Hello everybody,
I am wanting to use my arduino to run some LED's on my motorcycle with my turn signals, I am wondering if I can get away with powering a 7805 and using the 5 volt signal as an interrupt on pin 2 and 4. When the turn signals flash they will power the 7805, would the signal be too dirty to use? The reason I am considering going this route is mainly due to the fact that I have a HUGE amount of 7805's available to me.
No don't use this chip in this way. It will take too long to stablise, and wil not give you the stability you are after.
ok, so what would you recommend using? Keep in mind it's entirely likely my flasher voltage could vary a couple volts depending on engine RPM, the bike is 12 volts.
What current is this?
Use either a transistor of an FET, with lots of suppression on the base / gate.
not very much, 75ma, 100ma tops you'll have to forgive my ignorance I am relatively new to this world. I am trying to learn and make things work at the same time without releasing too much magic smoke.
Well a simple transistor will be fine.
Use a 10k base resistor and put a 0.1uF capacitor from base to ground. Have the LED in the collector and the emitter to ground.
This will be driving common anode RGB LED's I have them currently grounding through a ULN2803 I want to use my turn signals as an interrupt on my arduino as it is already dealing with a couple other tasks. When the turn signal comes on I would like the arduino to be interrupted and turn on the red and green of the RGB (making yellow for my signal) so I need to be able to interface my turn signal with the arduino and more specific I need to interrupt on pin 2 and 4 I believe.
Normall the two simple interrupts are on pins 2 & 3.
If you have a nominal 0 -12V signal comming in then I would use a 1K resistor to connect it to the interrupt pin, with a 5.1V zenner across the input pin to protect it, and a 0.1uF capacitor across the zenner.
and that is where the complication starts and the reason I was considering using the 7805, it would give me a constant voltage where as the flashers could differ considerably depending on engine RPM, upwards of 14 volts.
Yes and that is where the zenner comes in giving you a constant voltage at the input wether if you have 6 volts or 60 on the input.
ok, I am sure I am going to sound like an idiot asking this but I am gonna ask anyway. When you say connect the zenner across the input are you talking between the resistor and the input? Sorry just a bit confusing to my newb mind. Connecting the cap across the zenner I can visualize but having difficulties with the other. Thank you for your input by the way.
The zenner goes from the input - the cathode, to ground - the anode.
The resistor goes from the input to the signal, that is your voltage that you want to generate the interrupt from.
Make sure it is a 5.1V zenner although you could use a lesser one providing it is above 3V3.
Ohhhh ok that makes sense, sorry still trying to learn here your help is greatly appreciated!