DirA[9] := %0 grounds signal?

sccoupe

I am setting pin 9 to input via DirA[noparse][[/noparse]9] := %0 and its grounding my signal. What gives?

Steel

what is it connected to? Are you sure it's not your circuit gnding your signal?

sccoupe

I am tieing into a low voltage signal that signals an igniter to fire a spark plug. Checking with an o-scope is fine, running it right into a pin on the propeller causes that plug not to fire and the engine misses.

Mike Green

If your signal exceeds 3.3V, it will be clamped at 3.3V by the protective diodes on the I/O pins.

deSilva

Mike presumes you are not using a resistor (1..10k) to tap that signal, which I hardly can believe...

sccoupe

So that clamping at 3.3 volts also clamps the signal that goes on to the ignitor?



ECU

---

ignitor
·············· |
·············· |
·············· |
·············· |
·············· |
····PROPELLER INPUT

·

Bean

sccoupe,

Putting a resistor on the propeller pin will limit the current to protect the pin and also cause it not to ground out the signal. 10K or something like that.

You may have damaged the propeller pin if the ECU outputs 12V.

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I know what I know, don't confuse me with the facts...
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
www.hittconsulting.com
·

sccoupe

Thanks Bean, Ill give it a try. Perhaps Ill need to move that signal to another pin after a 12 volt shock. [noparse]:)[/noparse]

deSilva

I posted this sketch from some of my tutorials some time ago... here it is again. It was drawn to fight some phantastic misconceptions about a CMOS input

deSilva

sccoupe said...
I am setting pin 9 to input via DirA[noparse][[/noparse]9] := %0 and its grounding my signal. What gives?