EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: okw on November 07, 2024, 11:48:45 am
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I've been looking at these dangerous 230V to (e.g.) 5V circuits consisting of a bridge rectifier and capacitor dropper.
They work OK with known and steady loads (like fans, LEDs, etc), where the user is cut-off any handling. A better way is of course to have a transformer to drop the voltage considerably before the bridge rectifier, but they're expensive and heavy, so I get why they rather use a cheap capacitor dropper.
How much safer would it make this circuit using a 1:1 isolation transformer after the dropper?
(Users would still be cut off handling the circuit.)
It's for running an MCU to control a TRIAC and a relay.
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If you're going to use a transformer in your design, then you don't need the capacitor dropper at all!
Just use a normal low voltage transformer, bridge rectifier & regulator to power the MCU!
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No, a 1:1 isolation transformer (230VAC in => 230VAC out).
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I understand that
I'm saying that compared with a 1:1 isolation transformer, it's cheaper and less heavier to use a low voltage transformer to power the MCU, and delete the capacitor dropper.
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isolation transformers and regular transformers do not cost much different.
do not use capacitor droppers. want to make a low-cost product? :bullshit:
Design it with a 230V:9V transformer and a 7805.
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This schematic snippet shows you how to isolate your MCU by using a small transformer and optocoupled triac driver.
[attachimg=1]
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A better way is of course to have a transformer to drop the voltage considerably before the bridge rectifier, but they're expensive and heavy
How much is heavy?