I'm a beginner in the DIY electronics world and I'm trying to build a power supply with adjustable voltage and current. Currently, I have a 12-0-12 3 amp step-down transformer. I initially connected two of the three wires to a bridge rectifier, then added a 50V 4700µF filter capacitor, followed by a buck converter. At first, I got 14 volts without any load, but when I tried running a 775 DC motor that only uses 0.4 amps, the voltage dropped to 10 volts, which seems strange. I switched to a full-wave rectifier using all three output wires, but faced the same issue. Where is all the power going, and why am I experiencing voltage and current loss? Additionally, I'm using an LM7812 IC to power a 12V 0.12 amp cooling fan connected directly to the filter capacitor. Any insights would be appreciated!
2 Answers
Could you share some photos of your setup? That might help us spot any mistakes or issues. Sometimes it’s easier to see what's wrong visually rather than just through description.
Your transformer size matters a lot! If it's really 6 cm x 7 cm, that might be a hint that it's smaller than a 3 amp transformer. Usually, a 3 amp transformer would be noticeably larger. Also, make sure the diodes you're using are rated for at least 5 amps; using underpowered diodes can lead to voltage drops. Also, check the thickness of your wires – they need to handle the current without significant loss. It sounds like you did the right thing with the bridge rectifier and connecting both halves, so maybe look into those components further!
Yeah, I agree! Transformer size can definitely indicate its capabilities. And don’t forget about the quality of your connections; even a small issue there can affect performance too.
I'd love to share pictures, but I'm having trouble uploading them right now!