MonkeyBoy Posted December 8, 2005 Share Posted December 8, 2005 I'm looking at buying the parts for a megajolt project - unfortunately i know very little about electronics 😳 When someone refers to a rectifier, is this the same as a diode ? Or are they subtly different ? I need a DO41 1A 400v diode and have seen a description for the same thing described as a rectifier but don't know if i'm ordering something different ! Cheers Alistair Link to comment Share on other sites More sharing options...
Mick Day Posted December 8, 2005 Share Posted December 8, 2005 Have a look here. " In this discussion the term diode and rectifier will be used interchangeably; however, the term diode usually implies a small signal device with current typically in the milliamp range; and a rectifier, a power device, conducting from1 to 1000 amps or even higher. Many diodes or rectifiers are identified as 1NXXXX . A semiconductor diode consists of a PN junction and has two(2) terminals, an anode(+) and a cathode(-). Current flows from anode to cathode within the diode. " Link to comment Share on other sites More sharing options...
MonkeyBoy Posted December 8, 2005 Author Share Posted December 8, 2005 Brilliant, thanks. Think i have the right thing then...! Cheers Alistair Link to comment Share on other sites More sharing options...
Neil A Posted December 8, 2005 Share Posted December 8, 2005 If I remember correctly, rectifiers are made up of diodes. Fellas, smoke me a kipper, I'll be blatting for breakfast. Link to comment Share on other sites More sharing options...
EFA Posted December 8, 2005 Share Posted December 8, 2005 2 diodes in a half wave rectifier, 4 diodes in full wave rectification. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 8, 2005 Share Posted December 8, 2005 Nah! One diode = half wave rectifier, two diodes = full wave with centre tap transformer, 4 diodes = full wave without centre tap transformer. Link to comment Share on other sites More sharing options...
EFA Posted December 8, 2005 Share Posted December 8, 2005 Paul, Youa re clearly younger than me and remember your college days rather better....... Link to comment Share on other sites More sharing options...
jackb_ms Posted December 8, 2005 Share Posted December 8, 2005 No hate to say EFA was right. 1 diode you have half a sinusoidal, which mean the average output of the is about 6V 4 diode you have an rectified voltage which varies from 0V to +12V, the average output will be about 10V because of some ripple a recifier is 4 diodes Edited by - jackb_ms on 8 Dec 2005 22:12:03 Link to comment Share on other sites More sharing options...
EFA Posted December 8, 2005 Share Posted December 8, 2005 HA 😬 😬 😬 Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 8, 2005 Share Posted December 8, 2005 Oh Gawd, here we go! Strictly speaking the device is a diode and its function, when used in a power source to convert ac into dc, is known as rectification whether used in half wave or full wave circuits. The rectifier serves the same function as the commutator on a generator (as opposed to an alternator). Hence the term rectifier is often used interchangeably with diode in power circles. A half wave rectifier (single diode) only allows current to flow through the load during one half cycle. No current flows during the reverse cycle and hence the average dc voltage, assuming a resistive, non reactive load, will be approximately half the rms source voltage. The current is rectified as it only flows in one direction. A full wave rectifier, either a 4-diode bridge or 2 diodes with c/t transformer, allows current to flow during both half cycles and, hence, the average dc voltage approximately = the rms source voltage. The peak voltage is the same in both cases. Car alternators are generally polyphase (six I think) and deliver a smoother current because current is flowing at a higher level more of the time as the phases overlap. In power supply applications a storage capacitor is normally connected across the output of the rectifier to smooth the output voltage, ie filter out the ripple component. Provided the time constant of the storage capacitor and the resistive load is long enough, i.e. the capacitor has a high enough value, the voltage is maintained at the peak of the ac voltage (less the forward voltage drop of the diodes). Don't try this at home. What the heck does all this have to do with '7s? Link to comment Share on other sites More sharing options...
MartinWoodham Posted December 9, 2005 Share Posted December 9, 2005 you're all out of date, modern (ie post 1990) consumer electronics use switched mode power supplies rather than steam age transformer/ rectifier/ smoothing circuit. No-one does power packs with half- ton transformers in them anymore! But Paul is right, a diode is what it is, rectifying is one of its applications. So Alistair, get a diode that matches the voltage and curent spec and you're away. For you old guys, that means a silicon diode, not some old germanium thing you've had hanging around in a tin at the back of the garage for 40 years 😬 Martin Roadsports B If everything's under control you're going too slow (Emmerson Fittipaldi) Or your pants are too tight.(DB) Link to comment Share on other sites More sharing options...
EFA Posted December 9, 2005 Share Posted December 9, 2005 You're all wrong - Except Jack. Link to comment Share on other sites More sharing options...
