Regulated Breadboard PSU


SparkFun has released a breadboard power suppy that can provide regulated 3.3v or 5v. Unlike the supply we saw from adafruit industries earlier this summer, this one is based on an lm317. This small device features on/off switch, voltage selection swith, and appropriately spaced pin headers to plug into both the top and bottom rails of a standard breadboard.  Rather build it yourself? Take a look at the schematic provided (PDF).

15 thoughts on “Regulated Breadboard PSU

  1. What sort of current can this thing handle? I noticed there isn’t any sort of heat sink on it.

    The other thing I prefer about Limor’s version is the variable voltage option. Really handy when trying to figure out how a project you plan on powering with batteries will respond to lower volatages.

  2. when i was a child, i did not have $15 to waste so i scavenged lm317 regulators from TVs and VCRs i got from the local dumpsters.

    and still, you can get a much cheaper one from digikey. add two dirt cheap resistors, three capacitors, and voila! your power supply is built.

    this kind of “hack” only makes me laugh (or cry). but maybe it’s just paid advertisement for sparkfun?

  3. The junction-case resistance of the SOT version of the lm317 is 23.5°C/W. The copper pad under the regulator is very small and does not provide much less than the 140°C/W air-case resistance. This means that assuming an ambient temp of 25°C and max operating temp of 125°C, the regulator can dissipate a maximum of 0.6W. For example if you need to regulate 9V down to 5V the max current will be 150mA, and at this current the regulator will be very hot.

  4. I say this pretty much every time any voltage supply is posted here…

    The best voltage supply you can get for your project is an ATX power supply. I use a 250 watt PSU from 2001, and it works great. You can probably find them for <$20 if you don't have one lying around your house already. Some advantages:

    -Huge range of voltages (1.7V to +/-12V)
    -Huge power output (10's of amps)
    -Auto shutoff on short circuit – really useful, because you can put a reverse biased diode across the power lines of your breadboard, and if you connect the power backwards, it will shut off immediately.

  5. What’s really needed is a dual fixed 5V and 3.3V low drop-out (ldo) breadboard power supply. The LM317 is not low drop-out. If you’re going to regulate something like 5V from a 12V supply put a series dropping resistor between the 12V supply and the regulator.

    It’s likely this costs $5 more than the other Sparkfun regulator because it is factory assembled – the other one is a bag of through-hole parts you need to assemble.

  6. Hello!
    That’s perfect. It makes up for all of my earlier efforts….. Now I’m using a spare PC’s P/S. It has more oomph then the thing that Sparkfun has made, but still I might even buy it. (The thing from Sparkfun.) Strangely enough I am in agreement with Bullwinkle J. Moose there about that issue regarding the one I am using now.

  7. Be careful with what you choose to power these boards with. Try to keep the input voltage as close to the output voltage as possible. Even though the lm317 can take an input voltage of 20VDC , using that to output 5VDC would result in a lot of extra heat.

    Price is fine for what it is. If you are really cheap just use a 7805 with a clip on heat sink for $1.50 total cost.

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