Hi guys, I have an an Arduino MKR1000 where I connected some transistors to drive an LED Matrix. Now I am running in the follwoing problem: Before the setup routine is executed and the pinmode of the pins connected to the transistors are set to output mode, it seems there is a small current at the base of the transistors making them conduct. So all LEDs are on for a short time, this is in so far a problem because I overdrive the LEDs a bit to make them brigther. Being on with such a high current for circa 2 seconds could damage them. So what can I do that the transistors are not conducting at startup? Any help appreciated. Best clemens
That chip probably comes up with pull-ups enabled, or the firmware does this - I've not looked at the datasheet or played with one. Might you be able to high-side switch the power to the entire LED section with a pFET?
Note that it cannot source more than 7mA per pin according to the Arduino specs (again the datasheet is the real guide to this), so watch out for that.
You didn't happen to connect these to pins 6 and 7 on the module, did you?
No pins 6 and 7 were not involved. If I want to shut the power down for the LEDs when arduino is starting I would need a P-Channel depletion mode MOSFET right?
You refer to using "transistors" to control the LEDs. You do not happen to mean FETs?
Yes I am using transistors BC 337(NPN) and BC 327(PNP) with a 1kOhm resistor at base
Not sure where the PNP transistors come into the bargain.
Need to see a full diagram.