6 Sensors 1 Power Supply

Hello All,

I was wondering if there is anything wierd that might happen if I connect 6 IR Sensors to the single power and ground pins.(not using a breadboard)

The power wires would all be tied together then inserted into the single pin. Same for the ground.

The sensors are 6 infrared , all constantly reading distance for obstacle avoidance.

Anything you've ran into running multiple sensors off of the common 5V pin? (Using the arduino micro)

Even if you used a breadboard, they would still ultimately be powered from the same pin. The question to answer is, how much current do they draw. As long as their summed current (plus that of any other stuff you may not have mentioned) is below the Arduino 5V pin current limit, you're ok, even if there were dozens of sensors. I forget what that limit is: it's somewhere in the 100s of mA I think but don't quote me.)

Which Arduino and how much current does each sensor require? How is Arduino powered, USB or barrel jack / Vin pin?

ericfragola:
I was wondering if there is anything wierd that might happen if I connect 6 IR Sensors to the single power and ground pins.(not using a breadboard)

Yes: it most likely just works - that is, for most common low-power sensors. It'll just work. Weird, no? Or was that a misspelling of wired?

wvmarle:
Weird, no? Or was that a misspelling of wired?

It was certainly a misspelling of "weird".

ericfragola:
anything wierd that might happen

I can't seem to find how much the sensors draw so will connect one to the 5V pin and test it independently.

Yes I did mean weird ; I was curious if there may be any odd signal interference as each sensor is coming from a main power supply.
Although I suppose since it's just the power, I shouldn't have anything to worry about.

Power supply is a 7.4V pack. Using the arduino micro so no barrel jack.

From what I read, the 5V pin can supply 800ma max. I will double check though

It should be easy enough to measure the current drawn by each sensor with your ammeter.

Should have no interference as long as the total power draw is not too much. 800 mA supply by that little regulator sounds like a too big number, do double check the data sheet.

ericfragola:
Power supply is a 7.4V pack. Using the arduino micro so no barrel jack.
From what I read, the 5V pin can supply 800ma max. I will double check though

No way the regulator of a Micro can supply 800mA with 7.4volt input.
Maybe 200mA max. I suspect the regulator will overheat and shut down at ~250mA.
All depending on battery voltage and ambient temps.
Leo..

What IR sensors do you have ?

Okay so the Uno has an 800ma limit in the regulator which is what I was reading.

Still unsure of the Micros. I ended up switching a few things to draw less.

Using the fc51 IR sensors.
Switched to the Pro Trinket from Adafruit.
Both the 5V and 3V versions have a 150mA voltage regulator on board.

Opted for the 3V version as the sensors draw less (23mA vs 43mA)
23mA x 6 sensors = ~138mA. Too close to the 150mA limit for my taste so I ordered the L4931 voltage regulator as it has a 250mA capacity and will swap them out along with adding some 10uF capacitors to the input and output. I checked with Adafruit to verify that the Trinket can handle a higher rated regulator.

So now the set up utilises a 3.3V trinket, a 250mA voltage regulator linked to six 3.3V sensors.

I'm just concerned about noise coming from the sensors all being tied to a common power and ground. When the circuit is running the IR sensors will always be active.

ericfragola:
Okay so the Uno has an 800ma limit in the regulator which is what I was reading.

You probably only read half of the story, or the sales drones "forgot" to print the other half.

Linear regulators convert "voltdrop times current" into heat, which is usually the first limiting factor.

The linear regulator of an Uno can probably sustain a volt drop of 1volt with 800mA current draw for a long time. With a volt drop of 4volt (9volt supply), the same "heat" would already be generated at 200mA.

Current limit of the L4931 depends on the package.
Do the calculations.
Leo..

ericfragola:
23mA x 6 sensors = ~138mA. Too close to the 150mA limit for my taste so I ordered the L4931 voltage regulator as it has a 250mA capacity and will swap them out along with adding some 10uF capacitors to the input and output.

What is your input voltage?

Without an extra heatsink, you can burn off up to 0.6W.

(from the Adafruit link).

600 mW, 138 mA, you can drop no more than 4.3V so your input should be no more than 7.6V without heatsink (and even so it'll be getting pretty hot at those limits, maybe even painfully so to the touch).

Whoops, forgot to post the new battery specs as well. Because the sensors draw a lot less at 3.3v VS 5v I changed everything to work on a 3.3V system which allowed the battery to be changed as well.
It's a single 3.7V 18650. :slight_smile:

Previously: 5V Arduino Micro , 7.4V pack, 6 Sensors @ 43mA

New specs : 3.3V Pro Trinket , 3.7V pack , 6 Sensors @ 23mA , New voltage regulator @ 250mA

Yeah I definitely did not want to burn off a high voltage down to 3.3. Changing the entire system voktsge really helped clear up a lot of issues

Since the ATmega328P works at a minimum of 2.7V , the batteries voltage at complete discharge is 2.7 so that works out great

Looks like everything checks out, "on paper" atleast

You may have to reduce the clock speed of the atmega to 12 or even 8 MHz at this lower voltage.

Yes that is correct. The 3.3v pro trinket runs at a 12MHz clock speed