iliketurtiles

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13
[Solved. Don't get why solution works] Unexpected large number of external interrupts except when logic analyzer is connected to pin. (programming.dev)
submitted 21 hours ago* (last edited 20 hours ago) by [email protected] to c/[email protected]
1 comments fedilink
 

I'm using an Arduino and through a library working with an IC (MCP2515, a CAN controller) over SPI. The IC indicates interrupts by causing a falling edge on an interrupt pin.

Components are connected using jumper wires on a breadboard.

  • When a logic analyzer is not attached, the IRQ gets called a few hundred times. It should only be called once. I thought it must be noise on the external interrupt pin but a pull-up doesn't help. I've tried the internal pullup and an external one.
  • Trying to see if there is a ton of interrupts from the IC, or an error internal to the Arduino, I attach my logic analyzer. Now it works perfect.

Any idea what might cause such a weird issue? Looking around I haven't found anything.

EDIT: I found a Reddit post for a different circuit where a user suggested placing a small capacitor to make the edges of a signal rise slower. This has fixed my problem.

Since I've already created a post: does anyone know why I was getting an unending number of interrupts? Why would the edges of the interrupt signal changing too fast cause something like this?

How come there are components in TO220 packages that supposedly take 100A given their small legs? in c/[email protected]
[โ€“] [email protected] 5 points 1 week ago* (last edited 1 week ago)

For the IRF1404Z, under the absolute maximum ratings, continuous drain current is given as 140A. If it was for something like picoseconds, it doesn't seem meaningful labeling it 'continuous current'?

15
How come there are components in TO220 packages that supposedly take 100A given their small legs? (programming.dev)
submitted 1 week ago* (last edited 1 week ago) by [email protected] to c/[email protected]
5 comments fedilink
 

Not sure if this is a dumb question but this has me quite puzzled.

The legs on TO220 packages are very small. How is it that there are e.g MOSFETS rated as being able to continuously conduct ~100A? e.g IRF1404Z

From what I understand such large currents need busbars on PCBs and these appear a lot larger than the legs on these components.

How can I figure out which phases in a BLDC motor to power without knowing how its wound? in c/[email protected]
[โ€“] [email protected] 1 points 1 month ago

Thank you, will give that a go :)

9
How can I figure out which phases in a BLDC motor to power without knowing how its wound? (programming.dev)
 

I'm making a driver for a small 15V, hall sensored, 9-slot BLDC motor I got off of AliExpress. It has u,v,w inputs. Three hall outputs and Vcc, Gnd for them. No datasheet :)

I understand the working principle: I'll have to use the hall sensors to figure out the location of the rotor, then power the appropriate windings.

Trouble is, I don't know how the windings for the three phases are arranged within the motor. So I don't know which pin to give power to, because I don't know which windings within the motor will then be powered.

How can I figure out where the windings are for each phase?

I'm guessing I've got to manually spin the motor and do some detective work with back-emf measurements and hall sensor outputs to figure this out?