using 15v power supply

I am making a Model railroad base station using a Mega 2560 and an Adafruit motorshield, the track will require at least 15v and will be powered through the motorshield, my question is can I use a 15V power supply with the adafruit v2.3 and just remove the jumper?

Hello there!

I believe removing the jumper would break the connection from the supply to the Arduino. What you can do is power the shield from the 15V supply without the Arduino connected at all. Take a voltmeter and measure the voltage at the Vin pin where the Arduino would sit in and see what voltage is there with and without the jumper in place.

if removing the jumper would break the supply to the arduino then that is what I want to achieve, I will be supplying the arduino with power via the USB connection. But measuring the output is an excellent idea , thank you

I would also make sure that the shield does not put 5V on the 5V pin, which would also power the board. Powering the board through the 5V pin and USB at the same time may damage your board and/or your computer. Again I would recommend testing the pins before plugging it in.

After checking the shield with a 5v supply I got 0 reading in Vin with jumper out and 5v with jumper in. Got no reading to 5v or 3v with or without jumper. So I'm guessing I would be safe using a 15-18v power supply on the shield with jumper removed. Besides isn't the 5v and 3v pins fed by the mega.

Okay. Its kind of weird for it to put 5V on the Vin port as that would not put 5V on the 5V system of the Arduino, but give it a shot

You kinda lost me there. With the jumper in the Vin was reading 5v which would send 5v down to the arduino ( im aassuming), and if I were using a 15v supply this would probably fry the Arduino. but with the Jumper removed from the motorshield it is not sending any Voltage to the Vin pin.

so wouldn’t it be normal for the Vin pin to show 5V with the jumper inand this would also send 5v to the arduino?

Yes it would send 5V to the Arduino, and then to the regulator. There is a special characteristic of regulators known as dropout voltage. This voltage is the difference between the output voltage and the minimum input voltage to get the output voltage. In other terms, a 5V regulator with a 1V dropout voltage needs a minimum of 6V at the input. Hence with 5V as the input to the regulator, the output would be less than 5V. The recommended voltage range for the Vin pin is 7-12V.

How are you powering the shield so that it gets 5V at the Vin pin.

just with a 5V 2a power supply until my other power supply arrives, I was only using the 5v power supply to test the voltage at the Vin pin with the jumper in and out as you suggested.

Oh I see. Very good. My guess is that the voltage at the Vin pin will increase when you use the new power supply.

but my main concern is that with the jumper removed im not getting and Voltage t the Vin pin, therefore I can use my 15v power supply with jumper removed to power the shield and use the USB to power the Arduino.

you have been extremely helpful, this is my first project with and arduino, not my first Model railroad but its going to be interesting to see how well this works in MR as compared to 2-300 dollar base stations. this will also allow me to control turnouts as well as lighting on the railroad as well as controlling the trains. I am not an electrical engineer but I am trying to teach my grandchildren something that may become their lifes work or maybe just their Hobby as well.
thanks