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Need help with Digispark Halting Problem

Thread starter #1
I've been building Vaping Mods using 555 timer (PWM) driving a mosfet. It works like charm, very powerful and very decent battery life.

PWM-555.jpg

The schematic above is so good it can handle upto 200watts of power. All good.

However, I wanted to move up my project a bit, using a Digispark. Knowing it got hardware PWM, very small size and very low power consumption, it really fits the bill. Since most box mods run on dual 18650, I power the digispark through the Vin (accepts upto 12V). I've added wonderful functions like, prolonged firing protection, 3 clicks to lock etc. Tested it, all good but later realized at very high load like a 0.20Ohms coil, the Digispark halts and stops working. It won't fire, you need to remove the battery and power it up again. The 555 schematic above didn't have this issue.

Can someone help me on this? I'm suspecting that the linear regulator of the Digispark can't handle the Voltage dive when firing hi loads, which is non-existing using the 555 PWM version.

Thank you so much.

P.S. My friend ericgibbs maybe you could shed me some light on this. Thanks.
 

jpanhalt

Well-Known Member
Most Helpful Member
#3
The two views of the "schematic" you post are different. Please post a schematic for the version you actually built.
 

Ian Rogers

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Most Helpful Member
#4
If the Mosfet hasn't a flywheel diode ( or even if it has ) I would recommend you fit one.. The coil will be dumping energy back through the circuit...

Also did you code the digispark?? I used similar techniques with a Pic... I had to make all variables non volatile and use the watchdog as the wobble from the power supply was causing my program to freeze as well...
 
Thread starter #5
The two views of the "schematic" you post are different. Please post a schematic for the version you actually built.
PWM-digispark.jpg

I'm away from home so I made a really rough sketch on the circuit that I actually built. The circuit works, and functions the way I wanted it to be and only fails on higher loads (lower resistance coils around 0.36 and below). The digispark freezes and resets. The schematic on the OP is the 555 version that doesn't have issue with any load you throw at it.


If the Mosfet hasn't a flywheel diode ( or even if it has ) I would recommend you fit one.. The coil will be dumping energy back through the circuit...

Also did you code the digispark?? I used similar techniques with a Pic... I had to make all variables non volatile and use the watchdog as the wobble from the power supply was causing my program to freeze as well...
Yes, I did code the digispark. Even if the variables were non-volatile, the digispark stops sending PWM to the Mosfet then resets. Did try the flywheel diode technique but still has the same issue. 555 Timer has higher minimum voltage requirement than the digispark but it didn't have this issue.

The only thing I tried that worked is to supply the digispark with a separate battery source and joined the grounds of the both power source. But that would be very impractical.

Thank you!
 
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