Why Does Only LED 10 Light Up on My LM3915/LM3916 VU Meter Circuit?

51 8

#1 21669920 26 Sep 2013 23:48

Travis Moore Travis Moore

Anonymous

Post #1
21669920 26 Sep 2013 23:48

Greetings!

This is my first post in this forum. I am attempting to build the circuit from this post: "Volume Unit Measurement with LM3915 and LM3916()":http://www.eeweb.com/blog/circuit_projects/volume-unit-measurement-with-lm3915-and-lm3916

I can only assume that I have incorrectly put the circuit together, as the only thing that happens when I power it up is pin 10 (LED 10) is the only LED to light up, and nothing else happens. I'm stuck with this one. I've gone over the breadboard and schematic quite a few times, but I just can't seem to find the issue.

I've included a picture of the board just in case.

Any help and/or pointers would be great! Thank you!
ADVERTISEMENT
#2 21669921 27 Sep 2013 00:11

Steve Lawson Steve Lawson

Anonymous

Post #2
21669921 27 Sep 2013 00:11

I don't see anything connected to the input. Have you tried it with a signal on the input?
I see a two pin header and it looks like that is for +12 and -12, but are you also connecting a ground to the power source (i.e. a connection from the power source ground to "0V" on the circuit)?
Check all your power connections with a volt meter.

Do you have an oscilloscope? If so, connect a signal to the input and check to see if it's at pin 1 of IC1 and pin 5 of IC2.

Other than that, it difficult to fully check your connections from that photo. It's at a bad angle for some of the connections -- especially around the OpAmps.
ADVERTISEMENT
#3 21669922 27 Sep 2013 07:21

William Main William Main

Anonymous

Post #3
21669922 27 Sep 2013 07:21

I say the headers pins I am presume is for the +12 and -12. Where are you connecting the ground from the power supply?
#4 21669923 27 Sep 2013 08:33

Travis Moore Travis Moore

Anonymous

Post #4
21669923 27 Sep 2013 08:33

Thank you for the quick reply. I did have the input signal connected, but removed it just before I took the picture. One thing I wasn't terribly certain on was how I should hook up the +12 and -12. I've only built circuits with a positive and ground. Now that that was brought up, I can imagine that is this issue.

I do have an oscilloscope, so I will check that when I get home.

I will also take some top view pictures.

Thanks!
#5 21669924 27 Sep 2013 08:34

Travis Moore Travis Moore

Anonymous

Post #5
21669924 27 Sep 2013 08:34

Judging from the first reply, I think I have hooked it up incorrectly. Those two header pins were for +12 and ground. I'm not for sure how to hook it up for -12V.
ADVERTISEMENT
#6 21669925 27 Sep 2013 08:37

Travis Moore Travis Moore

Anonymous

Post #6
21669925 27 Sep 2013 08:37

Also, the input positive was connected to the positive side of C2.
ADVERTISEMENT
#7 21669926 27 Sep 2013 09:12

Steve Lawson Steve Lawson

Anonymous

Post #7
21669926 27 Sep 2013 09:12

Well, without -12V it won't work, so be sure to add that. Sounds like you are experiencing some of the same sort of "mindfreak" I used to back when I was getting started. -12 is no different than +12, it's just another supply line. Hook it up the same way you did with +12 -- only there is no busbar for it, so just connect it directly to IC1 pin 4, and then connect C4 from IC1 pin4 to Ground (0V).
#8 21669927 27 Sep 2013 09:15

Steve Lawson Steve Lawson

Anonymous

Post #8
21669927 27 Sep 2013 09:15

And did you connect the grounds together? You need to do that, too. In other words, connect the ground or "negative side" of your signal source to the ground ('0V') of VU circuit.
#9 21669928 28 Sep 2013 22:17

Travis Moore Travis Moore

Anonymous

Post #9
21669928 28 Sep 2013 22:17

Yes, the grounds are connected together. I've taken another look at the circuit, and rearranged some of the components to where they should be after you advised me on the + and - issue. I am still only getting LED 10 to light up, however, after I remove +12V from the op-amp, it scrolls through the LED's connected to the LM3916 almost instantly, then slowly scrolls through the LED's connected to the LM3915. When I connect +12V back to the op-amp, the scrolling ceases and LED 10 just stays lit. Now, this I neglected to say when I first posted that I didn't have a TL072, so I used a JRC4558D, LM741, and TL061, but all had the same outcome. I do have some TL072's on order, and should be here Monday.

I've attached a better picture of the breadboard. If you need any other angles, or closeups, please let me know.

Thanks again!
Create an account, log in here. You will receive points by participating in discussions.
Join this discussion.

Install Elektroda application

Didn't find an answer? Ask Artificial Intelligence

*I agree to send the question to OpenAI, Anthropic PBC, Perplexity AI, Inc., Kagi Inc., Google LLC - owners of language models in order to prepare the best response. The companies may monitor and log information entered into the form.

*I agree to publicly display my question and answer. The question and answer will be publicly available to everyone. The process may take a few minutes. Upon completion, you will be redirected to the page with the answer.

Wait...(2min)

Topic summary

A user building a VU meter circuit based on LM3915 and LM3916 ICs encountered an issue where only LED 10 lights up upon powering the circuit. The problem was suspected to be incorrect wiring, particularly regarding the power supply connections. The circuit requires a dual power supply of +12V and -12V along with a common ground, but the user initially connected only +12V and ground, lacking the -12V line. It was emphasized that the -12V supply is essential for proper operation and should be connected directly to pin 4 of IC1 with a decoupling capacitor to ground. Additionally, the grounds of the power supply and signal source must be connected together. The user confirmed having an input signal and a connected ground but used substitute op-amps (JRC4558D, LM741, TL061) instead of the recommended TL072, which may affect behavior. Without +12V to the op-amp, the LEDs scroll through rapidly, but with it connected, only LED 10 remains lit. The user plans to test with TL072 op-amps upon arrival. Troubleshooting steps include verifying power connections with a voltmeter, ensuring proper input signal presence at IC pins, and confirming common ground connections.
Summary generated by the language model.

Home page
/
Forum
/
Circuit Design
/
EEWeb Topics
/
Why Does Only LED 10 Light Up on My LM3915/LM3916 VU Meter Circuit?

Why Does Only LED 10 Light Up on My LM3915/LM3916 VU Meter Circuit?

Didn't find an answer? Ask Artificial Intelligence

Topic summary