LM317 basic adj regulator help

Thread Starter

Al Vince

Joined Feb 24, 2015
27
Al said "In the new photo I have the 240 installed... removed the pot and checked the resistance between the two pot connectors... I got -7.5 on the 20k voltmeter setting. I am guessing that is 7500? Not sure if the negative symbol means anything"

You can't check resistance on the voltage setting. What brand and model of meter do you have? I might be able to help you with the dial settings
so that you can measure resistance.
Sorry it was on the resistance settings... just meant the 20k resistance setting on the voltmeter
 

Thread Starter

Al Vince

Joined Feb 24, 2015
27
Replace the pot with a 1kΩ resistor and see what you get.

Also, your photo labels indicate that you are running this between +12V and -12V. Are you?
I will try this... no that is just the negative coming from the power supply I am using ...
 

ronv

Joined Nov 12, 2008
3,770
Hook the green wire from ground to row 5 (adjust pin). It acts like the wiper on the pot is open. If you move the wire it should measure 1.25 volts out.
 

WBahn

Joined Mar 31, 2012
24,849
In the new photo I have the 240 installed... removed the pot and checked the resistance between the two pot connectors... I got -7.5 on the 20k voltmeter setting. I am guessing that is 7500? Not sure if the negative symbol means anything.
I don't think you were on a resistance scale as I can't imagine it giving a negative reading for any reason.

How do you have the pot (a three-terminal device) wired up? You should tie the wiper to one of the fixed ends since you are using it as a rheostat.
 

Thread Starter

Al Vince

Joined Feb 24, 2015
27
Strange... so I can in this morning with a fresh cup of Starbucks... switched out the Vin power supply with a 9v battery.... and it works fine, then plugged in the original power supply to the Vin, and had the same issue... messed with the connectors and now the original power supply works fine... maybe the components were grounding out inside the breadboard or something?

I really appreciate everyone's help! This forum is great.
 
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