Board Power / Resistance Tutorial

RICoder

Does anyone know where I can find a good (rather it be brief and to the point) explanation of how power is served to a board, and how to determine resistor value when attaching components?

I understand this is a basic thing, but to date I have gotten by using schematics for the parts I get and combining them all in larger projects. The thing is, I ALWAYS use the 4 AA battery pack that came with the BoE, and I'd like to do a project where I design EVERYTHING from the ground up on a blank breadboard (even something as simple as an MC, couple of LEDs and a switch or 2). On said project (and future ones) I'd like to be able to plug into a wall wart of which I have about a zillion in my "Box of Abandoned Projects and Discarded Toys".

SRLM

Best thing to do would probably be to learn electronics.

http://forums.parallax.com/showthread.php?p=741483

gibbman

The US Navy has their Electronics training in the public domain, available as downloads at:

http://www.tech-systems-labs.com/navy.htm

21 volumes, 4100 pages, DC to daylight.

Jim

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In the end, it seems that it's all about getting the LEDs to blink....

kwinn

RICoder, hope this helps. Please keep in mind that the schematic is a very generic one I use as a starting point and modify to suit a specific project.

Section 1 – Input transformer:

The transformer must be able to provide the output voltage and current required by the circuit it is going to power. Choose a transformer that can provide 1.5 to 2 times the current the circuit draws.The input winding ( 1 – 2 ) must be chosen to handle the input voltage (usually 115V nominal in North America, 230V in Europe).
If the above transformer was to supply a circuit that required 5V at 0.5A from a 115V line then it should have the following ratings:
Input voltage: 115VAC
Output voltage: 6.3VAC
Output current: 1A (minimum 0.75A)

Section 2 – Rectifier:

This section converts the AC voltage to pulsating DC. In most cases a bridge rectifier (4 diodes in one package) is used which produces a pulse for both the positive and negative half cycle of the power line. If a single diode is used only the positive half cycle produces a pulse. Using only a diode requires a larger capacitor be used to smooth out the pulsating DC.

If you have a “wall wart” it will usually have the circuitry from sections 1 and 2 as well as the capacitor shown on the input to the 7805 built in to the case.

Section 3 – Regulator:

This takes the unregulated voltage on the input capacitor and outputs a regulated voltage (5V in this case) that powers the circuit. There is usually a smaller capacitor on the output of the regulator, or there may be one or more capacitors (bypass capacitors) on the circuit board the supply is powering.

Section 4 – Secondary Regulator:

Required if there is a need for a lower voltage for part of the circuitry.

Other:

This power supply also provides the unregulated pulsating DC voltage as an output for other uses (servo’s, motors, lights, etc.). The current any such circuit draws must be taken into account when selecting the transformer and bridge rectifier.
Diode D2 prevents current from flowing out of the capacitor and back to any circuitry connected to the unregulated output. This is to prevent a sag in the regulated output voltage if the unregulated output voltage should drop due to a large momentary current draw.
Diode D3 serves the same function for the 3.3V supply as diode D2 does for the 5V supply.

RICoder

Thanks guys. I've ordered a few books from amazon, and started reading a few different sites I found online based on the information from links here.