# variable power supply parts problem

Discussion in 'Electronics Homework Help' started by Amore Renze Papatalok, Sep 28, 2015.

1. ### Amore Renze Papatalok

1
0
Sep 28, 2015
im just a college student
how many amps can i put in this circuit(transformer T1)
what voltage of capacitor can i put in this circuit??

if your an expert can you do a very simple variable power supply with lm317 regulator and 1x pot with 5x capacitor(max) and i want it detailed from farads, voltage and current and a 24v 2amps transformer(max) i want my transformer with low amps as possible to save money and also 2 fixed resistor(max) and an LED it must have a bridge rectifier with 4x 1n4001 diodes

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Last edited: Sep 28, 2015
2. ### davennModerator

13,901
1,971
Sep 5, 2009
Mabuhay, Amore

OK you need a transformer, tho they say 24V,, it only needs to be about 18 - 20VAC and capable of 1.5A to 2A

the 1000uF capacitor really should be a 2200uF to 3300uF, 1000 is a bit low

the (now) 2200uF cap on the output of the bridge rectifier and the 1uF on the output of the regulator
should be 50V rated

You can put the LED and its series resistor across the 2200uF capacitor, use a 6k8 resistor for a standard 5mm red LED,
adj the resistor value slightly to get the LED brightness you require

cheers
Dave

hevans1944 likes this.
3. ### dorke

2,342
665
Jun 20, 2015
May I add that the input fuse value is too high, a 1A is enough.

Are you going to build this PS or is it just a theoretical drill?
Assuming a 20Vac transformer:
"full current=1.5A" is only possible for Vo>13V(about).
For Vo <13V, due to power dissipation limits of the regulator only 0.15A is guaranteed.

Practically the design is lacking...
look here

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