Regulating AMPs

The "Eleven" is our Uno-equivalent Arduino-compatible board, but with a number of improvements including prototyping area, a mini-USB connector, LEDs mounted near the edge, and the D13 LED isolated using a FET. [Product page]
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2mozzie
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Joined: Wed Jan 08, 2014 1:22 am

Regulating AMPs

Post by 2mozzie » Wed Jan 08, 2014 1:32 am

Hello Forum,

New to the Eleven and Freetronics world so forgive me for basic questions.

I'm creating a water flow meter to alert me to loosing water. We recently had a broken pipe by a horse in the paddock and lost 1/3 of the tank before realising!

Found this article showing how to wire up a flow meter (very helpful).
http://themakersworkbench.com/content/t ... te-arduino

However I managed to fry the halls sensor in the first flow meter using an incorrect power source. The flow meter works between 5-24 volts but only up to 10mA. How do I regulate the AMPs from the 5v pin? Do I wire in a resistor on the prototyping area of the eleven before connecting to the flow meter?

Regards
Paul.

andrew
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Re: Regulating AMPs

Post by andrew » Wed Jan 08, 2014 2:28 am

The circuit provided by Seeed on their wiki is appropriate:
http://www.seeedstudio.com/wiki/index.p ... low_sensor
According to their data the sensor will draw up to 15 mA when operating on 5V - which is fine with an Arduino Uno/Eleven. Just power it from the 5V pin on the board.

2mozzie
Posts: 2
Joined: Wed Jan 08, 2014 1:22 am

Re: Regulating AMPs

Post by 2mozzie » Wed Jan 08, 2014 8:52 am

Thanks John.

Does the 5v pin stay constant or change given the power input?

I have purchased a DFRobot GPS/GPRS/GSM Arduion Shield that plugs into the Eleven.

Its takes 6-12v and 100mA@7v - considering the flow meter is 10mA how do I regulate this to not blow the flow meter?

Regards
Paul

andrew
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Re: Regulating AMPs

Post by andrew » Wed Jan 08, 2014 9:18 pm

2mozzie wrote:Thanks John.

Does the 5v pin stay constant or change given the power input?

I have purchased a DFRobot GPS/GPRS/GSM Arduion Shield that plugs into the Eleven.

Its takes 6-12v and 100mA@7v - considering the flow meter is 10mA how do I regulate this to not blow the flow meter?

Regards
Paul
The 5V pin is always 5V, (unless there is a fault with the board) so nothing to worry about.
Make sure you power that shield with a supply that can offer up to 7~12v at 2A of current. You can get a 2A plugpack from Jaycar etc.

Every supplier I have seen neglects the fact that there is a burst current draw from those GSM modules of around 1.5A on power-up, and if you live in an area of not-perfect GSM coverage the power output increases and thus the current draw.

Finally if you're new to the world of Arduino you should check out the new book "Arduino Workshop" - http://www.freetronics.com/collections/ ... o-workshop

LukeW
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Re: Regulating AMPs

Post by LukeW » Sun Feb 23, 2014 1:56 pm

A device that runs at, say, 6-12V and draws a current of, say, 100mA doesn't need its current regulated to 100mA by the power supply - that's just the amount of current that it draws. The power supply needs to be capable of supplying 100mA, or more, but the power supply doesn't actually supply 1A (let's just suppose the power supply has a current capacity of say 1A, for argument's sake) unless the load device is actually drawing that much current.

If the sensor will draw 100mA then the power supply must be capable of supplying at least 100mA, but anything higher is perfectly fine - even, say, a power supply capable of supplying 20A is fine. But the voltage supplied by the power supply does have to be within the specified voltages.

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