okay, so i have a simple circuit setup and seem to be having problems with it that is beggning to want to make me smash stuff up.
im trying to make a 2n7000 actually do its job.
heres a photo of the circuit, the yellow wire from the mosfets center pin is connected to my arduino uno pin 13 running the blink program. the programs running as the built in led is functioning perfectly. the power supply is a 5v supply from an adaptor in the wall.
now, what you see in the picture is all i get. static, dim light.
according to the data sheets online, with the flat face facing you, pins from the left to right are 1(source) 2(gate) 3(drain)
supposedly N channel so running off the negative. switching to possitive just turns the led brighter.
im at a complete loss as ive tried several different ones as i bought a batch of them.
6v6gt:
Each led must have its own current limiting resistor if you are connecting these in parallel.
yup, got that, but its always the first installed led (and resistor)that gets driven.
never mind, with the gnd tied into the arduinos and the power supply it will drive multiple leds but they are still always partially on and blinking brighter instead of going fully off
its as if theres a current bleed keeping the led partially lit somwhere, maybe its cause im blind and tired but i just cant seem to see it, ive rebuilt the circuit a few times and just cannot work this out.
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
}
its the basic blink example.
i'll have to test the slower rate tomorrow and measure the voltage, but if lowering it to 2000ms solves it, thats a problem as i need to actually increase the flash rate
i programmed up an ATTiny45 with a blink program and set the circuit on that with 4 leds all on thier own resistor and it seems to be working fine, so i think that 02.3mv is what the problem is
The only thing I can think of is that the gate voltage is not going low enough to fully turn-off the MOSFET. That could be a "pin 13 problem" or it could be normal, or it could be some other problem... I'm not sure what "normal" logic-low is under these conditions.
Try disconnecting the Gate from the Arduino and connect it to the Source pin. That will give you VGS of zero and the MOSFET should turn off.
If it does turn off, disconnect the Gate-Source short, re-connect the Arduino and measure VGS with you multimeter (while writing digital zero). (Or you can connect it to an Arduino analog input and measure it that way.)
OK, sorry... Just some bad parts... I haven't been keeping-up on this thread and it looked like it was still alive and I was still thinking about it and trying to figure-out why a MOSFET wouldn't turn-off. :-[
He probably bought cheap parts from eBay or some unknown-unreliable supplier, or they've been damaged by ESD.
2019-11-04_10-02-55 by chris marsh, on Flickr
