You have to bear in mind the IV characteristics of a diode. The typical forward voltage drop of a single silicon diode will be about 0.6V when there is sufficient current (refer to datasheet graphs for actual values). If the current is very low, you can't make this assumption.
my amp caps get hot a high power & explode. might be the rectifier the reason? Toroidal is 63V & caps are 100V. I keep chaging them & they keep exploding. 🤔
If I placed 12vac on input, would I see 11.2vdc at output of bridge? Forward voltage drop of 0.8vdc? More likely over 1.5volts. Yes, testing with an a/c step down transformer. My app is flux welder conversion to electrode negative. So important to see forward drop value and full rectification. Ac step down transformer, repurposed to supply voltage for output check.
Short answer - no. Longer answer - Is that 12 V RMS or 12 V peak? If 12 V RMS, the peak input voltage would be 12 * SQRT(2) which equals 16.97 V peak. A full-wave bridge rectifier involves two diode drops and if we assume 0.7 V per diode that's 2 * 0.7 which equals 1.4 V. Therefore peak output voltage would be 16.97 - 1.4 which equals 15.57 V. It might be worthwhile recalling this is DC peak output voltage and not a steady output voltage. If you examined the output waveform it would be a DC current (always in one direction) but with humps at twice the frequency of the AC supply. I hope that helps.
@@PizzeyTechnology That does help. Diode check with Dmm and intregal paired sets were within 2mv of each other. In DC wire feed flux core, can wire stickout affect peak(and)constant voltage? As sold, my wire feed welders advertised secondary, non rectified voltage is 18v. So may I assume 1.4v forward voltage drop to 16.6v? 0.7v for silicon. I did read a bit on switching transistor. Current beginning to flow at 0.7v and fully open at 0.8v. Trying to learn a bit of rectifier control and then wave forms.
Typical silicon diode drop is about 0.6 to 0.7 V when forward biased. Less if no current is drawn. A rectifier converts from AC to DC, but it sounds like you also need a step down transformer or SMPS.
@@PizzeyTechnology Thanks for reply. I'm new at this stuff and you are correct, there is a step-down transformer in this power supply. I want to replace the 60 year old selenium full wave rectifier before it smokes out on me with this new bridge. After the power leaves the rectifier it goes into a 1000uf cap and through a 500ohm resistor.
I have no experience of using vintage selenium diodes. However, I understand they have a higher forward voltage drop than silicon. They can be leaky, which could have affected that capacitor too. If the capacitor is old is be considering changing that too.
I like channel presenters who instruct clearly without pointless music distracting the audience. Thanks.
Excellent explanation
3:08 What if you get lesser than 1volt (0.6v) when you measure across the diodes in series but each individual diode measures at around 0.55
You have to bear in mind the IV characteristics of a diode. The typical forward voltage drop of a single silicon diode will be about 0.6V when there is sufficient current (refer to datasheet graphs for actual values). If the current is very low, you can't make this assumption.
Great job on this short yet awesome explanation. Just gotta remember to check with the meter leads on opposites to see the voltage drop values.
my amp caps get hot a high power & explode.
might be the rectifier the reason?
Toroidal is 63V & caps are 100V. I keep chaging them & they keep exploding. 🤔
Excellent no nonsense video many thanks
That was quick
Do you have to isolate it from the PCB? or can you test them in place?
Looks like you can test them in place.
Bridge rectifiers can be tested in circuit. They need power (and a minimum load) to test the voltage drop across each PN junction.
Great sir, smart explaination, love you
Very good !
Thanks a lot!
If I placed 12vac on input, would I see 11.2vdc at output of bridge?
Forward voltage drop of 0.8vdc? More likely over 1.5volts.
Yes, testing with an a/c step down transformer. My app is flux welder conversion to electrode negative. So important to see forward drop value and full rectification.
Ac step down transformer, repurposed to supply voltage for output check.
Short answer - no. Longer answer - Is that 12 V RMS or 12 V peak? If 12 V RMS, the peak input voltage would be 12 * SQRT(2) which equals 16.97 V peak. A full-wave bridge rectifier involves two diode drops and if we assume 0.7 V per diode that's 2 * 0.7 which equals 1.4 V. Therefore peak output voltage would be 16.97 - 1.4 which equals 15.57 V. It might be worthwhile recalling this is DC peak output voltage and not a steady output voltage. If you examined the output waveform it would be a DC current (always in one direction) but with humps at twice the frequency of the AC supply. I hope that helps.
@@PizzeyTechnology That does help.
Diode check with Dmm and intregal paired sets were within 2mv of each other.
In DC wire feed flux core, can wire stickout affect peak(and)constant voltage?
As sold, my wire feed welders advertised secondary, non rectified voltage is 18v. So may I assume 1.4v forward voltage drop to 16.6v? 0.7v for silicon. I did read a bit on switching transistor. Current beginning to flow at 0.7v and fully open at 0.8v.
Trying to learn a bit of rectifier control and then wave forms.
Why were you expecting about .5 voltage drop? I'm looking to drop from 110 AC to 28v DC .... what rectifier do I use as I need to drop a lot.
Typical silicon diode drop is about 0.6 to 0.7 V when forward biased. Less if no current is drawn. A rectifier converts from AC to DC, but it sounds like you also need a step down transformer or SMPS.
@@PizzeyTechnology Thanks for reply. I'm new at this stuff and you are correct, there is a step-down transformer in this power supply. I want to replace the 60 year old selenium full wave rectifier before it smokes out on me with this new bridge. After the power leaves the rectifier it goes into a 1000uf cap and through a 500ohm resistor.
I have no experience of using vintage selenium diodes. However, I understand they have a higher forward voltage drop than silicon. They can be leaky, which could have affected that capacitor too. If the capacitor is old is be considering changing that too.
U presented this in conventional current flow?
Yes. Electron flow current is rarely used in these explanations.
U s
Can you test a diode when its still in the circuit thanks ...
You could measure the voltage drop across it, which for a silicon diode would be about 0.6 - 0.7 V, depending on current.
@@PizzeyTechnology Thanks
Hey Pizz,got a circuit to run by u need a second set of eyes on it.. email address or whatsap ?
Sorry, but I don't share contact details here due to student safeguarding issues.
@@PizzeyTechnology no problem. Just an interesting design u might have appreciated and be able to throw a diff angle on..
Well post a video on TH-cam and maybe we can all have a look. Good luck.
@@PizzeyTechnology cant do that... (it`s new tech shhhh)
@@gabrielsansar6187 If it's a perpetual energy machine... sorry but I've got two of those already.
Video too short need full explanation
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