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Just When I Thought it was Going to Be Easy

SparkyCal

Mar 11, 2020
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I ordered 30 plastic dc barrels. That ought to make things easier
 

SparkyCal

Mar 11, 2020
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I am not sure what is happening here.

I built the same old circuit, this time using a TL072 op amp. It worked perfectly.

Then, I received some plastic DC barrels (these ones to be precise).

https://www.amazon.ca/gp/product/B096XJWZJQ/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

I built the identical circuit, so that I can utilize my plastic DC barrels in this one. I followed my usual wiring , however, the circuit did not work. When I began measuring my voltages with a meter, I noticed that my voltage is not + 9 volts, but - 9 Volts.

I am pretty sure that the fact that the DC barrel is plastic, and it no longer presents the problem of trying to get it through the enclosure without it shorting, it likely has an impact on the way the volts are fed in to my circuit.

Presently, I have two wires streaming from the positive terminal of the DC barrel. One of these goes to the circuit board as the voltage supply, and the other goes to the top middle lug of the stomp box switch.

I then have two black wires running from the negative lug of the DC barrel. One of them goes to negative rail on the circuit board and the other goes to the negative lead of the LED that is supposed to light up each time the stompbox switch is on to activate the distortion effect.

Because I am using the plastic DC barrel, is this just a matter of switching the leads on the positive lug of the DC barrel to the negative lug of the DC barrel, and vice versa? Or is there more to it?

Note: The DC barrel has a positive leg, a negative lug and a ground lug. I initially was using the positive lug and the ground lug, but then I used the positive lug and the negative lug (rather than the ground), cause I thought this would fix things. I was wrong.

Your advice would be greatly appreciated

Thanks!
 

VenomBallistics

Aug 30, 2018
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Remember, your center pin is the negative terminal
it's the outer barrel that is positive.
your positive lugs are better described as a positive lug and a battery disconnect lug
 

SparkyCal

Mar 11, 2020
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Thanks VB...ok..because I got this whole circuit built, and I don't want t take a chance and fry it, what do I have to do to make sure the DC barrel's lugs are connected properly? My inkling is to reverse the wiring, but I don't want to fry the circuit if I am wrong.
 

VenomBallistics

Aug 30, 2018
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with all power off, probe it with an ohm meter to confirm what lugs go to what part of the connector.
From there you get yourself a pot of coffee and think through your connections.
 

SparkyCal

Mar 11, 2020
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well, I tried and I thought I had it, but it did not work and I may have blown the circuit. I noticed that the centre pin was now the inverse, so I switched the positive leads to negative and visa versa. Failed.
 

Audioguru

Sep 24, 2016
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If you used a new Name Brand 9V battery and its polarity was backwards then the IC is probably destroyed.
But if you used a no-name-brand "Super Heavy Duty" battery from China then it probably did not have enough power to do damage.
 

SparkyCal

Mar 11, 2020
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I used a dc barrel, not a battery. I’m not including a battery clip. The op amp is in a socket. So if it’s the only thing that is damaged, should not be a problem. But I need to know what to do, and then understand it. I tried it the other way around and it did not work out. In other words, what I thought would work, did not

I am also okay with scrapping this whole build and starting over, but I need to know what adjustments to make now that I have a plastic barrel
 

Audioguru

Sep 24, 2016
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I guess you need a multimeter to show DC polarity and AC and DC voltages. It also measures resistance and a diode voltage drop.
 

VenomBallistics

Aug 30, 2018
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I used a dc barrel, not a battery. I’m not including a battery clip. The op amp is in a socket. So if it’s the only thing that is damaged, should not be a problem. But I need to know what to do, and then understand it. I tried it the other way around and it did not work out. In other words, what I thought would work, did not

I am also okay with scrapping this whole build and starting over, but I need to know what adjustments to make now that I have a plastic barrel
You had this working before, it'll work again.
All this is, is you falling victim to a few common quirks of human nature as it applies to electronics.
one is confusing top and bottom view of ICs ... I dont believe this is the issue here.
another one is power supply neglect.
The power supply is always the most important part of the circuit. Our wizzbang gadgets no matter how advanced, simply manipulate this power. The power supply is also the most boring part of any circuit.
The center pin negative is counter intuitive. I honestly have no idea why this has been adopted as the gold standard in the stomp box field since is likes to create shorts through the case via your instrument jacks. But, here we are and we have to deal with it.
You got this man. Believe it. This is nothing you have not already dealt with.
3 lugs ... +, - , switched +
since you are omitting the battery clip, find the switched lug and leave it disconnected.
I think I recall you describing them as +,-, and ground ... therein lies the source of your confusion.
You should probably make a simple LED circuit to train yourself on power connections like this. A load is a load and there's far less emotional involvement with an LED as we slog through the single most boring part of electronics.
 

bertus

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Nov 8, 2019
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Hello,

On the amazon page you gave there was this picture:
sparky barrel back small.jpg
Measure the resistance between Ground and Negative, to see if there is a switch between them.
(just with the plus, with no power).
Then plug-in the power and measure where the positive and negative voltages come, with a voltmeter.

Bertus
 

VenomBallistics

Aug 30, 2018
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Hello,

On the amazon page you gave there was this picture:
View attachment 52714
Measure the resistance between Ground and Negative, to see if there is a switch between them.
(just with the plus, with no power).
Then plug-in the power and measure where the positive and negative voltages come, with a voltmeter.

Bertus
That'd do it...
Pic is right, but it's wrong because the center posts are negative in these applications.
 

SparkyCal

Mar 11, 2020
846
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Mar 11, 2020
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Hello,

On the amazon page you gave there was this picture:
View attachment 52714
Measure the resistance between Ground and Negative, to see if there is a switch between them.
(just with the plus, with no power).
Then plug-in the power and measure where the positive and negative voltages come, with a voltmeter.

Bertus

Thanks guys for your help and encouragement.

I believe that in the picture above, (the one on thread #91) the pin marked positive is actually negative. Treating it as such, gives me a proper positive 9 volts when I run that lug with the bigger base as negative and the one marked negative, as positive. The middle one marked ground, I am ignoring.

If this is correct, if I wire this circuit as such, will it work?
 

SparkyCal

Mar 11, 2020
846
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ok..I will try that when I get some. time and report back. Thanks
 

Audioguru

Sep 24, 2016
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It is a shame that Amazon and their sellers know nothing about and post wrong photos about the electronic parts they sell.
 

SparkyCal

Mar 11, 2020
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Hi guys. I did the fix and it worked. Thank-you for your advice and support.
 

SparkyCal

Mar 11, 2020
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Here is a pic of my in progress build. It is all built and it works. I am just glueing the LED in the steel box and letting it dry. But I thought I'd post this to let you see how small of a PCB board I am now using.
 

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