Low-noise voltage regulator

Mike(Mont) · #1 01-14-2019, 03:52 PM

Probably wasting my time here but was wondering if anyone knows about a low-noise voltage regulator? Have a 500ma load at five volts. I got one of those adjustable ones from ebay and it is noisy.

My theory is there is a large amount of electronic pollution and when it is near the receiver antenna probably where one of the problems is with the ToTeM. So far my solution has been to use the proper voltage battery (no regulator) and 5 volts not easy to come by. Used a 4.8 volt NiMH and it doesn't last very long. Any help would be appreciated. Need 500ma 5volts +-0.5v. thanks

Mike(Mont) · #2 01-14-2019, 04:35 PM

Well ,maybe my receiver is part of the problem. But it really picks up the noise from a few feet away and my guess is the same thing is happening with other devices. I've used two different types of regulators and both had the same issues. Something like the ToTeM the antenna is very near to the regulator. I don't know but if I had one i would try bypassing the regulator and use exact voltage battery.

Geo · #3 01-14-2019, 06:19 PM

Try to buy a better quality regulator from a local shop.
On ebay there are a lot of China trash.
Last days i had a similar problem with a LM317LZ.

Mike(Mont) · #4 01-15-2019, 12:06 AM

Thanks Geo. Oops, I got my wires crossed. Got confused with one of the ITMD projects. The ToTeM does not use a voltage regulator, at least on the plans.

I was thinking something like a LM7805. Does that sound okay?

Thanks.

Geo · #5 01-15-2019, 10:13 AM

Quote:

Originally Posted by Mike(Mont)

Thanks Geo. Oops, I got my wires crossed. Got confused with one of the ITMD projects. The ToTeM does not use a voltage regulator, at least on the plans.

I was thinking something like a LM7805. Does that sound okay?

Thanks.

Yes Mike, a 7805 its OK.
Also a lower drop out can be used as the classic LM317.
317 is more flexible because you can program the out voltage between 1.2 and 37V by the using of 2 external resistors.

Mike(Mont) · #6 01-15-2019, 12:44 PM

Okay, thanks Geo. I will check it out.

Mike(Mont) · #7 01-16-2019, 03:16 PM

Going with the LM7805 on this attempt. Cheap enough to try and see if it is quiet enough. Not expecting too much here. Datasheet says quiet so...

Mike(Mont) · #8 01-19-2019, 07:56 PM

L7805CV

Holy smoke! Not even a slight hiss with the receiver antenna one inch away. Can add capacitors if needed but no need. Okay, got that one solved. Very low cost, too.

That adjustable power supply i was using (LM2596) set off the threshold alarm from about two feet away.

Geo · #9 01-20-2019, 04:46 AM

OK, very good.
LM2596 is the worst choise for this because it has an oscillator at 125Khz. The noise was from this oscillator. Also LM2596 is a step - down switching converter not a clear voltage regulator.
Anyway.. end good all good

Mike(Mont) · #10 01-20-2019, 01:00 PM

Hi Geo,

I can't help but believe the step-down was causing enough interference to affect sensitivity and range. Won't know for sure until i do some real searching. Thanks for your help. Hope your project is advancing.

~~Mike

WM6 · #11 01-21-2019, 04:23 PM

Maybe this ca help:

http://www.wenzel.com/documents/finesse.html

Mike(Mont) · #12 01-22-2019, 02:40 AM

Already got it.

Mike(Mont) · #13 01-27-2019, 01:34 PM

Found out I got other issues causing the noise. This noise is affecting the sensitivity and in the process of figuring out how to isolate it. Capacitors probably.

Mike(Mont) · #14 01-27-2019, 04:44 PM

Worse than I thought. Signal comes back through signal generator into the power supply. Doesn't happen until I turn on the amplifier. Nothing to do with voltage regulator.

reza vir · #15 01-29-2019, 03:20 PM

Quote:

Originally Posted by Mike(Mont)

Probably wasting my time here but was wondering if anyone knows about a low-noise voltage regulator? Have a 500ma load at five volts. I got one of those adjustable ones from ebay and it is noisy.

