Ryan Thanks for the LED help; also a Q


Thanks for the LED help.

I did get it to run, and to respond to the CdS sensor, but it apparently sucks
so much amperage that the servos won’t run simultaneously with the LEDs.

Q: can I run the Arduino + servos + LEDs off a 9V 10A wall wart without frying the Arduino?

Would it be better to set up a second power wart for the servos + LEDs? Would this involve grounding problems?


John S. (John2pt0)

John -

While the Arduino has an onboard voltage regulator allowing it to be powered by supplies in the 7V-12V range, pulling 5V through that regulator to power other components is likely to release the magic smoke.

The correct approach in this case will probably be powering all the 5V components, including the Arduino, from a single 5V power supply. If you’re breadboarding, this is as simple as connecting a 5V wall wart to the negative and positive rails, powering everything from said rails, and connecting the control/logic lines as usual.

If you’d like, I can demonstrate this on Tuesday before or after the meeting. I have some barrel connectors available for this purpose.

  • Ry

Ryan -

Where do I connect the 5V in, to power the Arduino?
The web pages say “no less than 7V to get 5 (regulated) V on the Arduino board” and “don’t put 5V directly in to the “5V” pin”.

Also, can one use a PC power supply? The web, no, i mean The Web says one can get 30000 ma @ 5V from one of those! (Any old ones around the hive?)

As noted above, I cannot make it tonight. Hopefully Joseph can demonstrate the LED/CdS setup and can get face-to-face info re: powering the Arduino.


John S,

Ryan -

I looked at ( and implemented) the circuit you showed to Joseph, but the servos still didn’t like to run much when the LEDs were running.

I stumbled into a recommendation by AdaFruit to use a “more PWM friendly” servo library called “PWMServo”.
I installed that, and changed the software to “#include” it (and commented out the “Servo.h” library) and things seemed to look up.
The servos and LEDs seemed to run the software together OK on Wed.
Then, on Thurs, the LEDs would only blink briefly when the Arduino was powered up, and now they don’t light up at all.
I did not use any voltages other than 5V except when I ran 9V into the barrel connector on the Arduino (which should have produced 5V out to the 5V or Vin pins, yes?).

Any ideas as to what happened or what to try next?

Are the LEDs dead?


John S.

To quote the inestimable Han Solo “It’s not my fault!”

It’s very possible. In the absence of a smoothing capacitor, it’s pretty easy to cook those LEDs with a power-on voltage spike. Accidentally reversing the voltage usually does the trick too. I’ve managed to commit both errors several times. Generally, one LED fails and this interrupts communication with the remainder of the strip.

Don’t worry about the LEDs if that happened. I have many more available.

I’ll be down at the Hive this evening, and again on Monday and Tuesday. I can leave some more strips out somewhere for you to pick up.

Thanks for the note.
I wi try cutting the LED strip and adding the data line resistor & the voltage input capacitor. I will plan on Tuesday at the Hive.

Also trying to get the logo 3D printed for one half and laser cut for the other .

Hope to get something running by Thurs, as I am out if town thus weekend!

John S.

From the Western Spiral Arm

Ryan -

Family emergency. I cannot make it, but Joseph will pick an LED strip tonight.

Thanks again.

John S.

see below