Easy question. I'm a noob... I bought a MB102 breadboard power supply unit. But, it doesn't come with a manual. I need to get a 9V adapter for it. So, I'm not sure what I need.

MB102 Breadboard Power Supply

Does the 9V adapter's current matter or will any 9V wall wart work? What is the max. input mA for the MB102?


1 Answer 1


Here is the schematic:

enter image description here

It needs to be rated for the total output current (current on the 5V line plus current on the 3.3V line) you want plus a few tens of mA for the LEDs and regulators. Other than that, any regulated 9V adapter with the right polarity will work fine. Unregulated ones will also work provided the unloaded output voltage isn't too high.

  • \$\begingroup\$ Thanks for the info. I'm going to use Atmel ATMega microcontrollers and possibly a small DC motor in my project. Would you recommend a 1 A or 650 mA adapter? What do most folks use for basic projects? \$\endgroup\$
    – Laxmidi
    Commented Jun 17, 2015 at 14:47
  • \$\begingroup\$ Get the 1A one. \$\endgroup\$ Commented Jun 17, 2015 at 14:57
  • \$\begingroup\$ Awesome! I'll order it today. \$\endgroup\$
    – Laxmidi
    Commented Jun 17, 2015 at 22:15
  • \$\begingroup\$ So I can get a cellphone or some other charger like that that fits the barrel if is says 9v? 12v? What about 500mA? \$\endgroup\$
    – johnny
    Commented Oct 14, 2016 at 2:36
  • \$\begingroup\$ @SpehroPefhany The schematic above, is wrong. Yes, I checked. The USB female socket is an output, as it should be, and outputs 5V. Hitting the push button turns on the 5V output. The only input to the board is the barrel jack. Additionally, when the switch is off, the Vcc of the USB is connected to ground, which probably means the 5V is shorted to ground when it is off. I don't know what this may mean for the 3.3V reg, which does not have protection diodes across it. This also means... do not charge batteries with this thing, and importantly do not switch it off when done charging. \$\endgroup\$
    – Indraneel
    Commented Nov 19, 2018 at 18:37

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