I just keep coming up with that and thinking it SHOULD work but that it seems too simple!!!!.Īnd when I try to breadboard it, I don't seem to get correct value resistors, it seems to stick one way or the other. Then, in the line from collector of Q15 to the base of M13 put a resistor of LOWER value than R42!Īm I correct in thinking that when the arduino pin goes HIGH, transistor 1 will suck number 2 low, and when the arduino goes LOW number 1 base goes back high and number 2 will promptly trigger again. Quick question:why the 100Volt 14Amp Mosfet at M13?Īnd back to my dilemma: what if I used exactly that schematic but with 2 x BC558. Septillion has come up with VERY useful suggestions, but Paul_B,s little circuit is ALMOST exactly what I have been playing with in my mind. They are 25mA red and green LEDs, off the shelf. I want to use ONE single pin on the Arduino to switch one PAIR of LEDs on while simultaneously switchen ANOTHER pair OFF. Ignore the ammeters (comes from a simulation). Now, the alternate set of LEDs are connected with the same components, but the base resistor to this transistor comes from the collector of the first transistor. The collector goes to the resistor, LEDs and thence the 12 V supply. the emitter is always connected to ground. To drive some LEDs from an Arduino output, you have a 2k2 resistor feeding the base of the resistor from the Arduino output. It is unclear whether the OP wants to control the LEDs by Arduino or just by a switch. It's not a "flip-flop" and it's not an "OR". For a 12 V supply, you can have at least two LEDs in series, 3 is fine for any colour. Note that each transistor must have a series base resistor, and each LED must have a series current controlling resistor. What are needed are NPN transistors - whatever general purpose ones are rated at least 25 V and a few hundred mA. Would that not end up with the LEDs attached to one BC558 being on when those on the other were off?Ī BC558 is a PNP transistor - the wrong sort for this application as per septillion's comment. So can someone stoop down to my level, please?ĭo you not take the Arduino output and feed it to one BC558 and also through an inverter to a second BC558 ? And yes, I know a quad logic gate would do the trick but a) I'm having trouble even sourcing one that requires only one input per out and b) where I live it is all mail order stuff. I have looked in all kinds of places (tutorials, hobby kit circuits etc) and just can't quite get what I want. I just can't get my head around a stupid little circuit (using transistors) that takes care of that with just 1 on/off signal. And that's what is driving me nuts!!!īecause I just absolutely KNOW there is a better way with just those old BC448 or 558 that I have in my bin to combine each twin pair into an OR situation. Yes, a flip flop.Īnd yes, I already use old BC558s to drive each pair of LEDs. It's a simple logic thing, if one is ON the other HAS to be OFF. I am ALSO trying (for each switch) to to change one pair of LEDs to on, another pair to off.Īnd yes, I could simply use 8 pins instead of 4 on the Nano. Going to use a Nano to control 4 point motors by reading 4 switches (pulled either high or low, who cares) and then controlling 4 servos. Table: Display numbers on a seven-segment display in common cathode configurationīelow we are interfacing a 7-segment display to Arduino UNO for reference.It's probably a while since a question this basic got asked and my apologies for that but I haven't dabbled in electronics for nearly 30 years and the brain just doesn't work the way it used to so. Things change for common cathode configuration. Table: Display numbers on a seven-segment display in common anode configuration The below table shows the 0-9 codes for the seven-segment LED display. This is provided by the driver and is applied to the seven segments. So, a sufficient forward current has to be provided to these LEDs to glow with full intensity. The intensity of the LEDs depends on the forward current. These LEDs will glow when they are forward-biased. Seven-segment devices are generally made up of LEDs. All the negative thermals are left alone. Common Cathode 7 Segment Display:Īll the positive terminals (Cathode) of all the 8 LEDs are connected together. All the positive terminals are left alone. Common Anode 7 Segment Display:Īll the Negative terminals (Anode) of all the 8 LEDs are connected together. Common Anode and Common Cathode 7 Segment LED Display 1.
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