In all the threads/reading i've done on the DNA40, its seems to only happen at some point during the firing process, but essentially never happens during adjusting of settings.
Honestly your theory about what is happening with the display is the only one i've seen that actually makes sense (to an EE layman) and also explains why its such a hard thing for them to completely eliminate (absolute insanity it still exists after this long).
Here's a weird one for ya, ive got a V1 DNA40 chip from the week they came out and its glitched a total of three times in ~6months and it ONLY happens when i have left it out in the car in 35degree weather for at least an hour...
Also let me say it's nice to have another member with your seemingly very in-depth knowledge of EE/circuits, welcome aboard!
Thanks!
This vaping noob has already learned so much from the cool people who make up the ECF community! I'm hoping I can trade some EE info for it.
And thanks for the glitches-only-when-firing info!
You're having only cold weather glitching? Some possible causes include...
- Cell voltage under load drops considerably when it's cold. Cell internal resistance also goes up. These combine to produce a very sharp drop in voltage at the beginning of a discharge before the cell starts to heat up. If the drop is low enough, but not too low, it can cause what is callled a "brownout" condition. It's not a low enough voltage for the microprocessor (MPU) or display to shut down. It's at the edge of what the voltage needs for reliable operation. If the MCU and display (and supporting components) aren't set up to handle this brownout condition just about anything can happen.
- Component values drifting. At 35F though the components won't drift much compared to room temperatures.
- Firmware timing issue. If the firmware's timing for the commands and data sent to the display are right on the edge of what the display can deal with then component value shifts in the display might make the display controller intermittently misread or ignore commands or data being sent. Not too likely IMO since drifting is minimal at 35F.
- Bad or fractured solder joints. As the board and components shrink/shift different amounts as the board is cooled, it places stress on the solder joints. If any of those solder joints are questionable then the effective value of the component can shift. The solder joint can even actually fracture and open up, effectively removing the component from the circuit. This, as you can imagine, can cause all sorts of problems. Especially hard to debug as the problem goes away when the board heats back up to room temperature. And made even worse by the lead-free solder that is used now. Leaded solder is less brittle and better handles temperature swings. It's why it is still used for military and hi-reliability applications.
My guess...cell voltage dropping too much when firing (this can just be during the first few milliseconds, not seem on a mods volt meter) or bad solder joint(s).
