Breadboard supply A very low dropout adjustable power supply! This project details the design of a very low dropout adjustable power supply. A good power supply is essential to electronic projects. While there are many existing designs for adjustable power supplies, this one makes improvements that make it more useful for hobby designs
- MIC2941 regulator has guaranteed 1.25A output
- Low dropout, only 40mV – 400mV compared to 1.25V – 2.0V for LM317. This means you can use a wider range of output voltages including generating 3.3V from as low as 3.7V (such as 3 AA’s or a lithium ion battery)!
- Short circuit and overheating protection
- Input diode to protect circuitry from negative voltages or AC power supplies.
- 2.1mm DC jack and terminal connector for voltage inputs
- Two indicator LEDs for high and low voltages
- Output selection switch to select from 3.3v, 5v and Adjustable
- Onboard potentiometer for adjusting voltage from 1.25V up to within 0.5V of the input voltage. (20V max)
- On/Off switch for entire board
- Heat sink included
- Breadboard and battery clip or DC power supply is not included, you can use any DC power supply with 2.1mm plug (we have a nice one in the shop).
For design documents, instructions, parts list, etc. Check out the project webpage! And pick up one up at the Adafruit store!
I noticed the schematic shows a USB input as well as the terminal connector and 2.1 DC Jack. Was that left out of the final board design?
Comment by J. Peterson — July 16, 2009 @ 6:02 am
nope. it is an optional part. there wasnt space for both and i decided in the end that terminals were more useful than USB
If you have a spare usb-b jack you can solder that in, of course
Comment by ladyada — July 16, 2009 @ 10:13 am
Next time I order from Adafruit, I’ll be sure to include one of these.
I’m wondering what the two notches are for. I’m guessing its a style thing.
Comment by SiliconFarmer — July 16, 2009 @ 12:05 pm
I believe the two notches are so you can access the breadboard for when you’re using the header breakout pins.
Comment by daniel — July 16, 2009 @ 2:37 pm
yup. if you’re using 3M-style breadboards the side rails are not 0.1″ spacing (argh!) so you have to plug it in the middle of the board. So the notches let you wire it up. http://www.ladyada.net/images/bbpsup/headerwire_t.jpg
Comment by ladyada — July 16, 2009 @ 4:20 pm
What if the voltage levels were different on each side? Like say 3.3v on one side and 5v on the other. This is a very common occurrence. Great product and power supply design though. Just a thought. Thanks.
Comment by Dave — August 7, 2009 @ 12:55 am