I am a build by numbers guy who build the most basic of stuff as the rest has me snookered.
For some reason I cannot get this circuit to deliver less than about 10V and I need 9V. Input on the left and the diodes have the strip away from the board. This is the second time I have built the strip board from scratch (differently) with the same result?
Go to **broken link removed**
Enter 110 for R1 and 900 for R2 then push calculate.
You have the pot set to 18 volts.
You need to set the variable resistor to about 900 ohms or you can double the value of your 110 ohm resistor.
Many of those "calculate" programs are wrong.
The LM317 works very simply. It develops 1.25V across your 110 ohms resistor which causes a current of 1.25V/110 ohms= 11.36mA. The 1.25V will be part of the output voltage and you want an output of 9V so the pot will have 9V - 1.25V= 7.75V across it and will have 11.36mA in it then its value is 7.75V/11.36mA= 682 ohms. 680 is a standard value.
Your "pot" is 660 ohms so your output voltage should be 1.25V + (11.36mA x 660 ohms)= 8.75V.
Agree but the output is not 8.75V and therein lays the problem, either I have fried the LM317 or I need to check the circuit which I have done numerous time and simply cannot find the problem which I am sure is simply the translation to the strip board, will have to check again.
The regulator has only one purpose in life. It tries to make 1.25 volts across OUT to ADJ.
It sends power from IN to OUT until (OUT to ADJ) is 1.25V. If the voltage is above 1.25 it stop send power.
Your job is to find resistors that give you the right voltage.
Did business with people in Loveland, Electrom Corporation. The owners sold (they called him the Big Swede, he played steel guitar in a band), they moved to New Mexico and it is under new management.
Off Topic.
Did business with people in Loveland, Electrom Corporation. The owners sold (they called him the Big Swede, he played steel guitar in a band), they moved to New Mexico and it is under new management.
Yeah the original owner was a bit of a genius / maverick. The make high voltage impulse generators for testing electric motor windings. They use d.c. which is non destructive and they put a rather steep wave form into the windings (200us if I remember) trying to find inter turn winding faults. They have just brought out a digital version which I am told is outstanding. I was their agent in S.A. until our entire group of companies was liquidated (Chapter 11?) due to fraud by the two primary shareholders.
I to know this problem.
I watches a manager get away with some money. It cost the company $20 for every $1 stolen.
It is like if a bad man brakes down you house door and takes some money. The broken door costs more than the money.