406 ss monte said:
what does the rectifier do? doesn't it conver a/c to d/c current? what do the diodes do?
SIMPLE QUESTION WITH AN INVOLVED ANSWER:
Long read...
Doc here,
imp:
A rectifier does exactly that...Rectifies AC to DC voltage..and depending on how configured, is how well it does just that..1/4 wave, 1/2 wave, Full wave..usually From one to four diodes..(Battery charger to Filtered DC bench supply)
Diodes are usually semiconductor devices...(unless you are an old radio tech...then they are Passive devices) Or as fondly remembered ..TUBES..
A Diode, within reason (and tolerance) will conduct in ONE DIRECTION only..(OR Forward bias..) Think of it as a Check Valve for electrons..one way flows smooth, the other hits a brick wall..(again , within tolerance) To follow the flow..just follow the printing on the diode or schematic..
The direction of flow here will be from anode to cathode..
If you put a lamp on the cathode side to ground and 12 volts on the Anode side the lamp will light..reverse the wires on the diode..The Lamp will NOT light..in Fact, put the ground on the Anode side and power to the Cathode side...you have effective isolation..NOTHING happens..reverse it and the diode goes up in smoke.
When selecting a Diode..your concerns are Max Current..say, 1 amp...and PIV or peak inverse voltage..Say, 50..that voltage which WILL travel back through the diode and crowbar it shut..(making it just a Bidirectional wire..)
There or several other types of Diodes also, that can pick up Transmitted signal,(signal, switching, gunplexer) Reverse polarity protect a device (Zenier) Rectifier (single to Bridge types)
A Zenier is a voltage sensitive diode that auto~reverse biases when a specified voltage is seen between its conductors and purposely causes the diode to fail closed to prevent damage to a digital device that has seen a reverse polarity..(Faster than a speeding Fuse..More effective than a hamhanded Tech..) basically it senses a reverse voltage and crowbars shut across the power and ground of the device..no matter how many fuses you put in there they will just blow out UNTIL you repair / Replace the zenier..so you can't damage the unit EVEN if you correct the polarity issue..
A signal or switching diode does just that..detects signals in the air, in the circuit or however you configure it..Remember the "Cats Whisker " radio you made in school?? that was a diode..
A Gunplexer is a Diode array, that is configured as an antenna..used in devices from everything to PD Radar Guns..To Television Satellite antennas..to wave guides for your home dish antenna..
Switching diodes configured in the right manner will give you a transistor...and more than that on a chip..an Integrated circuit..to millions of them, a Microprocessor..you can follow the evolution from TUBE to Dime size Chip..
A Bridge rectifier, is commonly used in Well filtered, Regulated power supplies (bench supplies) as well as Power supplies for Radio and television , computers (with a slight twist..) to Car Alternators..and consists of 4 diodes placed in a "Bridge" configuration..
Full wave Bridge rectifier (Bad Dwg..Ignore AC~+ /- ...does not exsist in AC..sorry..)
If you note, the AC enters the bridge in Half wave stages..Then look forward of that..you'll see the the DC voltage WITH + and - polarity..
Were this a bench supply, the stage before it, would be a transformer that plugs into the wall..110 VAC, and drops it To 12 VAC..(for example)
The stage after it would be Capacitive filtering done with Electrolytic Caps and Mica bypass caps..
The stage after that would be a bleed off resistor..then on to a Regulator Chip..
From there out to a a Current meter , and Voltage meter as well as a fuse protection device ON BOTH the DC output side and The 110 Volt Transformer side..
Sounds pretty complex? Nope bare bones stuff..lower scale supply I wouldn't use for Digital powering..but good for a Novice to test a harness in the car..The current is dependent on the value of the transformer amperage , the Current handling of the Bridge, the WVDC (working Voltage DC ) of the caps..Depending on how Configured..from 1 MA to 10000 Amps..(slight exaggeration..)
NOW, yall wonder WHY I get up on my soapbox when I read it's OK ..I can use a battery charger for a testing supply...Without the fuses..without the current meter..this is a diagram of a Basic $29.95 charger...
On the top drawing , almost all 60 cycles of the AC are filtered out in each cycle..The Caps, the Regulator..help shape and buffer anything else..
On the lower diagram you'd be lucky to see 1/4 of a wave filtered at all leaving 3/4 of each cycle to AC..Don't know about you..Which would you rather have powering your $4000 Stereo..or your $800 performance ignition..or your $400 Dollar Computer..and it's sensors??
Try it yourself with a trash radio..put it straight to a charger and turn it on..I betting you won't hear a thing except a Very loud hum..I'm going with a top line bench supply!
An Alternator works the same way as the Bridge above..and more (usually 6 diodes) to rectify Raw AC generated within..The more diodes that fail or break down the LESS useable output it has...Same applies to the regulator EXCEPT it can slightly bias backward and impose a load on the battery just sitting...(Morning Sickness..) Overnight Dead battery's will start showing up..
OK , off the soap box... There is everything you DIDN'T want to know about diodes..Oh , this is just a breif overview..for more get a basic Electronics book..and do your own research...
NOTE: No Text was harmed in the creation of this post.. :drunk: :sweat: :nono:
Doc
imp: