I am trying to post a question about the lm317. I just want to know what size transformer for lm317 at full 30v. I know its a 24vac transformer but is it 1 amp or 5 amp transformer? I also know the datasheet says 1.5 amp output, but I am a newbie so that means nothing to me in regards to my question.

 

LM317 limited to around 1.5a, pay to have some margin so allow for a 3a to 5a Tfmr.
Max.

 

The transformer needs the current to be derated about 50-60% for a DC output, so for 1.5A output, the transformer rating should be at least 2.5Arms.

 

Hello,

With an 24 Vac transformer the input voltage of the LM317 will be about 33 Volts max.
What output voltage range is needed?
Keep in mind that a lower output voltage will result in more heat on the LM317.
A heatsink will be essential when going lower in output voltage at higher currents.

Bertus

 

Welcome to AAC!

I just want to know what size transformer for lm317 at full 30v. I know its a 24vac transformer

24VAC is a little low for a 30V output.

DC will be about 24*1.414 - 1.4 = 32.5V. The drop out voltage for LM317 is a couple volts at 1A. That'll require a large filter cap because you'll have little tolerance for ripple on the input.

From NatSemi datasheet: