5v output from Arduino/gShied motion controller

right now i connected to my PC power supply.just found this just need someone to confirm this for me.

sorry i suck on electronics but im learning lol.

FYI - Since you have a computer sitting there, you can get 5v from a USB port - a different one from the one powering your Arduino. Just take ANY USB cable, cut the end off - red wire is positive, black wire is negative. Else use ANY phone charger and to the same thing. If using a desktop computer you would also be looking for a red wire. Red is +5V, Yellow is +12V and Orange is +3.3V… all the blacks are negative.

If you have to tap the arduino, use the Vin, tab NOT the 5V out which probably runs through the onboard regulator for when you power it with 7-12volts DC and has very narrow current limitations. Vin is different from your 5V out. It is directly connected to the power supply for your Arduino, which in this case is your USB port. You should try to ensure that you are not drawing more than 500ma from any single USB port. Not sure what the Arduino plus shield’s normal current is, but if you use a different USB port it should be irrelevant.

thank you for the input,i guess ill just leave it connected to my pc power supply.

I am also looking for a way to get 5V output from the Arduino UNO. I have three pushbuttons installed for Reset, Hold and Continue connected to pins A0-A2 on the UNO. I also want the pushbuttons to trigger another Arduino Mini Pro card so I can show info on a LCD. To separate the two cards I have a 4 channel optocouplet card. The Optosmall. This card uses common VCC and common ground on the input side. Same thing on the output side from the other card.

UNO common ground is no problem and the A0-A2 pins are no problem, but common 5VDC is stacked under the gShield?

I guess the 24VDC gShield power is a no go in this case?


[1]: http://land-boards.com/content/index.php/optosmall

Look at this thread:

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The buttons are working very well, but problem is the powering of the Optosmall card with 5V.

I think I have solved it. The row of pins to the left of A0-A… on the UNO has both 5V and ground.
These pins have pinouts on the gShield also. I have soldered pins to the gShield and can now tap 5V.
It will be tight for the Y-motor threads but I think it will work :slight_smile:

You should probably tap VIN instead of 5v. The 5v runs through a voltage regulator and is not capable of providing much power. The Vin in this case is drawn directly from the the USB supplied 5v.

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Yes, I was thinking the same. I’m using Vin now and the testing is promisIng. The Optosmall card is working :smile:

I love this idea. What info do you plan to show on the LCD? What type LCD are you using (hd44780 or a graphic LCD)?

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Ok, so you say that the 5+ pin is a better choice then. I will test that one too.

First of all the lcd is showing temp and air humidity in the controller box.
Then i think it will show that you push the green, yellow and red buttons.
It’s a 20x4 lcd with an i2c controller. DHT22 probe for temp and humidity. Both connected to Arduino Mini Pro.

Actually looking at the schematic a little closer my earliear statement here is incorrect. Give me a few minutes and I’ll revise.


Ok, answered too quickly before without spending enough time to get the straight scoop, sorry.

Vin should not be used as a voltage source. It is connect to the inter-board socket, a diode, a voltage divider and the input to a voltage regulator.

An additional issue is that Vin is rated for 9 to 12 VDC. So if you used an external power supply with the Arduino your add on circuit could be damaged.

By all means use the +5 volt position and just make sure you don’t exceed the current available.

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How do you plan to track button presses? If you can get info from the arduino/g-shield you could also display CNC status and position. Is there a way to get that info? I might have to play some…lol

Don’t have a multimeter here but it’s worked for me in the past and I’ve drawn more than 250 ma.


You might want to keep a spare Arduino around.

I’ve edited my earlier post. Better information there.

In this case it is connected to a USB port supplying regulated 5V so unless he unplugs everything from his computer, finds a barrel jack power supply and plugs it in, I think he will be ok. If you supply >7 volts to your project via barrel jack it is perfectly acceptable to tap this from Vin (at less than 1 amp draw). Same with USB port but available power will be slightly less than regulated 5V (probably something like 4.7 v because of the diode which is rated at 1amp current). But it is safer for the Arduino to draw in excess of 250Ma from Vin than the 5 V pin. And though I admit to have dozens of them laying around, I’ve never fried one using this method. I have fried a few though.

I will connect the buttons trough the Optosmall card to the Arduino Mini Pro. Pin A0-A2. Just check if pin is activated and show some info on lcd.
So the same button push will trigger on two Arduinos.

You miss the point on the barrel jack. If his circuit is designed for 5 volts and he plugs in 12 volts then it could cause excessive current and burn out his circuit.

If Vin is powered (and greater than 6.6 volts the USB power is blocked by the Arduino.

If you use Vin as a voltage source you are drawing current from the inputs of three devices.

The relavent parts of the schematic are here:

So, you say, the 5+ pin is the most safe solution for tapping 5V from the Arduino?