, but I would not be surprised if some of the newer ones do use nichrome wire as you have found.

It is hard for me to keep up with all the continuous developments but it seems Heng Long has really been upping their game. I notice in pictures their new smokers drive the heating element and fan separately, which is a much better arrangement (we added that feature to the TCB last year). I've also seen pictures of their new differential transmission similar to the DKLM gearbox, but haven't seen it in action. I have one of the DKLM geardrives and I really like it, but I don't know if Heng Long plan to release versions of theirs compatible with all their old models or if it will only fit in certain newer ones.
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