5V breadboard mini PSU

Step 4 Enjoy

Plug it in your breadboard and start using

Comments

[DonTron]

To take things one step further, and again, I think I'd like to credit-reference Brown here if memory serves, lets presume that are source of raw DC is a wall-wart from a surplus vendor. These things can fail, cheapies seem to exhibit a MTBF < ano, in my experience. If we have a series fuse and a shunt Zener (now functioning in a crowbar-like fashion) we are protected from over-potentials from this source. But another failure mode is when the pass transistor (failing in the common way for a bipolar) on the voltage regulator blows open. Then we have the unregulated potential impressed upon the output, typically frying the semis on the thing. If we introduce another, fast fuse and Zener combo, we are also protected from this circumstance. The cost of the Zener is typically low. Large value Zs can be hard to cop nowadays. An alternative is to build a 'super Zener' out of a power bipolar and a signal Zener. Presuming NPN flavoring (generally preferable with Si), Bus cathode and collector, anode and base, use emmiter as cathode. Use your protection components, peoplezz!! They are invariably cheap relative to the circuits they are protecting. The computations-formalisms surrounding their deployment are nearly invariably first-order ones.

[DonTron]

Its those square braces I attempted to employ: "Low value of conductance" = "High value of conductance." There!

[DonTron]

Sorry, prior post came out funny, 'value conductor' should have come out: '[small value conductor], ' which is another way to say 'high value resistor.' I just came back to say that using protection diodes, like Zeners, Bi-directional Zeners and Shottky and gold-doped types, is common. These can be more robust in surge situations relative to ICs, due to their simplicity. Many practical circuits have more nascent parts that guard against the unusual circumstance than functional ones. Its a 'belt and suspenders' world in the engineering community.

[DonTron]

The analog designer has to account for all situations: How about the context of power-off? Here, we can have an unpowered regulator but a charged output filter capacitor (which, btw, esp. in larger supplies should have a resistor [low value conductor] in shunt, to assist its discharge) remaining across it. Really, the diode is common practice, used in about half of the designs of this type. A morning spent perusing application notes for this device should show this. Even 'though it is mostly about switchers, "Practical Switching Power Supply Design," By Marty Brown has a good section treating this topic, if memory serves.

[DonTron]

A fuse would have been nice. Some put a diode backwards across (input output) the regulator, protects it in some cases. A little strip of brass makes a nice heat sink for the regulator. To make this device more robust, a Zener, or a Zener in shunt with a Shottky diode backwards across the input (in gnd) can be used. There are a couple diode schemes that can protect against a reversed wall-wart. Series, PS doesn't operate, of FW rectifier, which allows for operation regardless of polarity. Not certain that, at these de minimus levels of power that a switcher is indicated.

[marius]

The 7805 ic should take care of protection. That's the advantage of using it.