Adjustable Voltage Regulator

[Vallka]

Hi All
First I have 0 background in electronics!! but the internet is great.
I want to build a couple Adjustable Voltage Regulators for a 12v power supply. Pretty sure I have it partly figured out except a couple things,
How to wire in the 5K ohm linear taper potentiometer.
What is the size of C1?
What is the meaning of the arrow on the R2, do I connect it there?

Thanks for all the help

 

[davenn]

hi there Vallka
welcome to the forums

The circuit diag tells you the value of C1 = 0.1uF, it will be a small dics ceramic or similar capacitor.
If the input to the regulator is coming directly from a Bridge rectifier, then you will need at least a 1000uF electrolytic capacitor between positive and negative prior to C1

The arrow is the wiper ( centre connection) of the trimpot or larger variable resistor
so you have a wire going from the negative rail ( long the bottom of the diagram) to the centre pin of the pot

Dave

 

[Vallka]

Did I mention I have no background in this stuff?
Small words, speak slowly please.

Can I use, say a 1uF 50V Multilayer Monolithic Ceramic Capacitor for C1?
And is that a yes to connecting the R2 to right to the negitive wire?
This is a video I watched

 

[davenn]

hi Vallka

a 1uF would be OK but a 0.1uF would be much better, you should really have a 0.1uF on the input and output and have them soldered as close to the regulator chip as possible
You still need the 1000uF on the input tho, otherwise you wont have any smoothing of the DC voltage from the bridge rectifier
the centre pin of the pot ( variable resistor) IS the one indicated by the arrow.... so as said in my last post, the centre pin goes to the negative line.

the circuit you have shown is opnly part of what you need in total here below is the full circuit......

now there are a couple of extras in here that you may or may not include, they are just for indication, if left out, wont affect the operation of the circuit.....

1) on the input to the regulator there is included a LED and a resistor R1 for power on indication

2) on the output there's a resistor, R3, a trimpot P2, and a voltmeter --- there to tell you what the voltage is set to. for an adjustable PSU you would find that VERY useful!!!

Dave