Wiring Voltage Regualtor

[pizoman]

Help Wiring Voltage Regualtor

I found this circuit diagram for a LM1084 regulator and I've wired it up on my bread board but I'm a little confused as to where the "final regulated voltage" is suppose to go. I've placed positive and negative multimeter probes accordingly and I get zero volts from the output voltages. Can someone help me out with this?

Here's the original schematic: http://www.electroniq.net/power-supply/lm1084-voltage-regulator-circuit.html

Breadboard Wiring. For some parts I used different values because those were what I had on hand.
Specs: Top R=470ohm, Bot R=1K, 1uF electrolytic cap, 0.1uF ceramic cap, 9 volt battery source

 

[(*steve*)]

Do you mean this?

I'd start with using the larger capacitor on the input, and I would recommend using a capacitor larger than 0.1uF on the output.

You could also start with the simplest design, remove all the resistors an connect the adj pin to ground. I expect you should see 1.25V on the output.

It's also worth checking the input voltage. If you're using a battery it is possible that it's flat and the current drawn is loading its voltage down.

 

[pizoman]

Yes, that's the one. Battery should be fine, I checked and it was about 8.6 Volts. I will try a larger capacitor and ground the adj with no resistor.

 

[pizoman]

Removed all the resistors and grounded the adj. Placed a probe on ground and one at the output pin of the regulator and read 7 Volts. The battery warms up too.

 

[(*steve*)]

Removed all the resistors and grounded the adj. Placed a probe on ground and one at the output pin of the regulator and read 7 Volts. The battery warms up too.

If the battery warms up, you have connected something wrong.

The output should be 1.25V with the ADJ pin grounded.

You may have the pins connected incorrectly.

You've removed ALL the resistors, right?

 

[pizoman]

Ok, I flipped the regulator over, I thought the pins were (from left to right) adj, out, in with the label of the regulator facing me. I get 1.3 Volts now, but the regulator heats up now.

Also, I switched out the caps to 10uF on the Vin side and 47uF on the Vout side.

 

[(*steve*)]

NOTHING should heat up. Are you sure you have no load attached?

 

[pizoman]

Nothing is attached.

 

[(*steve*)]

OK, we need so see a picture of your layout, because *something* is incorrect.

What is your source of 9V?

 

[pizoman]

Power source is a 9 volt duracell battery.

 

[davenn]

Power source is a 9 volt duracell battery.

no, we need to see an actual pic of your assembly so we can see if you have wired something incorrectly


Dave

 

[davenn]

looking at the datasheet for the regulator your last drawing layout is incorrect

you have the input voltage going to the adj pin

Dave

 

[davenn]

here's a modified layout

NOTE on the regulator
AD = Adjust
OT = Output
IN = Input


Dave

 

[pizoman]

Davenn, I tried your wiring and the battery no longer heats up, but I measure the output voltage to be 7.7 Volts now from what Steve said should be around 1.25V.

 

[davenn]

Davenn, I tried your wiring and the battery no longer heats up, but I measure the output voltage to be 7.7 Volts now from what Steve said should be around 1.25V.

OK I go back to my earlier comment again

SHOW us an actual photo of your setup

Dave

 

[pizoman]

The 9 Volt battery is on the other side of the board. The regulator I'm pretty sure is correct, from left to right Vin, Vout, Adj.

 

[(*steve*)]

OK, it's possible that the regulator needs to be lightly loaded or the output voltage will float high.

Try placing a 1k resistor across the output (something between about 220 ohms to 1k should be fine. Normally the voltage divider serves this function.

 

[EinarA]

My guess would be the regulator is dead.

 

[davenn]

The 9 Volt battery is on the other side of the board. The regulator I'm pretty sure is correct, from left to right Vin, Vout, Adj.

No your regulator pin conns are still incorrect
LOOK at the drawing I did the alterations on for you
left to right Adj Out In

this info is readily available in the datasheet for the device
maybe you need to google that

Dave