#DARLINGTON TRANSISTOR ARDUINO CODE#

I actually was not thinking about the led forward voltage because it is not shown on your simulation so I I first looked at the max forward current spec, and then found the forward current vs collector current plot. You were right about the LED resistor being too high.Īctually, it was just a SWAG (Scientific Wild Ass Guess). Try changing the led resistor in the first simulation to 100 ohms for 50 mA. Look at the collectorĬurrent difference between 30mA and 50 mA forward current ) Without external biasing, I am losing about 8 volts over the optocoupler although I believe I am staying in specification for the device In both cases, I am driving the internal LED hard. The circuit must be designed so that the VECO value (0.3V) will not be exceeded. Through this Di element, a current flows between the emitter and the collector. Owing to this, for VECO, the characteristics in the forward direction of the Di also appear VECO is thus specified with a very low (0.3V) value. When a transistor in a Darlington configuration with base-emitter resistance is incorporated into an Si chip, stray diode Di is put between the emitter and the collector in an equivalent manner. IS the photo-transistor facing the photon barrier so everything I said still applies. I know what a Darlington is, however, the 'first transistor' you refer to (the darlington driver) My reference to the first transistor, in case it is not clear, was to the first transistor in the Darlington pair facing the LED. You did understand the the construction of the that particular optocoupler was a photo Darlington pair and the conventional model in the specification has a representation of a base (even though it is not externally exposed in that case). Hence may original question relating to the voltage which could be switched with such devices. With external biasing, I can eliminate the voltage drop. Without external biasing, I am losing about 8 volts over the optocoupler although I believe I am staying in specification for the device. I have 2 diagrams, one without external biasing on the base and one with some. I'll simplify it a bit with another optocoupler (this time a single transistor design) which additionally exposes the base for optional external biasing. OK thanks for all that and a very entertaining style too.

Look up the collector emitter voltage drop when in saturation mode.

No base (at least no physical one because it's Since it is either on or off there is 130V or no voltage on the emitter so the word 'bias' is not even applicable here unless you describe it as Therefore vary the 'bias' as it were of the transistor, resulting in less than 130V on the emitter. Number of photons crossing the barrier and Source then it would be possible to vary the If the led were driven by a variable voltage Which I would hope you know is either on or off. Is that ALWAYS the case with opto- couplers ?Ī- Because the led is driven by a GPIO pin, It's a switch (with a slight voltage drop)Ĭan you see what happens when you turn on a switch ? 'I can't really see what happens when it's switching this voltage' I have put a 2.2 K Ohm resistor as in this pictureĪny idea? I remember I made this work even in more complicated settings, but now idea now what I am doing wrong.1- What's wrong with 'the first transistor ' PinMode(TIP120pin, OUTPUT) // Set pin for output to control TIP120 Base pinĪnalogWrite(TIP120pin, 255) // By changing values from 0 to 255 you can control motor speedĪlso tried digitalWrite(TIP120pin, HIGH) but nothing Int TIP120pin = A0 //for this project, I pick Arduino's PMW pin 11

#DARLINGTON TRANSISTOR ARDUINO CODE#

I tried this simple code // Define which pin to be used to communicate with Base pin of TIP120 transistor Pin A0 to the base of the TIP120G and the emitter of the TIPC120G to the negative of the fan. More specifically I connect the positive of the fan to the 5V of the Arduino. This should be trivial but the fan it is not moving at all when the transistor is activated by the arduino.

To make the fan go faster i charge a TIP120G (Darlington transistor) from the output power of the Arduino, (in this picture the nano but I have tried also other arduino). I am trying to do something with a fan (powered 6-12 volts).

Darlington transistor arduino