i want to activate a relay which its activation power is 3V dc 24mA. i activate it with my external power source but when i try to activate it with my arduino uno my outpout voltage of the arduino sinks from 4.6 volt dc to some milivolts and i have no current
or at least nowhere near the 40mA that the arduino uno pins provide. am i doing something wrong or the arduino uno does not
provide max 40mA output?
i have no current
or at least nowhere near the 40mA that the arduino uno pins provide. am i doing something wrong or the arduino uno does not
provide max 40mA output?
Don ever try to drive the relay directly from the pin itself.The output pin does not have enough current to drive the relay and you will damage the pin doing that.
You must put a transistor with the base connected to your pin and you relay connected in the collector of that transistor
Something like this:
http://www.google.pt/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&docid=CtLmbMCTlXe4WM&tbnid=ZEAmdAWluCP-sM:&ved=0CAUQjRw&url=http%3A%2F%2Fopenenergymonitor.org%2Femon%2Fbuildingblocks%2Fmains-ac-relay-module&ei=QOboUrnEH4Ob0AWJq4H4AQ&bvm=bv.60157871,d.d2k&psig=AFQjCNEu_qcN_TH-B9J8WLQxGYF_8id88w&ust=1391081403610282
You can drive very small relays with an aduino output directly.
Is 24mA@3V the exact specs? Then 5V from the output pin is way too much! Put a ~120 Ohm resistor in series. And very important: put a diode anti-parallel to the relay coil!
Anyway the output voltage should not drop to nearly 0. There is certainly another problem with your cabling
MORFEAKIS:
or at least nowhere near the 40mA that the arduino uno pins provide. am i doing something wrong or the arduino uno does not
provide max 40mA output?
a) Arduino pins don't provide 40mA. That's the current where the datasheet says "All bets are off" and "Damage may occur".
b) All currents will have voltage drops associated with them. Even at 20mA you'll drop to 4.4V. See Figure 29-70 in the datasheet (and notice it doesn't go past 20mA).