Help Me, LM3915 VU Meter

There's only two posibilities:

Either you have it set up for dot mode and your input signal is way too high, or you got it damaged.

Buy a new one and re-do the circuit.

Now that you've figured the Cap. to filter out the undesired frequencies, it's got to be a piece of cake to rebuild it.

This stuff happens, it's a universal truth of electronics.
Last week I took a good production board to use as a reference to fault find 5 faultly boards.
When I'd finished, I had 5 repaired boards and the production one had stopped working!

The only real way to fault find anything is with a circuit diagram, an oscilloscope and ideally a working board for reference.
Del

Hi,

I am pretty sure you blew it up. (static)

I'd change the LM3915

TTYL Jens

Does anyone on this electronic group know

where I should go to ask a question about diesel fuel and/or furnace fuel.

I searched the CR4 and could NOT find a group on chemistry

I wondered if I could run my diesel genset on my oilfurnace fuel.

A friend of mine told me NO, it will NOT run very good.

He told me his tractor did not like furnace fuel very much.

It only liked diesel. He had to flush all that furnace fuel out

and refill it with diesel fuel.

TTYL Jens

LOL on that.. seriously, it gets frustrating. When it worked, I was excited, showed all my friends, then forgot to take a picture. Redo it and it did not work. I'm pretty sure i did not blew as i'm only using 9V battery and the datasheet says that it can withstand up to 25V

What they meant when they said you possibly 'blew' it was static discharge into the IC which can be thousands of volts. You can acquire this charge just by walking through air and particularly by walking over carpets. You must discharge yourself into a grounded conductor before working on electronics.

The only sure way to tell if your LM3915 was damaged is to replace it (carefully) with a good one. There is also the possibility that there is a wiring error that you keep overlooking....it has happened to many of us. Is there anyone else who can look over your circuit for you? As they say, "a fresh pair of eyes can help out a lot." You might even have a component which looks connected but it isn't. Is the IC socketed? That should be the first thing to do if it isn't and if it is, check those solder joints to the socket's pins, they may look soldered but they may not be.

I almost always use sockets on ICs because it is very difficult to remove them when soldered to wires and components. There are a few cases where sockets are a bad idea but not in this case. One more thing, ICs can also be damaged by too much heat during soldering which is another good reason to use a socket and put the IC in after you are done soldering.

owh, sorry i overlooked the message, yeah probably the static discharge. It was on the breadboard, this project was just for fun. Im a starter. What i really wish to learn was the effects of band filters on the AC signals. It would have been easier if i had a oscilloscope. Thanks for all your replies! i will soon try a fresh piece of IC and see if it works. How do i close this topic?

There is no way to close a topic... you are ours now (cackles wildly).
You really need access to a 'scope to make much progress in electronics.
Good luck we all had to start somewhere, I remember trying to make simple series regulated power supplies and hi fi amps all from discrete components. My firs thi fi amp picked up the local taxi radio calls :)
Del

I see you are still on cat nip...fixed 5 boards but broke the reference board (cackling even more wildly). Yes, those hi fi amps are deucedly wicked at picking up radio signals instead of hi fi signals. Easy enough to get rid of though.

Yes, a scope, even a simple one, would be a great benefit, it is very difficult working 'in the dark'. A VOM would also be of good service.

Ease up on the nip, Del, purring nicely he said.

Like the others said, YOU NEED AN OSCILLOSCOPE. You can get a transistor analog one pretty cheep off eBay. My first scope could not survive a shipping, a 545B Tek. It's also a good space heater. Got it in 1982 for $17, but no plug in, that cost me.

But just look there and see. Then see if you can find someone whom wrote about that model and see if it's antiquated junk, or a usable machine. Even digital multichannel with 7 inch LCDs for less then $500, and speedy enough compared to the analog audio need. Figure out what bandwidth you need. You may end up with a throw away oscope, but if it works, it taught you something. But that one will tell you what the next one will need, if you go that far in this hobby, but will indicate need for features. But my guess is the cheep the better, and will do everything you need.

Well, I cant find any scope in malaysia that comes with a decent price, its either new stuff, or nothing at all. I tried ebay, second hand scope cost about RM500 and the shipping is what pains me. Plus, i do not know if the scope is really in good condition.