Doubt about the pnp transistor
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- exapod
- Posts: 15
- Joined: Tue Jul 12, 2011 1:58 pm
Doubt about the pnp transistor
If you use a pnp transistor for switch the npn that drives the leds is the pwm signal inverted? i mean if the pwm of the uc pin is high for 20us the led will be off for 20 us or i am wrong?
-
- Posts: 295
- Joined: Sat Dec 11, 2010 1:17 am
Re: Doubt about the pnp transistor
You are correct, when pin 5 is high, the IR leds are off, and when pin 5 is low, the IR leds are on.
- exapod
- Posts: 15
- Joined: Tue Jul 12, 2011 1:58 pm
Re: Doubt about the pnp transistor
So if i use the v1,2 software but control only one led with a npn it will not work??
-
- Posts: 295
- Joined: Sat Dec 11, 2010 1:17 am
Re: Doubt about the pnp transistor
If you want to do that then you'd have to modify the software to invert the signal on that pin. It's not too difficult, just changing a few lines in the main file.
I actually had to do this on my most-recent TV-B-Gone build, not for the IR LEDs but for the visible LED as my build had the visible LED wired to ground instead of Vcc.
I actually had to do this on my most-recent TV-B-Gone build, not for the IR LEDs but for the visible LED as my build had the visible LED wired to ground instead of Vcc.
- exapod
- Posts: 15
- Joined: Tue Jul 12, 2011 1:58 pm
Re: Doubt about the pnp transistor
Thank you for the help.
Please be positive and constructive with your questions and comments.