My theory is there is a large amount of electronic pollution and when it is near the receiver antenna probably where one of the problems is with the ToTeM. So far my solution has been to use the proper voltage battery (no regulator) and 5 volts not easy to come by. Used a 4.8 volt NiMH and it doesn't last very long. Any help would be appreciated. Need 500ma 5volts +-0.5v. thanks

Hello Brother
I accept more work regulators 78L05 and 79L05

Instead of the same regulators LM7805 and LM7905

Geo · #16 01-30-2019, 07:31 AM

Quote:

Originally Posted by Mike(Mont)

Worse than I thought. Signal comes back through signal generator into the power supply. Doesn't happen until I turn on the amplifier. Nothing to do with voltage regulator.

Are you sure it is noise or selfoscillations??

Mike(Mont) · #17 01-30-2019, 01:13 PM

Don't know. Just sounds like the exact same signal and loud. Not very skilled in electronics but it appears to be running through the ground wire back into the signal generator then into the signal generator power supply--voltage regulator heatsink (grounded) like a loudspeaker. So I either need to have someone with electronics degree look at it or buy some gasoline.

There is a 1000uF 35volt electrolytic capacitor between the pos and neg and I think it needs something bigger/more voltage but I do not care to risk electrocution so not going to attempt anything.

I probably have explained everything wrong. Anyway, thanks for trying to help.

Mike(Mont) · #18 01-30-2019, 02:27 PM

I'm guessing bigger capacitor/more voltage would help. I tried using two different battery systems but with a common ground (7.2 volts for amp and 5 volts 500mA step down for signal generator) and as soon as I turn on the amp, the voltage regulator for the signal generator starts to scream. Even with a separate 4.8 volt battery running the generator (no voltage regulator) it still makes a bunch of noise. That just has to be needing a bigger capacitor on the amp.

But looking at the datasheet for the regulator it shows you can add capacitors so I think I can safely try this and see if it helps. Yeah, I'm an idiot with brain damage.

Mike(Mont) · #19 01-30-2019, 03:30 PM

So if I was to replace the 1000uF 35volt electrolytic with a 150uF 450volt do you think that would work or would I be risking electrocution? Anything bigger capacity is expensive.

Mike(Mont) · #20 01-30-2019, 08:27 PM

Ordered the 450volt. This way is it burns up I won't have to buy any gasoline.

Geo · #21 01-31-2019, 05:04 PM

Quote:

Originally Posted by Mike(Mont)

Ordered the 450volt. This way is it burns up I won't have to buy any gasoline.

Ohhh 450V for a battery supply???

Mike(Mont) · #22 01-31-2019, 06:16 PM

Of course i don't know WTH i am doing. At full power there is 630 volts coming off the coil. The power supply cap is only 35 volts and I think that is where it is not enough. i was wishing somebody knew about this. The audio systems I looked at on the internet use this much voltage, only way more capacity, thousands of uF. I am trying to eliminate that signal that comes off the coil ground and travels through the ground wire back to the battery system.

I am starting to think this a fatal flaw in this locator. Got like a double signal, double vision sort of like noise cancelling headphones, it destroys the signal quality.

Geo · #23 02-01-2019, 05:28 AM

Why you don't attach here the schematic so to try to help you???

Mike(Mont) · #24 02-01-2019, 06:42 AM

I think I have it figured out maybe. And much less expensive than the big caps.
A nice power supply with transient protection 1500volts.

Mike(Mont) · #25 02-01-2019, 07:09 AM

Yeah, I'm sure I'm still an idiot, but a happy idiot on the manic side of manic-depressive. LOL

I was desperate there. That's what good prayers can do--find the answer.

I feel like I'm back in the game. Oh my my, oh hell yes...