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My question is probably pretty easy to answer for you smart people. But basically I'm building a Segway clone using an Arduino, two Jaguar speed controllers, and two 24 volt batteries (wired in parallel). I want to power my Arduino from the 24 volt batteries and am just wondering if I need any additional circuits to step down the voltage/current, stabilize/condition the power, or anything else that may need to be done before the Arduino can use the power.

I'm fairly new to basic electronic circuits and am more of a programmer. Can someone help me with my question?

Thanks!

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You are going to want to use a linear regulator. This will be very inefficient with respect to power efficiency, but your arduino should not use much power and this should make the power point moot.

Here is an example search for the part you would need on mouser. If you are going to pull very much current you are going to need a heatsink, this would probably amount to anything greater than 100mA in your case(just a ballpark so you have a way to estimate your threshhold).

It will require a couple of capacitors, but any good datasheet will tell you exactly what components you need.

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  • \$\begingroup\$ Kortuk, Thank you very much for the reply. I guess what I'm looking for is kind of a pre-built circuit, a schematic, or something simple I can create that I can connect to an Arduino development board and power it from 24 volts. I've read that the minimum voltage that the development board will accept is 7 volts. So do you know of anything like this: sparkfun.com/products/9948 that will output above 7 volts? I know that the development board has it's own voltage regulator on it it, and I'm sure it's not the best practice to step-down from 24 volts...continued... \$\endgroup\$ – Dylan Vester Mar 9 '11 at 5:19
  • \$\begingroup\$ and then let the development board step down again to 5 volts and 3.3 volts. But I just need something simple and reliable. \$\endgroup\$ – Dylan Vester Mar 9 '11 at 5:20
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    \$\begingroup\$ I found a good tutorial (ladyada.net/library/equipt/diypsupp.html) on creating a variable voltage regulator using this sparkfun.com/products/527 as well as some caps, a trim pot, and two diodes. I picked up a heatsink as well to be safe. Thanks again Kortuk. Btw, I chose an adjustable one, since I wanted to learn how to create it (for future projects). Also I'm going to ditch the dev board and create my own breadboard Arduino. \$\endgroup\$ – Dylan Vester Mar 9 '11 at 6:46
  • \$\begingroup\$ @DylanVester, I am glad my advice helped you, but it sounds like you found your own very specific solution. I may have guided you, but it seems like you could write your own answer about how you accomplished it and explain how to go about it. This could be very helpful to others. \$\endgroup\$ – Kortuk Mar 9 '11 at 7:15
  • \$\begingroup\$ Thank you Kortuk, you did help spur me to do a little research on linear vs. switching regulators, that is why I chose you. Also, you made me consider whether I wanted a squealing or heat. My parts should arive in a day or two, and once I put it together, I'll post my findings. Thanks again! \$\endgroup\$ – Dylan Vester Mar 11 '11 at 4:18
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The hardware documentation for the arduino uno says it can take up to 20v input, so powering it directly off 24v is likely to damage it. The older NG used a 7805 regulator which is good for up to 40v (but may overheat if drawing a lot of current from a 24v source, since linear regulators are not very efficient).

If you have a newer model Arduino with the 20v limit, definitely use an external regulator.

A convenient way to get an efficient 24v->5v regulator is to buy a phone charger intended for trucks (which have 24v batteries not 12v as in most cars). You can get these on ebay and elsewhere for about $7.

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There are switching regulators that are drop-in replacements for 78xx regulators. Digi-Key has a whole category for them. For getting 5V, you might want to try something such as this.

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