Chris W Posted December 9, 2005 Share Posted December 9, 2005 a diode = a rectifier . They're the same thing, the terms are used interchangeably. Re Jack's comment that: 1 diode you have half a sinusoidal, which mean the average output of the [sic] is about 6VFor a single diode operating with a transformer, you will have a half sinusoid for the period during which the diode is conducting and no output for the negative period of the sinusoid. Thus, if you run the maths, the average output over the whole cycle will be: Vav = (1/2pi X integral from 0 to pi of Sin x.dx) (since the second half cycle from pi to 2pi is zero) Evaulating this gives Vav = 1/pi x Vpk = 0.32 Vpk so the average voltage from a single diode using a transformer will be about one-third of the peak voltage. As someone pointed out though, it is rare to find this or any type of mains transformer in modern power supplies. Today, Switched Mode Power Supplies (SMPS) are utilised where the mains is rectified first at full voltage to produce a high DC level, it is then chopped up at around 50,000 cycles per second (50KHz) which means it can then be transformed down using a very tiny transformer at this frequency rather than the really large one necessary at the mains frequency of 50Hz. (a transformer only works with a varying (ac) voltage) It is then rectified again to produce a low value dc output. Your mobile phone charger works on this principle which is why they weigh virtually nothing compared to the heavy ones we used a few years ago because the transformer is very small and light. It is a SMPS. However SMPS's are more dangerous in general to risk of shock than a conventional power supply as the circuitry remains at mains potential until the final step down so precautions have to be more stringent in sealing them from prying fingers. Chris 2003 1.8K SV 140hp see it here Edited by - Chris W on 9 Dec 2005 11:32:05 Link to comment Share on other sites More sharing options...
Bozz Posted December 9, 2005 Share Posted December 9, 2005 A diode's not the same as a rectifier when used with DC Bozz It's not MANGO it's TANGO (McLaren Orange and Black 1.6SS) Link to comment Share on other sites More sharing options...
Chris W Posted December 9, 2005 Share Posted December 9, 2005 Of course it is Bozz - they are interchangeable terms. "Rectification" is the expression used when converting AC to DC. In a DC circuit, I agree one would tend to use the term "diode" rather than "rectifier" to describe the device but a single diode is still a "rectifier". They ARE the same device. A bridge "rectifier" consists of 4 diodes arranged in a special way in one package to perform conversion of AC to DC using "full wave" techniques. However, I have used bridge rectifiers many times in DC circuits (and they are still called "rectifiers"). They're useful for allowing connection of the DC supply either way round to make a circuit "idiot-proof". Chris 2003 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Bozz Posted December 9, 2005 Share Posted December 9, 2005 In the solenoid world we use the term 'diode' to decribe a single discrete device to protect from either reverse polarity connection or more specifically for back EMF protection. The term rectifer is used to describe a diode bridge (full wave) for convertion of AC to unsmoothed DC. Bozz It's not MANGO it's TANGO (McLaren Orange and Black 1.6SS) Edited by - Bozz on 9 Dec 2005 12:16:06 Link to comment Share on other sites More sharing options...
Chris W Posted December 9, 2005 Share Posted December 9, 2005 Bozz As they say in Parliament, "I would refer you to the answer I gave some moments ago". Chris 2003 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Nov-07 Posted December 9, 2005 Share Posted December 9, 2005 May I refer you all to the Dictionary of Science and Technology 🤔 "Diode - a semiconductor device with unidirectional and hence rectification properties, evolved from primitive crystal rectifiers for radio reception" "Rectifier - component for converting a.c to d.c" Like all such definitions, a bit circular 😬 You are all probably too young to remember Silicon-Controlled Rectifiers (SCR), on which I did some of the original research, but which are now called "Triacs", because they are not diodes Link to comment Share on other sites More sharing options...
Bozz Posted December 9, 2005 Share Posted December 9, 2005 Just shows what us Mechanical Engineers know about 'smarties' Bozz It's not MANGO it's TANGO (McLaren Orange and Black 1.6SS) Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 9, 2005 Share Posted December 9, 2005 anyone else remember selenium rectifiers? Very good for battery chargers as they had a relatively high forward resistance to provide a slightly more constant current. Yes, I do have one in the attic! And a cat's whisker somewhere. Then, of course, there were the 6X5, 5U4 etc thermionic diodes. Chris and Martin, thank you for your support, I shall wear it always. Paul Link to comment Share on other sites More sharing options...
Sheds Moderator Posted December 9, 2005 Share Posted December 9, 2005 ISTR that SCRs were thyristors. I haven't seen triacs referred to as SCRs, and since a triac is an AC device I don't think you could accurately describe it as a rectifier, silicon controlled or otherwise. Oh, and the engineers in this case (Chris W et al) are right, as usual. Look, I wouldn't argue about banking with Noger (it's boring anyway ) so I don't start on an electronic engineer when it comes to electronics. . Dunno why some of us will though, is it just a desire to start the Friday argument early? 😳 Link to comment Share on other sites More sharing options...
Hibster. Posted December 9, 2005 Share Posted December 9, 2005 No it isn't Supercheese R250 Caterham pictures here 😬 Link to comment Share on other sites More sharing options...
Sheds Moderator Posted December 9, 2005 Share Posted December 9, 2005 Oh yes it is. Damn, too late. 😬 Link to comment Share on other sites More sharing options...
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