Is my 600mA, 9V adapter suitable for a MB102 breadboard power supply?

Question

I've recently bought a 600mA, 9V adapter thinking that it would be suitable for a MB102 breadboard power supply but have now read that the maximum output of the MB102 breadboard power supply is 700mA and people in the community are recommending 1A, 9V adapters. Would my 600mA one still work?

Answer 1

Yes, it will still work fine, you just can't draw quite as much peak current.

Those numbers are pretty "optimistic".. if you draw 0.7A from the 5V supply the SOT223 AMS1117 alone would be attempting to dissipate almost 2.5W and if you drew it from the 3.3V output, the total dissipation on the little PCB would be about 4W. Typical schematic from here:

2.5W probably represents 300°C+ junction temperature rise from ambient (120°C-160°C/W) so the regulator will certainly shut down and it's unhealthy for it to do that.

Linear regulators are generally limited by thermal considerations, in terms of continuous current capability. Unless you anticipate working with a circuit that draws brief high current pulses from the power supply you won't notice any difference whatsoever.

Answer 2

It depends what you expect. 9V input is higher than what is required and will just make regulators heat up more than with lower voltage.

The lower the input voltage is, the less it heats up with the same current. It should not require more than 7V.

With recommended output current less than 700mA anyway, you are not missing much from the maximum if your supply only gives out 600mA max.

If people suggest 1A 9V adapters, it's likely because people statistically just have 1A adapters and they appear to work fine, and they don't have adapters that have less current output.