Need a heatsink for Arduino Duemilanove

Hi All,

I am a bit new to this and have a problem. I have a Arduino Duemilanove which i will be using to power a servo which has a camera mounted on it. This will all be mounted on a boat that is traveling at up to 58kph. That side of it all works with a bit of help from th esample sketches. the problem is that i am powering the Arduino Duemilanove from the boat 12v battery and the voltage regulator is getting very hot, as this will be on for several hours at a time. What are my options? I was looking for a heatsink that i can attach to the Arduino Duemilanove but can not find one that is small enough that will disapate enough heat?

I have seen posts about adding an external voltage regulator. Is this the way to go or is a heatsink better?

Thanks

Ian..

You'd be better off with a DC-DC converter to power the Arduino - much more efficient.

which i will be using to power a servo which has a camera mounted on

does this mean you're powering (as opposed to simply controlling) the servo from the Arduino's regulator?

Hi,

Yes, the servo is getting the 5v from the 5v pin on the Arduino. Its a standard model type servo, but quite a powerful one. The camera does not take a lot of power to move as it is mounted on a pivot. Will the Arduino cope with that sort of load?

What sort of DC-DC converter should i use. I have seen a few voltage regulators (3 pin chip type) that will convert the voltage from 12v to 5v. Is that what i need?

Thanks
Ian…

Power the servo with a separate power supply. The 40mA output is probably being a bit overloaded by the servo and pulling more juice then the onboard regulator can quickly dissipate (the copper area the regulator is mounted to is quite small).

Edit: use just a standard 5V regulator TO-220 so you can easily heatsink it, and swith it with a transistor.

or I found this which is a 1A 5V reg with an on/off pin. Maybe that works for your app too... http://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/PQ05RA1(1).pdf

Hi windhamrules,

Thanks for the info, on a very steep learning curve with this.

I will add an external voltage regulator. Can this power the Arduino and the servo, or should i have a seporate regulator to power each? also, i plan to mount everything inside an aluminium box. Can i just bolt the voltage regulator directly to the box to act as a heatsink?

Thanks again for all the help

Iian…

Hello Ian,

The Arduino Duemilanove has is own voltage regulator to handle its chip and to supply about 40mA to each of the pins. So this added voltage regulator will only be used for the servo you are driving.

So your power will look like this if you are using the switch able voltage reg…

  1. 12VDC → 5VDC External Reg → Servo → Gnd
  2. 12VDC → VIN pin or Power Jack
  3. DigiOut pin on Arduino ->control on the switch able reg

If you are using a transistor and a standard 3 pin reg…

  1. 12VDC → 5VDC External Reg-> PNP Transistor Emitter → PNP Transistor Collector → Servo → Gnd
  2. DigiOut pin on Arduino → 2k2 res → PNP Transistor Base (low = on / high = off)
  3. 12VDC → VIN pin or Power Jack

If you are using a mosfet and a standard 3 pin reg…

  1. 12VDC → 5VDC External Reg-> PNP mosfet Source ->PNP mosfet Drain → Servo → Gnd
  2. DigiOut pin on Arduino → 2k2 res → PNP mosfet Gate (low = on / high = off)
  3. 12VDC → VIN pin or Power Jack

That should do the trick. The 2k2 (2.2k resistor) is there to protect the Arduino pin some, so it could be omitted.

Just make sure the transistor or mosfet you pick has at least an amp rating of your regulator (say 1A).

You can definitely use the case as a heatsink and this is a wonderful idea. Just be sure to isolate the back of the transistor or mosfet with mica isolator and make sure you use a screw isolator too.

Here is the mica isolator and the screw isolator…
Screw Isolator 4-40/M3 http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=rp338-nd
Mica insolator TO-220 http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=4673k-nd

Hope this helps!

Hi,

Just wanted to say thanks for all the help. I now have all the bits and will be putting it together of the next couple of days.

Using a seporate voltage regulator seems really good, as the server now runs a lot faster that when it was powered via the arduino.

Once again, thanks

Ian...