• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help understanding power requirements for a project

Not open for further replies.


New Member
Hi, I'm a total newb at electrical engineering stuff and could use some help understanding how to handle the current/voltage requirements for my (perhaps over-zealous) project.

I have an art project that will consist of the following, which i've done my best to assemble volts and currents for. It has been suggested to me that i'll need MOSFETs or a Darlington Pair to get the current i need. i have not addressed the PSU since i don't know what i'll need yet.

3 channels (each with it's own color) of RGB LEDs, total of 11 lights x 20ma each = 220ma
3.2 volts per RGB LED

Regular LEDs:
7 red LEDs - a total of 16 x 20ma = 320ma
2v per LED

A controller (input) device – 5v – up to 500ma

Arduino – 7-12v up to 200 mA (but more like 50mA normally)

Arduino VoiceShield – 3v (Not sure of amps, but it's a shield for the above Arduino card) - VoiceShield

Daughter Board for controlling LEDs (74HC595 - Arduino - ShiftOut) = 5v Not sure of current.

Amp circuit – 6v - Mini 2W amplifier circuit | www.circuitstoday.com (330-660 mA)

Sonar Distance Sensor – 5v from Arduino, not sure of current - Arduino - Ping

I'm trying to figure out what my next step is in nailing down the power requirements and technology (MOSFETs/D.Pairs, etc?). If i'm omitting any important details, please let me know.


Sounds like the whole thing would run pretty well off a single large 5 volt power supply. You should be able to feed the Arduino power directly rather than through it's regulator (which is why it needs 7 volts) The Voice shield has an onboard 3V regulator so that'll be happy at 5 volts as well.. The Amplifier will still work at 5 volts (rather than the 6 you stated) but might not provide quiet as much power, if that's not acceptable use a seperate power supply for the amplifier.

Simple NPN transistor will work fine for the LED's just chose any general purpose switching transistor that meets your current requirements (you'll have plenty of choices)
Last edited:
Not open for further replies.

EE World Online Articles