I have a wall wart PS that puts on 5.5 volts at 2.5 a. I’m using the ps to supply 5 v to some incandescent lights and am wondering if I could use the 5.5 to power the Arduino on the 5 volt pin?
Or will the extra 5.5v cause problems or blow the board?
Or is there a chip I could use to drop the .5 v?
Thanks
The processor is rated up to 6V, don't now about the rest of the components.
Or add a diode in the line for a 0.5-0.7V drop. Make sure the diode can handle the current and power it has to dissipate.
To explain the forward drop across a diode suggested by wvmarle
Consider this -
Diode - Wikipedia
In a small silicon diode operating at its rated currents, the voltage drop is about 0.6 to 0.7 volts.
The value is different for other diode types—Schottky diodes can be rated as low as 0.2 V, germanium diodes 0.25 to 0.3 V, and red or blue light-emitting diodes (LEDs) can have values of 1.4 V and 4.0 V respectively.
At higher currents the forward voltage drop of the diode increases.
A drop of 1 V to 1.5 V is typical at full rated current for power diodes.
Thanks
I think I'm getting it, but let ask some dumb questions just to make sure.
If I install a diode (forward bias) it will act like a resistor and I get a voltage drop? (If so, very clever.)
Could I use a 1N4004? Looking at the specs, (hope I reading this correctly) it has a forward voltage drop of 1v
Is 4.5v good enough to power the Arduino?
1N4004 is rated at 1a average. Could I use 2 or 2 in parallel to get 2 or 3a? Or is that a dumb idea.
Between 0 and 1A drawn...
the datasheet you linked to - shows the forward voltage curve from 0.6V @ 0.01A, up to 0.9V drop @ 1A
(page 2 - top RH corner)
I wouldn't dream of pulling any more than 500mA max through the Arduino board.
(PCB tracks, chip & I/O pin limitations etc)
So a single 1N4004 diode should serve you well.
The cpu will be happy - worst case 5.5V minus 0.6 == 4.9V
Although you'd always be better off with with...
a 5V regulated supply into the 5V pins,
or a 9V supply into the VIN pin
Doug101:
If I install a diode (forward bias) it will act like a resistor and I get a voltage drop? (If so, very clever.)
A diode is NOT a resistor and also doesn't at all act like it, if only because it conducts in only one direction, which is the most common use of a diode. The voltage drop is fairly constant over the allowed current range, usually increasing slowly with increasing current. Check the data sheet of individual diodes on the actual voltage drop.
To calculate the power dissipated by a diode, take the voltage drop (0.6V) and multiply this by the current (for an Arduino typically about 150 mA - depending on peripherals), and you get 90 mW.
wvmarle:
A diode is NOT a resistor and also doesn't at all act like it, if only because it conducts in only one direction, which is the most common use of a diode. The voltage drop is fairly constant over the allowed current range, usually increasing slowly with increasing current. Check the data sheet of individual diodes on the actual voltage drop.To calculate the power dissipated by a diode, take the voltage drop (0.6V) and multiply this by the current (for an Arduino typically about 150 mA - depending on peripherals), and you get 90 mW.
I'm a bit confused. If a resistor causes a drop and a diode creates a voltage drop isn't the diode acting like a resitor. Could one not get a 0.6 voltage drop using a resitor. (Would't a 4 ohm resitor do thing as the diode in this circuit.
The diode drop is always the same, the drop across a resistor varies with voltage.
Similar is not same.
Is the power supply regulated or not? Ever use a DC-DC Buck Converter?
Voltage drop across a resistor depends on the current (following Ohm's law: V = I * R). Voltage drop across a diode is largely independent on the current. For many diode types and applications it's considered constant.
Got it.
I specificly used the word "act like" and "in this circuit.
Good point that a diode will always (almost) have a constant v drop.
I learned something.... Thank you.