In this mode, the junction J1 and J3 are forward biased but junction J2 is reverse biased. The term forward biased SCR implies that its anode terminal is positive with respect to cathode terminal with gate switch S open. Forward Blocking Modeįorward Blocking Mode is that operational mode of SCR in which it does not conduct even though it is forward biased. This is the reason, in reverse blocking mode an SCR may be treated as an open switch. When the reverse voltage is less than V BR, SCR offers high impedance in the reverse direction and hence do not conduct. Therefore the reverse voltage across the SCR terminals should not exceed reverse breakdown voltage during its operation. This increased reverse current may result in more losses in the SCR which in turn may damage the SCR. It can be seen that, there is a sharp increase in reverse current at this voltage. V BR represents this reverse breakdown voltage in the V-I characteristics. This critical reverse voltage is called Reverse Breakdown Voltage. If the reverse voltage is increased, then at some critical voltage an avalanche breakdown takes place at reverse biased junctions J1 and J3 which leads to sudden increase in reverse current.
#CATHODE ANODE DIAGRAM SERIES#
The device behaves as if two diodes are connected in series with reverse voltage applies across them.Ī small leakage current of the order of mili or micro ampere flows thorough the SCR in this mode. Consequently, junction J1 and J3 are reversed biased while the junction J2 is forward biased. This leads to reverse biasing of the SCR. This means that anode terminal is made negative with respect to cathode with switch S open. It is shown by OP in the V-I characteristics of SCR.Īs clear from the V-I curve, the anode to cathode voltage in is negative in this mode.
![cathode anode diagram cathode anode diagram](https://i.stack.imgur.com/0HLZa.gif)
Hence this mode is also known as OFF state of SCR. An SCR in reverse blocking mode behaves as if an open switch. Reverse Blocking Mode of SCR is that operational mode in which it offers high impedance for current flow and hence do not conduct. Let us now discuss each of the three modes one by one. Various Modes in V-I Characteristics of SCRĪ careful observation of the V-I characteristics reveal that an SCR has three basic mode of operation: Reverse Blocking Mode, Forward Blocking Mode and Forward Conduction Mode. Light_value = value_RED*((float)value/(float)gradation) ĪnalogWrite(ledpin1, y) // increase the voltage in pin 9 from random to 0 voltsĪnalogWrite(ledpin2, x) // increase the voltage in pin 10 from random to 0 voltsĪnalogWrite(ledpin3, w) // increase the voltage in pin 11 from random to 0 voltsĭelay(30) // waits for 30 milli seconds to see the dimming effectĭelay(700) // wait. Light_value = value_BLUE*((float)value/(float)gradation) Light_value = value_GREEN*((float)value/(float)gradation) Value_GREEN = 200 + random(56) // puts a random number between 0 and 255 into value_GREENįor(value = 200 value =200 value-=5) // ramp the number in "value" from 255 to 0 Value_BLUE = 200 + random(56) // puts a random number between 0 and 255 into value_BLUE
![cathode anode diagram cathode anode diagram](http://kongheng.com.sg/wp-content/uploads/2012/10/Plating-Diagram.png)
Value_RED = 200 + random(56) // puts a random number between 0 and 255 into value_RED Int ledpin3 = 11 // green LED connected to pwm pin 11 via 1K ohm resistor Int ledpin2 = 10 // blue LED connected to pwm pin 10 via 1K ohm resistor Int ledpin1 = 9 // red LED connected to pwm pin 9 via 1K ohm resistor random tri-color fading LED *common cathode* Does anyone have any ideas of where I can begin to get this RGB LED to work? Hints and ideas are appreciated at this point since I’ve been banging my head on a well for a couple of weeks.
#CATHODE ANODE DIAGRAM HOW TO#
I have some code that I found online (Update: Original post can be found at the old forum, it was written by Studio Bricolage) however I can’t figure out how to transform the code to work with a Common-Anode RGB LED using pull down resistors.