Voltage regulator problem

[bdg]

Hi, I am working on a medical device that works perfectly except for a problem I am having with voltage drop. The device is designed to work on DC with 12 volts going through a adjustable voltage regulator to get 9 out. When I hook the device up to an adjustable AC power source with 13 volts in I get 9.5 through the voltage regulator. As soon as I hook it up with 12 volts DC the voltage drops to about 5 or less out of the voltage regulator. I have tried a variety of battery packs 8AA or 2 9V in series but I just cant get a decent voltage out of the regulator. I have also tried different regulators. I really need this to run on DC but just don't know enough about electricity or circuits to figure this out. Any help on how batteries affect voltage regulators vs. AC would be helpful.

 

[davenn]

hi there
welcome to the forums

show us your schematic and a pic of your construction SHARP and WELL LIT

lets see if you are making any mistakes

cheers
Dave

 

[bdg]

Hi Dave,
I don't have a schematic because that would be way over my head. I was trying to upload some pics I took that show the below results but I don't see a link for attaching (other than as a URL)

8 AA batteries measure 11.88 volts through the multimeter (not hooked up adjustable voltage regulator)

8 AA batteries run through adjustable volt meter measure 7.45 volts out initially then keeps dropping. After a minute the multimeter reading is 7.33

2- 9Volt batteries (rechargeable) in series not hooked up to adj voltage regulator = 15.38 volts
2- 9 volt batteries in series hooked up to the voltage regulator = a paltry 5 volts out

Using an AC voltage regulator set to 12 volts gets 8.6 through the adjustable voltage regulator circuit (purchased online)

let me know the best way to upload photos

 

[(*steve*)]

If you don't have a schematic, then you are going to have to figure a way of telling us how you have wired up the regulator and what the regulator is.

Almost certainly, the regulator will not like an AC input.

 

[bdg]

pics attached

If you don't have a schematic, then you are going to have to figure a way of telling us how you have wired up the regulator and what the regulator is.

Almost certainly, the regulator will not like an AC input.

Hi,
I just saw the attachment clip which did not appear yesterday when I responded.

The first is the regulator hooked up to 8-AA
Second is 2-9V in series
Third is when it is put through a power source set to 12 volts
fourth is just a pic of the voltage regulator

Thanks very much

Brian

 

[(*steve*)]

OK, that's more than just a regulator

You can connect that up to low voltage AC, but stich to batteries for the moment.

Does the output voltage vary as you turn the pot?

Have you tried loading it a little? (a 1k resistor should be fine)

 

[bdg]

OK, that's more than just a regulator

You can connect that up to low voltage AC, but stich to batteries for the moment.

Does the output voltage vary as you turn the pot?

Have you tried loading it a little? (a 1k resistor should be fine)

Thanks Steve,
I looked online a lot for just a simple voltage regulator but was not able to find one. Not knowing much about electronics I did think there were a lot of resistors in the circuit. Do you think that is the reason for the voltage drop when using DC? If that is true, do you know where I can order a simple one? The pot does work.

 

[(*steve*)]

Can you point me to any specifications for the board you purchased? If you get a regulator on its own (that's the three legged black thing with the metal tab) then you're going to have to wire it up correctly and that may be harder.

 

[CDRIVE]

This is the stuff that makes me crazy! You got the board from someplace! Why not be done with it and post that info at the get go? Also, there's no solder on your alligator clips. Alligator clips present enough problems on there own accord without the added issue of twisted wire connections.

Chris

 

[(*steve*)]

I'm guessing it's this.

 

[davenn]

BDG

it requires an AC voltage input as Steve said ...
buy a AC to AC plugpack
dunno what country you are in so say 220VAC to 16VAC or 120VAC to 16VAC

connect the 16VAC to the input and you will get an adjustable DC voltage out

the initial voltage drop is because of the rectifier diodes on the input to the regulator

Dave

 

[CDRIVE]

I'm guessing it's this.

And why should you have had to search for it?

Chris

 

[(*steve*)]

And why should you have had to search for it?

Because maybe this is a test of my abilities to Google.

It would be really good to see an image of the other side of this board. It's a kit and we don't know how well soldered all the joints are.

It could be simply a bad joint.

I would imagine that a DC input of 4 or more volts higher than the desired output voltage should work as well as an AC input.

 

[bdg]

I'm guessing it's this.

Thanks Steve, you are correct

Because maybe this is a test of my abilities to Google.

It would be really good to see an image of the other side of this board. It's a kit and we don't know how well soldered all the joints are.

