Powering multiple items/sensors off the single 5V

I’m looking for ideas on how to wire up multiple sensors, buttons, etc to the single 5v terminal on the arduino. Right now i have 3 temp sensors (voltage divider config), 2 buttons w/pull up resistors, a pressure sensor, and a serial lcd. In their current configuration they are all attached by being looped together and taped at a single point.

I made a nice little board that powers everything in parallel and looks nice and i can plug things in and out of it. But, it’s useless because wiring it this way screws up the sensor readings.

So, my question is: How do you wire multiple things up to the arduino power supply pin while keeping things neat and easy to swap in and out?

well, i’m sure your problem could be solved adding resistors.
:sunglasses: :sunglasses: :slight_smile: :wink: :smiley: ;D >:( :frowning: :o :sunglasses: :-? ::slight_smile: :stuck_out_tongue: :-[ :-X :-/ :-* :’( :sunglasses: :sunglasses:
edit: i took away some of the smilies because of aligning issues

Holy carp that's a lot of smilies!

Could you explain more...I'm a coder not a EE so I don't really get this circuitry stuff.

ok, seriously. one or multiple of your sensors/buttons probably create some form of short-circuit, when "on". which means too much current is flowing directly to ground. another possibilty is, that you unintendedly build a voltage-divider. if you have a drawing of your setup, this shouldn't be a big deal.


Yeah, basically i have unintentionally created a complicated voltage divider.

http://img206.imageshack.us/my.php?image=snapshot20070830173253as0.jpg is the diagram. The diagram isn't proper though so i'll explain. All the sensors say they go to 5v+ which means they are connecting to that 5v+ breakout pictured at the top right. (I know this is going to sound cheesy but) The breakout is essentially a single row of an IC socket with all the pins connected on the bottom. This way I can plug a wire from the 5v pin to the first spot on the socket and then plug everything that needs power into the other sockets.

I am sure they are effecting each other as i get different readings/button presses based on where I plug them in in this configuration.

So it looks sort of like this.

5v+    temp1   temp2   temp3    buttonA   buttonB   pressure   accelerometer
 |        |           |           |            |               |            |               |  

And the ground looks about the same way:

Gnd    temp1   temp2   temp3    buttonA   buttonB   pressure   accelerometer
 |        |           |           |            |               |            |               |  

These all seemed to work together when they were crumily wired from a single point.

   /-----a sensor
5v+  ----  a sensor
   \ ----a sensor

i don't see an electrical difference between "how it is and does not work" and the seemingly working old setup. your schematics do look right, though i wanted to start this answer with Holy crap that's a lot of sensors. i couldn't yet find a voltage dividing anything. you should check the voltage at your multi-socket with the sensors connected.

maybe it's just not enough current? are you able to disconnect single sensors? when does it work? you could roughly calculate the current flowing through each sensor for different situations (warm/cold for the temp sensors for example). the current from your arduino is limited of course, depending on your power source, imagine one million of your temp sensor circuits (including the 220 ohms pull up resistor)... each sub-circuit draws a maximum of 22mA... that would be a theoretical 22kA current, which could be considered a "short". ... just to illustrate the problem: your setup might be right, but just over the limits.

this of course does not explain why it worked before. maybe you changed the supply from USB to external?

// kuk


I guess it's time to break out the multimeter. I'll report back when that's done.

You are correct in guessing that I was using USB power before and now I'm using and external power source (12V regulated).

Thanks for the help.

This is the full detail of the project if you are curious: http://www.iwsti.com/forums/showthread.php?t=84794

I finally got time to break out the multimeter. I found two things. 1) 3 of the 5v+ pins were actually dead (not properly connected) and 2) I was hooking the thermistor to the wrong pin (I have two temp sensors but only plug in one for testing).

In addition, powering things in a chain as diagrammed above is perfectly acceptable and works. I tested the various sensors at various loads and the pins downstream and upstream still read 5V+ as they should.

So, what can we learn from this... When in doubt break out the multimeter and take good notes. Also, you can use a deprecated IC socket + male header pins for a quick plug and play power hookup, but its probably not a good idea for a finished project.

so just one happy smiley this time:


I was reading 6 sensors and had weird crosstalk between the channels that was barely detectable with a multi-meter but caused havoc once I hooked it up to Max - values were "floating" and sensors were affecting each other. The solution was to add a 10k resistor between signal and ground of each sensor: problem solved.