Timeline for What is the purpose of this current sense resistor in my arc lighter?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 16, 2021 at 18:03 | vote | accept | Sod Almighty | ||
| Mar 16, 2021 at 18:03 | comment | added | Sod Almighty | Thank you. I will "accept" the answer. | |
| Mar 16, 2021 at 3:15 | comment | added | Dharmik | Yes, that what I am trying to say. Just, for example, a perfect arc on the secondary side gives feedback voltage around 3v. And when the battery voltage drops probably feedback voltage will be drop now controller will increase Ton time and also increase Toff time allowing the capacitor to charge and discharge more through the primary. It looks like C2 is used as storage cap here. | |
| Mar 15, 2021 at 18:13 | comment | added | Sod Almighty | Yes, I understand how the current through the MOSFET will affect the sensed voltage at pin 13. What I'm uncertain about, is how this helps the firmware perform its job effectively. Remember that its job isn't to generate a high current or voltage on the primary; but instead to cause an arc on the secondary. I guess maybe it knows how much current is needed in the primary to induce this effect, and will aim to achieve this. | |
| Mar 15, 2021 at 17:39 | comment | added | Dharmik | The microcontroller doesn't know the arc is happening or not but it can sense that the power flowing from the primary side of the coil. and from that, it can manage the duty cycle. Have created a simple simulation that might help to understand tinkercad.com/things/a0UqSvhkEnm vary the input voltage and observe the change at the output voltage from 4.7K resistor. | |
| Mar 15, 2021 at 17:34 | comment | added | Sod Almighty | What I don't understand though, is how it's possible to sense correct operation by monitoring pin 13. How can the microcontroller "know" if the arc is happening? | |
| Mar 15, 2021 at 17:04 | comment | added | Dharmik | It's tricky but you can build a simple variable square wave output pulse generating circuit with a 555 timer. or if your oscilloscope supports outputting a variable square wave pulse you can use that also. | |
| Mar 15, 2021 at 16:33 | comment | added | Sod Almighty | Do you have any idea how I could, by artificially generating the square wave, perform tests (without the original chip) to give me a good idea of the correct behaviour with regards to this pin? | |
| Mar 15, 2021 at 16:31 | comment | added | Sod Almighty | Unfortunately, I can't measure this, because the original chip is now broken. It was the output pin that snapped off :( | |
| Mar 15, 2021 at 16:18 | history | answered | Dharmik | CC BY-SA 4.0 |