I am confused, I currently have a 24VAC supply going through a full bridge rectifier. But the output is not what it should be, I am seeing a half wave rectifier, why is this? I have used four diodes as well as an full bridge IC and the output is the same. I Would expect to see, /\/\/\/\/\..., but i am seeing /\_/\_/\_... Can someone explain this?
Full bridge rectifier
- Thread starter berms03
- Start date
I believe that atleast one of the diodes is blown, but how is this happening? in rush current?
Well how much current do you want to draw from this setting. And do you connect a capacitor to the bridge. Also what kind of diodes do you use
I have this signal going to an opto-iso, that only should draw 10mA. I am using 1N4001. And I have used a bridge IC thats rated for 400V 1A. I have taken the opto-iso out of the circuit to look at the output of bridge and it's only a half wave and not a full wave, even with new diodes.
There is no capacitor on this circuit, i want to know when the sine wave goes to zero.
There is no capacitor on this circuit, i want to know when the sine wave goes to zero.
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I am not planning on using this circuit as a power supply. I am using the bridge rectifier to an opto- iso, which will allow me to know when the AC crosses 0, so when i hook the other side of the circuit to a uC i can tell if the signal is 50 Hz or 60 Hz. Regardless of load, I am not seeing a full wave, only a half wave. I am not getting the negative portion of the sine wave to be positive.
what do you see on the AC pins?
are you using an isolated supply for your ac, like from a transformer?
On the live side I see a nice sine wave, and the neutral line is relatively straight.
I am currently using a Variable AC (VAC) so if something is wrong it will blow the fuse in the VAC.
if I use a scope using the earth ground, on the + after the bridge i see, /\_/\_/\_...(half wave) and on the - after the bridge i see \/-\/-\/-... (negative half wave)
I isolated the earth ground from my three prong cord with a three prong to two prong adapter, so there is no long an earth ground for the scope. The Sine wave is now somewhat a square wave and I still don't get the full rectifier output. Also I plugged in the Three prong for my scope and lifted the ground from my scope and still saw the same half wave rectifier output as before.
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I have the VAC plugged directly to my wall outlet. I know my drawing isn't great, but should give you an idea what im trying to do. I am having an output with a frequency of 120Hz, and it should be 60 Hz. This is what lead to me look at the output of the bridge, and noticed it wasn't acting like a full bridge rectifier.
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With the whole thing disconnected from the mains,take a DMM on the ohms range,& check for continuity between the two DC output leads of the bridge & the AC input connections to the bridge.
There should be no continuity.
If you haven't somehow,got a direct connection between one of the DC outputs & the Neutral line,I would guess that you have one or more of the diodes in the bridge incorrectly oriented.
To check this,disconnect the AC input leads to the bridge,& measure with the DMM in diode test position between each bridge AC input in turn,& the +ve DC output connection(with the black lead on that point).
You should see a forward based diode in each position.
Do the same with the -ve Dc output connection,this time with the meter connections reversed.
Again,you should see two forward biased diodes.
There should be no continuity.
If you haven't somehow,got a direct connection between one of the DC outputs & the Neutral line,I would guess that you have one or more of the diodes in the bridge incorrectly oriented.
To check this,disconnect the AC input leads to the bridge,& measure with the DMM in diode test position between each bridge AC input in turn,& the +ve DC output connection(with the black lead on that point).
You should see a forward based diode in each position.
Do the same with the -ve Dc output connection,this time with the meter connections reversed.
Again,you should see two forward biased diodes.
