The 7805 Is Dead! Long Live The 7805!

The 78XX series of regulators are incredibly helpful to use. If you will need, say, a 5V regulator, you grab a 7805, add a capacitor for steadiness, and send in ample voltage for the regulator to work with. Low-priced and simple. Even so, the part is not without the need of its faults.

A inventory 7805 just cannot transform 5.1V to 5V. You need to have a very good little bit additional voltage coming in. But the much more voltage you place in, the more the part is going to dump out as warmth. So functioning from 9V is going to be cooler than jogging from 24V. All that warmth isn’t extremely energy economical on batteries, either. [Stefan] required to do better, so he made a fall-in substitute for these venerable regulators some time ago. But he’s lately designed the board layouts offered so you can develop your individual alternative, way too.

The machine accepts 4.5 to 16V, and you can decide on the output voltage making use of two resistors. You can attract up to 2A out of the regulator, which is a lot more than you can say for a inventory 7805.

The heart of the little board is an SD8942 buck converter. There are two voltage-location resistors, 1 a lot more resistor, a handful of capacitors, and — of program — an inductor. The schematic notes you can also swap the IC with an MT2492. With a right-angled header, you can swap the board in for a normal 78XX. Be aware the values on the schematic are set for 5V, but you can change them rather very easily.

This is a wonderful example of how surface area mount has altered so many items. We keep in mind previous 7805 “drop in” switching materials that were a lot fatter and they weren’t cheap. Boards are affordable these days, and if you want the boards assembled, it appears to be like like they’d price tag $20 or $25 every in modest portions. But most of that is in setup and loading, so in more substantial quantities, the unit price tag would fall promptly. Or just solder them oneself.

If you want to see how the serious McCoy will work, we have viewed [Ken] glance inside the 7805 just before. If you want to dive into the mechanics of buck converters, we did two simulations about that, too.