I’ve been googlin’ like mad to try and work out a way of running a string of parallel leds off of one arduino pin.
After mucking about with transistors I think what I needed was a FET. I wanted to run 10 leds of the one pin and came up with the circuit attached (hopefully self explanatory) but to be honest I really just had a look at other similar circuits hence the 100R resistor and 10K to ground. I put these in as I have seen them on many other similar circuits but don’t understand fully why (apart from limiting the output current of the arduino pin). I figured after a while (and some ebaying!!!) to hook this up and see if i got my desired result and it seems to work with the standard fade example, but was wondering if anyone had any reason why I shouldn’t do this, i.e blowing up my arduino, damaging pin etc.
Circuit attached and data sheet for the FET used.
BS170 N Channel FET rated at 500ma - www.fairchildsemi.com/ds/BS/BS170.pdf
Thanks for your time.