It could be simply a bad joint.

I would imagine that a DC input of 4 or more volts higher than the desired output voltage should work as well as an AC input.

Hi,
I will take a pic now and post

And why should you have had to search for it?

Chris

Hi Chris,
Sorry about not posting where I bought the regulator. I am new to electronics and did not know about clips and twisted wires. I know now, so won't make that mistake again

BDG

it requires an AC voltage input as Steve said ...
buy a AC to AC plugpack
dunno what country you are in so say 220VAC to 16VAC or 120VAC to 16VAC

connect the 16VAC to the input and you will get an adjustable DC voltage out

the initial voltage drop is because of the rectifier diodes on the input to the regulator

Dave

Thanks for the great information,

Hi,
I will take a pic now and post

Here is the pic

If you don't have a schematic, then you are going to have to figure a way of telling us how you have wired up the regulator and what the regulator is.

Almost certainly, the regulator will not like an AC input.

Hi Steve,
The regulator is UTC250313L (if I am reading it right). Originally I was using an LM317 on a bread board but was not successful in getting it to work, so I went online and bought what I thought was an adjustable voltage regulator. AC works perfectly through the circuit, It is DC that is a problem. Once I hook up this circuit board to the AC power source and set it to 12 volts, it works perfectly. It is when I try to use DC that the voltage drops too much

 

[(*steve*)]

I can't find any reference to a UTC250313L. In any case, an LM317 *IS* an adjustable regulator. <<< Edit: That would be this kit (UTC250313L), right?

Is the regulator getting hot?

What is the load you're trying to power?

Does the voltage drop immediately, or after a short delay?

Is that your soldering, or did this device come pre-assembled?

 

[bdg]

Because maybe this is a test of my abilities to Google.

It would be really good to see an image of the other side of this board. It's a kit and we don't know how well soldered all the joints are.

It could be simply a bad joint.

I would imagine that a DC input of 4 or more volts higher than the desired output voltage should work as well as an AC input.

Hi,
is there a problem with putting 2-9V batteries in series? when I do I get 15 volts but when attached to the regulator circuit board, it drops to 5 volts.

 

[bdg]

I can't find any reference to a UTC250313L. In any case, an LM317 *IS* an adjustable regulator. <<< Edit: That would be this kit (UTC250313L), right?

Is the regulator getting hot?

What is the load you're trying to power?

Does the voltage drop immediately, or after a short delay?

Is that your soldering, or did this device come pre-assembled?

it was pre-assembled. I will test the heat now. I hooked up the 8 AA which have 10.73 volts in and when attached have an out of 7.28. A minute later it is 7.10 volts. Another couple of minutes it is at 7.0 What is the difference between 9V and AA's? I know that I wont get a sold 12 out of the AA's but why do the 2-9Volts drop so much? I am connecting to what is known as a kapton thermofoil heater, which is about he size of a quarter and gets several hundred degrees hot. I only need a constant 9 volts out to get it where I need it but cant find a DC source that works. I can touch the heat sink about 3 seconds before I have to let go

 

[(*steve*)]

Hi,
is there a problem with putting 2-9V batteries in series? when I do I get 15 volts but when attached to the regulator circuit board, it drops to 5 volts.

We need to know something about the load you have attached.

Please try to answer the questions we ask or we won't be able to help you.

 

[(*steve*)]

it was pre-assembled. I will test the heat now. I hooked up the 8 AA which have 10.73 volts in and when attached have an out of 7.28. A minute later it is 7.10 volts. Another couple of minutes it is at 7.0 What is the difference between 9V and AA's? I know that I wont get a sold 12 out of the AA's but why do the 2-9Volts drop so much? I am connecting to what is known as a kapton thermofoil heater, which is about he size of a quarter and gets several hundred degrees hot. I only need a constant 9 volts out to get it where I need it but cant find a DC source that works. I can touch the heat sink about 3 seconds before I have to let go

Aaagh, try not to split up your posts like that.

What current does it draw? I suspect it is far too high for these batteries.

OK, if the regulator is getting that hot it may also be shutting down. You need to connect a heatsink to it.

 

[bdg]

Aaagh, try not to split up your posts like that.

What current does it draw? I suspect it is far too high for these batteries.

OK, if the regulator is getting that hot it may also be shutting down. You need to connect a heatsink to it.

Thanks Steve,
sorry for splitting up the posts. Too much draw seems like a good suggestion. I think I will sleep on it tonight and think about a solution tomorrow