Just wanted to say thanks for your ground up guides to specific components - it's difficult to find explanations of individual components, with others majoring on circuit design. Keep up the good work!!
Finally someone explaining biasing a transistor in a simple enough way to understand ;) I realize not the complete story but good enough for a decent working start. Thanks.
Links: Using the ULN2003A Transistor Array with Arduino Using the ULN2003A Transistor Array with Arduino www.bristolwatch.com/ele/uln2003a.htm ULN2003A Darlington Transistor Array with Circuit Examples ----- Using the TIP120 & TIP120 Darlington Transistors with Arduino Using the TIP120 & TIP120 Darlington Transistors with Arduino www.bristolwatch.com/ele/tr3.htm Tutorial Using TIP120 and TIP125 Power Darlington Transistors ----- Using Power MOSFETS with Arduino Using Power MOSFETS with Arduino www.bristolwatch.com/ele/tr2.htm N-Channel Power MOSFET Switching Tutorial www.bristolwatch.com/ele/tr1.htm P-Channel Power MOSFET Switch Tutorial ----- Using PNP Bipolar Transistors with Arduino, PIC Using PNP Bipolar Transistors with Arduino, PIC Using NPN Biploar Transistors with Arduino, PIC Using NPN Biploar Transistors with Arduino, PIC www.bristolwatch.com/ele/tr4.htm Understanding Bipolar Transistor Switches ----- How to build a Transistor H-Bridge for Arduino, PIC How to build a Transistor H-Bridge for Arduino, PIC www.bristolwatch.com/ele/tr5.htm Build a High Power Transistor H-Bridge Motor Control www.bristolwatch.com/ele/tr6.htm Driving 2N3055-MJ2955 Power Transistors with Darlington Transistors ----- Build a Power MOSFET H-Bridge for Arduino, PIC Build a Power MOSFET H-Bridge for Arduino, PIC www.bristolwatch.com/ele/h_bridge.htm H-Bridge Motor Control with Power MOSFETS www.bristolwatch.com/ele/tr7.htm More Power MOSFET H-Bridge Circuit Examples
Maybe I'm forgetting things but when I was back in school we were taught the current flows from positive to negative. This was by convention for circuit analysis. Electrons flow from negative to positive.
Old argument. I came through the military where we use electron flow which is correct. I switched to positive because that is what everyone uses today even if incorrect. Electrons in a solid conductor are the only moving charges. Gases liquids can have both.
Hi Lewis. Great video. Not a lot of people can explain things as clear and concise as you can. I have a question. Your calculations seem to imply that for a given BJT the BETA value (in your case 20) is fixed. However almost all datasheets will give you a range of BETA (hfe) values and collector currents (Ic). For example, the datasheet for my BC108 NPN transistor gives Ic(max) = 200mA, hfe = 40 for Ic = 20uA and hfe=200 for Ic=20mA. This implies that the hfe very much depends on Ic. My question is if I wanted, for example, Ic=100mA what is the BETA value to work out base current (Ib)? Suggestions on the internet say Ib should be Ic/hfe(min)* ODF (Over Drive Factor between 2 and 10) What's your opinion? I will appreciate a response.
Ic depends on Ib and hfe. this is an example and you bring up a good point - hfe varies somewhat from transistor to transistor. Here I'm using them as a switch and use enough Ib to assure the transistor does switch fully on. If this was an audio amplifier life would be far more complex.
Lots of good details. Thanks. Am I reading something wrong regarding the Arduino digital pin current limits? My reading on the Arduino website says it's 40mA.
RimstarOrg It's 20 as far as I know let me check.The atmega328 is 40 mA but I'm going by the atmega168 which really isn't specific. Most are 20 mA - this was also a video for PICs. But you are correct. Thanks.
At 8:58, the 12V NEG and Arduino GND are connected together, will it hurt the Arduino device, because there's 12 volts potential in the battery versus 5 vots potental in the Arduino device? Will the greater potential (12 volts) will cause a current to flow from 12 v battery to the 5 v Arduino? Or is this a case where ground are cosidered zero votage therefore no current will flow from the greater potential to the lower potential??
No, the Arduino is fine unless the transistor develops a collector-to-base short. I often use optocouplers to prevent noise and short circuits in the Arduino.
