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Electronics => Beginners => Topic started by: LooseJunkHater on April 02, 2021, 10:08:58 pm

Title: (SOLVED) Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: LooseJunkHater on April 02, 2021, 10:08:58 pm
Seriously, I want to pull my hair out. With [this](https://ibb.co/80n1knK (https://ibb.co/80n1knK)) wiring of my LM317, feeding in 12V, I get ~10V at the output tab! With [this](https://www.st.com/en/power-management/lm317.html (https://www.st.com/en/power-management/lm317.html)) calculator, I should be getting ~5V!

I'm so frustrated trying to get this to work. Please help.

Edit: I've also used 2 different LM317's (both branded ST), so I don't think it's a faulty part. I think I'm just being stupid and wiring it wrong, and it's so frustrating. 
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Vovk_Z on April 02, 2021, 10:24:20 pm
Something is wrong. If you have 10V instead of 5V, then there is a broken wire or broken contact.

First picture is unclear. Is resistor 240 R - a potentiometer?
700/240 R resistors must give 4.9VDC at the output, if everythyng is ok.
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: wraper on April 02, 2021, 10:29:14 pm
How it comes that a wire to 700 Ohm resistor is going from the middle of 240 Ohm resistor?
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: LooseJunkHater on April 02, 2021, 10:30:18 pm
Here's another image of it [dead-bug style](https://ibb.co/sjX9hKZ)

Hopefully this slightly clears up what I'm talking about.

I'm glad I'm somehow doing the circuit wrong!

Edit: 12V Pos + Neg is being fed into both legs of the capacitor
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: wraper on April 02, 2021, 10:33:23 pm
You connected 680 Ohm resistor from output pin to GND, why do you expect it to work?
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Vovk_Z on April 02, 2021, 10:37:46 pm
First leg must has both two resistors connected, but not one.
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: LooseJunkHater on April 02, 2021, 10:47:20 pm
I'm a bit confused. Sp
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Andy Watson on April 02, 2021, 10:51:14 pm
Attach the 680 between adjust and output. Attach the 220 between adjust and ground.

Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: LooseJunkHater on April 02, 2021, 10:52:33 pm
WOOPS. Wow that was a silly mistake. Now it works and produces ~5.1V on both resistors.

Thanks for the help! Solved!
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Vovk_Z on April 02, 2021, 11:18:19 pm
Quote from: Andy Watson on April 02, 2021, 10:51:14 pm
Attach the 680 between adjust and output. Attach the 220 between adjust and ground.
Vice versa?
Title: Re: Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Andy Watson on April 02, 2021, 11:32:49 pm
Quote from: Vovk_Z on April 02, 2021, 11:18:19 pm
Quote from: Andy Watson on April 02, 2021, 10:51:14 pm
Attach the 680 between adjust and output. Attach the 220 between adjust and ground.
Vice versa?
Possibly ;) Good catch.
Title: Re: (SOLVED) Can someone PLEASE explain how I'm wiring the LM317 wrong?????
Post by: Terry Bites on April 03, 2021, 04:32:58 pm
What's the deal here? It's a standard jellyfish part!