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Topic: Splitting up a power source (Read 1 time) previous topic - next topic

dptdpt

If you haven't read my other posts - I'm an electronics newbie trying to build a board using the Arduino, that will control various motors. I have a power supply that provides 24 volts, 3 amps, that I have to use. So I need to "split off" 5 volts to power the Arduino board - and then "send" the rest to circuitry that the Arduino will talk to through mosfets or some such.  Right?

So can anyone please advise as to how I design a circuit to split up the power like this? Voltage regulator?

Cactusface

Hi,
        Then surely all you need is a 7805 voltage reg! which will give you 5v at upto 1Amp, more then enough I think. You will still get the full 24v for the FETS, etc.

If your not sure just google 7805 circuit, it just needs a 0.1uF cap on the input and 0.1-0.47 on the output, with 24 volts it will run HOT and will need a good heat sink!!

Hope it helps, Regards.

Mel.
Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

MarkT

DC DC converter is the way to go here, find one rated at a nominal 18V in (these work
from 9V to 36V usually) and you'll have a pretty robust system without any heatsink needed.

For instance for upto 200mA: http://uk.farnell.com/murata-power-solutions/ncs1s2405sc/dc-dc-conv-iso-pol-1o-p-1w-5v/dp/2400826

Or save money but waste power with 7805+heatsink.
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dptdpt


weedpharma

Hi,
        Then surely all you need is a 7805 voltage reg! which will give you 5v at upto 1Amp, more then enough I think. You will still get the full 24v for the FETS, etc.

If your not sure just google 7805 circuit, it just needs a 0.1uF cap on the input and 0.1-0.47 on the output, with 24 volts it will run HOT and will need a good heat sink!!

Hope it helps, Regards.

Mel.
At one amp you will also need a heat sink about a metre square

dptdpt

Weedpharma - what do you think of that switching voltage regulator I linked to above?  Will that meet my needs?  Any better ideas?

And I see from your sig you're trying to relearn C. That's something I do know - let me know if you need any help!


weedpharma

As has been said in many posts on similar themes (using higher voltage and dropping to 5v), the switchmode is the way to go.

With a linear regulator, the "extra" power required to be got rid of is lost as heat.

Power to dissipate = voltage to drop x current drawn. With 24 volts in with a draw of say 0.5 amp, you have 19 x 0.5 = 9.5 watts. This is enough to run a small soldering iron!! The efficiency is very low.

A switchmode supply has an efficiency of better than 90%.

Weedpharma

JimboZA

That switching regulator replacement for 7805 looks sensible to my inexperienced eyes.

Question though: do you need the 24V for the motors or are you just using a 24V supply because it was handy? Because if you don't need the 24V it would be much easier to start with a lower voltage in the first place..... but I'm sure you thought of that  :smiley-cool:
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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

dptdpt

#8
Nov 19, 2014, 11:56 am Last Edit: Nov 22, 2014, 01:44 pm by dptdpt
Jumbo - this thing I'm working on is to replace a control box that's connected to a robot. The control box it's replacing is connected to the robot, which provides the 24 volt, 2.5 amp power. The robot needs the 24 volts for its motors. The control box contains all the circuitry to control the robot motors - it needs 5 volts for the digital PCB side of things, and 24 volts for the control of the robot motors. So it's not an option for me to use a different power supply.

Weedpharma - that converter I linked to is a switch mode converter - no?  Did you look at it?  Any specific better or cheaper alternatives would be appreciated!

- Dave

weedpharma

The switching regulator would be good as long as it fits your power requirement at 5v.

There are cheaper ones available (Deal Extreme, not endorsed as I have not used them, long delivery time).

Yours is a nice little package.

Weedpharma

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