Just When I Thought it was Going to Be Easy

[VenomBallistics]

Very basic stuff
https://www.ti.com/lit/ds/symlink/t...rl=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTL081
Page 28
Figure 1
R / C network at output is optional.

 

[VenomBallistics]

Very basic stuff
https://www.ti.com/lit/ds/symlink/tl081.pdf?ts=1627298401632&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTL081
Page 28
Figure 1
R / C network at output is optional.

Signal in = signal out
You'll just need to add a 1M bias resistor and some caps at in and out.
If sound comes out, you're using it right

 

[SparkyCal]

Hmmm. I have an idea. I just built another circuit using the 4558D op amp. It initially did not work, until I tried the following:

I noticed that I had one of the jacks, daisy chained to ground by passing it through the other jack, which went to ground. I had never done it this way, and so I wondered if it was causing the circuit not to work. Sure enough, when I disconnected the ground wire that was daisy chaining, and instead, ran both jacks directly to the ground rail with their own individual wires, I got sound and all worked as it should.

Could this have been the issue with the single op amp chip? I was using he same wiring as above, but I did not think to rewire it.

 

[VenomBallistics]

it's plausible, Some of these jacks have switches too.

 

[SparkyCal]

it's plausible, Some of these jacks have switches too.

Do you think it could have affected the Pin readings?

 

[VenomBallistics]

Do you think it could have affected the Pin readings?

At least some of them. Thing is, you somehow had voltage on a dummy pin. The TL081 is technically just a 7 pin device. That tells me that the jack issue was not the only issue.
Tear it down to a bare breadboard and start over fresh so you don't carry a legacy error into the next attempt

 

[SparkyCal]

I don't understand this. My dual op amp circuit is working great, up until I put it into the box. But this time, I know what the problem is. But I don't why it is happening and how to fix it.

Because there is no room for a battery, my circuit uses only the DC barrel. It all works perfectly, until I fasten the DC barrel into the box. When I do that, the LED no longer lights and the circuit is silent. But when I hold the DC barrel outside the box and connect power, all is well.

So, it seems to be that when the metal of the DC barrel touches the metal of the box (which is almost unavoidable, as I have to fasten the DC barrel into the box, with it's nut and washer), it causes the circuit to go dead.

What is happening and why? and how do I prevent it? It seems so illogical.

Thank-you

 

[WHONOES]

Can you post a circuit diagram of what you are doing?

 

[VenomBallistics]

I don't understand this. My dual op amp circuit is working great, up until I put it into the box. But this time, I know what the problem is. But I don't why it is happening and how to fix it.

Because there is no room for a battery, my circuit uses only the DC barrel. It all works perfectly, until I fasten the DC barrel into the box. When I do that, the LED no longer lights and the circuit is silent. But when I hold the DC barrel outside the box and connect power, all is well.

So, it seems to be that when the metal of the DC barrel touches the metal of the box (which is almost unavoidable, as I have to fasten the DC barrel into the box, with it's nut and washer), it causes the circuit to go dead.

What is happening and why? and how do I prevent it? It seems so illogical.

Thank-you

Your signal jacks are negative grounded, meaning the frame is negative side.
The barrel connector is Positive frame, with the inner pin negative.
In a metal box, your short your power through the connector frames.
measure voltage between the frames outside the box, and it'll become crystal clear

 

[SparkyCal]

Can you post a circuit diagram of what you are doing?

It is on the very first post on this thread

 

[SparkyCal]

Your signal jacks are negative grounded, meaning the frame is negative side.
The barrel connector is Positive frame, with the inner pin negative.
In a metal box, your short your power through the connector frames.
measure voltage between the frames outside the box, and it'll become crystal clear

 

[SparkyCal]

That makes sense. Does that mean I should reverse the barrel wiring?

 

[VenomBallistics]

That makes sense. Does that mean I should reverse the barrel wiring?

Absolutely not. Then your power supply puts reverse voltage to your project.
The thing to do here is figure out some way of insulating the barrel jack from the metal case.
Dead minimum, I'd give the case a heavy powder coating to act as insulation. better still is a plastic pass through.

 

[SparkyCal]

thanks for that. Maybe a little coat of hot glue?

 

[VenomBallistics]

thanks for that. Maybe a little coat of hot glue?

kinda sketchy .... Punch the case hole oversize and fill it in with epoxy putty. once set, drill the epoxy plug for the barrel connector
Hot glue likes to fail in roles like these.

 

[bertus]

Hello,

For isolation, you could also use some heat shrink tubing.
Those are available in many sizes:
https://www.amazon.ca/s?k=heat+shri...d=1627498452&rnid=12035754011&ref=sr_nr_p_6_7

Bertus

 

[VenomBallistics]

Hello,

For isolation, you could also use some heat shrink tubing.
Those are available in many sizes:
https://www.amazon.ca/s?k=heat+shrink+tubing&i=automotive&rh=p_6:A3DWYIK6Y9EEQB&dc&qid=1627498452&rnid=12035754011&ref=sr_nr_p_6_7

Bertus

clamping action of the fastening hardware needs to be considered.
Roland / Boss addresses this issue with a square plastic jack that slips into a rectangular cut out

 

[SparkyCal]

Thanks guys. I have a ton of shrink tubing. I may try that first.

 

[SparkyCal]

Hey Bertus- the shrink tubing fit like a glove. Not as durable as plastic, no doubt, but we'll see if it holds. this is still a prototype anyway (see attached)

 

[VenomBallistics]

Hey Bertus- the shrink tubing fit like a glove. Not as durable as plastic, no doubt, but we'll see if it holds. this is still a prototype anyway (see attached)

You still have a path via the threads and the nut